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SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1129 AM CDT Sat May 18 2024 Valid 181630Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NORTH FLORIDA AND SOUTHERN GEORGIA...AND PARTS OF THE WESTERN GREAT LAKES... ...SUMMARY... The greatest severe-thunderstorm potential today appears to be from the Florida Panhandle eastward to the southern Atlantic Coast, and portions of the western Great Lakes region. ...North FL/South GA... A persistent band of widespread showers and thunderstorms extends from the FL Panhandle into southern GA. This band will sag southward through the day, with occasional intensification along the leading edge as daytime heating destabilizes the upstream environment. Locally gusty/damaging winds appear to be the main threat. ...FL East Coast... Strong heating is occurring along the FL peninsula, where hot/humid conditions will be present this afternoon. Westerly low-level flow will focus a rather strong sea-breeze circulation, with most CAM solutions suggesting scattered thunderstorm development. It is uncertain whether the activity will be along the immediate coastline, or offshore. However, sufficient vertical shear and CAPE profiles indicate a risk of supercells capable of large hail and perhaps a tornado/waterspout or two. ...Western Great Lakes into Central Plains... A surface cold front will extend from western WI into parts of IA/MO/KS by mid-afternoon. Scattered thunderstorms are expected to form along the front from the MN Arrowhead southward into western WI, with more isolated convection from there southward into the Plains states. Forecast soundings in MI/WI/Upper MI show favorable vertical shear profiles for a few supercell structures capable of hail and damaging wind gusts. Therefore have added a SLGT risk area for that scenario. From IA south, relatively weak winds in the lowest 6km and a deep sub-cloud layer suggest outflow dominant storms with a more marginal severe threat. ...CO/Western KS... Model guidance and water vapor imagery show a plume of mid-level moisture spreading into central CO. This should result in a cluster of thunderstorms over the mountains by mid-afternoon, spreading eastward into the Plains this evening. Inverted-v sounding profiles and favorable westerly flow aloft will promote gusty/damaging wind potential in some of this activity. ...MS/AL into the Carolinas... A relatively moist and unstable air mass is in place today across the TN Valley into the Carolinas. Little cap and pockets of daytime heating will lead to scattered afternoon thunderstorms throughout the region - with some potential for locally gusty/damaging wind gusts. Areas of slightly greater focus for concern of strong storms are 1) Ahead of the MCV currently over northern MS, and 2) an axis from northern AL into central NC along the northern edge of slightly stronger winds aloft. ..Hart/Jewell.. 05/18/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1129 AM CDT Sat May 18 2024 Valid 181630Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NORTH FLORIDA AND SOUTHERN GEORGIA...AND PARTS OF THE WESTERN GREAT LAKES... ...SUMMARY... The greatest severe-thunderstorm potential today appears to be from the Florida Panhandle eastward to the southern Atlantic Coast, and portions of the western Great Lakes region. ...North FL/South GA... A persistent band of widespread showers and thunderstorms extends from the FL Panhandle into southern GA. This band will sag southward through the day, with occasional intensification along the leading edge as daytime heating destabilizes the upstream environment. Locally gusty/damaging winds appear to be the main threat. ...FL East Coast... Strong heating is occurring along the FL peninsula, where hot/humid conditions will be present this afternoon. Westerly low-level flow will focus a rather strong sea-breeze circulation, with most CAM solutions suggesting scattered thunderstorm development. It is uncertain whether the activity will be along the immediate coastline, or offshore. However, sufficient vertical shear and CAPE profiles indicate a risk of supercells capable of large hail and perhaps a tornado/waterspout or two. ...Western Great Lakes into Central Plains... A surface cold front will extend from western WI into parts of IA/MO/KS by mid-afternoon. Scattered thunderstorms are expected to form along the front from the MN Arrowhead southward into western WI, with more isolated convection from there southward into the Plains states. Forecast soundings in MI/WI/Upper MI show favorable vertical shear profiles for a few supercell structures capable of hail and damaging wind gusts. Therefore have added a SLGT risk area for that scenario. From IA south, relatively weak winds in the lowest 6km and a deep sub-cloud layer suggest outflow dominant storms with a more marginal severe threat. ...CO/Western KS... Model guidance and water vapor imagery show a plume of mid-level moisture spreading into central CO. This should result in a cluster of thunderstorms over the mountains by mid-afternoon, spreading eastward into the Plains this evening. Inverted-v sounding profiles and favorable westerly flow aloft will promote gusty/damaging wind potential in some of this activity. ...MS/AL into the Carolinas... A relatively moist and unstable air mass is in place today across the TN Valley into the Carolinas. Little cap and pockets of daytime heating will lead to scattered afternoon thunderstorms throughout the region - with some potential for locally gusty/damaging wind gusts. Areas of slightly greater focus for concern of strong storms are 1) Ahead of the MCV currently over northern MS, and 2) an axis from northern AL into central NC along the northern edge of slightly stronger winds aloft. ..Hart/Jewell.. 05/18/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1129 AM CDT Sat May 18 2024 Valid 181630Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NORTH FLORIDA AND SOUTHERN GEORGIA...AND PARTS OF THE WESTERN GREAT LAKES... ...SUMMARY... The greatest severe-thunderstorm potential today appears to be from the Florida Panhandle eastward to the southern Atlantic Coast, and portions of the western Great Lakes region. ...North FL/South GA... A persistent band of widespread showers and thunderstorms extends from the FL Panhandle into southern GA. This band will sag southward through the day, with occasional intensification along the leading edge as daytime heating destabilizes the upstream environment. Locally gusty/damaging winds appear to be the main threat. ...FL East Coast... Strong heating is occurring along the FL peninsula, where hot/humid conditions will be present this afternoon. Westerly low-level flow will focus a rather strong sea-breeze circulation, with most CAM solutions suggesting scattered thunderstorm development. It is uncertain whether the activity will be along the immediate coastline, or offshore. However, sufficient vertical shear and CAPE profiles indicate a risk of supercells capable of large hail and perhaps a tornado/waterspout or two. ...Western Great Lakes into Central Plains... A surface cold front will extend from western WI into parts of IA/MO/KS by mid-afternoon. Scattered thunderstorms are expected to form along the front from the MN Arrowhead southward into western WI, with more isolated convection from there southward into the Plains states. Forecast soundings in MI/WI/Upper MI show favorable vertical shear profiles for a few supercell structures capable of hail and damaging wind gusts. Therefore have added a SLGT risk area for that scenario. From IA south, relatively weak winds in the lowest 6km and a deep sub-cloud layer suggest outflow dominant storms with a more marginal severe threat. ...CO/Western KS... Model guidance and water vapor imagery show a plume of mid-level moisture spreading into central CO. This should result in a cluster of thunderstorms over the mountains by mid-afternoon, spreading eastward into the Plains this evening. Inverted-v sounding profiles and favorable westerly flow aloft will promote gusty/damaging wind potential in some of this activity. ...MS/AL into the Carolinas... A relatively moist and unstable air mass is in place today across the TN Valley into the Carolinas. Little cap and pockets of daytime heating will lead to scattered afternoon thunderstorms throughout the region - with some potential for locally gusty/damaging wind gusts. Areas of slightly greater focus for concern of strong storms are 1) Ahead of the MCV currently over northern MS, and 2) an axis from northern AL into central NC along the northern edge of slightly stronger winds aloft. ..Hart/Jewell.. 05/18/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1129 AM CDT Sat May 18 2024 Valid 181630Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NORTH FLORIDA AND SOUTHERN GEORGIA...AND PARTS OF THE WESTERN GREAT LAKES... ...SUMMARY... The greatest severe-thunderstorm potential today appears to be from the Florida Panhandle eastward to the southern Atlantic Coast, and portions of the western Great Lakes region. ...North FL/South GA... A persistent band of widespread showers and thunderstorms extends from the FL Panhandle into southern GA. This band will sag southward through the day, with occasional intensification along the leading edge as daytime heating destabilizes the upstream environment. Locally gusty/damaging winds appear to be the main threat. ...FL East Coast... Strong heating is occurring along the FL peninsula, where hot/humid conditions will be present this afternoon. Westerly low-level flow will focus a rather strong sea-breeze circulation, with most CAM solutions suggesting scattered thunderstorm development. It is uncertain whether the activity will be along the immediate coastline, or offshore. However, sufficient vertical shear and CAPE profiles indicate a risk of supercells capable of large hail and perhaps a tornado/waterspout or two. ...Western Great Lakes into Central Plains... A surface cold front will extend from western WI into parts of IA/MO/KS by mid-afternoon. Scattered thunderstorms are expected to form along the front from the MN Arrowhead southward into western WI, with more isolated convection from there southward into the Plains states. Forecast soundings in MI/WI/Upper MI show favorable vertical shear profiles for a few supercell structures capable of hail and damaging wind gusts. Therefore have added a SLGT risk area for that scenario. From IA south, relatively weak winds in the lowest 6km and a deep sub-cloud layer suggest outflow dominant storms with a more marginal severe threat. ...CO/Western KS... Model guidance and water vapor imagery show a plume of mid-level moisture spreading into central CO. This should result in a cluster of thunderstorms over the mountains by mid-afternoon, spreading eastward into the Plains this evening. Inverted-v sounding profiles and favorable westerly flow aloft will promote gusty/damaging wind potential in some of this activity. ...MS/AL into the Carolinas... A relatively moist and unstable air mass is in place today across the TN Valley into the Carolinas. Little cap and pockets of daytime heating will lead to scattered afternoon thunderstorms throughout the region - with some potential for locally gusty/damaging wind gusts. Areas of slightly greater focus for concern of strong storms are 1) Ahead of the MCV currently over northern MS, and 2) an axis from northern AL into central NC along the northern edge of slightly stronger winds aloft. ..Hart/Jewell.. 05/18/2024 Read more

MD 0823 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR NORTH FL INTO SOUTH GA AND EXTREME SOUTHEAST AL
Mesoscale Discussion 0823 NWS Storm Prediction Center Norman OK 0909 AM CDT Sat May 18 2024 Areas affected...North FL into south GA and extreme southeast AL Concerning...Severe potential...Watch possible Valid 181409Z - 181615Z Probability of Watch Issuance...40 percent SUMMARY...Some threat for locally damaging wind will spread eastward through the morning. DISCUSSION...Extensive convection is ongoing this morning from the north-central Gulf of Mexico into north FL, southeast AL, and south GA. Downstream of the ongoing convection, rich low-level moisture is supporting MLCAPE of greater than 1500 J/kg within a moderately sheared environment, but generally weak low/midlevel lapse rates (as noted on the 12Z TLH sounding) may tend to limit storm organization and intensity through the morning. There is some potential for one or more small bowing segments to evolve with time, which could pose a threat for locally damaging wind, especially if areas of somewhat stronger diurnal heating can evolve beneath the extensive cirrus plume, and if convection can avoid being undercut by increasingly extensive outflow. ..Dean/Hart.. 05/18/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...CHS...JAX...FFC...TAE... LAT...LON 30178627 31518487 31718375 32098232 32228163 32068102 31638114 30898205 30078320 29658437 29548483 29708611 30178627 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0757 AM CDT Sat May 18 2024 Valid 181300Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF NORTHERN FLORIDA AND THE FLORIDA PANHANDLE TO PORTIONS OF THE SOUTHERN ATLANTIC COAST... ...SUMMARY... The greatest severe-thunderstorm potential today appears to be from the Florida Panhandle eastward to the southern Atlantic Coast, with damaging gusts the main concern. ...Synopsis... Distinct northern- and southern-stream features over nearly opposite parts of the CONUS will continue to exert the greatest influence on severe-thunderstorm potential. In the North, a well-developed, zonal to cyclonic mid/upper-level jet core was evident from the coastal Northwest to the northern Plains. Some amplification in that belt is likely overnight, as a shortwave trough digs southeastward across the Pacific Northwest. Downstream, a compact but strong shortwave trough -- evident in moisture-channel imagery over western ND and southeastern SK -- should move east-northeastward to southern MB and northern MN by 00Z, forming a closed 500-mb low over the Lake Winnipeg vicinity. The attached trough should eject northeastward to northwestern ON by 12Z tomorrow. The associated surface cold front -- drawn at 11Z over eastern MN to near FSD, EAR, GLD and PUB -- should reach Lake Superior, northern WI, central IA, and south-central KS by 00Z, stalling across southwestern KS into eastern CO. By 12Z, the front should reach northern Lower MI, northern to west-central IL, and northern MO, while moving northward as a warm front near the I-70 corridor in KS. Meanwhile, a positively tilted mid/upper-level shortwave trough -- with several associated vorticity maxima -- was evident in moisture-channel imagery from KY across the Mid-South to south-central TX. The main vorticity lobe -- now over the northeastern AR/western TN area -- should shift eastward to middle TN by 00Z, with trough southwestward to TX shelf waters of the Gulf. By 12Z, the trough should extend from the western Carolinas across southern AL. The associated surface low -- analyzed at 11Z near MEM -- should move eastward today and devolve into a weak trough. An outflow-reinforced marine front was analyzed over shelf waters off the middle Texas Coast to just southeast of the Mississippi River mouth to near PNS, then across southern parts of GA and SC. This boundary should drift eastward over the north-central Gulf Coast region and across GA. ...Southeast... Scattered thunderstorms in clusters -- including occasional/embedded supercells -- have been persistent this morning just offshore from the LA/MS/AL coastline to near the western FL Panhandle, reinforcing the marine/outflow boundary on the southern margins of that convection. That, and persistent rainfall north of the boundary across southeastern LA to the AL Gulf Coast, have led to decreasing unconditional severe potential over those areas. Instead, the greatest threat today should be with the eastern/inland extent of the loosely organized Gulf convective plume, which extends along and north of the boundary over the FL Panhandle and southern GA. Damaging wind will be the main concern, with a tornado or two possible, and isolated large hail. This region should continue to exhibit the greatest low-level moisture/instability through the day as the convection undergoes a net eastward shift, with surface dewpoints commonly in the 70s F, areas of cloud-tempered diurnal heating, weak MLCINH and MLCAPE reaching the 2000-2500 J/kg range. Deep shear will favor organized convection, with effective-shear vectors continuing to be commonly in the 40-50-kt range -- albeit aligned with a substantial component parallel to the main swath of convective lift. As such, mode should remain somewhat messy, clustered to linear, with some embedded supercell/bow structures possible. Elsewhere, less-organized convection (mainly due to weaker shear) should occur near the peninsular FL Atlantic Coast, and ahead of the midlevel vorticity lobe and surface low/trough, from the Mid-South across the Tennessee Valley. Isolated damaging gusts and marginally severe hail will be possible. ...Midwest... Thunderstorms should develop from mid/late afternoon into early evening along the cold front -- with coverage diminishing from scattered across the Lake Superior and WI/northeastern IA regions to widely scattered or isolated from southern IA to portions of KS. Damaging gusts will be the main concern, though any sustained, relatively discrete cell may rotate and produce locally large hail as well. Development should occur later over the MO/KS segment than farther north, due to the presence of capping related to an EML. The strongest flow aloft and deep shear should remain behind the surface front, with effective-shear magnitudes generally ranging from around 45-50 kt over the MN Arrowhead to less than 30 kt over southeastern KS. Low/middle-level lapse rates and boundary-layer moisture also should increase with southward extent, but the opposite will be true for deep-layer lift/forcing. A narrow corridor of favorable MLCAPE should develop today ahead of the front, ranging from around 1000 J/kg either side of western Lake Superior to 2000 J/kg over east- central KS. These offsetting factors and the probable quick evolution to quasi-linear mode in northern areas -- combined with a narrow east-west and temporal window for the most vigorous convection before nocturnal stabilization contribute to weakening -- support keeping unconditional probabilities at marginal levels for this update. ...Central High Plains... Widely scattered, high-based, somewhat skeletal thunderstorms are expected to develop over the mountains and foothills of central/ south-central CO this afternoon near the front, and move east-northeastward over the adjoining High Plains from late afternoon into parts of tonight. The main concern will be isolated strong-severe downbursts. Activity will be supported initially by diurnal heating of higher terrain, with marginal but adequate moisture to support convection at those altitudes. While strong gusts are possible in the mountains, the activity should move atop a deep, well-mixed subcloud layer over the downshear central High Plains. That deep boundary layer will be characterized by nearly dry-adiabatic lapse rates, and enough moisture to support 200-500 J/kg MLCAPE. Eastward extent of the threat is uncertain, but in general, should diminish overnight as nocturnal stabilizing of the near-surface profile proceeds. ..Edwards/Goss.. 05/18/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0757 AM CDT Sat May 18 2024 Valid 181300Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF NORTHERN FLORIDA AND THE FLORIDA PANHANDLE TO PORTIONS OF THE SOUTHERN ATLANTIC COAST... ...SUMMARY... The greatest severe-thunderstorm potential today appears to be from the Florida Panhandle eastward to the southern Atlantic Coast, with damaging gusts the main concern. ...Synopsis... Distinct northern- and southern-stream features over nearly opposite parts of the CONUS will continue to exert the greatest influence on severe-thunderstorm potential. In the North, a well-developed, zonal to cyclonic mid/upper-level jet core was evident from the coastal Northwest to the northern Plains. Some amplification in that belt is likely overnight, as a shortwave trough digs southeastward across the Pacific Northwest. Downstream, a compact but strong shortwave trough -- evident in moisture-channel imagery over western ND and southeastern SK -- should move east-northeastward to southern MB and northern MN by 00Z, forming a closed 500-mb low over the Lake Winnipeg vicinity. The attached trough should eject northeastward to northwestern ON by 12Z tomorrow. The associated surface cold front -- drawn at 11Z over eastern MN to near FSD, EAR, GLD and PUB -- should reach Lake Superior, northern WI, central IA, and south-central KS by 00Z, stalling across southwestern KS into eastern CO. By 12Z, the front should reach northern Lower MI, northern to west-central IL, and northern MO, while moving northward as a warm front near the I-70 corridor in KS. Meanwhile, a positively tilted mid/upper-level shortwave trough -- with several associated vorticity maxima -- was evident in moisture-channel imagery from KY across the Mid-South to south-central TX. The main vorticity lobe -- now over the northeastern AR/western TN area -- should shift eastward to middle TN by 00Z, with trough southwestward to TX shelf waters of the Gulf. By 12Z, the trough should extend from the western Carolinas across southern AL. The associated surface low -- analyzed at 11Z near MEM -- should move eastward today and devolve into a weak trough. An outflow-reinforced marine front was analyzed over shelf waters off the middle Texas Coast to just southeast of the Mississippi River mouth to near PNS, then across southern parts of GA and SC. This boundary should drift eastward over the north-central Gulf Coast region and across GA. ...Southeast... Scattered thunderstorms in clusters -- including occasional/embedded supercells -- have been persistent this morning just offshore from the LA/MS/AL coastline to near the western FL Panhandle, reinforcing the marine/outflow boundary on the southern margins of that convection. That, and persistent rainfall north of the boundary across southeastern LA to the AL Gulf Coast, have led to decreasing unconditional severe potential over those areas. Instead, the greatest threat today should be with the eastern/inland extent of the loosely organized Gulf convective plume, which extends along and north of the boundary over the FL Panhandle and southern GA. Damaging wind will be the main concern, with a tornado or two possible, and isolated large hail. This region should continue to exhibit the greatest low-level moisture/instability through the day as the convection undergoes a net eastward shift, with surface dewpoints commonly in the 70s F, areas of cloud-tempered diurnal heating, weak MLCINH and MLCAPE reaching the 2000-2500 J/kg range. Deep shear will favor organized convection, with effective-shear vectors continuing to be commonly in the 40-50-kt range -- albeit aligned with a substantial component parallel to the main swath of convective lift. As such, mode should remain somewhat messy, clustered to linear, with some embedded supercell/bow structures possible. Elsewhere, less-organized convection (mainly due to weaker shear) should occur near the peninsular FL Atlantic Coast, and ahead of the midlevel vorticity lobe and surface low/trough, from the Mid-South across the Tennessee Valley. Isolated damaging gusts and marginally severe hail will be possible. ...Midwest... Thunderstorms should develop from mid/late afternoon into early evening along the cold front -- with coverage diminishing from scattered across the Lake Superior and WI/northeastern IA regions to widely scattered or isolated from southern IA to portions of KS. Damaging gusts will be the main concern, though any sustained, relatively discrete cell may rotate and produce locally large hail as well. Development should occur later over the MO/KS segment than farther north, due to the presence of capping related to an EML. The strongest flow aloft and deep shear should remain behind the surface front, with effective-shear magnitudes generally ranging from around 45-50 kt over the MN Arrowhead to less than 30 kt over southeastern KS. Low/middle-level lapse rates and boundary-layer moisture also should increase with southward extent, but the opposite will be true for deep-layer lift/forcing. A narrow corridor of favorable MLCAPE should develop today ahead of the front, ranging from around 1000 J/kg either side of western Lake Superior to 2000 J/kg over east- central KS. These offsetting factors and the probable quick evolution to quasi-linear mode in northern areas -- combined with a narrow east-west and temporal window for the most vigorous convection before nocturnal stabilization contribute to weakening -- support keeping unconditional probabilities at marginal levels for this update. ...Central High Plains... Widely scattered, high-based, somewhat skeletal thunderstorms are expected to develop over the mountains and foothills of central/ south-central CO this afternoon near the front, and move east-northeastward over the adjoining High Plains from late afternoon into parts of tonight. The main concern will be isolated strong-severe downbursts. Activity will be supported initially by diurnal heating of higher terrain, with marginal but adequate moisture to support convection at those altitudes. While strong gusts are possible in the mountains, the activity should move atop a deep, well-mixed subcloud layer over the downshear central High Plains. That deep boundary layer will be characterized by nearly dry-adiabatic lapse rates, and enough moisture to support 200-500 J/kg MLCAPE. Eastward extent of the threat is uncertain, but in general, should diminish overnight as nocturnal stabilizing of the near-surface profile proceeds. ..Edwards/Goss.. 05/18/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0757 AM CDT Sat May 18 2024 Valid 181300Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF NORTHERN FLORIDA AND THE FLORIDA PANHANDLE TO PORTIONS OF THE SOUTHERN ATLANTIC COAST... ...SUMMARY... The greatest severe-thunderstorm potential today appears to be from the Florida Panhandle eastward to the southern Atlantic Coast, with damaging gusts the main concern. ...Synopsis... Distinct northern- and southern-stream features over nearly opposite parts of the CONUS will continue to exert the greatest influence on severe-thunderstorm potential. In the North, a well-developed, zonal to cyclonic mid/upper-level jet core was evident from the coastal Northwest to the northern Plains. Some amplification in that belt is likely overnight, as a shortwave trough digs southeastward across the Pacific Northwest. Downstream, a compact but strong shortwave trough -- evident in moisture-channel imagery over western ND and southeastern SK -- should move east-northeastward to southern MB and northern MN by 00Z, forming a closed 500-mb low over the Lake Winnipeg vicinity. The attached trough should eject northeastward to northwestern ON by 12Z tomorrow. The associated surface cold front -- drawn at 11Z over eastern MN to near FSD, EAR, GLD and PUB -- should reach Lake Superior, northern WI, central IA, and south-central KS by 00Z, stalling across southwestern KS into eastern CO. By 12Z, the front should reach northern Lower MI, northern to west-central IL, and northern MO, while moving northward as a warm front near the I-70 corridor in KS. Meanwhile, a positively tilted mid/upper-level shortwave trough -- with several associated vorticity maxima -- was evident in moisture-channel imagery from KY across the Mid-South to south-central TX. The main vorticity lobe -- now over the northeastern AR/western TN area -- should shift eastward to middle TN by 00Z, with trough southwestward to TX shelf waters of the Gulf. By 12Z, the trough should extend from the western Carolinas across southern AL. The associated surface low -- analyzed at 11Z near MEM -- should move eastward today and devolve into a weak trough. An outflow-reinforced marine front was analyzed over shelf waters off the middle Texas Coast to just southeast of the Mississippi River mouth to near PNS, then across southern parts of GA and SC. This boundary should drift eastward over the north-central Gulf Coast region and across GA. ...Southeast... Scattered thunderstorms in clusters -- including occasional/embedded supercells -- have been persistent this morning just offshore from the LA/MS/AL coastline to near the western FL Panhandle, reinforcing the marine/outflow boundary on the southern margins of that convection. That, and persistent rainfall north of the boundary across southeastern LA to the AL Gulf Coast, have led to decreasing unconditional severe potential over those areas. Instead, the greatest threat today should be with the eastern/inland extent of the loosely organized Gulf convective plume, which extends along and north of the boundary over the FL Panhandle and southern GA. Damaging wind will be the main concern, with a tornado or two possible, and isolated large hail. This region should continue to exhibit the greatest low-level moisture/instability through the day as the convection undergoes a net eastward shift, with surface dewpoints commonly in the 70s F, areas of cloud-tempered diurnal heating, weak MLCINH and MLCAPE reaching the 2000-2500 J/kg range. Deep shear will favor organized convection, with effective-shear vectors continuing to be commonly in the 40-50-kt range -- albeit aligned with a substantial component parallel to the main swath of convective lift. As such, mode should remain somewhat messy, clustered to linear, with some embedded supercell/bow structures possible. Elsewhere, less-organized convection (mainly due to weaker shear) should occur near the peninsular FL Atlantic Coast, and ahead of the midlevel vorticity lobe and surface low/trough, from the Mid-South across the Tennessee Valley. Isolated damaging gusts and marginally severe hail will be possible. ...Midwest... Thunderstorms should develop from mid/late afternoon into early evening along the cold front -- with coverage diminishing from scattered across the Lake Superior and WI/northeastern IA regions to widely scattered or isolated from southern IA to portions of KS. Damaging gusts will be the main concern, though any sustained, relatively discrete cell may rotate and produce locally large hail as well. Development should occur later over the MO/KS segment than farther north, due to the presence of capping related to an EML. The strongest flow aloft and deep shear should remain behind the surface front, with effective-shear magnitudes generally ranging from around 45-50 kt over the MN Arrowhead to less than 30 kt over southeastern KS. Low/middle-level lapse rates and boundary-layer moisture also should increase with southward extent, but the opposite will be true for deep-layer lift/forcing. A narrow corridor of favorable MLCAPE should develop today ahead of the front, ranging from around 1000 J/kg either side of western Lake Superior to 2000 J/kg over east- central KS. These offsetting factors and the probable quick evolution to quasi-linear mode in northern areas -- combined with a narrow east-west and temporal window for the most vigorous convection before nocturnal stabilization contribute to weakening -- support keeping unconditional probabilities at marginal levels for this update. ...Central High Plains... Widely scattered, high-based, somewhat skeletal thunderstorms are expected to develop over the mountains and foothills of central/ south-central CO this afternoon near the front, and move east-northeastward over the adjoining High Plains from late afternoon into parts of tonight. The main concern will be isolated strong-severe downbursts. Activity will be supported initially by diurnal heating of higher terrain, with marginal but adequate moisture to support convection at those altitudes. While strong gusts are possible in the mountains, the activity should move atop a deep, well-mixed subcloud layer over the downshear central High Plains. That deep boundary layer will be characterized by nearly dry-adiabatic lapse rates, and enough moisture to support 200-500 J/kg MLCAPE. Eastward extent of the threat is uncertain, but in general, should diminish overnight as nocturnal stabilizing of the near-surface profile proceeds. ..Edwards/Goss.. 05/18/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0757 AM CDT Sat May 18 2024 Valid 181300Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF NORTHERN FLORIDA AND THE FLORIDA PANHANDLE TO PORTIONS OF THE SOUTHERN ATLANTIC COAST... ...SUMMARY... The greatest severe-thunderstorm potential today appears to be from the Florida Panhandle eastward to the southern Atlantic Coast, with damaging gusts the main concern. ...Synopsis... Distinct northern- and southern-stream features over nearly opposite parts of the CONUS will continue to exert the greatest influence on severe-thunderstorm potential. In the North, a well-developed, zonal to cyclonic mid/upper-level jet core was evident from the coastal Northwest to the northern Plains. Some amplification in that belt is likely overnight, as a shortwave trough digs southeastward across the Pacific Northwest. Downstream, a compact but strong shortwave trough -- evident in moisture-channel imagery over western ND and southeastern SK -- should move east-northeastward to southern MB and northern MN by 00Z, forming a closed 500-mb low over the Lake Winnipeg vicinity. The attached trough should eject northeastward to northwestern ON by 12Z tomorrow. The associated surface cold front -- drawn at 11Z over eastern MN to near FSD, EAR, GLD and PUB -- should reach Lake Superior, northern WI, central IA, and south-central KS by 00Z, stalling across southwestern KS into eastern CO. By 12Z, the front should reach northern Lower MI, northern to west-central IL, and northern MO, while moving northward as a warm front near the I-70 corridor in KS. Meanwhile, a positively tilted mid/upper-level shortwave trough -- with several associated vorticity maxima -- was evident in moisture-channel imagery from KY across the Mid-South to south-central TX. The main vorticity lobe -- now over the northeastern AR/western TN area -- should shift eastward to middle TN by 00Z, with trough southwestward to TX shelf waters of the Gulf. By 12Z, the trough should extend from the western Carolinas across southern AL. The associated surface low -- analyzed at 11Z near MEM -- should move eastward today and devolve into a weak trough. An outflow-reinforced marine front was analyzed over shelf waters off the middle Texas Coast to just southeast of the Mississippi River mouth to near PNS, then across southern parts of GA and SC. This boundary should drift eastward over the north-central Gulf Coast region and across GA. ...Southeast... Scattered thunderstorms in clusters -- including occasional/embedded supercells -- have been persistent this morning just offshore from the LA/MS/AL coastline to near the western FL Panhandle, reinforcing the marine/outflow boundary on the southern margins of that convection. That, and persistent rainfall north of the boundary across southeastern LA to the AL Gulf Coast, have led to decreasing unconditional severe potential over those areas. Instead, the greatest threat today should be with the eastern/inland extent of the loosely organized Gulf convective plume, which extends along and north of the boundary over the FL Panhandle and southern GA. Damaging wind will be the main concern, with a tornado or two possible, and isolated large hail. This region should continue to exhibit the greatest low-level moisture/instability through the day as the convection undergoes a net eastward shift, with surface dewpoints commonly in the 70s F, areas of cloud-tempered diurnal heating, weak MLCINH and MLCAPE reaching the 2000-2500 J/kg range. Deep shear will favor organized convection, with effective-shear vectors continuing to be commonly in the 40-50-kt range -- albeit aligned with a substantial component parallel to the main swath of convective lift. As such, mode should remain somewhat messy, clustered to linear, with some embedded supercell/bow structures possible. Elsewhere, less-organized convection (mainly due to weaker shear) should occur near the peninsular FL Atlantic Coast, and ahead of the midlevel vorticity lobe and surface low/trough, from the Mid-South across the Tennessee Valley. Isolated damaging gusts and marginally severe hail will be possible. ...Midwest... Thunderstorms should develop from mid/late afternoon into early evening along the cold front -- with coverage diminishing from scattered across the Lake Superior and WI/northeastern IA regions to widely scattered or isolated from southern IA to portions of KS. Damaging gusts will be the main concern, though any sustained, relatively discrete cell may rotate and produce locally large hail as well. Development should occur later over the MO/KS segment than farther north, due to the presence of capping related to an EML. The strongest flow aloft and deep shear should remain behind the surface front, with effective-shear magnitudes generally ranging from around 45-50 kt over the MN Arrowhead to less than 30 kt over southeastern KS. Low/middle-level lapse rates and boundary-layer moisture also should increase with southward extent, but the opposite will be true for deep-layer lift/forcing. A narrow corridor of favorable MLCAPE should develop today ahead of the front, ranging from around 1000 J/kg either side of western Lake Superior to 2000 J/kg over east- central KS. These offsetting factors and the probable quick evolution to quasi-linear mode in northern areas -- combined with a narrow east-west and temporal window for the most vigorous convection before nocturnal stabilization contribute to weakening -- support keeping unconditional probabilities at marginal levels for this update. ...Central High Plains... Widely scattered, high-based, somewhat skeletal thunderstorms are expected to develop over the mountains and foothills of central/ south-central CO this afternoon near the front, and move east-northeastward over the adjoining High Plains from late afternoon into parts of tonight. The main concern will be isolated strong-severe downbursts. Activity will be supported initially by diurnal heating of higher terrain, with marginal but adequate moisture to support convection at those altitudes. While strong gusts are possible in the mountains, the activity should move atop a deep, well-mixed subcloud layer over the downshear central High Plains. That deep boundary layer will be characterized by nearly dry-adiabatic lapse rates, and enough moisture to support 200-500 J/kg MLCAPE. Eastward extent of the threat is uncertain, but in general, should diminish overnight as nocturnal stabilizing of the near-surface profile proceeds. ..Edwards/Goss.. 05/18/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0757 AM CDT Sat May 18 2024 Valid 181300Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF NORTHERN FLORIDA AND THE FLORIDA PANHANDLE TO PORTIONS OF THE SOUTHERN ATLANTIC COAST... ...SUMMARY... The greatest severe-thunderstorm potential today appears to be from the Florida Panhandle eastward to the southern Atlantic Coast, with damaging gusts the main concern. ...Synopsis... Distinct northern- and southern-stream features over nearly opposite parts of the CONUS will continue to exert the greatest influence on severe-thunderstorm potential. In the North, a well-developed, zonal to cyclonic mid/upper-level jet core was evident from the coastal Northwest to the northern Plains. Some amplification in that belt is likely overnight, as a shortwave trough digs southeastward across the Pacific Northwest. Downstream, a compact but strong shortwave trough -- evident in moisture-channel imagery over western ND and southeastern SK -- should move east-northeastward to southern MB and northern MN by 00Z, forming a closed 500-mb low over the Lake Winnipeg vicinity. The attached trough should eject northeastward to northwestern ON by 12Z tomorrow. The associated surface cold front -- drawn at 11Z over eastern MN to near FSD, EAR, GLD and PUB -- should reach Lake Superior, northern WI, central IA, and south-central KS by 00Z, stalling across southwestern KS into eastern CO. By 12Z, the front should reach northern Lower MI, northern to west-central IL, and northern MO, while moving northward as a warm front near the I-70 corridor in KS. Meanwhile, a positively tilted mid/upper-level shortwave trough -- with several associated vorticity maxima -- was evident in moisture-channel imagery from KY across the Mid-South to south-central TX. The main vorticity lobe -- now over the northeastern AR/western TN area -- should shift eastward to middle TN by 00Z, with trough southwestward to TX shelf waters of the Gulf. By 12Z, the trough should extend from the western Carolinas across southern AL. The associated surface low -- analyzed at 11Z near MEM -- should move eastward today and devolve into a weak trough. An outflow-reinforced marine front was analyzed over shelf waters off the middle Texas Coast to just southeast of the Mississippi River mouth to near PNS, then across southern parts of GA and SC. This boundary should drift eastward over the north-central Gulf Coast region and across GA. ...Southeast... Scattered thunderstorms in clusters -- including occasional/embedded supercells -- have been persistent this morning just offshore from the LA/MS/AL coastline to near the western FL Panhandle, reinforcing the marine/outflow boundary on the southern margins of that convection. That, and persistent rainfall north of the boundary across southeastern LA to the AL Gulf Coast, have led to decreasing unconditional severe potential over those areas. Instead, the greatest threat today should be with the eastern/inland extent of the loosely organized Gulf convective plume, which extends along and north of the boundary over the FL Panhandle and southern GA. Damaging wind will be the main concern, with a tornado or two possible, and isolated large hail. This region should continue to exhibit the greatest low-level moisture/instability through the day as the convection undergoes a net eastward shift, with surface dewpoints commonly in the 70s F, areas of cloud-tempered diurnal heating, weak MLCINH and MLCAPE reaching the 2000-2500 J/kg range. Deep shear will favor organized convection, with effective-shear vectors continuing to be commonly in the 40-50-kt range -- albeit aligned with a substantial component parallel to the main swath of convective lift. As such, mode should remain somewhat messy, clustered to linear, with some embedded supercell/bow structures possible. Elsewhere, less-organized convection (mainly due to weaker shear) should occur near the peninsular FL Atlantic Coast, and ahead of the midlevel vorticity lobe and surface low/trough, from the Mid-South across the Tennessee Valley. Isolated damaging gusts and marginally severe hail will be possible. ...Midwest... Thunderstorms should develop from mid/late afternoon into early evening along the cold front -- with coverage diminishing from scattered across the Lake Superior and WI/northeastern IA regions to widely scattered or isolated from southern IA to portions of KS. Damaging gusts will be the main concern, though any sustained, relatively discrete cell may rotate and produce locally large hail as well. Development should occur later over the MO/KS segment than farther north, due to the presence of capping related to an EML. The strongest flow aloft and deep shear should remain behind the surface front, with effective-shear magnitudes generally ranging from around 45-50 kt over the MN Arrowhead to less than 30 kt over southeastern KS. Low/middle-level lapse rates and boundary-layer moisture also should increase with southward extent, but the opposite will be true for deep-layer lift/forcing. A narrow corridor of favorable MLCAPE should develop today ahead of the front, ranging from around 1000 J/kg either side of western Lake Superior to 2000 J/kg over east- central KS. These offsetting factors and the probable quick evolution to quasi-linear mode in northern areas -- combined with a narrow east-west and temporal window for the most vigorous convection before nocturnal stabilization contribute to weakening -- support keeping unconditional probabilities at marginal levels for this update. ...Central High Plains... Widely scattered, high-based, somewhat skeletal thunderstorms are expected to develop over the mountains and foothills of central/ south-central CO this afternoon near the front, and move east-northeastward over the adjoining High Plains from late afternoon into parts of tonight. The main concern will be isolated strong-severe downbursts. Activity will be supported initially by diurnal heating of higher terrain, with marginal but adequate moisture to support convection at those altitudes. While strong gusts are possible in the mountains, the activity should move atop a deep, well-mixed subcloud layer over the downshear central High Plains. That deep boundary layer will be characterized by nearly dry-adiabatic lapse rates, and enough moisture to support 200-500 J/kg MLCAPE. Eastward extent of the threat is uncertain, but in general, should diminish overnight as nocturnal stabilizing of the near-surface profile proceeds. ..Edwards/Goss.. 05/18/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0757 AM CDT Sat May 18 2024 Valid 181300Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF NORTHERN FLORIDA AND THE FLORIDA PANHANDLE TO PORTIONS OF THE SOUTHERN ATLANTIC COAST... ...SUMMARY... The greatest severe-thunderstorm potential today appears to be from the Florida Panhandle eastward to the southern Atlantic Coast, with damaging gusts the main concern. ...Synopsis... Distinct northern- and southern-stream features over nearly opposite parts of the CONUS will continue to exert the greatest influence on severe-thunderstorm potential. In the North, a well-developed, zonal to cyclonic mid/upper-level jet core was evident from the coastal Northwest to the northern Plains. Some amplification in that belt is likely overnight, as a shortwave trough digs southeastward across the Pacific Northwest. Downstream, a compact but strong shortwave trough -- evident in moisture-channel imagery over western ND and southeastern SK -- should move east-northeastward to southern MB and northern MN by 00Z, forming a closed 500-mb low over the Lake Winnipeg vicinity. The attached trough should eject northeastward to northwestern ON by 12Z tomorrow. The associated surface cold front -- drawn at 11Z over eastern MN to near FSD, EAR, GLD and PUB -- should reach Lake Superior, northern WI, central IA, and south-central KS by 00Z, stalling across southwestern KS into eastern CO. By 12Z, the front should reach northern Lower MI, northern to west-central IL, and northern MO, while moving northward as a warm front near the I-70 corridor in KS. Meanwhile, a positively tilted mid/upper-level shortwave trough -- with several associated vorticity maxima -- was evident in moisture-channel imagery from KY across the Mid-South to south-central TX. The main vorticity lobe -- now over the northeastern AR/western TN area -- should shift eastward to middle TN by 00Z, with trough southwestward to TX shelf waters of the Gulf. By 12Z, the trough should extend from the western Carolinas across southern AL. The associated surface low -- analyzed at 11Z near MEM -- should move eastward today and devolve into a weak trough. An outflow-reinforced marine front was analyzed over shelf waters off the middle Texas Coast to just southeast of the Mississippi River mouth to near PNS, then across southern parts of GA and SC. This boundary should drift eastward over the north-central Gulf Coast region and across GA. ...Southeast... Scattered thunderstorms in clusters -- including occasional/embedded supercells -- have been persistent this morning just offshore from the LA/MS/AL coastline to near the western FL Panhandle, reinforcing the marine/outflow boundary on the southern margins of that convection. That, and persistent rainfall north of the boundary across southeastern LA to the AL Gulf Coast, have led to decreasing unconditional severe potential over those areas. Instead, the greatest threat today should be with the eastern/inland extent of the loosely organized Gulf convective plume, which extends along and north of the boundary over the FL Panhandle and southern GA. Damaging wind will be the main concern, with a tornado or two possible, and isolated large hail. This region should continue to exhibit the greatest low-level moisture/instability through the day as the convection undergoes a net eastward shift, with surface dewpoints commonly in the 70s F, areas of cloud-tempered diurnal heating, weak MLCINH and MLCAPE reaching the 2000-2500 J/kg range. Deep shear will favor organized convection, with effective-shear vectors continuing to be commonly in the 40-50-kt range -- albeit aligned with a substantial component parallel to the main swath of convective lift. As such, mode should remain somewhat messy, clustered to linear, with some embedded supercell/bow structures possible. Elsewhere, less-organized convection (mainly due to weaker shear) should occur near the peninsular FL Atlantic Coast, and ahead of the midlevel vorticity lobe and surface low/trough, from the Mid-South across the Tennessee Valley. Isolated damaging gusts and marginally severe hail will be possible. ...Midwest... Thunderstorms should develop from mid/late afternoon into early evening along the cold front -- with coverage diminishing from scattered across the Lake Superior and WI/northeastern IA regions to widely scattered or isolated from southern IA to portions of KS. Damaging gusts will be the main concern, though any sustained, relatively discrete cell may rotate and produce locally large hail as well. Development should occur later over the MO/KS segment than farther north, due to the presence of capping related to an EML. The strongest flow aloft and deep shear should remain behind the surface front, with effective-shear magnitudes generally ranging from around 45-50 kt over the MN Arrowhead to less than 30 kt over southeastern KS. Low/middle-level lapse rates and boundary-layer moisture also should increase with southward extent, but the opposite will be true for deep-layer lift/forcing. A narrow corridor of favorable MLCAPE should develop today ahead of the front, ranging from around 1000 J/kg either side of western Lake Superior to 2000 J/kg over east- central KS. These offsetting factors and the probable quick evolution to quasi-linear mode in northern areas -- combined with a narrow east-west and temporal window for the most vigorous convection before nocturnal stabilization contribute to weakening -- support keeping unconditional probabilities at marginal levels for this update. ...Central High Plains... Widely scattered, high-based, somewhat skeletal thunderstorms are expected to develop over the mountains and foothills of central/ south-central CO this afternoon near the front, and move east-northeastward over the adjoining High Plains from late afternoon into parts of tonight. The main concern will be isolated strong-severe downbursts. Activity will be supported initially by diurnal heating of higher terrain, with marginal but adequate moisture to support convection at those altitudes. While strong gusts are possible in the mountains, the activity should move atop a deep, well-mixed subcloud layer over the downshear central High Plains. That deep boundary layer will be characterized by nearly dry-adiabatic lapse rates, and enough moisture to support 200-500 J/kg MLCAPE. Eastward extent of the threat is uncertain, but in general, should diminish overnight as nocturnal stabilizing of the near-surface profile proceeds. ..Edwards/Goss.. 05/18/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0757 AM CDT Sat May 18 2024 Valid 181300Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF NORTHERN FLORIDA AND THE FLORIDA PANHANDLE TO PORTIONS OF THE SOUTHERN ATLANTIC COAST... ...SUMMARY... The greatest severe-thunderstorm potential today appears to be from the Florida Panhandle eastward to the southern Atlantic Coast, with damaging gusts the main concern. ...Synopsis... Distinct northern- and southern-stream features over nearly opposite parts of the CONUS will continue to exert the greatest influence on severe-thunderstorm potential. In the North, a well-developed, zonal to cyclonic mid/upper-level jet core was evident from the coastal Northwest to the northern Plains. Some amplification in that belt is likely overnight, as a shortwave trough digs southeastward across the Pacific Northwest. Downstream, a compact but strong shortwave trough -- evident in moisture-channel imagery over western ND and southeastern SK -- should move east-northeastward to southern MB and northern MN by 00Z, forming a closed 500-mb low over the Lake Winnipeg vicinity. The attached trough should eject northeastward to northwestern ON by 12Z tomorrow. The associated surface cold front -- drawn at 11Z over eastern MN to near FSD, EAR, GLD and PUB -- should reach Lake Superior, northern WI, central IA, and south-central KS by 00Z, stalling across southwestern KS into eastern CO. By 12Z, the front should reach northern Lower MI, northern to west-central IL, and northern MO, while moving northward as a warm front near the I-70 corridor in KS. Meanwhile, a positively tilted mid/upper-level shortwave trough -- with several associated vorticity maxima -- was evident in moisture-channel imagery from KY across the Mid-South to south-central TX. The main vorticity lobe -- now over the northeastern AR/western TN area -- should shift eastward to middle TN by 00Z, with trough southwestward to TX shelf waters of the Gulf. By 12Z, the trough should extend from the western Carolinas across southern AL. The associated surface low -- analyzed at 11Z near MEM -- should move eastward today and devolve into a weak trough. An outflow-reinforced marine front was analyzed over shelf waters off the middle Texas Coast to just southeast of the Mississippi River mouth to near PNS, then across southern parts of GA and SC. This boundary should drift eastward over the north-central Gulf Coast region and across GA. ...Southeast... Scattered thunderstorms in clusters -- including occasional/embedded supercells -- have been persistent this morning just offshore from the LA/MS/AL coastline to near the western FL Panhandle, reinforcing the marine/outflow boundary on the southern margins of that convection. That, and persistent rainfall north of the boundary across southeastern LA to the AL Gulf Coast, have led to decreasing unconditional severe potential over those areas. Instead, the greatest threat today should be with the eastern/inland extent of the loosely organized Gulf convective plume, which extends along and north of the boundary over the FL Panhandle and southern GA. Damaging wind will be the main concern, with a tornado or two possible, and isolated large hail. This region should continue to exhibit the greatest low-level moisture/instability through the day as the convection undergoes a net eastward shift, with surface dewpoints commonly in the 70s F, areas of cloud-tempered diurnal heating, weak MLCINH and MLCAPE reaching the 2000-2500 J/kg range. Deep shear will favor organized convection, with effective-shear vectors continuing to be commonly in the 40-50-kt range -- albeit aligned with a substantial component parallel to the main swath of convective lift. As such, mode should remain somewhat messy, clustered to linear, with some embedded supercell/bow structures possible. Elsewhere, less-organized convection (mainly due to weaker shear) should occur near the peninsular FL Atlantic Coast, and ahead of the midlevel vorticity lobe and surface low/trough, from the Mid-South across the Tennessee Valley. Isolated damaging gusts and marginally severe hail will be possible. ...Midwest... Thunderstorms should develop from mid/late afternoon into early evening along the cold front -- with coverage diminishing from scattered across the Lake Superior and WI/northeastern IA regions to widely scattered or isolated from southern IA to portions of KS. Damaging gusts will be the main concern, though any sustained, relatively discrete cell may rotate and produce locally large hail as well. Development should occur later over the MO/KS segment than farther north, due to the presence of capping related to an EML. The strongest flow aloft and deep shear should remain behind the surface front, with effective-shear magnitudes generally ranging from around 45-50 kt over the MN Arrowhead to less than 30 kt over southeastern KS. Low/middle-level lapse rates and boundary-layer moisture also should increase with southward extent, but the opposite will be true for deep-layer lift/forcing. A narrow corridor of favorable MLCAPE should develop today ahead of the front, ranging from around 1000 J/kg either side of western Lake Superior to 2000 J/kg over east- central KS. These offsetting factors and the probable quick evolution to quasi-linear mode in northern areas -- combined with a narrow east-west and temporal window for the most vigorous convection before nocturnal stabilization contribute to weakening -- support keeping unconditional probabilities at marginal levels for this update. ...Central High Plains... Widely scattered, high-based, somewhat skeletal thunderstorms are expected to develop over the mountains and foothills of central/ south-central CO this afternoon near the front, and move east-northeastward over the adjoining High Plains from late afternoon into parts of tonight. The main concern will be isolated strong-severe downbursts. Activity will be supported initially by diurnal heating of higher terrain, with marginal but adequate moisture to support convection at those altitudes. While strong gusts are possible in the mountains, the activity should move atop a deep, well-mixed subcloud layer over the downshear central High Plains. That deep boundary layer will be characterized by nearly dry-adiabatic lapse rates, and enough moisture to support 200-500 J/kg MLCAPE. Eastward extent of the threat is uncertain, but in general, should diminish overnight as nocturnal stabilizing of the near-surface profile proceeds. ..Edwards/Goss.. 05/18/2024 Read more

000
ABPZ20 KNHC 181136
TWOEP

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
500 AM PDT Sat May 18 2024

For the eastern North Pacific...east of 140 degrees west longitude:

South of the Coast of Southwestern Mexico:
An elongated area of low pressure located several hundred miles
offshore of the coast of southwestern Mexico continues to produce an
area of showers and thunderstorms. Dry air nearby and marginal
environmental conditions are likely to limit significant
development. This system should remain nearly stationary during the
next day or so, but by the end of the weekend, the low is forecast
to interact or merge with another system to its east.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 7 days...low...10 percent.

South of the Coast of Southern Mexico:
A trough of low pressure continues to produce disorganized showers
and thunderstorms several hundred miles to the south of the coast
of southern Mexico. Development of this system, if any, should be
slow to occur as it moves slowly westward during the next few days.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 7 days...low...20 percent.

$$
Forecaster Kelly

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0358 AM CDT Sat May 18 2024 Valid 211200Z - 261200Z ...DISCUSSION... ...Day 4/Tue -- Southern Plains to the Mid/Upper MS Valley... Medium-range guidance has been fairly consistent the past several cycles in showing a negatively tilted upper shortwave trough ejecting across the central Plains to the upper Great Lakes on Tuesday. As this occurs, a surface cyclone over NE/KS will deepen and track northeast to MN/WI by 06z. As this occurs, a surface cold front will develop east across the region, becoming oriented from near Lake Michigan southwestward to northwest TX by Wednesday morning. Across the warm sector, mid/upper 60s F dewpoints will be widespread, aiding in moderate to strong destabilization during the day. Storms will likely develop by early afternoon near the surface low and cold front across western IA southward into eastern KS. The current expectation is that a linear MCS will evolve over IA/MO and shift east through the evening. While damaging gusts will be the primary hazard, large hail and tornadoes also will be possible. With southward extent into OK and portions of the Ozarks, convective coverage may be less. This area will be further removed from stronger large-scale ascent, and capping may erode less efficiently as a result. Nevertheless, where storms can develop, supercell wind profiles amid a very moist and unstable airmass will support an all-hazards risk. ...Day 5/Wed -- ArkLaTex to the Ohio Valley... Forecast guidance differs quite a bit on Wednesday with regards to the evolving the upper trough/low over the Great Lakes. The surface cold front will likely continue eastward into parts of the Ohio Valley. A moist airmass will be in place, but degree of downstream destabilization ahead of likely ongoing convection Wednesday morning is uncertain. The front will likely stall across the Mid-South into the southern Plains as upper support moves well north of the region. This could focus severe-thunderstorm potential during the afternoon along the stalled boundary. However, capping may be a concern given weak forcing aloft and a generally low-amplitude upper pattern over the region. While some severe potential will exist across this broad region, confidence is too low to include a 15 percent area at this time. ...Days 6-8/Thu-Sat... Most guidance maintains a mean upper trough over the western U.S. late in the period. An upper shortwave trough is forecast to eject eastward across the southern Plains to the Lower MS Valley Day 6/Thu. A very moist and unstable airmass will already be in place as favorable vertical shear and large-scale ascent overspread the region, likely resulting in severe-thunderstorm potential across parts of OK into the ArkLaTex. By Day 7/Fri, spread among forecast guidance increases considerably and predictability is low. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0358 AM CDT Sat May 18 2024 Valid 211200Z - 261200Z ...DISCUSSION... ...Day 4/Tue -- Southern Plains to the Mid/Upper MS Valley... Medium-range guidance has been fairly consistent the past several cycles in showing a negatively tilted upper shortwave trough ejecting across the central Plains to the upper Great Lakes on Tuesday. As this occurs, a surface cyclone over NE/KS will deepen and track northeast to MN/WI by 06z. As this occurs, a surface cold front will develop east across the region, becoming oriented from near Lake Michigan southwestward to northwest TX by Wednesday morning. Across the warm sector, mid/upper 60s F dewpoints will be widespread, aiding in moderate to strong destabilization during the day. Storms will likely develop by early afternoon near the surface low and cold front across western IA southward into eastern KS. The current expectation is that a linear MCS will evolve over IA/MO and shift east through the evening. While damaging gusts will be the primary hazard, large hail and tornadoes also will be possible. With southward extent into OK and portions of the Ozarks, convective coverage may be less. This area will be further removed from stronger large-scale ascent, and capping may erode less efficiently as a result. Nevertheless, where storms can develop, supercell wind profiles amid a very moist and unstable airmass will support an all-hazards risk. ...Day 5/Wed -- ArkLaTex to the Ohio Valley... Forecast guidance differs quite a bit on Wednesday with regards to the evolving the upper trough/low over the Great Lakes. The surface cold front will likely continue eastward into parts of the Ohio Valley. A moist airmass will be in place, but degree of downstream destabilization ahead of likely ongoing convection Wednesday morning is uncertain. The front will likely stall across the Mid-South into the southern Plains as upper support moves well north of the region. This could focus severe-thunderstorm potential during the afternoon along the stalled boundary. However, capping may be a concern given weak forcing aloft and a generally low-amplitude upper pattern over the region. While some severe potential will exist across this broad region, confidence is too low to include a 15 percent area at this time. ...Days 6-8/Thu-Sat... Most guidance maintains a mean upper trough over the western U.S. late in the period. An upper shortwave trough is forecast to eject eastward across the southern Plains to the Lower MS Valley Day 6/Thu. A very moist and unstable airmass will already be in place as favorable vertical shear and large-scale ascent overspread the region, likely resulting in severe-thunderstorm potential across parts of OK into the ArkLaTex. By Day 7/Fri, spread among forecast guidance increases considerably and predictability is low. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0358 AM CDT Sat May 18 2024 Valid 211200Z - 261200Z ...DISCUSSION... ...Day 4/Tue -- Southern Plains to the Mid/Upper MS Valley... Medium-range guidance has been fairly consistent the past several cycles in showing a negatively tilted upper shortwave trough ejecting across the central Plains to the upper Great Lakes on Tuesday. As this occurs, a surface cyclone over NE/KS will deepen and track northeast to MN/WI by 06z. As this occurs, a surface cold front will develop east across the region, becoming oriented from near Lake Michigan southwestward to northwest TX by Wednesday morning. Across the warm sector, mid/upper 60s F dewpoints will be widespread, aiding in moderate to strong destabilization during the day. Storms will likely develop by early afternoon near the surface low and cold front across western IA southward into eastern KS. The current expectation is that a linear MCS will evolve over IA/MO and shift east through the evening. While damaging gusts will be the primary hazard, large hail and tornadoes also will be possible. With southward extent into OK and portions of the Ozarks, convective coverage may be less. This area will be further removed from stronger large-scale ascent, and capping may erode less efficiently as a result. Nevertheless, where storms can develop, supercell wind profiles amid a very moist and unstable airmass will support an all-hazards risk. ...Day 5/Wed -- ArkLaTex to the Ohio Valley... Forecast guidance differs quite a bit on Wednesday with regards to the evolving the upper trough/low over the Great Lakes. The surface cold front will likely continue eastward into parts of the Ohio Valley. A moist airmass will be in place, but degree of downstream destabilization ahead of likely ongoing convection Wednesday morning is uncertain. The front will likely stall across the Mid-South into the southern Plains as upper support moves well north of the region. This could focus severe-thunderstorm potential during the afternoon along the stalled boundary. However, capping may be a concern given weak forcing aloft and a generally low-amplitude upper pattern over the region. While some severe potential will exist across this broad region, confidence is too low to include a 15 percent area at this time. ...Days 6-8/Thu-Sat... Most guidance maintains a mean upper trough over the western U.S. late in the period. An upper shortwave trough is forecast to eject eastward across the southern Plains to the Lower MS Valley Day 6/Thu. A very moist and unstable airmass will already be in place as favorable vertical shear and large-scale ascent overspread the region, likely resulting in severe-thunderstorm potential across parts of OK into the ArkLaTex. By Day 7/Fri, spread among forecast guidance increases considerably and predictability is low. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0358 AM CDT Sat May 18 2024 Valid 211200Z - 261200Z ...DISCUSSION... ...Day 4/Tue -- Southern Plains to the Mid/Upper MS Valley... Medium-range guidance has been fairly consistent the past several cycles in showing a negatively tilted upper shortwave trough ejecting across the central Plains to the upper Great Lakes on Tuesday. As this occurs, a surface cyclone over NE/KS will deepen and track northeast to MN/WI by 06z. As this occurs, a surface cold front will develop east across the region, becoming oriented from near Lake Michigan southwestward to northwest TX by Wednesday morning. Across the warm sector, mid/upper 60s F dewpoints will be widespread, aiding in moderate to strong destabilization during the day. Storms will likely develop by early afternoon near the surface low and cold front across western IA southward into eastern KS. The current expectation is that a linear MCS will evolve over IA/MO and shift east through the evening. While damaging gusts will be the primary hazard, large hail and tornadoes also will be possible. With southward extent into OK and portions of the Ozarks, convective coverage may be less. This area will be further removed from stronger large-scale ascent, and capping may erode less efficiently as a result. Nevertheless, where storms can develop, supercell wind profiles amid a very moist and unstable airmass will support an all-hazards risk. ...Day 5/Wed -- ArkLaTex to the Ohio Valley... Forecast guidance differs quite a bit on Wednesday with regards to the evolving the upper trough/low over the Great Lakes. The surface cold front will likely continue eastward into parts of the Ohio Valley. A moist airmass will be in place, but degree of downstream destabilization ahead of likely ongoing convection Wednesday morning is uncertain. The front will likely stall across the Mid-South into the southern Plains as upper support moves well north of the region. This could focus severe-thunderstorm potential during the afternoon along the stalled boundary. However, capping may be a concern given weak forcing aloft and a generally low-amplitude upper pattern over the region. While some severe potential will exist across this broad region, confidence is too low to include a 15 percent area at this time. ...Days 6-8/Thu-Sat... Most guidance maintains a mean upper trough over the western U.S. late in the period. An upper shortwave trough is forecast to eject eastward across the southern Plains to the Lower MS Valley Day 6/Thu. A very moist and unstable airmass will already be in place as favorable vertical shear and large-scale ascent overspread the region, likely resulting in severe-thunderstorm potential across parts of OK into the ArkLaTex. By Day 7/Fri, spread among forecast guidance increases considerably and predictability is low. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0358 AM CDT Sat May 18 2024 Valid 211200Z - 261200Z ...DISCUSSION... ...Day 4/Tue -- Southern Plains to the Mid/Upper MS Valley... Medium-range guidance has been fairly consistent the past several cycles in showing a negatively tilted upper shortwave trough ejecting across the central Plains to the upper Great Lakes on Tuesday. As this occurs, a surface cyclone over NE/KS will deepen and track northeast to MN/WI by 06z. As this occurs, a surface cold front will develop east across the region, becoming oriented from near Lake Michigan southwestward to northwest TX by Wednesday morning. Across the warm sector, mid/upper 60s F dewpoints will be widespread, aiding in moderate to strong destabilization during the day. Storms will likely develop by early afternoon near the surface low and cold front across western IA southward into eastern KS. The current expectation is that a linear MCS will evolve over IA/MO and shift east through the evening. While damaging gusts will be the primary hazard, large hail and tornadoes also will be possible. With southward extent into OK and portions of the Ozarks, convective coverage may be less. This area will be further removed from stronger large-scale ascent, and capping may erode less efficiently as a result. Nevertheless, where storms can develop, supercell wind profiles amid a very moist and unstable airmass will support an all-hazards risk. ...Day 5/Wed -- ArkLaTex to the Ohio Valley... Forecast guidance differs quite a bit on Wednesday with regards to the evolving the upper trough/low over the Great Lakes. The surface cold front will likely continue eastward into parts of the Ohio Valley. A moist airmass will be in place, but degree of downstream destabilization ahead of likely ongoing convection Wednesday morning is uncertain. The front will likely stall across the Mid-South into the southern Plains as upper support moves well north of the region. This could focus severe-thunderstorm potential during the afternoon along the stalled boundary. However, capping may be a concern given weak forcing aloft and a generally low-amplitude upper pattern over the region. While some severe potential will exist across this broad region, confidence is too low to include a 15 percent area at this time. ...Days 6-8/Thu-Sat... Most guidance maintains a mean upper trough over the western U.S. late in the period. An upper shortwave trough is forecast to eject eastward across the southern Plains to the Lower MS Valley Day 6/Thu. A very moist and unstable airmass will already be in place as favorable vertical shear and large-scale ascent overspread the region, likely resulting in severe-thunderstorm potential across parts of OK into the ArkLaTex. By Day 7/Fri, spread among forecast guidance increases considerably and predictability is low. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0227 AM CDT Sat May 18 2024 Valid 201200Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF NEBRASKA...KANSAS...SOUTHWEST IOWA AND NORTHWEST MISSOURI... ...SUMMARY... Severe thunderstorms are possible across parts of Nebraska and Kansas into western Iowa and northwest Missouri Monday afternoon into Monday night. More isolated strong to severe storms may extend into parts of the Middle Mississippi Valley and southern Wisconsin. ...Synopsis... An upper shortwave trough is expected to be located over the Lower MO Valley early Monday. This trough will lift northeast across the upper Great Lakes through Monday night. Meanwhile, a broad area of southwesterly flow will continued across the southern/central Plains east of a deepening upper trough over the western U.S. Deep-layer flow will become more amplified and stronger across the central Plains after 00z, as the western trough ejects east toward the High Plains by early Tuesday. At the surface, a cold front will be located from the eastern Dakotas into central NE. This front will continue to shift east through the evening before stalling from southern MN into eastern NE and central KS. Southerly low-level flow ahead of the front will result in a broad area of low to mid 60s F dew points from the Mid/Upper MS Valley into the central/southern Plains. ...KS/NE into southwest IA/northwest MO... Large-scale ascent will be nebulous through the afternoon, and capping will likely suppress convection through at least mid-afternoon. Thereafter, vertical shear will increase along with stronger ascent spreading into the Plains during the evening/overnight as the western trough ejects east. Thunderstorm clusters may initiate by early evening, with the potential for MCS development during the nighttime hours. Convective initiation and evolution is a bit uncertain given several rounds of convection expected for portions of the region prior to Monday evening. However, the overall large-scale pattern supports severe convection capable of all hazards into early Tuesday morning. ...Lower MO Valley to WI... Convection may be ongoing Monday morning from the MO River into central IA, northward into northern WI. How this convection evolves is a bit uncertain. However, some severe potential appears possible into the afternoon, as at least modest destabilization occurs amid somewhat favorable vertical shear. Hail and strong gusts will be possible with this activity through Monday evening. ..Leitman.. 05/18/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0227 AM CDT Sat May 18 2024 Valid 201200Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF NEBRASKA...KANSAS...SOUTHWEST IOWA AND NORTHWEST MISSOURI... ...SUMMARY... Severe thunderstorms are possible across parts of Nebraska and Kansas into western Iowa and northwest Missouri Monday afternoon into Monday night. More isolated strong to severe storms may extend into parts of the Middle Mississippi Valley and southern Wisconsin. ...Synopsis... An upper shortwave trough is expected to be located over the Lower MO Valley early Monday. This trough will lift northeast across the upper Great Lakes through Monday night. Meanwhile, a broad area of southwesterly flow will continued across the southern/central Plains east of a deepening upper trough over the western U.S. Deep-layer flow will become more amplified and stronger across the central Plains after 00z, as the western trough ejects east toward the High Plains by early Tuesday. At the surface, a cold front will be located from the eastern Dakotas into central NE. This front will continue to shift east through the evening before stalling from southern MN into eastern NE and central KS. Southerly low-level flow ahead of the front will result in a broad area of low to mid 60s F dew points from the Mid/Upper MS Valley into the central/southern Plains. ...KS/NE into southwest IA/northwest MO... Large-scale ascent will be nebulous through the afternoon, and capping will likely suppress convection through at least mid-afternoon. Thereafter, vertical shear will increase along with stronger ascent spreading into the Plains during the evening/overnight as the western trough ejects east. Thunderstorm clusters may initiate by early evening, with the potential for MCS development during the nighttime hours. Convective initiation and evolution is a bit uncertain given several rounds of convection expected for portions of the region prior to Monday evening. However, the overall large-scale pattern supports severe convection capable of all hazards into early Tuesday morning. ...Lower MO Valley to WI... Convection may be ongoing Monday morning from the MO River into central IA, northward into northern WI. How this convection evolves is a bit uncertain. However, some severe potential appears possible into the afternoon, as at least modest destabilization occurs amid somewhat favorable vertical shear. Hail and strong gusts will be possible with this activity through Monday evening. ..Leitman.. 05/18/2024 Read more