Severe Storms

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0303 AM CDT Wed Sep 18 2019 Valid 211200Z - 261200Z ...DISCUSSION... On Sat/D4, a shortwave trough will move from the northern Plains to the upper MS Valley with modest southwest flow aloft remaining over the central Plains. Models solutions vary with the timing of this wave, and also with the position of the cold front. In general, storms are most likely from MN/WI southwestward into KS, and a few damaging wind gusts or hail will be possible. However, predictability is too low to denote a risk area. By Sun/D5, the main trough will move toward the Great Lakes, but predictability lessens further. Regardless, only a low chance of severe wind is likely as a southwest/northeast oriented plume of moisture ahead of the wave narrows and flow aloft becomes parallel to the front from the mid MS Valley to the OH Valley. For the Mon/D6 to Tue/D7 period, models show a strong upper low developing southward across CA and into AZ. This will enhance lift, and increase wind fields aloft. The primary question will be timing of this wave and destabilization. Most likely, a low-end severe risk will be possible and could be reflected in later outlooks. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0303 AM CDT Wed Sep 18 2019 Valid 211200Z - 261200Z ...DISCUSSION... On Sat/D4, a shortwave trough will move from the northern Plains to the upper MS Valley with modest southwest flow aloft remaining over the central Plains. Models solutions vary with the timing of this wave, and also with the position of the cold front. In general, storms are most likely from MN/WI southwestward into KS, and a few damaging wind gusts or hail will be possible. However, predictability is too low to denote a risk area. By Sun/D5, the main trough will move toward the Great Lakes, but predictability lessens further. Regardless, only a low chance of severe wind is likely as a southwest/northeast oriented plume of moisture ahead of the wave narrows and flow aloft becomes parallel to the front from the mid MS Valley to the OH Valley. For the Mon/D6 to Tue/D7 period, models show a strong upper low developing southward across CA and into AZ. This will enhance lift, and increase wind fields aloft. The primary question will be timing of this wave and destabilization. Most likely, a low-end severe risk will be possible and could be reflected in later outlooks. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0303 AM CDT Wed Sep 18 2019 Valid 211200Z - 261200Z ...DISCUSSION... On Sat/D4, a shortwave trough will move from the northern Plains to the upper MS Valley with modest southwest flow aloft remaining over the central Plains. Models solutions vary with the timing of this wave, and also with the position of the cold front. In general, storms are most likely from MN/WI southwestward into KS, and a few damaging wind gusts or hail will be possible. However, predictability is too low to denote a risk area. By Sun/D5, the main trough will move toward the Great Lakes, but predictability lessens further. Regardless, only a low chance of severe wind is likely as a southwest/northeast oriented plume of moisture ahead of the wave narrows and flow aloft becomes parallel to the front from the mid MS Valley to the OH Valley. For the Mon/D6 to Tue/D7 period, models show a strong upper low developing southward across CA and into AZ. This will enhance lift, and increase wind fields aloft. The primary question will be timing of this wave and destabilization. Most likely, a low-end severe risk will be possible and could be reflected in later outlooks. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0208 AM CDT Wed Sep 18 2019 Valid 201200Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER THE NORTHERN PLAINS... ...SUMMARY... Scattered severe storms are possible on Friday across the northern Plains, with isolated activity into the central High Plains. ...Synopsis... An upper trough will move across the Rockies and into the Plains, with an upper low deepening over MT. Modest south/southwest winds aloft will exist during the day over the Plains before a strengthening wave pivots northeast out of WY and CO overnight. Low pressure will develop over the northern High Plains during the day, shifting into Canada overnight. Southerly winds across the Plains will maintain 60s F dewpoints with areas of moderate instability supporting strong to severe storms ahead of a cold front that will sweep east across the Dakotas and Nebraska late. ...Northern Plains... A few storms may be ongoing Friday morning over ND in a warm advection regime with hail possible. Continued height falls aloft as well as a warming boundary layer will lead to an uncapped air mass extending south along the surface trough/wind shift, with additional scattered storms expected by 21Z from the central Dakotas into western NE. Subtle hodograph details/weaknesses aside, generally veering and increasing winds with height combined with the strong instability will generally support severe hail, wind, and perhaps a couple tornadoes. Given the meridional winds aloft and front orientation, storm mode may become complex with merging cells as the corridor of storms gradually translates east, possibly reaching western MN by Saturday morning. To the south, strong heating and sufficient convergence near the surface trough may lead to isolated late-afternoon storms over eastern CO and western KS. Ample deep-layer shear as well as 30+ kt south/southeast winds at 850 mb will conditionally support a supercell or two capable of large hail and perhaps a brief tornado. At this time, storm coverage is uncertain but a Slight Risk may be needed for parts of the central High Plains in later outlooks should expected coverage increase. ..Jewell.. 09/18/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0208 AM CDT Wed Sep 18 2019 Valid 201200Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER THE NORTHERN PLAINS... ...SUMMARY... Scattered severe storms are possible on Friday across the northern Plains, with isolated activity into the central High Plains. ...Synopsis... An upper trough will move across the Rockies and into the Plains, with an upper low deepening over MT. Modest south/southwest winds aloft will exist during the day over the Plains before a strengthening wave pivots northeast out of WY and CO overnight. Low pressure will develop over the northern High Plains during the day, shifting into Canada overnight. Southerly winds across the Plains will maintain 60s F dewpoints with areas of moderate instability supporting strong to severe storms ahead of a cold front that will sweep east across the Dakotas and Nebraska late. ...Northern Plains... A few storms may be ongoing Friday morning over ND in a warm advection regime with hail possible. Continued height falls aloft as well as a warming boundary layer will lead to an uncapped air mass extending south along the surface trough/wind shift, with additional scattered storms expected by 21Z from the central Dakotas into western NE. Subtle hodograph details/weaknesses aside, generally veering and increasing winds with height combined with the strong instability will generally support severe hail, wind, and perhaps a couple tornadoes. Given the meridional winds aloft and front orientation, storm mode may become complex with merging cells as the corridor of storms gradually translates east, possibly reaching western MN by Saturday morning. To the south, strong heating and sufficient convergence near the surface trough may lead to isolated late-afternoon storms over eastern CO and western KS. Ample deep-layer shear as well as 30+ kt south/southeast winds at 850 mb will conditionally support a supercell or two capable of large hail and perhaps a brief tornado. At this time, storm coverage is uncertain but a Slight Risk may be needed for parts of the central High Plains in later outlooks should expected coverage increase. ..Jewell.. 09/18/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0208 AM CDT Wed Sep 18 2019 Valid 201200Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER THE NORTHERN PLAINS... ...SUMMARY... Scattered severe storms are possible on Friday across the northern Plains, with isolated activity into the central High Plains. ...Synopsis... An upper trough will move across the Rockies and into the Plains, with an upper low deepening over MT. Modest south/southwest winds aloft will exist during the day over the Plains before a strengthening wave pivots northeast out of WY and CO overnight. Low pressure will develop over the northern High Plains during the day, shifting into Canada overnight. Southerly winds across the Plains will maintain 60s F dewpoints with areas of moderate instability supporting strong to severe storms ahead of a cold front that will sweep east across the Dakotas and Nebraska late. ...Northern Plains... A few storms may be ongoing Friday morning over ND in a warm advection regime with hail possible. Continued height falls aloft as well as a warming boundary layer will lead to an uncapped air mass extending south along the surface trough/wind shift, with additional scattered storms expected by 21Z from the central Dakotas into western NE. Subtle hodograph details/weaknesses aside, generally veering and increasing winds with height combined with the strong instability will generally support severe hail, wind, and perhaps a couple tornadoes. Given the meridional winds aloft and front orientation, storm mode may become complex with merging cells as the corridor of storms gradually translates east, possibly reaching western MN by Saturday morning. To the south, strong heating and sufficient convergence near the surface trough may lead to isolated late-afternoon storms over eastern CO and western KS. Ample deep-layer shear as well as 30+ kt south/southeast winds at 850 mb will conditionally support a supercell or two capable of large hail and perhaps a brief tornado. At this time, storm coverage is uncertain but a Slight Risk may be needed for parts of the central High Plains in later outlooks should expected coverage increase. ..Jewell.. 09/18/2019 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0130 AM CDT Wed Sep 18 2019 Valid 191200Z - 201200Z ...CRITICAL FIRE WEATHER AREA FOR NORTHWEST ARIZONA AND SOUTHERN UTAH... ...Synopsis... A strong mid-level jet streak will traverse the base of the mid-level trough in the western CONUS on Thursday and overspread dry portions of the southwest and Great Basin. This stronger mid-level flow is expected to mix to the surface with wind speeds as high as 30 to 35 mph in northern Arizona and southwest Utah. In addition, relative humidity in this area is forecast to be in the 10 to 20 percent range. 20 to 30 mph surface winds are expected ahead of the surface front in northern Utah and into southern Wyoming as well, but relative humidity farther north is expected to be 20 to 25 percent. Therefore, an elevated delineation has been added across this region with a critical delineation in southern Utah and northwest Arizona where relative humidity is expected to be lower and surface winds are expected to be higher. ..Bentley.. 09/18/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0130 AM CDT Wed Sep 18 2019 Valid 191200Z - 201200Z ...CRITICAL FIRE WEATHER AREA FOR NORTHWEST ARIZONA AND SOUTHERN UTAH... ...Synopsis... A strong mid-level jet streak will traverse the base of the mid-level trough in the western CONUS on Thursday and overspread dry portions of the southwest and Great Basin. This stronger mid-level flow is expected to mix to the surface with wind speeds as high as 30 to 35 mph in northern Arizona and southwest Utah. In addition, relative humidity in this area is forecast to be in the 10 to 20 percent range. 20 to 30 mph surface winds are expected ahead of the surface front in northern Utah and into southern Wyoming as well, but relative humidity farther north is expected to be 20 to 25 percent. Therefore, an elevated delineation has been added across this region with a critical delineation in southern Utah and northwest Arizona where relative humidity is expected to be lower and surface winds are expected to be higher. ..Bentley.. 09/18/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0130 AM CDT Wed Sep 18 2019 Valid 191200Z - 201200Z ...CRITICAL FIRE WEATHER AREA FOR NORTHWEST ARIZONA AND SOUTHERN UTAH... ...Synopsis... A strong mid-level jet streak will traverse the base of the mid-level trough in the western CONUS on Thursday and overspread dry portions of the southwest and Great Basin. This stronger mid-level flow is expected to mix to the surface with wind speeds as high as 30 to 35 mph in northern Arizona and southwest Utah. In addition, relative humidity in this area is forecast to be in the 10 to 20 percent range. 20 to 30 mph surface winds are expected ahead of the surface front in northern Utah and into southern Wyoming as well, but relative humidity farther north is expected to be 20 to 25 percent. Therefore, an elevated delineation has been added across this region with a critical delineation in southern Utah and northwest Arizona where relative humidity is expected to be lower and surface winds are expected to be higher. ..Bentley.. 09/18/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0129 AM CDT Wed Sep 18 2019 Valid 181200Z - 191200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE SOUTHERN GREAT BASIN... ...Synopsis... A mid-level trough will amplify across the western CONUS today. This will lead to strengthening southwesterly mid-level flow by this afternoon/evening across much of the Great Basin. At the surface, a cold front will be moving southeastward across the Great Basin. Ahead of this front, stronger mid-level flow is expected to mix toward the surface with winds of 20 to 25 mph and relative humidity around 10 to 15 percent. Elevated fire weather conditions are expected to extend into eastern Idaho and portions of Wyoming where RH should be around 15 to 20 percent and winds should be 15 to 20 mph. ..Bentley.. 09/18/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0129 AM CDT Wed Sep 18 2019 Valid 181200Z - 191200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE SOUTHERN GREAT BASIN... ...Synopsis... A mid-level trough will amplify across the western CONUS today. This will lead to strengthening southwesterly mid-level flow by this afternoon/evening across much of the Great Basin. At the surface, a cold front will be moving southeastward across the Great Basin. Ahead of this front, stronger mid-level flow is expected to mix toward the surface with winds of 20 to 25 mph and relative humidity around 10 to 15 percent. Elevated fire weather conditions are expected to extend into eastern Idaho and portions of Wyoming where RH should be around 15 to 20 percent and winds should be 15 to 20 mph. ..Bentley.. 09/18/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0129 AM CDT Wed Sep 18 2019 Valid 181200Z - 191200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE SOUTHERN GREAT BASIN... ...Synopsis... A mid-level trough will amplify across the western CONUS today. This will lead to strengthening southwesterly mid-level flow by this afternoon/evening across much of the Great Basin. At the surface, a cold front will be moving southeastward across the Great Basin. Ahead of this front, stronger mid-level flow is expected to mix toward the surface with winds of 20 to 25 mph and relative humidity around 10 to 15 percent. Elevated fire weather conditions are expected to extend into eastern Idaho and portions of Wyoming where RH should be around 15 to 20 percent and winds should be 15 to 20 mph. ..Bentley.. 09/18/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1233 AM CDT Wed Sep 18 2019 Valid 191200Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE NORTHERN HIGH PLAINS... ...SUMMARY... At least isolated storms producing large hail are possible Thursday evening and overnight across the northern High Plains. ...Synopsis... An upper trough will swing east across the Great Basin, with increasingly meridional upper-level winds into WY and MT. Ahead of this trough, height rises will occur over the northern Plains, upper MS Valley, and Great Lakes with the upper high centered over the central Gulf Coast states. High pressure will remain at the surface over much of the East as low pressure develops over the northern High Plains. This will maintain southerly winds across the Plains with a warm front lifting north across the Dakotas. The moistening air mass along with cool temperatures aloft will result in moderate destabilization over the northern Plains, and will support scattered strong storms mainly late in the day and overnight from eastern MT into ND. Elsewhere, the remnants of TC Imelda will bring heavy rain to parts of east TX as it drifts north, with warm temperatures aloft minimizing instability. ...Eastern MT/WY into the western Dakotas... As low pressure deepens over WY and MT, southeast winds will increase across the northern Plains, with 30 kt southeast flow at 850 mb by late afternoon. This will allow for moistening, but most of the area will remain capped through the day. Steeper low level lapse rates will exist over WY and eastern MT, and into far western SD and NE closer to the surface trough. At least isolated late-day storms are expected in this zone, with increasing storm coverage through the evening due to warm advection with the low-level jet. Cool temperatures aloft and marginal deep-layer shear will favor a few cells capable of large hail. Winds aloft decrease with eastern extent, but cool temperatures aloft and a persistent low-level jet will likely support elevated hail into parts of ND overnight. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 5% - Marginal Hail: 5% - Marginal ..Jewell.. 09/18/2019 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1233 AM CDT Wed Sep 18 2019 Valid 191200Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE NORTHERN HIGH PLAINS... ...SUMMARY... At least isolated storms producing large hail are possible Thursday evening and overnight across the northern High Plains. ...Synopsis... An upper trough will swing east across the Great Basin, with increasingly meridional upper-level winds into WY and MT. Ahead of this trough, height rises will occur over the northern Plains, upper MS Valley, and Great Lakes with the upper high centered over the central Gulf Coast states. High pressure will remain at the surface over much of the East as low pressure develops over the northern High Plains. This will maintain southerly winds across the Plains with a warm front lifting north across the Dakotas. The moistening air mass along with cool temperatures aloft will result in moderate destabilization over the northern Plains, and will support scattered strong storms mainly late in the day and overnight from eastern MT into ND. Elsewhere, the remnants of TC Imelda will bring heavy rain to parts of east TX as it drifts north, with warm temperatures aloft minimizing instability. ...Eastern MT/WY into the western Dakotas... As low pressure deepens over WY and MT, southeast winds will increase across the northern Plains, with 30 kt southeast flow at 850 mb by late afternoon. This will allow for moistening, but most of the area will remain capped through the day. Steeper low level lapse rates will exist over WY and eastern MT, and into far western SD and NE closer to the surface trough. At least isolated late-day storms are expected in this zone, with increasing storm coverage through the evening due to warm advection with the low-level jet. Cool temperatures aloft and marginal deep-layer shear will favor a few cells capable of large hail. Winds aloft decrease with eastern extent, but cool temperatures aloft and a persistent low-level jet will likely support elevated hail into parts of ND overnight. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 5% - Marginal Hail: 5% - Marginal ..Jewell.. 09/18/2019 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1233 AM CDT Wed Sep 18 2019 Valid 191200Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE NORTHERN HIGH PLAINS... ...SUMMARY... At least isolated storms producing large hail are possible Thursday evening and overnight across the northern High Plains. ...Synopsis... An upper trough will swing east across the Great Basin, with increasingly meridional upper-level winds into WY and MT. Ahead of this trough, height rises will occur over the northern Plains, upper MS Valley, and Great Lakes with the upper high centered over the central Gulf Coast states. High pressure will remain at the surface over much of the East as low pressure develops over the northern High Plains. This will maintain southerly winds across the Plains with a warm front lifting north across the Dakotas. The moistening air mass along with cool temperatures aloft will result in moderate destabilization over the northern Plains, and will support scattered strong storms mainly late in the day and overnight from eastern MT into ND. Elsewhere, the remnants of TC Imelda will bring heavy rain to parts of east TX as it drifts north, with warm temperatures aloft minimizing instability. ...Eastern MT/WY into the western Dakotas... As low pressure deepens over WY and MT, southeast winds will increase across the northern Plains, with 30 kt southeast flow at 850 mb by late afternoon. This will allow for moistening, but most of the area will remain capped through the day. Steeper low level lapse rates will exist over WY and eastern MT, and into far western SD and NE closer to the surface trough. At least isolated late-day storms are expected in this zone, with increasing storm coverage through the evening due to warm advection with the low-level jet. Cool temperatures aloft and marginal deep-layer shear will favor a few cells capable of large hail. Winds aloft decrease with eastern extent, but cool temperatures aloft and a persistent low-level jet will likely support elevated hail into parts of ND overnight. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 5% - Marginal Hail: 5% - Marginal ..Jewell.. 09/18/2019 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1215 AM CDT Wed Sep 18 2019 Valid 181200Z - 191200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... A few strong thunderstorms are possible across parts of the Upper Midwest this afternoon and evening, but the risk for organized severe weather appears low. ...Upper Midwest Vicinity... An amplified upper ridge will stretch from the southern Plains to the Great Lakes today. A compact shortwave trough over eastern ND/northwest MN early this morning will quickly shift northeast across the international border. Thunderstorms associated with this wave will diminish through the morning hours. South/southwesterly flow will maintain mid 60s to low 70s dewpoints across the mid-MO Valley into the upper MS Valley ahead of a southeastward-advancing cold front. Thunderstorms will likely redevelop along the front during the late afternoon and into the evening/overnight hours as a southwesterly low level jet increases. Moderate to strong instability is expected to develop as temperatures warm into the 80s, but upper forcing will be modest at best as the upper shortwave trough continues to lift northeast into Ontario after 18z. Furthermore, effective shear will likewise remain modest, around 20-25 kt, limiting organized thunderstorm activity. A couple of strong storms could produce gusty winds, but overall severe threat appears too limited to include probabilities. ...TX/LA... Tropical Depression Imelda would continue to drift north and east in the vicinity of east Texas and the Sabine Valley. Heavy rain will continue to be the main concern with this system. Low level shear may be sufficient for occasional, weakly rotating cells across far southeast TX into far southwest LA. However, conditions are expected to remain too marginal for inclusion of tornado probabilities. ..Leitman/Bentley.. 09/18/2019 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1215 AM CDT Wed Sep 18 2019 Valid 181200Z - 191200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... A few strong thunderstorms are possible across parts of the Upper Midwest this afternoon and evening, but the risk for organized severe weather appears low. ...Upper Midwest Vicinity... An amplified upper ridge will stretch from the southern Plains to the Great Lakes today. A compact shortwave trough over eastern ND/northwest MN early this morning will quickly shift northeast across the international border. Thunderstorms associated with this wave will diminish through the morning hours. South/southwesterly flow will maintain mid 60s to low 70s dewpoints across the mid-MO Valley into the upper MS Valley ahead of a southeastward-advancing cold front. Thunderstorms will likely redevelop along the front during the late afternoon and into the evening/overnight hours as a southwesterly low level jet increases. Moderate to strong instability is expected to develop as temperatures warm into the 80s, but upper forcing will be modest at best as the upper shortwave trough continues to lift northeast into Ontario after 18z. Furthermore, effective shear will likewise remain modest, around 20-25 kt, limiting organized thunderstorm activity. A couple of strong storms could produce gusty winds, but overall severe threat appears too limited to include probabilities. ...TX/LA... Tropical Depression Imelda would continue to drift north and east in the vicinity of east Texas and the Sabine Valley. Heavy rain will continue to be the main concern with this system. Low level shear may be sufficient for occasional, weakly rotating cells across far southeast TX into far southwest LA. However, conditions are expected to remain too marginal for inclusion of tornado probabilities. ..Leitman/Bentley.. 09/18/2019 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1215 AM CDT Wed Sep 18 2019 Valid 181200Z - 191200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... A few strong thunderstorms are possible across parts of the Upper Midwest this afternoon and evening, but the risk for organized severe weather appears low. ...Upper Midwest Vicinity... An amplified upper ridge will stretch from the southern Plains to the Great Lakes today. A compact shortwave trough over eastern ND/northwest MN early this morning will quickly shift northeast across the international border. Thunderstorms associated with this wave will diminish through the morning hours. South/southwesterly flow will maintain mid 60s to low 70s dewpoints across the mid-MO Valley into the upper MS Valley ahead of a southeastward-advancing cold front. Thunderstorms will likely redevelop along the front during the late afternoon and into the evening/overnight hours as a southwesterly low level jet increases. Moderate to strong instability is expected to develop as temperatures warm into the 80s, but upper forcing will be modest at best as the upper shortwave trough continues to lift northeast into Ontario after 18z. Furthermore, effective shear will likewise remain modest, around 20-25 kt, limiting organized thunderstorm activity. A couple of strong storms could produce gusty winds, but overall severe threat appears too limited to include probabilities. ...TX/LA... Tropical Depression Imelda would continue to drift north and east in the vicinity of east Texas and the Sabine Valley. Heavy rain will continue to be the main concern with this system. Low level shear may be sufficient for occasional, weakly rotating cells across far southeast TX into far southwest LA. However, conditions are expected to remain too marginal for inclusion of tornado probabilities. ..Leitman/Bentley.. 09/18/2019 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1215 AM CDT Wed Sep 18 2019 Valid 181200Z - 191200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... A few strong thunderstorms are possible across parts of the Upper Midwest this afternoon and evening, but the risk for organized severe weather appears low. ...Upper Midwest Vicinity... An amplified upper ridge will stretch from the southern Plains to the Great Lakes today. A compact shortwave trough over eastern ND/northwest MN early this morning will quickly shift northeast across the international border. Thunderstorms associated with this wave will diminish through the morning hours. South/southwesterly flow will maintain mid 60s to low 70s dewpoints across the mid-MO Valley into the upper MS Valley ahead of a southeastward-advancing cold front. Thunderstorms will likely redevelop along the front during the late afternoon and into the evening/overnight hours as a southwesterly low level jet increases. Moderate to strong instability is expected to develop as temperatures warm into the 80s, but upper forcing will be modest at best as the upper shortwave trough continues to lift northeast into Ontario after 18z. Furthermore, effective shear will likewise remain modest, around 20-25 kt, limiting organized thunderstorm activity. A couple of strong storms could produce gusty winds, but overall severe threat appears too limited to include probabilities. ...TX/LA... Tropical Depression Imelda would continue to drift north and east in the vicinity of east Texas and the Sabine Valley. Heavy rain will continue to be the main concern with this system. Low level shear may be sufficient for occasional, weakly rotating cells across far southeast TX into far southwest LA. However, conditions are expected to remain too marginal for inclusion of tornado probabilities. ..Leitman/Bentley.. 09/18/2019 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0758 PM CDT Tue Sep 17 2019 Valid 180100Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN HIGH PLAINS THIS EVENING AND ACROSS PARTS OF THE UPPER MIDWEST OVERNIGHT... ...SUMMARY... A severe storm or two remains possible across the northern High Plains for a few more hours this evening, and overnight in parts of the Upper Midwest. ...Northern High Plains... Thunderstorms ongoing across eastern MT into western SD/ND have produced several reports of 50+ mph wind gusts, with two severe gusts measuring 67 and 72 mph across western SD in the past couple of hours. This threat will continue to shift northeast across eastern MT and western ND over the next few hours before storms cross the international border. ...Upper Midwest Vicinity... Thunderstorms have developed across central SD in weak low level convergence along the surface dryline/effective cold front. Convection is expected to continue northeast and increase in coverage toward eastern SD into parts of MN and northwest IA overnight as a low level jet increases and modest forcing associated with the shortwave trough over MT/WY glances the region. Most of this activity will likely be elevated given convection is not expected until after 03z, but modest lapse rates in a favorable shear environment could produce some isolated, marginal severe hail with the strongest cells. There is a small chance that an isolated cell could become nearly surface-based along the immediate frontal boundary from central MN into northwest IA. If this occurs, strong gusts be possible. Furthermore, while very low, a brief tornado cannot be ruled out given higher-quality moisture with eastward extent and backed low level flow enhancing 0-1 km SRH. ...Upper TX Coast to Southwest LA coast... Heavy rain is the main concern with Tropical Depression Imelda overnight. While backed low level flow in a moist and weakly unstable tropical airmass will result in effective SRH approaching 100-150 m2/s2 over the next 6 hours or so, stronger cells from Chambers County TX to Cameron Parish LA have only shown very weak cyclonic shear. Shear will become less favorable after around 06-09z and the threat for any tropical cyclone-related tornadoes appears negligible. ..Leitman.. 09/18/2019 Read more