Severe Storms

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1055 AM CST Wed Dec 06 2023 Valid 061700Z - 071200Z ...NO CRITICAL AREAS... No changes. See previous discussion below. ..Bentley.. 12/06/2023 .PREV DISCUSSION... /ISSUED 1224 AM CST Wed Dec 06 2023/ ...Synopsis... An upper-level high will continue to shift eastward across the central US as troughing develops across the west coast on Wednesday. Surface pressure gradients will increase between a surface high across the southeast and a surface low across the Rockies, with southwesterly breezes possible across portions of the High Plains. Pockets of locally elevated fire weather are possible in the southern High Plains and perhaps parts of southeast Wyoming should sufficiently dry fine fuels exist. ...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 1055 AM CST Wed Dec 06 2023 Valid 061700Z - 071200Z ...NO CRITICAL AREAS... No changes. See previous discussion below. ..Bentley.. 12/06/2023 .PREV DISCUSSION... /ISSUED 1224 AM CST Wed Dec 06 2023/ ...Synopsis... An upper-level high will continue to shift eastward across the central US as troughing develops across the west coast on Wednesday. Surface pressure gradients will increase between a surface high across the southeast and a surface low across the Rockies, with southwesterly breezes possible across portions of the High Plains. Pockets of locally elevated fire weather are possible in the southern High Plains and perhaps parts of southeast Wyoming should sufficiently dry fine fuels exist. ...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 1055 AM CST Wed Dec 06 2023 Valid 061700Z - 071200Z ...NO CRITICAL AREAS... No changes. See previous discussion below. ..Bentley.. 12/06/2023 .PREV DISCUSSION... /ISSUED 1224 AM CST Wed Dec 06 2023/ ...Synopsis... An upper-level high will continue to shift eastward across the central US as troughing develops across the west coast on Wednesday. Surface pressure gradients will increase between a surface high across the southeast and a surface low across the Rockies, with southwesterly breezes possible across portions of the High Plains. Pockets of locally elevated fire weather are possible in the southern High Plains and perhaps parts of southeast Wyoming should sufficiently dry fine fuels exist. ...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 1055 AM CST Wed Dec 06 2023 Valid 061700Z - 071200Z ...NO CRITICAL AREAS... No changes. See previous discussion below. ..Bentley.. 12/06/2023 .PREV DISCUSSION... /ISSUED 1224 AM CST Wed Dec 06 2023/ ...Synopsis... An upper-level high will continue to shift eastward across the central US as troughing develops across the west coast on Wednesday. Surface pressure gradients will increase between a surface high across the southeast and a surface low across the Rockies, with southwesterly breezes possible across portions of the High Plains. Pockets of locally elevated fire weather are possible in the southern High Plains and perhaps parts of southeast Wyoming should sufficiently dry fine fuels exist. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1027 AM CST Wed Dec 06 2023 Valid 061630Z - 071200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are unlikely through tonight. ...Western OR and northern CA... A strong upper trough is approaching the coast of northern CA and southwest OR, with the associated surface cold front moving ashore in the next couple of hours. Strong onshore flow, lift in vicinity of the front, and cold temperatures aloft may result in isolated lightning flashes this afternoon along the coastal ranges and interior mountains of northern CA/western OR. Present indications are that this activity will be quite sparse. ...ID/MT... Later tonight, the aforementioned shortwave trough will track inland and affect portions of ID/MT. Steep mid-level lapse rates and continued strong large scale lift will result in convective showers over the mountains of central ID into western MT. Profiles will be quite cold, but pockets of weak instability may be sufficient for a few lightning flashes - mainly after midnight. ..Hart/Lyons.. 12/06/2023 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1027 AM CST Wed Dec 06 2023 Valid 061630Z - 071200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are unlikely through tonight. ...Western OR and northern CA... A strong upper trough is approaching the coast of northern CA and southwest OR, with the associated surface cold front moving ashore in the next couple of hours. Strong onshore flow, lift in vicinity of the front, and cold temperatures aloft may result in isolated lightning flashes this afternoon along the coastal ranges and interior mountains of northern CA/western OR. Present indications are that this activity will be quite sparse. ...ID/MT... Later tonight, the aforementioned shortwave trough will track inland and affect portions of ID/MT. Steep mid-level lapse rates and continued strong large scale lift will result in convective showers over the mountains of central ID into western MT. Profiles will be quite cold, but pockets of weak instability may be sufficient for a few lightning flashes - mainly after midnight. ..Hart/Lyons.. 12/06/2023 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1027 AM CST Wed Dec 06 2023 Valid 061630Z - 071200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are unlikely through tonight. ...Western OR and northern CA... A strong upper trough is approaching the coast of northern CA and southwest OR, with the associated surface cold front moving ashore in the next couple of hours. Strong onshore flow, lift in vicinity of the front, and cold temperatures aloft may result in isolated lightning flashes this afternoon along the coastal ranges and interior mountains of northern CA/western OR. Present indications are that this activity will be quite sparse. ...ID/MT... Later tonight, the aforementioned shortwave trough will track inland and affect portions of ID/MT. Steep mid-level lapse rates and continued strong large scale lift will result in convective showers over the mountains of central ID into western MT. Profiles will be quite cold, but pockets of weak instability may be sufficient for a few lightning flashes - mainly after midnight. ..Hart/Lyons.. 12/06/2023 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1027 AM CST Wed Dec 06 2023 Valid 061630Z - 071200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are unlikely through tonight. ...Western OR and northern CA... A strong upper trough is approaching the coast of northern CA and southwest OR, with the associated surface cold front moving ashore in the next couple of hours. Strong onshore flow, lift in vicinity of the front, and cold temperatures aloft may result in isolated lightning flashes this afternoon along the coastal ranges and interior mountains of northern CA/western OR. Present indications are that this activity will be quite sparse. ...ID/MT... Later tonight, the aforementioned shortwave trough will track inland and affect portions of ID/MT. Steep mid-level lapse rates and continued strong large scale lift will result in convective showers over the mountains of central ID into western MT. Profiles will be quite cold, but pockets of weak instability may be sufficient for a few lightning flashes - mainly after midnight. ..Hart/Lyons.. 12/06/2023 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1027 AM CST Wed Dec 06 2023 Valid 061630Z - 071200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are unlikely through tonight. ...Western OR and northern CA... A strong upper trough is approaching the coast of northern CA and southwest OR, with the associated surface cold front moving ashore in the next couple of hours. Strong onshore flow, lift in vicinity of the front, and cold temperatures aloft may result in isolated lightning flashes this afternoon along the coastal ranges and interior mountains of northern CA/western OR. Present indications are that this activity will be quite sparse. ...ID/MT... Later tonight, the aforementioned shortwave trough will track inland and affect portions of ID/MT. Steep mid-level lapse rates and continued strong large scale lift will result in convective showers over the mountains of central ID into western MT. Profiles will be quite cold, but pockets of weak instability may be sufficient for a few lightning flashes - mainly after midnight. ..Hart/Lyons.. 12/06/2023 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0614 AM CST Wed Dec 06 2023 Valid 061300Z - 071200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are unlikely through tonight. ...Synopsis... In mid/upper levels, a progressive and highly amplified synoptic pattern will continue through the period. A substantial trough -- now just inland from and nearly parallel to the U.S. Atlantic Coast -- will move seaward before 00Z. Cold frontal passages related to this system will render the airmass over and east of the Intermountain West too stable and/or dry for thunderstorms. Meanwhile, upstream ridging will shift eastward from the Rockies across the Great Plains. This will occur as a Pacific synoptic trough -- along with a series of accompanying shortwaves and vorticity maxima -- shift inland across the Pacific Coast States from central CA northward. The leading -- and currently strongest -- of the shortwave troughs was apparent in moisture-channel imagery near 135W between about 33N-45N, preceded (as common for such troughs) by a baroclinic-leaf formation on satellite imagery. An associated band of frontogenetic forcing accompanied by a precip band should reach the coastline today. As that occurs -- and especially afterward in cooling air aloft (-20 to -30 deg C) and steepening low/middle-level lapse rates accompanying the strongest DCVA -- some of the convection may extend into icing layers suitable for lightning production. Isolated thunderstorm potential appears most probable over portions of northern CA and western OR, as well as overnight in the Bitterroots vicinity with columnar cooling/moistening. In each area, around 50-100 J/kg MUCAPE will support the convection. ..Edwards/Kerr.. 12/06/2023 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0614 AM CST Wed Dec 06 2023 Valid 061300Z - 071200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are unlikely through tonight. ...Synopsis... In mid/upper levels, a progressive and highly amplified synoptic pattern will continue through the period. A substantial trough -- now just inland from and nearly parallel to the U.S. Atlantic Coast -- will move seaward before 00Z. Cold frontal passages related to this system will render the airmass over and east of the Intermountain West too stable and/or dry for thunderstorms. Meanwhile, upstream ridging will shift eastward from the Rockies across the Great Plains. This will occur as a Pacific synoptic trough -- along with a series of accompanying shortwaves and vorticity maxima -- shift inland across the Pacific Coast States from central CA northward. The leading -- and currently strongest -- of the shortwave troughs was apparent in moisture-channel imagery near 135W between about 33N-45N, preceded (as common for such troughs) by a baroclinic-leaf formation on satellite imagery. An associated band of frontogenetic forcing accompanied by a precip band should reach the coastline today. As that occurs -- and especially afterward in cooling air aloft (-20 to -30 deg C) and steepening low/middle-level lapse rates accompanying the strongest DCVA -- some of the convection may extend into icing layers suitable for lightning production. Isolated thunderstorm potential appears most probable over portions of northern CA and western OR, as well as overnight in the Bitterroots vicinity with columnar cooling/moistening. In each area, around 50-100 J/kg MUCAPE will support the convection. ..Edwards/Kerr.. 12/06/2023 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0614 AM CST Wed Dec 06 2023 Valid 061300Z - 071200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are unlikely through tonight. ...Synopsis... In mid/upper levels, a progressive and highly amplified synoptic pattern will continue through the period. A substantial trough -- now just inland from and nearly parallel to the U.S. Atlantic Coast -- will move seaward before 00Z. Cold frontal passages related to this system will render the airmass over and east of the Intermountain West too stable and/or dry for thunderstorms. Meanwhile, upstream ridging will shift eastward from the Rockies across the Great Plains. This will occur as a Pacific synoptic trough -- along with a series of accompanying shortwaves and vorticity maxima -- shift inland across the Pacific Coast States from central CA northward. The leading -- and currently strongest -- of the shortwave troughs was apparent in moisture-channel imagery near 135W between about 33N-45N, preceded (as common for such troughs) by a baroclinic-leaf formation on satellite imagery. An associated band of frontogenetic forcing accompanied by a precip band should reach the coastline today. As that occurs -- and especially afterward in cooling air aloft (-20 to -30 deg C) and steepening low/middle-level lapse rates accompanying the strongest DCVA -- some of the convection may extend into icing layers suitable for lightning production. Isolated thunderstorm potential appears most probable over portions of northern CA and western OR, as well as overnight in the Bitterroots vicinity with columnar cooling/moistening. In each area, around 50-100 J/kg MUCAPE will support the convection. ..Edwards/Kerr.. 12/06/2023 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0614 AM CST Wed Dec 06 2023 Valid 061300Z - 071200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are unlikely through tonight. ...Synopsis... In mid/upper levels, a progressive and highly amplified synoptic pattern will continue through the period. A substantial trough -- now just inland from and nearly parallel to the U.S. Atlantic Coast -- will move seaward before 00Z. Cold frontal passages related to this system will render the airmass over and east of the Intermountain West too stable and/or dry for thunderstorms. Meanwhile, upstream ridging will shift eastward from the Rockies across the Great Plains. This will occur as a Pacific synoptic trough -- along with a series of accompanying shortwaves and vorticity maxima -- shift inland across the Pacific Coast States from central CA northward. The leading -- and currently strongest -- of the shortwave troughs was apparent in moisture-channel imagery near 135W between about 33N-45N, preceded (as common for such troughs) by a baroclinic-leaf formation on satellite imagery. An associated band of frontogenetic forcing accompanied by a precip band should reach the coastline today. As that occurs -- and especially afterward in cooling air aloft (-20 to -30 deg C) and steepening low/middle-level lapse rates accompanying the strongest DCVA -- some of the convection may extend into icing layers suitable for lightning production. Isolated thunderstorm potential appears most probable over portions of northern CA and western OR, as well as overnight in the Bitterroots vicinity with columnar cooling/moistening. In each area, around 50-100 J/kg MUCAPE will support the convection. ..Edwards/Kerr.. 12/06/2023 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0614 AM CST Wed Dec 06 2023 Valid 061300Z - 071200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are unlikely through tonight. ...Synopsis... In mid/upper levels, a progressive and highly amplified synoptic pattern will continue through the period. A substantial trough -- now just inland from and nearly parallel to the U.S. Atlantic Coast -- will move seaward before 00Z. Cold frontal passages related to this system will render the airmass over and east of the Intermountain West too stable and/or dry for thunderstorms. Meanwhile, upstream ridging will shift eastward from the Rockies across the Great Plains. This will occur as a Pacific synoptic trough -- along with a series of accompanying shortwaves and vorticity maxima -- shift inland across the Pacific Coast States from central CA northward. The leading -- and currently strongest -- of the shortwave troughs was apparent in moisture-channel imagery near 135W between about 33N-45N, preceded (as common for such troughs) by a baroclinic-leaf formation on satellite imagery. An associated band of frontogenetic forcing accompanied by a precip band should reach the coastline today. As that occurs -- and especially afterward in cooling air aloft (-20 to -30 deg C) and steepening low/middle-level lapse rates accompanying the strongest DCVA -- some of the convection may extend into icing layers suitable for lightning production. Isolated thunderstorm potential appears most probable over portions of northern CA and western OR, as well as overnight in the Bitterroots vicinity with columnar cooling/moistening. In each area, around 50-100 J/kg MUCAPE will support the convection. ..Edwards/Kerr.. 12/06/2023 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0344 AM CST Wed Dec 06 2023 Valid 091200Z - 141200Z ...DISCUSSION... ...East TX to the Lower OH Valley and Deep South... A moderately unstable air mass should become established during the day on D4/Sat from southeast TX to the Ark-La-Tex and Ark-La-Miss ahead of a cold front pushing southeastward. With increasing mid-level height falls across the warm sector downstream of a highly amplified/positive-tilt upper trough over the central states, thunderstorm development will become widespread both along and ahead of the front by afternoon. Stronger low-level flow will be coincident with correspondingly weaker instability in the northeast portion of the warm sector. Low-level southwesterlies will be more moderate and subsiding with southwest extent where instability should be larger. As such, below-average confidence exists regarding the distribution of severe hazards, but signal remains sufficient to maintain a highlighted 15 percent area embedded within a broad low severe probability. Primary change with this outlook is to expand the areal delineation farther northeast in the Mid-South. ...Southeast to Mid-Atlantic States... Guidance has trended towards increased agreement with a highly amplified upper trough centered across much of the MS Valley at 12Z Sun to rapidly progress towards the Northeast and Mid-Atlantic during the D5 period. This will result in a deepening surface cyclone tracking roughly from the OH Valley to the St. Lawrence Valley. This type of evolution should result in very strong to extreme southerly low-level winds largely paralleling the meridional orientation of the surface cold front sweeping east. Unlike on D4 where the 00Z deterministic ECMWF and its ensemble probabilities had less instability forecast with northern extent than the 00Z deterministic GFS and its GEFS probabilities, the opposite is progged for D5. Still, a thermodynamically limited warm sector is likely given weak mid-level lapse rates and meager buoyancy at most. But with conditional potential for this to overlap the strengthening low-level southerlies, low severe probabilities remain apparent over at least the central/eastern Carolinas to the Delmarva. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0344 AM CST Wed Dec 06 2023 Valid 091200Z - 141200Z ...DISCUSSION... ...East TX to the Lower OH Valley and Deep South... A moderately unstable air mass should become established during the day on D4/Sat from southeast TX to the Ark-La-Tex and Ark-La-Miss ahead of a cold front pushing southeastward. With increasing mid-level height falls across the warm sector downstream of a highly amplified/positive-tilt upper trough over the central states, thunderstorm development will become widespread both along and ahead of the front by afternoon. Stronger low-level flow will be coincident with correspondingly weaker instability in the northeast portion of the warm sector. Low-level southwesterlies will be more moderate and subsiding with southwest extent where instability should be larger. As such, below-average confidence exists regarding the distribution of severe hazards, but signal remains sufficient to maintain a highlighted 15 percent area embedded within a broad low severe probability. Primary change with this outlook is to expand the areal delineation farther northeast in the Mid-South. ...Southeast to Mid-Atlantic States... Guidance has trended towards increased agreement with a highly amplified upper trough centered across much of the MS Valley at 12Z Sun to rapidly progress towards the Northeast and Mid-Atlantic during the D5 period. This will result in a deepening surface cyclone tracking roughly from the OH Valley to the St. Lawrence Valley. This type of evolution should result in very strong to extreme southerly low-level winds largely paralleling the meridional orientation of the surface cold front sweeping east. Unlike on D4 where the 00Z deterministic ECMWF and its ensemble probabilities had less instability forecast with northern extent than the 00Z deterministic GFS and its GEFS probabilities, the opposite is progged for D5. Still, a thermodynamically limited warm sector is likely given weak mid-level lapse rates and meager buoyancy at most. But with conditional potential for this to overlap the strengthening low-level southerlies, low severe probabilities remain apparent over at least the central/eastern Carolinas to the Delmarva. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0344 AM CST Wed Dec 06 2023 Valid 091200Z - 141200Z ...DISCUSSION... ...East TX to the Lower OH Valley and Deep South... A moderately unstable air mass should become established during the day on D4/Sat from southeast TX to the Ark-La-Tex and Ark-La-Miss ahead of a cold front pushing southeastward. With increasing mid-level height falls across the warm sector downstream of a highly amplified/positive-tilt upper trough over the central states, thunderstorm development will become widespread both along and ahead of the front by afternoon. Stronger low-level flow will be coincident with correspondingly weaker instability in the northeast portion of the warm sector. Low-level southwesterlies will be more moderate and subsiding with southwest extent where instability should be larger. As such, below-average confidence exists regarding the distribution of severe hazards, but signal remains sufficient to maintain a highlighted 15 percent area embedded within a broad low severe probability. Primary change with this outlook is to expand the areal delineation farther northeast in the Mid-South. ...Southeast to Mid-Atlantic States... Guidance has trended towards increased agreement with a highly amplified upper trough centered across much of the MS Valley at 12Z Sun to rapidly progress towards the Northeast and Mid-Atlantic during the D5 period. This will result in a deepening surface cyclone tracking roughly from the OH Valley to the St. Lawrence Valley. This type of evolution should result in very strong to extreme southerly low-level winds largely paralleling the meridional orientation of the surface cold front sweeping east. Unlike on D4 where the 00Z deterministic ECMWF and its ensemble probabilities had less instability forecast with northern extent than the 00Z deterministic GFS and its GEFS probabilities, the opposite is progged for D5. Still, a thermodynamically limited warm sector is likely given weak mid-level lapse rates and meager buoyancy at most. But with conditional potential for this to overlap the strengthening low-level southerlies, low severe probabilities remain apparent over at least the central/eastern Carolinas to the Delmarva. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0344 AM CST Wed Dec 06 2023 Valid 091200Z - 141200Z ...DISCUSSION... ...East TX to the Lower OH Valley and Deep South... A moderately unstable air mass should become established during the day on D4/Sat from southeast TX to the Ark-La-Tex and Ark-La-Miss ahead of a cold front pushing southeastward. With increasing mid-level height falls across the warm sector downstream of a highly amplified/positive-tilt upper trough over the central states, thunderstorm development will become widespread both along and ahead of the front by afternoon. Stronger low-level flow will be coincident with correspondingly weaker instability in the northeast portion of the warm sector. Low-level southwesterlies will be more moderate and subsiding with southwest extent where instability should be larger. As such, below-average confidence exists regarding the distribution of severe hazards, but signal remains sufficient to maintain a highlighted 15 percent area embedded within a broad low severe probability. Primary change with this outlook is to expand the areal delineation farther northeast in the Mid-South. ...Southeast to Mid-Atlantic States... Guidance has trended towards increased agreement with a highly amplified upper trough centered across much of the MS Valley at 12Z Sun to rapidly progress towards the Northeast and Mid-Atlantic during the D5 period. This will result in a deepening surface cyclone tracking roughly from the OH Valley to the St. Lawrence Valley. This type of evolution should result in very strong to extreme southerly low-level winds largely paralleling the meridional orientation of the surface cold front sweeping east. Unlike on D4 where the 00Z deterministic ECMWF and its ensemble probabilities had less instability forecast with northern extent than the 00Z deterministic GFS and its GEFS probabilities, the opposite is progged for D5. Still, a thermodynamically limited warm sector is likely given weak mid-level lapse rates and meager buoyancy at most. But with conditional potential for this to overlap the strengthening low-level southerlies, low severe probabilities remain apparent over at least the central/eastern Carolinas to the Delmarva. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0344 AM CST Wed Dec 06 2023 Valid 091200Z - 141200Z ...DISCUSSION... ...East TX to the Lower OH Valley and Deep South... A moderately unstable air mass should become established during the day on D4/Sat from southeast TX to the Ark-La-Tex and Ark-La-Miss ahead of a cold front pushing southeastward. With increasing mid-level height falls across the warm sector downstream of a highly amplified/positive-tilt upper trough over the central states, thunderstorm development will become widespread both along and ahead of the front by afternoon. Stronger low-level flow will be coincident with correspondingly weaker instability in the northeast portion of the warm sector. Low-level southwesterlies will be more moderate and subsiding with southwest extent where instability should be larger. As such, below-average confidence exists regarding the distribution of severe hazards, but signal remains sufficient to maintain a highlighted 15 percent area embedded within a broad low severe probability. Primary change with this outlook is to expand the areal delineation farther northeast in the Mid-South. ...Southeast to Mid-Atlantic States... Guidance has trended towards increased agreement with a highly amplified upper trough centered across much of the MS Valley at 12Z Sun to rapidly progress towards the Northeast and Mid-Atlantic during the D5 period. This will result in a deepening surface cyclone tracking roughly from the OH Valley to the St. Lawrence Valley. This type of evolution should result in very strong to extreme southerly low-level winds largely paralleling the meridional orientation of the surface cold front sweeping east. Unlike on D4 where the 00Z deterministic ECMWF and its ensemble probabilities had less instability forecast with northern extent than the 00Z deterministic GFS and its GEFS probabilities, the opposite is progged for D5. Still, a thermodynamically limited warm sector is likely given weak mid-level lapse rates and meager buoyancy at most. But with conditional potential for this to overlap the strengthening low-level southerlies, low severe probabilities remain apparent over at least the central/eastern Carolinas to the Delmarva. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0344 AM CST Wed Dec 06 2023 Valid 091200Z - 141200Z ...DISCUSSION... ...East TX to the Lower OH Valley and Deep South... A moderately unstable air mass should become established during the day on D4/Sat from southeast TX to the Ark-La-Tex and Ark-La-Miss ahead of a cold front pushing southeastward. With increasing mid-level height falls across the warm sector downstream of a highly amplified/positive-tilt upper trough over the central states, thunderstorm development will become widespread both along and ahead of the front by afternoon. Stronger low-level flow will be coincident with correspondingly weaker instability in the northeast portion of the warm sector. Low-level southwesterlies will be more moderate and subsiding with southwest extent where instability should be larger. As such, below-average confidence exists regarding the distribution of severe hazards, but signal remains sufficient to maintain a highlighted 15 percent area embedded within a broad low severe probability. Primary change with this outlook is to expand the areal delineation farther northeast in the Mid-South. ...Southeast to Mid-Atlantic States... Guidance has trended towards increased agreement with a highly amplified upper trough centered across much of the MS Valley at 12Z Sun to rapidly progress towards the Northeast and Mid-Atlantic during the D5 period. This will result in a deepening surface cyclone tracking roughly from the OH Valley to the St. Lawrence Valley. This type of evolution should result in very strong to extreme southerly low-level winds largely paralleling the meridional orientation of the surface cold front sweeping east. Unlike on D4 where the 00Z deterministic ECMWF and its ensemble probabilities had less instability forecast with northern extent than the 00Z deterministic GFS and its GEFS probabilities, the opposite is progged for D5. Still, a thermodynamically limited warm sector is likely given weak mid-level lapse rates and meager buoyancy at most. But with conditional potential for this to overlap the strengthening low-level southerlies, low severe probabilities remain apparent over at least the central/eastern Carolinas to the Delmarva. Read more