Severe Storms

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Tue May 21 2024 Valid 221200Z - 231200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTHERN TEXAS AND SOUTHEAST OKLAHOMA ACROSS THE OZARKS AND TOWARD THE MISSOURI BOOTHEEL... ...SUMMARY... Severe thunderstorms posing a risk for damaging gusts and hail will be possible from central Texas into the Ohio Valley and lower Great Lakes area on Wednesday. The greatest threat of damaging hail and wind is forecast from north Texas across the Ozarks. ...Synopsis... A broad zone of moderate to strong southwest flow will stretch from the Plains to the Great Lakes, with the primary shortwave trough affecting the upper MS Valley and Great Lakes through 00Z. This wave will eject northeastward into Ontario and Quebec thereafter, with various convectively enhanced disturbances trailing southwestward within the southwest flow toward Texas. At the surface, low pressure near Lake Superior early Wednesday will fill as it occludes into Ontario, with a cold front roughly from lower MI into southern MO and into northwest TX by midday. Ahead of this front, ample moisture will exist from TX into the lower OH Valley, with various rounds of severe thunderstorms throughout the period. ...Southern Plains into the Ozarks and Mid South... Severe regimes are forecast on both sides of the synoptic front, beginning early on Wednesday. Scattered storms are expected early Wednesday morning over parts of OK, and expanding into southern MO. Here, forecast soundings show extreme elevated instability, along with very favorable hodographs supporting splitting elevated hail storms. Northeast winds north of the front beneath moderate southwest flow will result in lengthy hodographs and good effective-layer storm relative inflow. While the precise corridor is difficult to place, it will likely be just north of the surface front, with potential swaths of significant damaging hail. Western portions of the front into northwest TX will also favor relatively early development, with steep lapse rates aloft and lengthy hodographs again favoring damaging hail. As heating occurs ahead of the boundary, additional storms will develop across northern TX, producing damaging hail and areas of damaging winds. A couple tornadoes will be possible, especially if the boundary briefly stalls or robust cells develop along old outflows. Given that the boundary is roughly parallel to the flow aloft, a prolonged splitting hail storm event will be possible, from the Red River region across the Ozarks. Additional clusters of storms are likely to develop and translate south/southeast across AR and into western TN/MS where ample moisture and instability will favor areas of damaging wind and hail. ...OH Valley into PA/NY... Although the region will be well ahead of the main upper wave, gradual height falls are forecast to occur atop the moistening air mass ahead of the cold front. Strong heating will lead to an uncapped air mass, with weak but sufficient lift timed with peak heating. Scattered cells are forecast from the OH River toward the southern shores of Lakes Erie and Ontario by around 21Z, and modest veering with height may support a few longer lived cells capable of hail spreading east. ..Jewell.. 05/21/2024 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Tue May 21 2024 Valid 221200Z - 231200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTHERN TEXAS AND SOUTHEAST OKLAHOMA ACROSS THE OZARKS AND TOWARD THE MISSOURI BOOTHEEL... ...SUMMARY... Severe thunderstorms posing a risk for damaging gusts and hail will be possible from central Texas into the Ohio Valley and lower Great Lakes area on Wednesday. The greatest threat of damaging hail and wind is forecast from north Texas across the Ozarks. ...Synopsis... A broad zone of moderate to strong southwest flow will stretch from the Plains to the Great Lakes, with the primary shortwave trough affecting the upper MS Valley and Great Lakes through 00Z. This wave will eject northeastward into Ontario and Quebec thereafter, with various convectively enhanced disturbances trailing southwestward within the southwest flow toward Texas. At the surface, low pressure near Lake Superior early Wednesday will fill as it occludes into Ontario, with a cold front roughly from lower MI into southern MO and into northwest TX by midday. Ahead of this front, ample moisture will exist from TX into the lower OH Valley, with various rounds of severe thunderstorms throughout the period. ...Southern Plains into the Ozarks and Mid South... Severe regimes are forecast on both sides of the synoptic front, beginning early on Wednesday. Scattered storms are expected early Wednesday morning over parts of OK, and expanding into southern MO. Here, forecast soundings show extreme elevated instability, along with very favorable hodographs supporting splitting elevated hail storms. Northeast winds north of the front beneath moderate southwest flow will result in lengthy hodographs and good effective-layer storm relative inflow. While the precise corridor is difficult to place, it will likely be just north of the surface front, with potential swaths of significant damaging hail. Western portions of the front into northwest TX will also favor relatively early development, with steep lapse rates aloft and lengthy hodographs again favoring damaging hail. As heating occurs ahead of the boundary, additional storms will develop across northern TX, producing damaging hail and areas of damaging winds. A couple tornadoes will be possible, especially if the boundary briefly stalls or robust cells develop along old outflows. Given that the boundary is roughly parallel to the flow aloft, a prolonged splitting hail storm event will be possible, from the Red River region across the Ozarks. Additional clusters of storms are likely to develop and translate south/southeast across AR and into western TN/MS where ample moisture and instability will favor areas of damaging wind and hail. ...OH Valley into PA/NY... Although the region will be well ahead of the main upper wave, gradual height falls are forecast to occur atop the moistening air mass ahead of the cold front. Strong heating will lead to an uncapped air mass, with weak but sufficient lift timed with peak heating. Scattered cells are forecast from the OH River toward the southern shores of Lakes Erie and Ontario by around 21Z, and modest veering with height may support a few longer lived cells capable of hail spreading east. ..Jewell.. 05/21/2024 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Tue May 21 2024 Valid 221200Z - 231200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTHERN TEXAS AND SOUTHEAST OKLAHOMA ACROSS THE OZARKS AND TOWARD THE MISSOURI BOOTHEEL... ...SUMMARY... Severe thunderstorms posing a risk for damaging gusts and hail will be possible from central Texas into the Ohio Valley and lower Great Lakes area on Wednesday. The greatest threat of damaging hail and wind is forecast from north Texas across the Ozarks. ...Synopsis... A broad zone of moderate to strong southwest flow will stretch from the Plains to the Great Lakes, with the primary shortwave trough affecting the upper MS Valley and Great Lakes through 00Z. This wave will eject northeastward into Ontario and Quebec thereafter, with various convectively enhanced disturbances trailing southwestward within the southwest flow toward Texas. At the surface, low pressure near Lake Superior early Wednesday will fill as it occludes into Ontario, with a cold front roughly from lower MI into southern MO and into northwest TX by midday. Ahead of this front, ample moisture will exist from TX into the lower OH Valley, with various rounds of severe thunderstorms throughout the period. ...Southern Plains into the Ozarks and Mid South... Severe regimes are forecast on both sides of the synoptic front, beginning early on Wednesday. Scattered storms are expected early Wednesday morning over parts of OK, and expanding into southern MO. Here, forecast soundings show extreme elevated instability, along with very favorable hodographs supporting splitting elevated hail storms. Northeast winds north of the front beneath moderate southwest flow will result in lengthy hodographs and good effective-layer storm relative inflow. While the precise corridor is difficult to place, it will likely be just north of the surface front, with potential swaths of significant damaging hail. Western portions of the front into northwest TX will also favor relatively early development, with steep lapse rates aloft and lengthy hodographs again favoring damaging hail. As heating occurs ahead of the boundary, additional storms will develop across northern TX, producing damaging hail and areas of damaging winds. A couple tornadoes will be possible, especially if the boundary briefly stalls or robust cells develop along old outflows. Given that the boundary is roughly parallel to the flow aloft, a prolonged splitting hail storm event will be possible, from the Red River region across the Ozarks. Additional clusters of storms are likely to develop and translate south/southeast across AR and into western TN/MS where ample moisture and instability will favor areas of damaging wind and hail. ...OH Valley into PA/NY... Although the region will be well ahead of the main upper wave, gradual height falls are forecast to occur atop the moistening air mass ahead of the cold front. Strong heating will lead to an uncapped air mass, with weak but sufficient lift timed with peak heating. Scattered cells are forecast from the OH River toward the southern shores of Lakes Erie and Ontario by around 21Z, and modest veering with height may support a few longer lived cells capable of hail spreading east. ..Jewell.. 05/21/2024 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Tue May 21 2024 Valid 221200Z - 231200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTHERN TEXAS AND SOUTHEAST OKLAHOMA ACROSS THE OZARKS AND TOWARD THE MISSOURI BOOTHEEL... ...SUMMARY... Severe thunderstorms posing a risk for damaging gusts and hail will be possible from central Texas into the Ohio Valley and lower Great Lakes area on Wednesday. The greatest threat of damaging hail and wind is forecast from north Texas across the Ozarks. ...Synopsis... A broad zone of moderate to strong southwest flow will stretch from the Plains to the Great Lakes, with the primary shortwave trough affecting the upper MS Valley and Great Lakes through 00Z. This wave will eject northeastward into Ontario and Quebec thereafter, with various convectively enhanced disturbances trailing southwestward within the southwest flow toward Texas. At the surface, low pressure near Lake Superior early Wednesday will fill as it occludes into Ontario, with a cold front roughly from lower MI into southern MO and into northwest TX by midday. Ahead of this front, ample moisture will exist from TX into the lower OH Valley, with various rounds of severe thunderstorms throughout the period. ...Southern Plains into the Ozarks and Mid South... Severe regimes are forecast on both sides of the synoptic front, beginning early on Wednesday. Scattered storms are expected early Wednesday morning over parts of OK, and expanding into southern MO. Here, forecast soundings show extreme elevated instability, along with very favorable hodographs supporting splitting elevated hail storms. Northeast winds north of the front beneath moderate southwest flow will result in lengthy hodographs and good effective-layer storm relative inflow. While the precise corridor is difficult to place, it will likely be just north of the surface front, with potential swaths of significant damaging hail. Western portions of the front into northwest TX will also favor relatively early development, with steep lapse rates aloft and lengthy hodographs again favoring damaging hail. As heating occurs ahead of the boundary, additional storms will develop across northern TX, producing damaging hail and areas of damaging winds. A couple tornadoes will be possible, especially if the boundary briefly stalls or robust cells develop along old outflows. Given that the boundary is roughly parallel to the flow aloft, a prolonged splitting hail storm event will be possible, from the Red River region across the Ozarks. Additional clusters of storms are likely to develop and translate south/southeast across AR and into western TN/MS where ample moisture and instability will favor areas of damaging wind and hail. ...OH Valley into PA/NY... Although the region will be well ahead of the main upper wave, gradual height falls are forecast to occur atop the moistening air mass ahead of the cold front. Strong heating will lead to an uncapped air mass, with weak but sufficient lift timed with peak heating. Scattered cells are forecast from the OH River toward the southern shores of Lakes Erie and Ontario by around 21Z, and modest veering with height may support a few longer lived cells capable of hail spreading east. ..Jewell.. 05/21/2024 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Tue May 21 2024 Valid 221200Z - 231200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTHERN TEXAS AND SOUTHEAST OKLAHOMA ACROSS THE OZARKS AND TOWARD THE MISSOURI BOOTHEEL... ...SUMMARY... Severe thunderstorms posing a risk for damaging gusts and hail will be possible from central Texas into the Ohio Valley and lower Great Lakes area on Wednesday. The greatest threat of damaging hail and wind is forecast from north Texas across the Ozarks. ...Synopsis... A broad zone of moderate to strong southwest flow will stretch from the Plains to the Great Lakes, with the primary shortwave trough affecting the upper MS Valley and Great Lakes through 00Z. This wave will eject northeastward into Ontario and Quebec thereafter, with various convectively enhanced disturbances trailing southwestward within the southwest flow toward Texas. At the surface, low pressure near Lake Superior early Wednesday will fill as it occludes into Ontario, with a cold front roughly from lower MI into southern MO and into northwest TX by midday. Ahead of this front, ample moisture will exist from TX into the lower OH Valley, with various rounds of severe thunderstorms throughout the period. ...Southern Plains into the Ozarks and Mid South... Severe regimes are forecast on both sides of the synoptic front, beginning early on Wednesday. Scattered storms are expected early Wednesday morning over parts of OK, and expanding into southern MO. Here, forecast soundings show extreme elevated instability, along with very favorable hodographs supporting splitting elevated hail storms. Northeast winds north of the front beneath moderate southwest flow will result in lengthy hodographs and good effective-layer storm relative inflow. While the precise corridor is difficult to place, it will likely be just north of the surface front, with potential swaths of significant damaging hail. Western portions of the front into northwest TX will also favor relatively early development, with steep lapse rates aloft and lengthy hodographs again favoring damaging hail. As heating occurs ahead of the boundary, additional storms will develop across northern TX, producing damaging hail and areas of damaging winds. A couple tornadoes will be possible, especially if the boundary briefly stalls or robust cells develop along old outflows. Given that the boundary is roughly parallel to the flow aloft, a prolonged splitting hail storm event will be possible, from the Red River region across the Ozarks. Additional clusters of storms are likely to develop and translate south/southeast across AR and into western TN/MS where ample moisture and instability will favor areas of damaging wind and hail. ...OH Valley into PA/NY... Although the region will be well ahead of the main upper wave, gradual height falls are forecast to occur atop the moistening air mass ahead of the cold front. Strong heating will lead to an uncapped air mass, with weak but sufficient lift timed with peak heating. Scattered cells are forecast from the OH River toward the southern shores of Lakes Erie and Ontario by around 21Z, and modest veering with height may support a few longer lived cells capable of hail spreading east. ..Jewell.. 05/21/2024 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Tue May 21 2024 Valid 221200Z - 231200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTHERN TEXAS AND SOUTHEAST OKLAHOMA ACROSS THE OZARKS AND TOWARD THE MISSOURI BOOTHEEL... ...SUMMARY... Severe thunderstorms posing a risk for damaging gusts and hail will be possible from central Texas into the Ohio Valley and lower Great Lakes area on Wednesday. The greatest threat of damaging hail and wind is forecast from north Texas across the Ozarks. ...Synopsis... A broad zone of moderate to strong southwest flow will stretch from the Plains to the Great Lakes, with the primary shortwave trough affecting the upper MS Valley and Great Lakes through 00Z. This wave will eject northeastward into Ontario and Quebec thereafter, with various convectively enhanced disturbances trailing southwestward within the southwest flow toward Texas. At the surface, low pressure near Lake Superior early Wednesday will fill as it occludes into Ontario, with a cold front roughly from lower MI into southern MO and into northwest TX by midday. Ahead of this front, ample moisture will exist from TX into the lower OH Valley, with various rounds of severe thunderstorms throughout the period. ...Southern Plains into the Ozarks and Mid South... Severe regimes are forecast on both sides of the synoptic front, beginning early on Wednesday. Scattered storms are expected early Wednesday morning over parts of OK, and expanding into southern MO. Here, forecast soundings show extreme elevated instability, along with very favorable hodographs supporting splitting elevated hail storms. Northeast winds north of the front beneath moderate southwest flow will result in lengthy hodographs and good effective-layer storm relative inflow. While the precise corridor is difficult to place, it will likely be just north of the surface front, with potential swaths of significant damaging hail. Western portions of the front into northwest TX will also favor relatively early development, with steep lapse rates aloft and lengthy hodographs again favoring damaging hail. As heating occurs ahead of the boundary, additional storms will develop across northern TX, producing damaging hail and areas of damaging winds. A couple tornadoes will be possible, especially if the boundary briefly stalls or robust cells develop along old outflows. Given that the boundary is roughly parallel to the flow aloft, a prolonged splitting hail storm event will be possible, from the Red River region across the Ozarks. Additional clusters of storms are likely to develop and translate south/southeast across AR and into western TN/MS where ample moisture and instability will favor areas of damaging wind and hail. ...OH Valley into PA/NY... Although the region will be well ahead of the main upper wave, gradual height falls are forecast to occur atop the moistening air mass ahead of the cold front. Strong heating will lead to an uncapped air mass, with weak but sufficient lift timed with peak heating. Scattered cells are forecast from the OH River toward the southern shores of Lakes Erie and Ontario by around 21Z, and modest veering with height may support a few longer lived cells capable of hail spreading east. ..Jewell.. 05/21/2024 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Tue May 21 2024 Valid 221200Z - 231200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTHERN TEXAS AND SOUTHEAST OKLAHOMA ACROSS THE OZARKS AND TOWARD THE MISSOURI BOOTHEEL... ...SUMMARY... Severe thunderstorms posing a risk for damaging gusts and hail will be possible from central Texas into the Ohio Valley and lower Great Lakes area on Wednesday. The greatest threat of damaging hail and wind is forecast from north Texas across the Ozarks. ...Synopsis... A broad zone of moderate to strong southwest flow will stretch from the Plains to the Great Lakes, with the primary shortwave trough affecting the upper MS Valley and Great Lakes through 00Z. This wave will eject northeastward into Ontario and Quebec thereafter, with various convectively enhanced disturbances trailing southwestward within the southwest flow toward Texas. At the surface, low pressure near Lake Superior early Wednesday will fill as it occludes into Ontario, with a cold front roughly from lower MI into southern MO and into northwest TX by midday. Ahead of this front, ample moisture will exist from TX into the lower OH Valley, with various rounds of severe thunderstorms throughout the period. ...Southern Plains into the Ozarks and Mid South... Severe regimes are forecast on both sides of the synoptic front, beginning early on Wednesday. Scattered storms are expected early Wednesday morning over parts of OK, and expanding into southern MO. Here, forecast soundings show extreme elevated instability, along with very favorable hodographs supporting splitting elevated hail storms. Northeast winds north of the front beneath moderate southwest flow will result in lengthy hodographs and good effective-layer storm relative inflow. While the precise corridor is difficult to place, it will likely be just north of the surface front, with potential swaths of significant damaging hail. Western portions of the front into northwest TX will also favor relatively early development, with steep lapse rates aloft and lengthy hodographs again favoring damaging hail. As heating occurs ahead of the boundary, additional storms will develop across northern TX, producing damaging hail and areas of damaging winds. A couple tornadoes will be possible, especially if the boundary briefly stalls or robust cells develop along old outflows. Given that the boundary is roughly parallel to the flow aloft, a prolonged splitting hail storm event will be possible, from the Red River region across the Ozarks. Additional clusters of storms are likely to develop and translate south/southeast across AR and into western TN/MS where ample moisture and instability will favor areas of damaging wind and hail. ...OH Valley into PA/NY... Although the region will be well ahead of the main upper wave, gradual height falls are forecast to occur atop the moistening air mass ahead of the cold front. Strong heating will lead to an uncapped air mass, with weak but sufficient lift timed with peak heating. Scattered cells are forecast from the OH River toward the southern shores of Lakes Erie and Ontario by around 21Z, and modest veering with height may support a few longer lived cells capable of hail spreading east. ..Jewell.. 05/21/2024 Read more

MD 0869 CONCERNING SEVERE POTENTIAL...WATCH LIKELY FOR EASTERN NE...WESTERN IA...FAR SOUTHEAST SD
Mesoscale Discussion 0869 NWS Storm Prediction Center Norman OK 1027 AM CDT Tue May 21 2024 Areas affected...Eastern NE...Western IA...Far Southeast SD Concerning...Severe potential...Watch likely Valid 211527Z - 211730Z Probability of Watch Issuance...80 percent SUMMARY...Fast-moving supercells capable of all severe hazards will be possible, including large to very large hail, strong gusts up to 70 mph, and tornadoes. A Tornado Watch will likely be needed for portions of the area with in the next hour or two. DISCUSSION...Recent surface analysis places the primary surface low over north-central KS (just southwest of CNK), with a warm front extending northeastward into southeast NE and then more east-northeastward across southern IA. A cold front also extends from this low southwestward through central KS and the eastern OK Panhandle. There is a secondary surface low farther north near the IA/SD/MN border intersection, with weak surface troughing connecting these two lows. Given the position of the surface features, the recent thunderstorm activity along the central NE/KS border is likely elevated, initiated by strong ascent attendant to the approaching shortwave trough. However, as the primary surface low moves quickly northeastward, and the warm front correspondingly moves northward, the airmass across eastern NE and western IA (particularly east-central/southeast NE and west-central/southwest IA) is expected to become increasingly supportive of surface-based storms. Within the warm sector, fast-moving supercells capable of all severe hazards will be possible, including large to very large hail, strong gusts up to 70 mph, and tornadoes. Large hail and strong gusts will be possible with the elevated storms as well. Given this severe potential, a Tornado Watch will likely be needed for portions of the area with in the next hour or two. ..Mosier/Guyer.. 05/21/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...DMX...EAX...FSD...OAX... LAT...LON 41339704 42939678 42989574 42349509 40339546 40159723 41339704 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1140 AM CDT Tue May 21 2024 Valid 211630Z - 221200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS IOWA...NORTHERN MISSOURI...NORTHWEST ILLINOIS...SOUTHEAST MINNESOTA...AND SOUTHERN WISCONSIN... ...SUMMARY... An outbreak of severe thunderstorms, including the potential for strong tornadoes, large hail, and widespread damaging winds, is expected this afternoon through evening, especially across eastern Nebraska, Iowa, and Missouri to northern Illinois, southeast Minnesota, and southern Wisconsin. ...Middle/Lower Missouri Valley and Midwest... As an outbreak precursor, a well-organized cluster of storms across south-central/east-central Iowa mid-late this morning has had a history of producing at least isolated/episodic severe weather since the predawn hours. These storms are focused along/north of an outflow-reinforced warm front that will lift northward through late today into tonight. This will be heavily influenced by a highly dynamic mass response to a northeast-moving mid-level shortwave trough that is readily evident in water vapor imagery over the central High Plains this morning. That said, some short-term uncertainties exist as of 15z observational data, with gusty post-convective northeasterly winds still present across south-central Iowa, which relates to some uncertainty with the northward extent of the higher-magnitude severe risk across Minnesota/Wisconsin later today, although latest 16z data features a recent abatement of those northerly winds. Regardless, intense storm development is anticipated into the afternoon across a broad north/south corridor. A synoptically evident and regional outbreak-favorable setup exists, especially by mid/late May standards, highlighted by a coupled upper jet structure over the Upper Midwest, strengthening deep-layer wind fields, and steady cyclogenesis from the Nebraska/Kansas border vicinity this morning northeastward toward the Minnesota/Wisconsin border tonight. Low-level winds will remain strong diurnally ahead of the primary cyclone, but a noteworthy strengthening of mid-level winds 3-7 km AGL (reference 700mb/500mb) will rapidly occur through the afternoon/evening, which will likely have direct outbreak-relevant influences on initial supercell intensity, QLCS evolution and overall fast east-northeastward storm motions later today. Steepening mid-level lapse rates, noted in upstream 12z observed soundings such as Topeka/Dodge City KS and Springfield MO, will overspread an increasingly moist airmass generally characterized by mid/upper 60s F surface dewpoints, contributing to warm-sector MLCAPE to upwards of 2500-3000 J/kg this afternoon. Scattered to numerous thunderstorms, including scattered fast-moving supercells, are expected to initially form over parts of eastern Nebraska by late morning/midday, and into Iowa and northern/central Missouri this afternoon. This will occur as the cold front impinges on a retreating outflow boundary from the morning storms, and an airmass destabilizing rapidly on both sides of the boundary from a combination of diurnal heating and intense warm advection. Additional, initially semi-discrete, supercellular development is also plausible farther east across Iowa this afternoon in vicinity of modifying outflow/warm front. Sufficient airmass recovery for a surface-based, all-hazards severe threat is expected across most of Iowa and potentially into southern Minnesota as well, spreading into parts of western/northern Illinois and Wisconsin. Several tornadoes, including some strong with EF2+ potential, are expected, along with large, damaging hail and severe downdrafts. This includes the possibility of long-track supercells/tornadoes and swaths of locally intense wind damage. Later tonight, storms should begin to gradually outrun the corridor of favorable surface-based buoyancy in the evening after crossing the Mississippi River, but may remain well-organized in terms of severe-wind threat across Lake Michigan vicinity. ...Ozarks/Oklahoma to south Texas... Isolated to scattered thunderstorms are expected to form from mid afternoon into evening near the front and dryline, offering large to very large hail and locally severe gusts. Hail at least 3 inches in diameter is possible. A tornado or two is not out of the question, especially in northern areas (Ozarks vicinity) under the fringes of the gradient-flow/deep-shear influence from the ejecting shortwave trough, and with high-CAPE storm-scale processes amid favorable deep shear elsewhere. Renewed storm development, potentially severe, could also occur in the predawn hours of Wednesday across Oklahoma near the front. Though capping from an EML will limit convective potential for much of the day, a combination of strong surface heating, rich boundary- layer moisture, and frontal/dryline lift will weaken MLCINH enough by mid/late afternoon to support deep convective development. Upper 60s to low 70s F surface dewpoints should become common beneath a high equilibrium level (deep troposphere) and steep mid-level lapse rates, supporting a corridor of 3000-4000 J/kg MLCAPE (locally higher). Sufficient veering of winds with height, and effective-shear magnitudes in the 45-60 kt range, will support supercell potential. Activity over Texas my weaken within a few hours after sunset as nocturnal boundary-layer cooling re-establishes the strong capping beneath the EML. However, farther north across parts of Arkansas/Missouri, a weaker EML influence may permit activity to persist later and farther east this evening, before weakening. ...Adirondacks region to northern New England... Widely scattered to scattered thunderstorms should develop over portions of the Adirondacks and White Mountains today, and perhaps also move into the area from nearby parts of extreme eastern Ontario and southernmost Quebec. Damaging gusts and isolated severe hail will be possible. A mid/upper-level shortwave trough and embedded MCV -- related to the significantly severe MCS over Kansas two days ago -- is apparent in satellite imagery over Lake Huron. This feature will move eastward toward northern New York/New England and times well with the diurnal-heating cycle there. Activity should form as large-scale DCVA/lift and enhancement of midlevel flow -- preceding the MCV/shortwave trough -- spread atop a destabilized, suitably moist boundary layer, heated to convective temperature over elevated terrain. These processes will erode MLCINH to negligible levels, fostering MLCAPE commonly in the 1000-1500 J/kg range, locally/briefly near 2000 J/kg. Deep shear should remain modest, with effective-shear magnitudes generally 25-35 kt, though enough veering with height in low levels may develop to shape somewhat enlarged hodographs. Multicell and transient supercell modes should predominate, with the severe threat diminishing markedly after sunset. ..Guyer/Wendt.. 05/21/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1140 AM CDT Tue May 21 2024 Valid 211630Z - 221200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS IOWA...NORTHERN MISSOURI...NORTHWEST ILLINOIS...SOUTHEAST MINNESOTA...AND SOUTHERN WISCONSIN... ...SUMMARY... An outbreak of severe thunderstorms, including the potential for strong tornadoes, large hail, and widespread damaging winds, is expected this afternoon through evening, especially across eastern Nebraska, Iowa, and Missouri to northern Illinois, southeast Minnesota, and southern Wisconsin. ...Middle/Lower Missouri Valley and Midwest... As an outbreak precursor, a well-organized cluster of storms across south-central/east-central Iowa mid-late this morning has had a history of producing at least isolated/episodic severe weather since the predawn hours. These storms are focused along/north of an outflow-reinforced warm front that will lift northward through late today into tonight. This will be heavily influenced by a highly dynamic mass response to a northeast-moving mid-level shortwave trough that is readily evident in water vapor imagery over the central High Plains this morning. That said, some short-term uncertainties exist as of 15z observational data, with gusty post-convective northeasterly winds still present across south-central Iowa, which relates to some uncertainty with the northward extent of the higher-magnitude severe risk across Minnesota/Wisconsin later today, although latest 16z data features a recent abatement of those northerly winds. Regardless, intense storm development is anticipated into the afternoon across a broad north/south corridor. A synoptically evident and regional outbreak-favorable setup exists, especially by mid/late May standards, highlighted by a coupled upper jet structure over the Upper Midwest, strengthening deep-layer wind fields, and steady cyclogenesis from the Nebraska/Kansas border vicinity this morning northeastward toward the Minnesota/Wisconsin border tonight. Low-level winds will remain strong diurnally ahead of the primary cyclone, but a noteworthy strengthening of mid-level winds 3-7 km AGL (reference 700mb/500mb) will rapidly occur through the afternoon/evening, which will likely have direct outbreak-relevant influences on initial supercell intensity, QLCS evolution and overall fast east-northeastward storm motions later today. Steepening mid-level lapse rates, noted in upstream 12z observed soundings such as Topeka/Dodge City KS and Springfield MO, will overspread an increasingly moist airmass generally characterized by mid/upper 60s F surface dewpoints, contributing to warm-sector MLCAPE to upwards of 2500-3000 J/kg this afternoon. Scattered to numerous thunderstorms, including scattered fast-moving supercells, are expected to initially form over parts of eastern Nebraska by late morning/midday, and into Iowa and northern/central Missouri this afternoon. This will occur as the cold front impinges on a retreating outflow boundary from the morning storms, and an airmass destabilizing rapidly on both sides of the boundary from a combination of diurnal heating and intense warm advection. Additional, initially semi-discrete, supercellular development is also plausible farther east across Iowa this afternoon in vicinity of modifying outflow/warm front. Sufficient airmass recovery for a surface-based, all-hazards severe threat is expected across most of Iowa and potentially into southern Minnesota as well, spreading into parts of western/northern Illinois and Wisconsin. Several tornadoes, including some strong with EF2+ potential, are expected, along with large, damaging hail and severe downdrafts. This includes the possibility of long-track supercells/tornadoes and swaths of locally intense wind damage. Later tonight, storms should begin to gradually outrun the corridor of favorable surface-based buoyancy in the evening after crossing the Mississippi River, but may remain well-organized in terms of severe-wind threat across Lake Michigan vicinity. ...Ozarks/Oklahoma to south Texas... Isolated to scattered thunderstorms are expected to form from mid afternoon into evening near the front and dryline, offering large to very large hail and locally severe gusts. Hail at least 3 inches in diameter is possible. A tornado or two is not out of the question, especially in northern areas (Ozarks vicinity) under the fringes of the gradient-flow/deep-shear influence from the ejecting shortwave trough, and with high-CAPE storm-scale processes amid favorable deep shear elsewhere. Renewed storm development, potentially severe, could also occur in the predawn hours of Wednesday across Oklahoma near the front. Though capping from an EML will limit convective potential for much of the day, a combination of strong surface heating, rich boundary- layer moisture, and frontal/dryline lift will weaken MLCINH enough by mid/late afternoon to support deep convective development. Upper 60s to low 70s F surface dewpoints should become common beneath a high equilibrium level (deep troposphere) and steep mid-level lapse rates, supporting a corridor of 3000-4000 J/kg MLCAPE (locally higher). Sufficient veering of winds with height, and effective-shear magnitudes in the 45-60 kt range, will support supercell potential. Activity over Texas my weaken within a few hours after sunset as nocturnal boundary-layer cooling re-establishes the strong capping beneath the EML. However, farther north across parts of Arkansas/Missouri, a weaker EML influence may permit activity to persist later and farther east this evening, before weakening. ...Adirondacks region to northern New England... Widely scattered to scattered thunderstorms should develop over portions of the Adirondacks and White Mountains today, and perhaps also move into the area from nearby parts of extreme eastern Ontario and southernmost Quebec. Damaging gusts and isolated severe hail will be possible. A mid/upper-level shortwave trough and embedded MCV -- related to the significantly severe MCS over Kansas two days ago -- is apparent in satellite imagery over Lake Huron. This feature will move eastward toward northern New York/New England and times well with the diurnal-heating cycle there. Activity should form as large-scale DCVA/lift and enhancement of midlevel flow -- preceding the MCV/shortwave trough -- spread atop a destabilized, suitably moist boundary layer, heated to convective temperature over elevated terrain. These processes will erode MLCINH to negligible levels, fostering MLCAPE commonly in the 1000-1500 J/kg range, locally/briefly near 2000 J/kg. Deep shear should remain modest, with effective-shear magnitudes generally 25-35 kt, though enough veering with height in low levels may develop to shape somewhat enlarged hodographs. Multicell and transient supercell modes should predominate, with the severe threat diminishing markedly after sunset. ..Guyer/Wendt.. 05/21/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1140 AM CDT Tue May 21 2024 Valid 211630Z - 221200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS IOWA...NORTHERN MISSOURI...NORTHWEST ILLINOIS...SOUTHEAST MINNESOTA...AND SOUTHERN WISCONSIN... ...SUMMARY... An outbreak of severe thunderstorms, including the potential for strong tornadoes, large hail, and widespread damaging winds, is expected this afternoon through evening, especially across eastern Nebraska, Iowa, and Missouri to northern Illinois, southeast Minnesota, and southern Wisconsin. ...Middle/Lower Missouri Valley and Midwest... As an outbreak precursor, a well-organized cluster of storms across south-central/east-central Iowa mid-late this morning has had a history of producing at least isolated/episodic severe weather since the predawn hours. These storms are focused along/north of an outflow-reinforced warm front that will lift northward through late today into tonight. This will be heavily influenced by a highly dynamic mass response to a northeast-moving mid-level shortwave trough that is readily evident in water vapor imagery over the central High Plains this morning. That said, some short-term uncertainties exist as of 15z observational data, with gusty post-convective northeasterly winds still present across south-central Iowa, which relates to some uncertainty with the northward extent of the higher-magnitude severe risk across Minnesota/Wisconsin later today, although latest 16z data features a recent abatement of those northerly winds. Regardless, intense storm development is anticipated into the afternoon across a broad north/south corridor. A synoptically evident and regional outbreak-favorable setup exists, especially by mid/late May standards, highlighted by a coupled upper jet structure over the Upper Midwest, strengthening deep-layer wind fields, and steady cyclogenesis from the Nebraska/Kansas border vicinity this morning northeastward toward the Minnesota/Wisconsin border tonight. Low-level winds will remain strong diurnally ahead of the primary cyclone, but a noteworthy strengthening of mid-level winds 3-7 km AGL (reference 700mb/500mb) will rapidly occur through the afternoon/evening, which will likely have direct outbreak-relevant influences on initial supercell intensity, QLCS evolution and overall fast east-northeastward storm motions later today. Steepening mid-level lapse rates, noted in upstream 12z observed soundings such as Topeka/Dodge City KS and Springfield MO, will overspread an increasingly moist airmass generally characterized by mid/upper 60s F surface dewpoints, contributing to warm-sector MLCAPE to upwards of 2500-3000 J/kg this afternoon. Scattered to numerous thunderstorms, including scattered fast-moving supercells, are expected to initially form over parts of eastern Nebraska by late morning/midday, and into Iowa and northern/central Missouri this afternoon. This will occur as the cold front impinges on a retreating outflow boundary from the morning storms, and an airmass destabilizing rapidly on both sides of the boundary from a combination of diurnal heating and intense warm advection. Additional, initially semi-discrete, supercellular development is also plausible farther east across Iowa this afternoon in vicinity of modifying outflow/warm front. Sufficient airmass recovery for a surface-based, all-hazards severe threat is expected across most of Iowa and potentially into southern Minnesota as well, spreading into parts of western/northern Illinois and Wisconsin. Several tornadoes, including some strong with EF2+ potential, are expected, along with large, damaging hail and severe downdrafts. This includes the possibility of long-track supercells/tornadoes and swaths of locally intense wind damage. Later tonight, storms should begin to gradually outrun the corridor of favorable surface-based buoyancy in the evening after crossing the Mississippi River, but may remain well-organized in terms of severe-wind threat across Lake Michigan vicinity. ...Ozarks/Oklahoma to south Texas... Isolated to scattered thunderstorms are expected to form from mid afternoon into evening near the front and dryline, offering large to very large hail and locally severe gusts. Hail at least 3 inches in diameter is possible. A tornado or two is not out of the question, especially in northern areas (Ozarks vicinity) under the fringes of the gradient-flow/deep-shear influence from the ejecting shortwave trough, and with high-CAPE storm-scale processes amid favorable deep shear elsewhere. Renewed storm development, potentially severe, could also occur in the predawn hours of Wednesday across Oklahoma near the front. Though capping from an EML will limit convective potential for much of the day, a combination of strong surface heating, rich boundary- layer moisture, and frontal/dryline lift will weaken MLCINH enough by mid/late afternoon to support deep convective development. Upper 60s to low 70s F surface dewpoints should become common beneath a high equilibrium level (deep troposphere) and steep mid-level lapse rates, supporting a corridor of 3000-4000 J/kg MLCAPE (locally higher). Sufficient veering of winds with height, and effective-shear magnitudes in the 45-60 kt range, will support supercell potential. Activity over Texas my weaken within a few hours after sunset as nocturnal boundary-layer cooling re-establishes the strong capping beneath the EML. However, farther north across parts of Arkansas/Missouri, a weaker EML influence may permit activity to persist later and farther east this evening, before weakening. ...Adirondacks region to northern New England... Widely scattered to scattered thunderstorms should develop over portions of the Adirondacks and White Mountains today, and perhaps also move into the area from nearby parts of extreme eastern Ontario and southernmost Quebec. Damaging gusts and isolated severe hail will be possible. A mid/upper-level shortwave trough and embedded MCV -- related to the significantly severe MCS over Kansas two days ago -- is apparent in satellite imagery over Lake Huron. This feature will move eastward toward northern New York/New England and times well with the diurnal-heating cycle there. Activity should form as large-scale DCVA/lift and enhancement of midlevel flow -- preceding the MCV/shortwave trough -- spread atop a destabilized, suitably moist boundary layer, heated to convective temperature over elevated terrain. These processes will erode MLCINH to negligible levels, fostering MLCAPE commonly in the 1000-1500 J/kg range, locally/briefly near 2000 J/kg. Deep shear should remain modest, with effective-shear magnitudes generally 25-35 kt, though enough veering with height in low levels may develop to shape somewhat enlarged hodographs. Multicell and transient supercell modes should predominate, with the severe threat diminishing markedly after sunset. ..Guyer/Wendt.. 05/21/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1140 AM CDT Tue May 21 2024 Valid 211630Z - 221200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS IOWA...NORTHERN MISSOURI...NORTHWEST ILLINOIS...SOUTHEAST MINNESOTA...AND SOUTHERN WISCONSIN... ...SUMMARY... An outbreak of severe thunderstorms, including the potential for strong tornadoes, large hail, and widespread damaging winds, is expected this afternoon through evening, especially across eastern Nebraska, Iowa, and Missouri to northern Illinois, southeast Minnesota, and southern Wisconsin. ...Middle/Lower Missouri Valley and Midwest... As an outbreak precursor, a well-organized cluster of storms across south-central/east-central Iowa mid-late this morning has had a history of producing at least isolated/episodic severe weather since the predawn hours. These storms are focused along/north of an outflow-reinforced warm front that will lift northward through late today into tonight. This will be heavily influenced by a highly dynamic mass response to a northeast-moving mid-level shortwave trough that is readily evident in water vapor imagery over the central High Plains this morning. That said, some short-term uncertainties exist as of 15z observational data, with gusty post-convective northeasterly winds still present across south-central Iowa, which relates to some uncertainty with the northward extent of the higher-magnitude severe risk across Minnesota/Wisconsin later today, although latest 16z data features a recent abatement of those northerly winds. Regardless, intense storm development is anticipated into the afternoon across a broad north/south corridor. A synoptically evident and regional outbreak-favorable setup exists, especially by mid/late May standards, highlighted by a coupled upper jet structure over the Upper Midwest, strengthening deep-layer wind fields, and steady cyclogenesis from the Nebraska/Kansas border vicinity this morning northeastward toward the Minnesota/Wisconsin border tonight. Low-level winds will remain strong diurnally ahead of the primary cyclone, but a noteworthy strengthening of mid-level winds 3-7 km AGL (reference 700mb/500mb) will rapidly occur through the afternoon/evening, which will likely have direct outbreak-relevant influences on initial supercell intensity, QLCS evolution and overall fast east-northeastward storm motions later today. Steepening mid-level lapse rates, noted in upstream 12z observed soundings such as Topeka/Dodge City KS and Springfield MO, will overspread an increasingly moist airmass generally characterized by mid/upper 60s F surface dewpoints, contributing to warm-sector MLCAPE to upwards of 2500-3000 J/kg this afternoon. Scattered to numerous thunderstorms, including scattered fast-moving supercells, are expected to initially form over parts of eastern Nebraska by late morning/midday, and into Iowa and northern/central Missouri this afternoon. This will occur as the cold front impinges on a retreating outflow boundary from the morning storms, and an airmass destabilizing rapidly on both sides of the boundary from a combination of diurnal heating and intense warm advection. Additional, initially semi-discrete, supercellular development is also plausible farther east across Iowa this afternoon in vicinity of modifying outflow/warm front. Sufficient airmass recovery for a surface-based, all-hazards severe threat is expected across most of Iowa and potentially into southern Minnesota as well, spreading into parts of western/northern Illinois and Wisconsin. Several tornadoes, including some strong with EF2+ potential, are expected, along with large, damaging hail and severe downdrafts. This includes the possibility of long-track supercells/tornadoes and swaths of locally intense wind damage. Later tonight, storms should begin to gradually outrun the corridor of favorable surface-based buoyancy in the evening after crossing the Mississippi River, but may remain well-organized in terms of severe-wind threat across Lake Michigan vicinity. ...Ozarks/Oklahoma to south Texas... Isolated to scattered thunderstorms are expected to form from mid afternoon into evening near the front and dryline, offering large to very large hail and locally severe gusts. Hail at least 3 inches in diameter is possible. A tornado or two is not out of the question, especially in northern areas (Ozarks vicinity) under the fringes of the gradient-flow/deep-shear influence from the ejecting shortwave trough, and with high-CAPE storm-scale processes amid favorable deep shear elsewhere. Renewed storm development, potentially severe, could also occur in the predawn hours of Wednesday across Oklahoma near the front. Though capping from an EML will limit convective potential for much of the day, a combination of strong surface heating, rich boundary- layer moisture, and frontal/dryline lift will weaken MLCINH enough by mid/late afternoon to support deep convective development. Upper 60s to low 70s F surface dewpoints should become common beneath a high equilibrium level (deep troposphere) and steep mid-level lapse rates, supporting a corridor of 3000-4000 J/kg MLCAPE (locally higher). Sufficient veering of winds with height, and effective-shear magnitudes in the 45-60 kt range, will support supercell potential. Activity over Texas my weaken within a few hours after sunset as nocturnal boundary-layer cooling re-establishes the strong capping beneath the EML. However, farther north across parts of Arkansas/Missouri, a weaker EML influence may permit activity to persist later and farther east this evening, before weakening. ...Adirondacks region to northern New England... Widely scattered to scattered thunderstorms should develop over portions of the Adirondacks and White Mountains today, and perhaps also move into the area from nearby parts of extreme eastern Ontario and southernmost Quebec. Damaging gusts and isolated severe hail will be possible. A mid/upper-level shortwave trough and embedded MCV -- related to the significantly severe MCS over Kansas two days ago -- is apparent in satellite imagery over Lake Huron. This feature will move eastward toward northern New York/New England and times well with the diurnal-heating cycle there. Activity should form as large-scale DCVA/lift and enhancement of midlevel flow -- preceding the MCV/shortwave trough -- spread atop a destabilized, suitably moist boundary layer, heated to convective temperature over elevated terrain. These processes will erode MLCINH to negligible levels, fostering MLCAPE commonly in the 1000-1500 J/kg range, locally/briefly near 2000 J/kg. Deep shear should remain modest, with effective-shear magnitudes generally 25-35 kt, though enough veering with height in low levels may develop to shape somewhat enlarged hodographs. Multicell and transient supercell modes should predominate, with the severe threat diminishing markedly after sunset. ..Guyer/Wendt.. 05/21/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1140 AM CDT Tue May 21 2024 Valid 211630Z - 221200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS IOWA...NORTHERN MISSOURI...NORTHWEST ILLINOIS...SOUTHEAST MINNESOTA...AND SOUTHERN WISCONSIN... ...SUMMARY... An outbreak of severe thunderstorms, including the potential for strong tornadoes, large hail, and widespread damaging winds, is expected this afternoon through evening, especially across eastern Nebraska, Iowa, and Missouri to northern Illinois, southeast Minnesota, and southern Wisconsin. ...Middle/Lower Missouri Valley and Midwest... As an outbreak precursor, a well-organized cluster of storms across south-central/east-central Iowa mid-late this morning has had a history of producing at least isolated/episodic severe weather since the predawn hours. These storms are focused along/north of an outflow-reinforced warm front that will lift northward through late today into tonight. This will be heavily influenced by a highly dynamic mass response to a northeast-moving mid-level shortwave trough that is readily evident in water vapor imagery over the central High Plains this morning. That said, some short-term uncertainties exist as of 15z observational data, with gusty post-convective northeasterly winds still present across south-central Iowa, which relates to some uncertainty with the northward extent of the higher-magnitude severe risk across Minnesota/Wisconsin later today, although latest 16z data features a recent abatement of those northerly winds. Regardless, intense storm development is anticipated into the afternoon across a broad north/south corridor. A synoptically evident and regional outbreak-favorable setup exists, especially by mid/late May standards, highlighted by a coupled upper jet structure over the Upper Midwest, strengthening deep-layer wind fields, and steady cyclogenesis from the Nebraska/Kansas border vicinity this morning northeastward toward the Minnesota/Wisconsin border tonight. Low-level winds will remain strong diurnally ahead of the primary cyclone, but a noteworthy strengthening of mid-level winds 3-7 km AGL (reference 700mb/500mb) will rapidly occur through the afternoon/evening, which will likely have direct outbreak-relevant influences on initial supercell intensity, QLCS evolution and overall fast east-northeastward storm motions later today. Steepening mid-level lapse rates, noted in upstream 12z observed soundings such as Topeka/Dodge City KS and Springfield MO, will overspread an increasingly moist airmass generally characterized by mid/upper 60s F surface dewpoints, contributing to warm-sector MLCAPE to upwards of 2500-3000 J/kg this afternoon. Scattered to numerous thunderstorms, including scattered fast-moving supercells, are expected to initially form over parts of eastern Nebraska by late morning/midday, and into Iowa and northern/central Missouri this afternoon. This will occur as the cold front impinges on a retreating outflow boundary from the morning storms, and an airmass destabilizing rapidly on both sides of the boundary from a combination of diurnal heating and intense warm advection. Additional, initially semi-discrete, supercellular development is also plausible farther east across Iowa this afternoon in vicinity of modifying outflow/warm front. Sufficient airmass recovery for a surface-based, all-hazards severe threat is expected across most of Iowa and potentially into southern Minnesota as well, spreading into parts of western/northern Illinois and Wisconsin. Several tornadoes, including some strong with EF2+ potential, are expected, along with large, damaging hail and severe downdrafts. This includes the possibility of long-track supercells/tornadoes and swaths of locally intense wind damage. Later tonight, storms should begin to gradually outrun the corridor of favorable surface-based buoyancy in the evening after crossing the Mississippi River, but may remain well-organized in terms of severe-wind threat across Lake Michigan vicinity. ...Ozarks/Oklahoma to south Texas... Isolated to scattered thunderstorms are expected to form from mid afternoon into evening near the front and dryline, offering large to very large hail and locally severe gusts. Hail at least 3 inches in diameter is possible. A tornado or two is not out of the question, especially in northern areas (Ozarks vicinity) under the fringes of the gradient-flow/deep-shear influence from the ejecting shortwave trough, and with high-CAPE storm-scale processes amid favorable deep shear elsewhere. Renewed storm development, potentially severe, could also occur in the predawn hours of Wednesday across Oklahoma near the front. Though capping from an EML will limit convective potential for much of the day, a combination of strong surface heating, rich boundary- layer moisture, and frontal/dryline lift will weaken MLCINH enough by mid/late afternoon to support deep convective development. Upper 60s to low 70s F surface dewpoints should become common beneath a high equilibrium level (deep troposphere) and steep mid-level lapse rates, supporting a corridor of 3000-4000 J/kg MLCAPE (locally higher). Sufficient veering of winds with height, and effective-shear magnitudes in the 45-60 kt range, will support supercell potential. Activity over Texas my weaken within a few hours after sunset as nocturnal boundary-layer cooling re-establishes the strong capping beneath the EML. However, farther north across parts of Arkansas/Missouri, a weaker EML influence may permit activity to persist later and farther east this evening, before weakening. ...Adirondacks region to northern New England... Widely scattered to scattered thunderstorms should develop over portions of the Adirondacks and White Mountains today, and perhaps also move into the area from nearby parts of extreme eastern Ontario and southernmost Quebec. Damaging gusts and isolated severe hail will be possible. A mid/upper-level shortwave trough and embedded MCV -- related to the significantly severe MCS over Kansas two days ago -- is apparent in satellite imagery over Lake Huron. This feature will move eastward toward northern New York/New England and times well with the diurnal-heating cycle there. Activity should form as large-scale DCVA/lift and enhancement of midlevel flow -- preceding the MCV/shortwave trough -- spread atop a destabilized, suitably moist boundary layer, heated to convective temperature over elevated terrain. These processes will erode MLCINH to negligible levels, fostering MLCAPE commonly in the 1000-1500 J/kg range, locally/briefly near 2000 J/kg. Deep shear should remain modest, with effective-shear magnitudes generally 25-35 kt, though enough veering with height in low levels may develop to shape somewhat enlarged hodographs. Multicell and transient supercell modes should predominate, with the severe threat diminishing markedly after sunset. ..Guyer/Wendt.. 05/21/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1140 AM CDT Tue May 21 2024 Valid 211630Z - 221200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS IOWA...NORTHERN MISSOURI...NORTHWEST ILLINOIS...SOUTHEAST MINNESOTA...AND SOUTHERN WISCONSIN... ...SUMMARY... An outbreak of severe thunderstorms, including the potential for strong tornadoes, large hail, and widespread damaging winds, is expected this afternoon through evening, especially across eastern Nebraska, Iowa, and Missouri to northern Illinois, southeast Minnesota, and southern Wisconsin. ...Middle/Lower Missouri Valley and Midwest... As an outbreak precursor, a well-organized cluster of storms across south-central/east-central Iowa mid-late this morning has had a history of producing at least isolated/episodic severe weather since the predawn hours. These storms are focused along/north of an outflow-reinforced warm front that will lift northward through late today into tonight. This will be heavily influenced by a highly dynamic mass response to a northeast-moving mid-level shortwave trough that is readily evident in water vapor imagery over the central High Plains this morning. That said, some short-term uncertainties exist as of 15z observational data, with gusty post-convective northeasterly winds still present across south-central Iowa, which relates to some uncertainty with the northward extent of the higher-magnitude severe risk across Minnesota/Wisconsin later today, although latest 16z data features a recent abatement of those northerly winds. Regardless, intense storm development is anticipated into the afternoon across a broad north/south corridor. A synoptically evident and regional outbreak-favorable setup exists, especially by mid/late May standards, highlighted by a coupled upper jet structure over the Upper Midwest, strengthening deep-layer wind fields, and steady cyclogenesis from the Nebraska/Kansas border vicinity this morning northeastward toward the Minnesota/Wisconsin border tonight. Low-level winds will remain strong diurnally ahead of the primary cyclone, but a noteworthy strengthening of mid-level winds 3-7 km AGL (reference 700mb/500mb) will rapidly occur through the afternoon/evening, which will likely have direct outbreak-relevant influences on initial supercell intensity, QLCS evolution and overall fast east-northeastward storm motions later today. Steepening mid-level lapse rates, noted in upstream 12z observed soundings such as Topeka/Dodge City KS and Springfield MO, will overspread an increasingly moist airmass generally characterized by mid/upper 60s F surface dewpoints, contributing to warm-sector MLCAPE to upwards of 2500-3000 J/kg this afternoon. Scattered to numerous thunderstorms, including scattered fast-moving supercells, are expected to initially form over parts of eastern Nebraska by late morning/midday, and into Iowa and northern/central Missouri this afternoon. This will occur as the cold front impinges on a retreating outflow boundary from the morning storms, and an airmass destabilizing rapidly on both sides of the boundary from a combination of diurnal heating and intense warm advection. Additional, initially semi-discrete, supercellular development is also plausible farther east across Iowa this afternoon in vicinity of modifying outflow/warm front. Sufficient airmass recovery for a surface-based, all-hazards severe threat is expected across most of Iowa and potentially into southern Minnesota as well, spreading into parts of western/northern Illinois and Wisconsin. Several tornadoes, including some strong with EF2+ potential, are expected, along with large, damaging hail and severe downdrafts. This includes the possibility of long-track supercells/tornadoes and swaths of locally intense wind damage. Later tonight, storms should begin to gradually outrun the corridor of favorable surface-based buoyancy in the evening after crossing the Mississippi River, but may remain well-organized in terms of severe-wind threat across Lake Michigan vicinity. ...Ozarks/Oklahoma to south Texas... Isolated to scattered thunderstorms are expected to form from mid afternoon into evening near the front and dryline, offering large to very large hail and locally severe gusts. Hail at least 3 inches in diameter is possible. A tornado or two is not out of the question, especially in northern areas (Ozarks vicinity) under the fringes of the gradient-flow/deep-shear influence from the ejecting shortwave trough, and with high-CAPE storm-scale processes amid favorable deep shear elsewhere. Renewed storm development, potentially severe, could also occur in the predawn hours of Wednesday across Oklahoma near the front. Though capping from an EML will limit convective potential for much of the day, a combination of strong surface heating, rich boundary- layer moisture, and frontal/dryline lift will weaken MLCINH enough by mid/late afternoon to support deep convective development. Upper 60s to low 70s F surface dewpoints should become common beneath a high equilibrium level (deep troposphere) and steep mid-level lapse rates, supporting a corridor of 3000-4000 J/kg MLCAPE (locally higher). Sufficient veering of winds with height, and effective-shear magnitudes in the 45-60 kt range, will support supercell potential. Activity over Texas my weaken within a few hours after sunset as nocturnal boundary-layer cooling re-establishes the strong capping beneath the EML. However, farther north across parts of Arkansas/Missouri, a weaker EML influence may permit activity to persist later and farther east this evening, before weakening. ...Adirondacks region to northern New England... Widely scattered to scattered thunderstorms should develop over portions of the Adirondacks and White Mountains today, and perhaps also move into the area from nearby parts of extreme eastern Ontario and southernmost Quebec. Damaging gusts and isolated severe hail will be possible. A mid/upper-level shortwave trough and embedded MCV -- related to the significantly severe MCS over Kansas two days ago -- is apparent in satellite imagery over Lake Huron. This feature will move eastward toward northern New York/New England and times well with the diurnal-heating cycle there. Activity should form as large-scale DCVA/lift and enhancement of midlevel flow -- preceding the MCV/shortwave trough -- spread atop a destabilized, suitably moist boundary layer, heated to convective temperature over elevated terrain. These processes will erode MLCINH to negligible levels, fostering MLCAPE commonly in the 1000-1500 J/kg range, locally/briefly near 2000 J/kg. Deep shear should remain modest, with effective-shear magnitudes generally 25-35 kt, though enough veering with height in low levels may develop to shape somewhat enlarged hodographs. Multicell and transient supercell modes should predominate, with the severe threat diminishing markedly after sunset. ..Guyer/Wendt.. 05/21/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1140 AM CDT Tue May 21 2024 Valid 211630Z - 221200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS IOWA...NORTHERN MISSOURI...NORTHWEST ILLINOIS...SOUTHEAST MINNESOTA...AND SOUTHERN WISCONSIN... ...SUMMARY... An outbreak of severe thunderstorms, including the potential for strong tornadoes, large hail, and widespread damaging winds, is expected this afternoon through evening, especially across eastern Nebraska, Iowa, and Missouri to northern Illinois, southeast Minnesota, and southern Wisconsin. ...Middle/Lower Missouri Valley and Midwest... As an outbreak precursor, a well-organized cluster of storms across south-central/east-central Iowa mid-late this morning has had a history of producing at least isolated/episodic severe weather since the predawn hours. These storms are focused along/north of an outflow-reinforced warm front that will lift northward through late today into tonight. This will be heavily influenced by a highly dynamic mass response to a northeast-moving mid-level shortwave trough that is readily evident in water vapor imagery over the central High Plains this morning. That said, some short-term uncertainties exist as of 15z observational data, with gusty post-convective northeasterly winds still present across south-central Iowa, which relates to some uncertainty with the northward extent of the higher-magnitude severe risk across Minnesota/Wisconsin later today, although latest 16z data features a recent abatement of those northerly winds. Regardless, intense storm development is anticipated into the afternoon across a broad north/south corridor. A synoptically evident and regional outbreak-favorable setup exists, especially by mid/late May standards, highlighted by a coupled upper jet structure over the Upper Midwest, strengthening deep-layer wind fields, and steady cyclogenesis from the Nebraska/Kansas border vicinity this morning northeastward toward the Minnesota/Wisconsin border tonight. Low-level winds will remain strong diurnally ahead of the primary cyclone, but a noteworthy strengthening of mid-level winds 3-7 km AGL (reference 700mb/500mb) will rapidly occur through the afternoon/evening, which will likely have direct outbreak-relevant influences on initial supercell intensity, QLCS evolution and overall fast east-northeastward storm motions later today. Steepening mid-level lapse rates, noted in upstream 12z observed soundings such as Topeka/Dodge City KS and Springfield MO, will overspread an increasingly moist airmass generally characterized by mid/upper 60s F surface dewpoints, contributing to warm-sector MLCAPE to upwards of 2500-3000 J/kg this afternoon. Scattered to numerous thunderstorms, including scattered fast-moving supercells, are expected to initially form over parts of eastern Nebraska by late morning/midday, and into Iowa and northern/central Missouri this afternoon. This will occur as the cold front impinges on a retreating outflow boundary from the morning storms, and an airmass destabilizing rapidly on both sides of the boundary from a combination of diurnal heating and intense warm advection. Additional, initially semi-discrete, supercellular development is also plausible farther east across Iowa this afternoon in vicinity of modifying outflow/warm front. Sufficient airmass recovery for a surface-based, all-hazards severe threat is expected across most of Iowa and potentially into southern Minnesota as well, spreading into parts of western/northern Illinois and Wisconsin. Several tornadoes, including some strong with EF2+ potential, are expected, along with large, damaging hail and severe downdrafts. This includes the possibility of long-track supercells/tornadoes and swaths of locally intense wind damage. Later tonight, storms should begin to gradually outrun the corridor of favorable surface-based buoyancy in the evening after crossing the Mississippi River, but may remain well-organized in terms of severe-wind threat across Lake Michigan vicinity. ...Ozarks/Oklahoma to south Texas... Isolated to scattered thunderstorms are expected to form from mid afternoon into evening near the front and dryline, offering large to very large hail and locally severe gusts. Hail at least 3 inches in diameter is possible. A tornado or two is not out of the question, especially in northern areas (Ozarks vicinity) under the fringes of the gradient-flow/deep-shear influence from the ejecting shortwave trough, and with high-CAPE storm-scale processes amid favorable deep shear elsewhere. Renewed storm development, potentially severe, could also occur in the predawn hours of Wednesday across Oklahoma near the front. Though capping from an EML will limit convective potential for much of the day, a combination of strong surface heating, rich boundary- layer moisture, and frontal/dryline lift will weaken MLCINH enough by mid/late afternoon to support deep convective development. Upper 60s to low 70s F surface dewpoints should become common beneath a high equilibrium level (deep troposphere) and steep mid-level lapse rates, supporting a corridor of 3000-4000 J/kg MLCAPE (locally higher). Sufficient veering of winds with height, and effective-shear magnitudes in the 45-60 kt range, will support supercell potential. Activity over Texas my weaken within a few hours after sunset as nocturnal boundary-layer cooling re-establishes the strong capping beneath the EML. However, farther north across parts of Arkansas/Missouri, a weaker EML influence may permit activity to persist later and farther east this evening, before weakening. ...Adirondacks region to northern New England... Widely scattered to scattered thunderstorms should develop over portions of the Adirondacks and White Mountains today, and perhaps also move into the area from nearby parts of extreme eastern Ontario and southernmost Quebec. Damaging gusts and isolated severe hail will be possible. A mid/upper-level shortwave trough and embedded MCV -- related to the significantly severe MCS over Kansas two days ago -- is apparent in satellite imagery over Lake Huron. This feature will move eastward toward northern New York/New England and times well with the diurnal-heating cycle there. Activity should form as large-scale DCVA/lift and enhancement of midlevel flow -- preceding the MCV/shortwave trough -- spread atop a destabilized, suitably moist boundary layer, heated to convective temperature over elevated terrain. These processes will erode MLCINH to negligible levels, fostering MLCAPE commonly in the 1000-1500 J/kg range, locally/briefly near 2000 J/kg. Deep shear should remain modest, with effective-shear magnitudes generally 25-35 kt, though enough veering with height in low levels may develop to shape somewhat enlarged hodographs. Multicell and transient supercell modes should predominate, with the severe threat diminishing markedly after sunset. ..Guyer/Wendt.. 05/21/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1140 AM CDT Tue May 21 2024 Valid 211630Z - 221200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS IOWA...NORTHERN MISSOURI...NORTHWEST ILLINOIS...SOUTHEAST MINNESOTA...AND SOUTHERN WISCONSIN... ...SUMMARY... An outbreak of severe thunderstorms, including the potential for strong tornadoes, large hail, and widespread damaging winds, is expected this afternoon through evening, especially across eastern Nebraska, Iowa, and Missouri to northern Illinois, southeast Minnesota, and southern Wisconsin. ...Middle/Lower Missouri Valley and Midwest... As an outbreak precursor, a well-organized cluster of storms across south-central/east-central Iowa mid-late this morning has had a history of producing at least isolated/episodic severe weather since the predawn hours. These storms are focused along/north of an outflow-reinforced warm front that will lift northward through late today into tonight. This will be heavily influenced by a highly dynamic mass response to a northeast-moving mid-level shortwave trough that is readily evident in water vapor imagery over the central High Plains this morning. That said, some short-term uncertainties exist as of 15z observational data, with gusty post-convective northeasterly winds still present across south-central Iowa, which relates to some uncertainty with the northward extent of the higher-magnitude severe risk across Minnesota/Wisconsin later today, although latest 16z data features a recent abatement of those northerly winds. Regardless, intense storm development is anticipated into the afternoon across a broad north/south corridor. A synoptically evident and regional outbreak-favorable setup exists, especially by mid/late May standards, highlighted by a coupled upper jet structure over the Upper Midwest, strengthening deep-layer wind fields, and steady cyclogenesis from the Nebraska/Kansas border vicinity this morning northeastward toward the Minnesota/Wisconsin border tonight. Low-level winds will remain strong diurnally ahead of the primary cyclone, but a noteworthy strengthening of mid-level winds 3-7 km AGL (reference 700mb/500mb) will rapidly occur through the afternoon/evening, which will likely have direct outbreak-relevant influences on initial supercell intensity, QLCS evolution and overall fast east-northeastward storm motions later today. Steepening mid-level lapse rates, noted in upstream 12z observed soundings such as Topeka/Dodge City KS and Springfield MO, will overspread an increasingly moist airmass generally characterized by mid/upper 60s F surface dewpoints, contributing to warm-sector MLCAPE to upwards of 2500-3000 J/kg this afternoon. Scattered to numerous thunderstorms, including scattered fast-moving supercells, are expected to initially form over parts of eastern Nebraska by late morning/midday, and into Iowa and northern/central Missouri this afternoon. This will occur as the cold front impinges on a retreating outflow boundary from the morning storms, and an airmass destabilizing rapidly on both sides of the boundary from a combination of diurnal heating and intense warm advection. Additional, initially semi-discrete, supercellular development is also plausible farther east across Iowa this afternoon in vicinity of modifying outflow/warm front. Sufficient airmass recovery for a surface-based, all-hazards severe threat is expected across most of Iowa and potentially into southern Minnesota as well, spreading into parts of western/northern Illinois and Wisconsin. Several tornadoes, including some strong with EF2+ potential, are expected, along with large, damaging hail and severe downdrafts. This includes the possibility of long-track supercells/tornadoes and swaths of locally intense wind damage. Later tonight, storms should begin to gradually outrun the corridor of favorable surface-based buoyancy in the evening after crossing the Mississippi River, but may remain well-organized in terms of severe-wind threat across Lake Michigan vicinity. ...Ozarks/Oklahoma to south Texas... Isolated to scattered thunderstorms are expected to form from mid afternoon into evening near the front and dryline, offering large to very large hail and locally severe gusts. Hail at least 3 inches in diameter is possible. A tornado or two is not out of the question, especially in northern areas (Ozarks vicinity) under the fringes of the gradient-flow/deep-shear influence from the ejecting shortwave trough, and with high-CAPE storm-scale processes amid favorable deep shear elsewhere. Renewed storm development, potentially severe, could also occur in the predawn hours of Wednesday across Oklahoma near the front. Though capping from an EML will limit convective potential for much of the day, a combination of strong surface heating, rich boundary- layer moisture, and frontal/dryline lift will weaken MLCINH enough by mid/late afternoon to support deep convective development. Upper 60s to low 70s F surface dewpoints should become common beneath a high equilibrium level (deep troposphere) and steep mid-level lapse rates, supporting a corridor of 3000-4000 J/kg MLCAPE (locally higher). Sufficient veering of winds with height, and effective-shear magnitudes in the 45-60 kt range, will support supercell potential. Activity over Texas my weaken within a few hours after sunset as nocturnal boundary-layer cooling re-establishes the strong capping beneath the EML. However, farther north across parts of Arkansas/Missouri, a weaker EML influence may permit activity to persist later and farther east this evening, before weakening. ...Adirondacks region to northern New England... Widely scattered to scattered thunderstorms should develop over portions of the Adirondacks and White Mountains today, and perhaps also move into the area from nearby parts of extreme eastern Ontario and southernmost Quebec. Damaging gusts and isolated severe hail will be possible. A mid/upper-level shortwave trough and embedded MCV -- related to the significantly severe MCS over Kansas two days ago -- is apparent in satellite imagery over Lake Huron. This feature will move eastward toward northern New York/New England and times well with the diurnal-heating cycle there. Activity should form as large-scale DCVA/lift and enhancement of midlevel flow -- preceding the MCV/shortwave trough -- spread atop a destabilized, suitably moist boundary layer, heated to convective temperature over elevated terrain. These processes will erode MLCINH to negligible levels, fostering MLCAPE commonly in the 1000-1500 J/kg range, locally/briefly near 2000 J/kg. Deep shear should remain modest, with effective-shear magnitudes generally 25-35 kt, though enough veering with height in low levels may develop to shape somewhat enlarged hodographs. Multicell and transient supercell modes should predominate, with the severe threat diminishing markedly after sunset. ..Guyer/Wendt.. 05/21/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1140 AM CDT Tue May 21 2024 Valid 211630Z - 221200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS IOWA...NORTHERN MISSOURI...NORTHWEST ILLINOIS...SOUTHEAST MINNESOTA...AND SOUTHERN WISCONSIN... ...SUMMARY... An outbreak of severe thunderstorms, including the potential for strong tornadoes, large hail, and widespread damaging winds, is expected this afternoon through evening, especially across eastern Nebraska, Iowa, and Missouri to northern Illinois, southeast Minnesota, and southern Wisconsin. ...Middle/Lower Missouri Valley and Midwest... As an outbreak precursor, a well-organized cluster of storms across south-central/east-central Iowa mid-late this morning has had a history of producing at least isolated/episodic severe weather since the predawn hours. These storms are focused along/north of an outflow-reinforced warm front that will lift northward through late today into tonight. This will be heavily influenced by a highly dynamic mass response to a northeast-moving mid-level shortwave trough that is readily evident in water vapor imagery over the central High Plains this morning. That said, some short-term uncertainties exist as of 15z observational data, with gusty post-convective northeasterly winds still present across south-central Iowa, which relates to some uncertainty with the northward extent of the higher-magnitude severe risk across Minnesota/Wisconsin later today, although latest 16z data features a recent abatement of those northerly winds. Regardless, intense storm development is anticipated into the afternoon across a broad north/south corridor. A synoptically evident and regional outbreak-favorable setup exists, especially by mid/late May standards, highlighted by a coupled upper jet structure over the Upper Midwest, strengthening deep-layer wind fields, and steady cyclogenesis from the Nebraska/Kansas border vicinity this morning northeastward toward the Minnesota/Wisconsin border tonight. Low-level winds will remain strong diurnally ahead of the primary cyclone, but a noteworthy strengthening of mid-level winds 3-7 km AGL (reference 700mb/500mb) will rapidly occur through the afternoon/evening, which will likely have direct outbreak-relevant influences on initial supercell intensity, QLCS evolution and overall fast east-northeastward storm motions later today. Steepening mid-level lapse rates, noted in upstream 12z observed soundings such as Topeka/Dodge City KS and Springfield MO, will overspread an increasingly moist airmass generally characterized by mid/upper 60s F surface dewpoints, contributing to warm-sector MLCAPE to upwards of 2500-3000 J/kg this afternoon. Scattered to numerous thunderstorms, including scattered fast-moving supercells, are expected to initially form over parts of eastern Nebraska by late morning/midday, and into Iowa and northern/central Missouri this afternoon. This will occur as the cold front impinges on a retreating outflow boundary from the morning storms, and an airmass destabilizing rapidly on both sides of the boundary from a combination of diurnal heating and intense warm advection. Additional, initially semi-discrete, supercellular development is also plausible farther east across Iowa this afternoon in vicinity of modifying outflow/warm front. Sufficient airmass recovery for a surface-based, all-hazards severe threat is expected across most of Iowa and potentially into southern Minnesota as well, spreading into parts of western/northern Illinois and Wisconsin. Several tornadoes, including some strong with EF2+ potential, are expected, along with large, damaging hail and severe downdrafts. This includes the possibility of long-track supercells/tornadoes and swaths of locally intense wind damage. Later tonight, storms should begin to gradually outrun the corridor of favorable surface-based buoyancy in the evening after crossing the Mississippi River, but may remain well-organized in terms of severe-wind threat across Lake Michigan vicinity. ...Ozarks/Oklahoma to south Texas... Isolated to scattered thunderstorms are expected to form from mid afternoon into evening near the front and dryline, offering large to very large hail and locally severe gusts. Hail at least 3 inches in diameter is possible. A tornado or two is not out of the question, especially in northern areas (Ozarks vicinity) under the fringes of the gradient-flow/deep-shear influence from the ejecting shortwave trough, and with high-CAPE storm-scale processes amid favorable deep shear elsewhere. Renewed storm development, potentially severe, could also occur in the predawn hours of Wednesday across Oklahoma near the front. Though capping from an EML will limit convective potential for much of the day, a combination of strong surface heating, rich boundary- layer moisture, and frontal/dryline lift will weaken MLCINH enough by mid/late afternoon to support deep convective development. Upper 60s to low 70s F surface dewpoints should become common beneath a high equilibrium level (deep troposphere) and steep mid-level lapse rates, supporting a corridor of 3000-4000 J/kg MLCAPE (locally higher). Sufficient veering of winds with height, and effective-shear magnitudes in the 45-60 kt range, will support supercell potential. Activity over Texas my weaken within a few hours after sunset as nocturnal boundary-layer cooling re-establishes the strong capping beneath the EML. However, farther north across parts of Arkansas/Missouri, a weaker EML influence may permit activity to persist later and farther east this evening, before weakening. ...Adirondacks region to northern New England... Widely scattered to scattered thunderstorms should develop over portions of the Adirondacks and White Mountains today, and perhaps also move into the area from nearby parts of extreme eastern Ontario and southernmost Quebec. Damaging gusts and isolated severe hail will be possible. A mid/upper-level shortwave trough and embedded MCV -- related to the significantly severe MCS over Kansas two days ago -- is apparent in satellite imagery over Lake Huron. This feature will move eastward toward northern New York/New England and times well with the diurnal-heating cycle there. Activity should form as large-scale DCVA/lift and enhancement of midlevel flow -- preceding the MCV/shortwave trough -- spread atop a destabilized, suitably moist boundary layer, heated to convective temperature over elevated terrain. These processes will erode MLCINH to negligible levels, fostering MLCAPE commonly in the 1000-1500 J/kg range, locally/briefly near 2000 J/kg. Deep shear should remain modest, with effective-shear magnitudes generally 25-35 kt, though enough veering with height in low levels may develop to shape somewhat enlarged hodographs. Multicell and transient supercell modes should predominate, with the severe threat diminishing markedly after sunset. ..Guyer/Wendt.. 05/21/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1140 AM CDT Tue May 21 2024 Valid 211630Z - 221200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS IOWA...NORTHERN MISSOURI...NORTHWEST ILLINOIS...SOUTHEAST MINNESOTA...AND SOUTHERN WISCONSIN... ...SUMMARY... An outbreak of severe thunderstorms, including the potential for strong tornadoes, large hail, and widespread damaging winds, is expected this afternoon through evening, especially across eastern Nebraska, Iowa, and Missouri to northern Illinois, southeast Minnesota, and southern Wisconsin. ...Middle/Lower Missouri Valley and Midwest... As an outbreak precursor, a well-organized cluster of storms across south-central/east-central Iowa mid-late this morning has had a history of producing at least isolated/episodic severe weather since the predawn hours. These storms are focused along/north of an outflow-reinforced warm front that will lift northward through late today into tonight. This will be heavily influenced by a highly dynamic mass response to a northeast-moving mid-level shortwave trough that is readily evident in water vapor imagery over the central High Plains this morning. That said, some short-term uncertainties exist as of 15z observational data, with gusty post-convective northeasterly winds still present across south-central Iowa, which relates to some uncertainty with the northward extent of the higher-magnitude severe risk across Minnesota/Wisconsin later today, although latest 16z data features a recent abatement of those northerly winds. Regardless, intense storm development is anticipated into the afternoon across a broad north/south corridor. A synoptically evident and regional outbreak-favorable setup exists, especially by mid/late May standards, highlighted by a coupled upper jet structure over the Upper Midwest, strengthening deep-layer wind fields, and steady cyclogenesis from the Nebraska/Kansas border vicinity this morning northeastward toward the Minnesota/Wisconsin border tonight. Low-level winds will remain strong diurnally ahead of the primary cyclone, but a noteworthy strengthening of mid-level winds 3-7 km AGL (reference 700mb/500mb) will rapidly occur through the afternoon/evening, which will likely have direct outbreak-relevant influences on initial supercell intensity, QLCS evolution and overall fast east-northeastward storm motions later today. Steepening mid-level lapse rates, noted in upstream 12z observed soundings such as Topeka/Dodge City KS and Springfield MO, will overspread an increasingly moist airmass generally characterized by mid/upper 60s F surface dewpoints, contributing to warm-sector MLCAPE to upwards of 2500-3000 J/kg this afternoon. Scattered to numerous thunderstorms, including scattered fast-moving supercells, are expected to initially form over parts of eastern Nebraska by late morning/midday, and into Iowa and northern/central Missouri this afternoon. This will occur as the cold front impinges on a retreating outflow boundary from the morning storms, and an airmass destabilizing rapidly on both sides of the boundary from a combination of diurnal heating and intense warm advection. Additional, initially semi-discrete, supercellular development is also plausible farther east across Iowa this afternoon in vicinity of modifying outflow/warm front. Sufficient airmass recovery for a surface-based, all-hazards severe threat is expected across most of Iowa and potentially into southern Minnesota as well, spreading into parts of western/northern Illinois and Wisconsin. Several tornadoes, including some strong with EF2+ potential, are expected, along with large, damaging hail and severe downdrafts. This includes the possibility of long-track supercells/tornadoes and swaths of locally intense wind damage. Later tonight, storms should begin to gradually outrun the corridor of favorable surface-based buoyancy in the evening after crossing the Mississippi River, but may remain well-organized in terms of severe-wind threat across Lake Michigan vicinity. ...Ozarks/Oklahoma to south Texas... Isolated to scattered thunderstorms are expected to form from mid afternoon into evening near the front and dryline, offering large to very large hail and locally severe gusts. Hail at least 3 inches in diameter is possible. A tornado or two is not out of the question, especially in northern areas (Ozarks vicinity) under the fringes of the gradient-flow/deep-shear influence from the ejecting shortwave trough, and with high-CAPE storm-scale processes amid favorable deep shear elsewhere. Renewed storm development, potentially severe, could also occur in the predawn hours of Wednesday across Oklahoma near the front. Though capping from an EML will limit convective potential for much of the day, a combination of strong surface heating, rich boundary- layer moisture, and frontal/dryline lift will weaken MLCINH enough by mid/late afternoon to support deep convective development. Upper 60s to low 70s F surface dewpoints should become common beneath a high equilibrium level (deep troposphere) and steep mid-level lapse rates, supporting a corridor of 3000-4000 J/kg MLCAPE (locally higher). Sufficient veering of winds with height, and effective-shear magnitudes in the 45-60 kt range, will support supercell potential. Activity over Texas my weaken within a few hours after sunset as nocturnal boundary-layer cooling re-establishes the strong capping beneath the EML. However, farther north across parts of Arkansas/Missouri, a weaker EML influence may permit activity to persist later and farther east this evening, before weakening. ...Adirondacks region to northern New England... Widely scattered to scattered thunderstorms should develop over portions of the Adirondacks and White Mountains today, and perhaps also move into the area from nearby parts of extreme eastern Ontario and southernmost Quebec. Damaging gusts and isolated severe hail will be possible. A mid/upper-level shortwave trough and embedded MCV -- related to the significantly severe MCS over Kansas two days ago -- is apparent in satellite imagery over Lake Huron. This feature will move eastward toward northern New York/New England and times well with the diurnal-heating cycle there. Activity should form as large-scale DCVA/lift and enhancement of midlevel flow -- preceding the MCV/shortwave trough -- spread atop a destabilized, suitably moist boundary layer, heated to convective temperature over elevated terrain. These processes will erode MLCINH to negligible levels, fostering MLCAPE commonly in the 1000-1500 J/kg range, locally/briefly near 2000 J/kg. Deep shear should remain modest, with effective-shear magnitudes generally 25-35 kt, though enough veering with height in low levels may develop to shape somewhat enlarged hodographs. Multicell and transient supercell modes should predominate, with the severe threat diminishing markedly after sunset. ..Guyer/Wendt.. 05/21/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1140 AM CDT Tue May 21 2024 Valid 211630Z - 221200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS IOWA...NORTHERN MISSOURI...NORTHWEST ILLINOIS...SOUTHEAST MINNESOTA...AND SOUTHERN WISCONSIN... ...SUMMARY... An outbreak of severe thunderstorms, including the potential for strong tornadoes, large hail, and widespread damaging winds, is expected this afternoon through evening, especially across eastern Nebraska, Iowa, and Missouri to northern Illinois, southeast Minnesota, and southern Wisconsin. ...Middle/Lower Missouri Valley and Midwest... As an outbreak precursor, a well-organized cluster of storms across south-central/east-central Iowa mid-late this morning has had a history of producing at least isolated/episodic severe weather since the predawn hours. These storms are focused along/north of an outflow-reinforced warm front that will lift northward through late today into tonight. This will be heavily influenced by a highly dynamic mass response to a northeast-moving mid-level shortwave trough that is readily evident in water vapor imagery over the central High Plains this morning. That said, some short-term uncertainties exist as of 15z observational data, with gusty post-convective northeasterly winds still present across south-central Iowa, which relates to some uncertainty with the northward extent of the higher-magnitude severe risk across Minnesota/Wisconsin later today, although latest 16z data features a recent abatement of those northerly winds. Regardless, intense storm development is anticipated into the afternoon across a broad north/south corridor. A synoptically evident and regional outbreak-favorable setup exists, especially by mid/late May standards, highlighted by a coupled upper jet structure over the Upper Midwest, strengthening deep-layer wind fields, and steady cyclogenesis from the Nebraska/Kansas border vicinity this morning northeastward toward the Minnesota/Wisconsin border tonight. Low-level winds will remain strong diurnally ahead of the primary cyclone, but a noteworthy strengthening of mid-level winds 3-7 km AGL (reference 700mb/500mb) will rapidly occur through the afternoon/evening, which will likely have direct outbreak-relevant influences on initial supercell intensity, QLCS evolution and overall fast east-northeastward storm motions later today. Steepening mid-level lapse rates, noted in upstream 12z observed soundings such as Topeka/Dodge City KS and Springfield MO, will overspread an increasingly moist airmass generally characterized by mid/upper 60s F surface dewpoints, contributing to warm-sector MLCAPE to upwards of 2500-3000 J/kg this afternoon. Scattered to numerous thunderstorms, including scattered fast-moving supercells, are expected to initially form over parts of eastern Nebraska by late morning/midday, and into Iowa and northern/central Missouri this afternoon. This will occur as the cold front impinges on a retreating outflow boundary from the morning storms, and an airmass destabilizing rapidly on both sides of the boundary from a combination of diurnal heating and intense warm advection. Additional, initially semi-discrete, supercellular development is also plausible farther east across Iowa this afternoon in vicinity of modifying outflow/warm front. Sufficient airmass recovery for a surface-based, all-hazards severe threat is expected across most of Iowa and potentially into southern Minnesota as well, spreading into parts of western/northern Illinois and Wisconsin. Several tornadoes, including some strong with EF2+ potential, are expected, along with large, damaging hail and severe downdrafts. This includes the possibility of long-track supercells/tornadoes and swaths of locally intense wind damage. Later tonight, storms should begin to gradually outrun the corridor of favorable surface-based buoyancy in the evening after crossing the Mississippi River, but may remain well-organized in terms of severe-wind threat across Lake Michigan vicinity. ...Ozarks/Oklahoma to south Texas... Isolated to scattered thunderstorms are expected to form from mid afternoon into evening near the front and dryline, offering large to very large hail and locally severe gusts. Hail at least 3 inches in diameter is possible. A tornado or two is not out of the question, especially in northern areas (Ozarks vicinity) under the fringes of the gradient-flow/deep-shear influence from the ejecting shortwave trough, and with high-CAPE storm-scale processes amid favorable deep shear elsewhere. Renewed storm development, potentially severe, could also occur in the predawn hours of Wednesday across Oklahoma near the front. Though capping from an EML will limit convective potential for much of the day, a combination of strong surface heating, rich boundary- layer moisture, and frontal/dryline lift will weaken MLCINH enough by mid/late afternoon to support deep convective development. Upper 60s to low 70s F surface dewpoints should become common beneath a high equilibrium level (deep troposphere) and steep mid-level lapse rates, supporting a corridor of 3000-4000 J/kg MLCAPE (locally higher). Sufficient veering of winds with height, and effective-shear magnitudes in the 45-60 kt range, will support supercell potential. Activity over Texas my weaken within a few hours after sunset as nocturnal boundary-layer cooling re-establishes the strong capping beneath the EML. However, farther north across parts of Arkansas/Missouri, a weaker EML influence may permit activity to persist later and farther east this evening, before weakening. ...Adirondacks region to northern New England... Widely scattered to scattered thunderstorms should develop over portions of the Adirondacks and White Mountains today, and perhaps also move into the area from nearby parts of extreme eastern Ontario and southernmost Quebec. Damaging gusts and isolated severe hail will be possible. A mid/upper-level shortwave trough and embedded MCV -- related to the significantly severe MCS over Kansas two days ago -- is apparent in satellite imagery over Lake Huron. This feature will move eastward toward northern New York/New England and times well with the diurnal-heating cycle there. Activity should form as large-scale DCVA/lift and enhancement of midlevel flow -- preceding the MCV/shortwave trough -- spread atop a destabilized, suitably moist boundary layer, heated to convective temperature over elevated terrain. These processes will erode MLCINH to negligible levels, fostering MLCAPE commonly in the 1000-1500 J/kg range, locally/briefly near 2000 J/kg. Deep shear should remain modest, with effective-shear magnitudes generally 25-35 kt, though enough veering with height in low levels may develop to shape somewhat enlarged hodographs. Multicell and transient supercell modes should predominate, with the severe threat diminishing markedly after sunset. ..Guyer/Wendt.. 05/21/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1140 AM CDT Tue May 21 2024 Valid 211630Z - 221200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS IOWA...NORTHERN MISSOURI...NORTHWEST ILLINOIS...SOUTHEAST MINNESOTA...AND SOUTHERN WISCONSIN... ...SUMMARY... An outbreak of severe thunderstorms, including the potential for strong tornadoes, large hail, and widespread damaging winds, is expected this afternoon through evening, especially across eastern Nebraska, Iowa, and Missouri to northern Illinois, southeast Minnesota, and southern Wisconsin. ...Middle/Lower Missouri Valley and Midwest... As an outbreak precursor, a well-organized cluster of storms across south-central/east-central Iowa mid-late this morning has had a history of producing at least isolated/episodic severe weather since the predawn hours. These storms are focused along/north of an outflow-reinforced warm front that will lift northward through late today into tonight. This will be heavily influenced by a highly dynamic mass response to a northeast-moving mid-level shortwave trough that is readily evident in water vapor imagery over the central High Plains this morning. That said, some short-term uncertainties exist as of 15z observational data, with gusty post-convective northeasterly winds still present across south-central Iowa, which relates to some uncertainty with the northward extent of the higher-magnitude severe risk across Minnesota/Wisconsin later today, although latest 16z data features a recent abatement of those northerly winds. Regardless, intense storm development is anticipated into the afternoon across a broad north/south corridor. A synoptically evident and regional outbreak-favorable setup exists, especially by mid/late May standards, highlighted by a coupled upper jet structure over the Upper Midwest, strengthening deep-layer wind fields, and steady cyclogenesis from the Nebraska/Kansas border vicinity this morning northeastward toward the Minnesota/Wisconsin border tonight. Low-level winds will remain strong diurnally ahead of the primary cyclone, but a noteworthy strengthening of mid-level winds 3-7 km AGL (reference 700mb/500mb) will rapidly occur through the afternoon/evening, which will likely have direct outbreak-relevant influences on initial supercell intensity, QLCS evolution and overall fast east-northeastward storm motions later today. Steepening mid-level lapse rates, noted in upstream 12z observed soundings such as Topeka/Dodge City KS and Springfield MO, will overspread an increasingly moist airmass generally characterized by mid/upper 60s F surface dewpoints, contributing to warm-sector MLCAPE to upwards of 2500-3000 J/kg this afternoon. Scattered to numerous thunderstorms, including scattered fast-moving supercells, are expected to initially form over parts of eastern Nebraska by late morning/midday, and into Iowa and northern/central Missouri this afternoon. This will occur as the cold front impinges on a retreating outflow boundary from the morning storms, and an airmass destabilizing rapidly on both sides of the boundary from a combination of diurnal heating and intense warm advection. Additional, initially semi-discrete, supercellular development is also plausible farther east across Iowa this afternoon in vicinity of modifying outflow/warm front. Sufficient airmass recovery for a surface-based, all-hazards severe threat is expected across most of Iowa and potentially into southern Minnesota as well, spreading into parts of western/northern Illinois and Wisconsin. Several tornadoes, including some strong with EF2+ potential, are expected, along with large, damaging hail and severe downdrafts. This includes the possibility of long-track supercells/tornadoes and swaths of locally intense wind damage. Later tonight, storms should begin to gradually outrun the corridor of favorable surface-based buoyancy in the evening after crossing the Mississippi River, but may remain well-organized in terms of severe-wind threat across Lake Michigan vicinity. ...Ozarks/Oklahoma to south Texas... Isolated to scattered thunderstorms are expected to form from mid afternoon into evening near the front and dryline, offering large to very large hail and locally severe gusts. Hail at least 3 inches in diameter is possible. A tornado or two is not out of the question, especially in northern areas (Ozarks vicinity) under the fringes of the gradient-flow/deep-shear influence from the ejecting shortwave trough, and with high-CAPE storm-scale processes amid favorable deep shear elsewhere. Renewed storm development, potentially severe, could also occur in the predawn hours of Wednesday across Oklahoma near the front. Though capping from an EML will limit convective potential for much of the day, a combination of strong surface heating, rich boundary- layer moisture, and frontal/dryline lift will weaken MLCINH enough by mid/late afternoon to support deep convective development. Upper 60s to low 70s F surface dewpoints should become common beneath a high equilibrium level (deep troposphere) and steep mid-level lapse rates, supporting a corridor of 3000-4000 J/kg MLCAPE (locally higher). Sufficient veering of winds with height, and effective-shear magnitudes in the 45-60 kt range, will support supercell potential. Activity over Texas my weaken within a few hours after sunset as nocturnal boundary-layer cooling re-establishes the strong capping beneath the EML. However, farther north across parts of Arkansas/Missouri, a weaker EML influence may permit activity to persist later and farther east this evening, before weakening. ...Adirondacks region to northern New England... Widely scattered to scattered thunderstorms should develop over portions of the Adirondacks and White Mountains today, and perhaps also move into the area from nearby parts of extreme eastern Ontario and southernmost Quebec. Damaging gusts and isolated severe hail will be possible. A mid/upper-level shortwave trough and embedded MCV -- related to the significantly severe MCS over Kansas two days ago -- is apparent in satellite imagery over Lake Huron. This feature will move eastward toward northern New York/New England and times well with the diurnal-heating cycle there. Activity should form as large-scale DCVA/lift and enhancement of midlevel flow -- preceding the MCV/shortwave trough -- spread atop a destabilized, suitably moist boundary layer, heated to convective temperature over elevated terrain. These processes will erode MLCINH to negligible levels, fostering MLCAPE commonly in the 1000-1500 J/kg range, locally/briefly near 2000 J/kg. Deep shear should remain modest, with effective-shear magnitudes generally 25-35 kt, though enough veering with height in low levels may develop to shape somewhat enlarged hodographs. Multicell and transient supercell modes should predominate, with the severe threat diminishing markedly after sunset. ..Guyer/Wendt.. 05/21/2024 Read more