Severe Storms

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0227 AM CDT Wed Sep 03 2025 Valid 051200Z - 061200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms will be possible across much of the West, the southern Rockies, Florida, and along and near a frontal boundary from New England into the southern Plains. Widespread organized severe weather is not anticipated. ... Discussion ... The amplified midlevel pattern of the previous few days will persist through Friday/Day-3 across North America, with a western Canada ridge and a continental-scale trough across eastern Canada and the eastern US. Within the eastern trough, a seasonably strong closed low over Ontario should begin to fill by late in the forecast period. As this is occurring, multiple shortwave troughs traversing the larger scale flow field will rotate around the Ontario low. The strongest of these shortwave troughs will have moved south through Canada the day before and should be located in the vicinity of the Lower Great Lakes at the start of the forecast period. In response to this shortwave trough, strong northerly low-to-mid-level flow across the Plains overnight Thursday into Friday will help tighten the low-level thermal gradient across the Plains. This front will slowly move south through Friday into Friday night. A modest surface low is expected to develop across southwest Oklahoma or northwest Texas, along the surface front, by Friday morning. This surface low should slowly sag south through the day with the front. Despite moving south, away from Oklahoma, the flow around this surface low will still be able to draw Gulf moisture northward into Oklahoma and Arkansas. As this increasing low-level moisture converges along the front, diurnal heating of this moistening airmass will yield most-unstable CAPE values perhaps in excess of 3000 J/kg along and south of the surface front. Despite the strong instability and strong thermal gradient, the slow moving nature of the front will tend to favor anafrontal circulations. This appears to be borne out in the latest operational guidance suite with precipitation being favored on the cold side of the thermal gradient. This would tend to limit the overall risk of severe weather. However, given the degree of instability and the presence of a strong cold front, the risk of warm-sector convection remains. If confidence in warm-sector convection occurring increases, severe probabilities may be warranted across portions of eastern Oklahoma east through Arkansas into western Tennessee and northern Mississippi. ..Marsh.. 09/03/2025 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0227 AM CDT Wed Sep 03 2025 Valid 051200Z - 061200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms will be possible across much of the West, the southern Rockies, Florida, and along and near a frontal boundary from New England into the southern Plains. Widespread organized severe weather is not anticipated. ... Discussion ... The amplified midlevel pattern of the previous few days will persist through Friday/Day-3 across North America, with a western Canada ridge and a continental-scale trough across eastern Canada and the eastern US. Within the eastern trough, a seasonably strong closed low over Ontario should begin to fill by late in the forecast period. As this is occurring, multiple shortwave troughs traversing the larger scale flow field will rotate around the Ontario low. The strongest of these shortwave troughs will have moved south through Canada the day before and should be located in the vicinity of the Lower Great Lakes at the start of the forecast period. In response to this shortwave trough, strong northerly low-to-mid-level flow across the Plains overnight Thursday into Friday will help tighten the low-level thermal gradient across the Plains. This front will slowly move south through Friday into Friday night. A modest surface low is expected to develop across southwest Oklahoma or northwest Texas, along the surface front, by Friday morning. This surface low should slowly sag south through the day with the front. Despite moving south, away from Oklahoma, the flow around this surface low will still be able to draw Gulf moisture northward into Oklahoma and Arkansas. As this increasing low-level moisture converges along the front, diurnal heating of this moistening airmass will yield most-unstable CAPE values perhaps in excess of 3000 J/kg along and south of the surface front. Despite the strong instability and strong thermal gradient, the slow moving nature of the front will tend to favor anafrontal circulations. This appears to be borne out in the latest operational guidance suite with precipitation being favored on the cold side of the thermal gradient. This would tend to limit the overall risk of severe weather. However, given the degree of instability and the presence of a strong cold front, the risk of warm-sector convection remains. If confidence in warm-sector convection occurring increases, severe probabilities may be warranted across portions of eastern Oklahoma east through Arkansas into western Tennessee and northern Mississippi. ..Marsh.. 09/03/2025 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0227 AM CDT Wed Sep 03 2025 Valid 051200Z - 061200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms will be possible across much of the West, the southern Rockies, Florida, and along and near a frontal boundary from New England into the southern Plains. Widespread organized severe weather is not anticipated. ... Discussion ... The amplified midlevel pattern of the previous few days will persist through Friday/Day-3 across North America, with a western Canada ridge and a continental-scale trough across eastern Canada and the eastern US. Within the eastern trough, a seasonably strong closed low over Ontario should begin to fill by late in the forecast period. As this is occurring, multiple shortwave troughs traversing the larger scale flow field will rotate around the Ontario low. The strongest of these shortwave troughs will have moved south through Canada the day before and should be located in the vicinity of the Lower Great Lakes at the start of the forecast period. In response to this shortwave trough, strong northerly low-to-mid-level flow across the Plains overnight Thursday into Friday will help tighten the low-level thermal gradient across the Plains. This front will slowly move south through Friday into Friday night. A modest surface low is expected to develop across southwest Oklahoma or northwest Texas, along the surface front, by Friday morning. This surface low should slowly sag south through the day with the front. Despite moving south, away from Oklahoma, the flow around this surface low will still be able to draw Gulf moisture northward into Oklahoma and Arkansas. As this increasing low-level moisture converges along the front, diurnal heating of this moistening airmass will yield most-unstable CAPE values perhaps in excess of 3000 J/kg along and south of the surface front. Despite the strong instability and strong thermal gradient, the slow moving nature of the front will tend to favor anafrontal circulations. This appears to be borne out in the latest operational guidance suite with precipitation being favored on the cold side of the thermal gradient. This would tend to limit the overall risk of severe weather. However, given the degree of instability and the presence of a strong cold front, the risk of warm-sector convection remains. If confidence in warm-sector convection occurring increases, severe probabilities may be warranted across portions of eastern Oklahoma east through Arkansas into western Tennessee and northern Mississippi. ..Marsh.. 09/03/2025 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0227 AM CDT Wed Sep 03 2025 Valid 051200Z - 061200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms will be possible across much of the West, the southern Rockies, Florida, and along and near a frontal boundary from New England into the southern Plains. Widespread organized severe weather is not anticipated. ... Discussion ... The amplified midlevel pattern of the previous few days will persist through Friday/Day-3 across North America, with a western Canada ridge and a continental-scale trough across eastern Canada and the eastern US. Within the eastern trough, a seasonably strong closed low over Ontario should begin to fill by late in the forecast period. As this is occurring, multiple shortwave troughs traversing the larger scale flow field will rotate around the Ontario low. The strongest of these shortwave troughs will have moved south through Canada the day before and should be located in the vicinity of the Lower Great Lakes at the start of the forecast period. In response to this shortwave trough, strong northerly low-to-mid-level flow across the Plains overnight Thursday into Friday will help tighten the low-level thermal gradient across the Plains. This front will slowly move south through Friday into Friday night. A modest surface low is expected to develop across southwest Oklahoma or northwest Texas, along the surface front, by Friday morning. This surface low should slowly sag south through the day with the front. Despite moving south, away from Oklahoma, the flow around this surface low will still be able to draw Gulf moisture northward into Oklahoma and Arkansas. As this increasing low-level moisture converges along the front, diurnal heating of this moistening airmass will yield most-unstable CAPE values perhaps in excess of 3000 J/kg along and south of the surface front. Despite the strong instability and strong thermal gradient, the slow moving nature of the front will tend to favor anafrontal circulations. This appears to be borne out in the latest operational guidance suite with precipitation being favored on the cold side of the thermal gradient. This would tend to limit the overall risk of severe weather. However, given the degree of instability and the presence of a strong cold front, the risk of warm-sector convection remains. If confidence in warm-sector convection occurring increases, severe probabilities may be warranted across portions of eastern Oklahoma east through Arkansas into western Tennessee and northern Mississippi. ..Marsh.. 09/03/2025 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0150 AM CDT Wed Sep 03 2025 Valid 041200Z - 051200Z ...Synopsis... As the upper-level trough departs the Pacific Northwest on D2/Thursday, thunderstorm activity will diminish. It does appear that some lingering risk for isolated dry thunderstorm activity will continue past 12z into D2/Thursday mainly across portions of central Oregon. As such, an isolated dry thunderstorm area was added with this outlook. Otherwise, fire weather concerns will remain low across the CONUS with generally light winds and building high pressure across the western US. ..Thornton.. 09/03/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0150 AM CDT Wed Sep 03 2025 Valid 041200Z - 051200Z ...Synopsis... As the upper-level trough departs the Pacific Northwest on D2/Thursday, thunderstorm activity will diminish. It does appear that some lingering risk for isolated dry thunderstorm activity will continue past 12z into D2/Thursday mainly across portions of central Oregon. As such, an isolated dry thunderstorm area was added with this outlook. Otherwise, fire weather concerns will remain low across the CONUS with generally light winds and building high pressure across the western US. ..Thornton.. 09/03/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0150 AM CDT Wed Sep 03 2025 Valid 041200Z - 051200Z ...Synopsis... As the upper-level trough departs the Pacific Northwest on D2/Thursday, thunderstorm activity will diminish. It does appear that some lingering risk for isolated dry thunderstorm activity will continue past 12z into D2/Thursday mainly across portions of central Oregon. As such, an isolated dry thunderstorm area was added with this outlook. Otherwise, fire weather concerns will remain low across the CONUS with generally light winds and building high pressure across the western US. ..Thornton.. 09/03/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0150 AM CDT Wed Sep 03 2025 Valid 041200Z - 051200Z ...Synopsis... As the upper-level trough departs the Pacific Northwest on D2/Thursday, thunderstorm activity will diminish. It does appear that some lingering risk for isolated dry thunderstorm activity will continue past 12z into D2/Thursday mainly across portions of central Oregon. As such, an isolated dry thunderstorm area was added with this outlook. Otherwise, fire weather concerns will remain low across the CONUS with generally light winds and building high pressure across the western US. ..Thornton.. 09/03/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0150 AM CDT Wed Sep 03 2025 Valid 041200Z - 051200Z ...Synopsis... As the upper-level trough departs the Pacific Northwest on D2/Thursday, thunderstorm activity will diminish. It does appear that some lingering risk for isolated dry thunderstorm activity will continue past 12z into D2/Thursday mainly across portions of central Oregon. As such, an isolated dry thunderstorm area was added with this outlook. Otherwise, fire weather concerns will remain low across the CONUS with generally light winds and building high pressure across the western US. ..Thornton.. 09/03/2025 ...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 0149 AM CDT Wed Sep 03 2025 Valid 031200Z - 041200Z ...Synopsis... A weak upper-level trough will continue to move northward across northern California into the Pacific Northwest on Wednesday. Lift associated with this feature will promote isolated to scattered thunderstorm activity. Thunderstorms will likely be ongoing at the beginning of the period with a second round developing by the afternoon. Overall, a mix of wet/dry thunderstorms is expected across the driest fuels in northern California, far western Nevada, and central Oregon. While locally higher totals will be possible in the strongest storms, ensemble guidance generally shows < 0.10" across much of this region. New lightning starts were reported on Tuesday in these areas, with rainfall amounts 0.10-0.25". An isolated dry thunderstorm area was maintained with this outlook to support this potential. ..Thornton.. 09/03/2025 ...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 0149 AM CDT Wed Sep 03 2025 Valid 031200Z - 041200Z ...Synopsis... A weak upper-level trough will continue to move northward across northern California into the Pacific Northwest on Wednesday. Lift associated with this feature will promote isolated to scattered thunderstorm activity. Thunderstorms will likely be ongoing at the beginning of the period with a second round developing by the afternoon. Overall, a mix of wet/dry thunderstorms is expected across the driest fuels in northern California, far western Nevada, and central Oregon. While locally higher totals will be possible in the strongest storms, ensemble guidance generally shows < 0.10" across much of this region. New lightning starts were reported on Tuesday in these areas, with rainfall amounts 0.10-0.25". An isolated dry thunderstorm area was maintained with this outlook to support this potential. ..Thornton.. 09/03/2025 ...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 0149 AM CDT Wed Sep 03 2025 Valid 031200Z - 041200Z ...Synopsis... A weak upper-level trough will continue to move northward across northern California into the Pacific Northwest on Wednesday. Lift associated with this feature will promote isolated to scattered thunderstorm activity. Thunderstorms will likely be ongoing at the beginning of the period with a second round developing by the afternoon. Overall, a mix of wet/dry thunderstorms is expected across the driest fuels in northern California, far western Nevada, and central Oregon. While locally higher totals will be possible in the strongest storms, ensemble guidance generally shows < 0.10" across much of this region. New lightning starts were reported on Tuesday in these areas, with rainfall amounts 0.10-0.25". An isolated dry thunderstorm area was maintained with this outlook to support this potential. ..Thornton.. 09/03/2025 ...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 0149 AM CDT Wed Sep 03 2025 Valid 031200Z - 041200Z ...Synopsis... A weak upper-level trough will continue to move northward across northern California into the Pacific Northwest on Wednesday. Lift associated with this feature will promote isolated to scattered thunderstorm activity. Thunderstorms will likely be ongoing at the beginning of the period with a second round developing by the afternoon. Overall, a mix of wet/dry thunderstorms is expected across the driest fuels in northern California, far western Nevada, and central Oregon. While locally higher totals will be possible in the strongest storms, ensemble guidance generally shows < 0.10" across much of this region. New lightning starts were reported on Tuesday in these areas, with rainfall amounts 0.10-0.25". An isolated dry thunderstorm area was maintained with this outlook to support this potential. ..Thornton.. 09/03/2025 ...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 0149 AM CDT Wed Sep 03 2025 Valid 031200Z - 041200Z ...Synopsis... A weak upper-level trough will continue to move northward across northern California into the Pacific Northwest on Wednesday. Lift associated with this feature will promote isolated to scattered thunderstorm activity. Thunderstorms will likely be ongoing at the beginning of the period with a second round developing by the afternoon. Overall, a mix of wet/dry thunderstorms is expected across the driest fuels in northern California, far western Nevada, and central Oregon. While locally higher totals will be possible in the strongest storms, ensemble guidance generally shows < 0.10" across much of this region. New lightning starts were reported on Tuesday in these areas, with rainfall amounts 0.10-0.25". An isolated dry thunderstorm area was maintained with this outlook to support this potential. ..Thornton.. 09/03/2025 ...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 0149 AM CDT Wed Sep 03 2025 Valid 031200Z - 041200Z ...Synopsis... A weak upper-level trough will continue to move northward across northern California into the Pacific Northwest on Wednesday. Lift associated with this feature will promote isolated to scattered thunderstorm activity. Thunderstorms will likely be ongoing at the beginning of the period with a second round developing by the afternoon. Overall, a mix of wet/dry thunderstorms is expected across the driest fuels in northern California, far western Nevada, and central Oregon. While locally higher totals will be possible in the strongest storms, ensemble guidance generally shows < 0.10" across much of this region. New lightning starts were reported on Tuesday in these areas, with rainfall amounts 0.10-0.25". An isolated dry thunderstorm area was maintained with this outlook to support this potential. ..Thornton.. 09/03/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1253 AM CDT Wed Sep 03 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN TENNESSEE NORTHWARD INTO NORTHERN NEW YORK... ...SUMMARY... Scattered strong thunderstorms may impact a corridor from east Tennessee northward to the US-Canadian border across northern New York on Thursday, accompanied by a risk for potentially damaging wind gusts. ... Synopsis ... A highly amplified midlevel pattern will continue through Thursday/Day-2 as a large ridge pushes north through western Canada and a downstream trough persists across much of the eastern United States. Within this amplified pattern, a seasonably cold midlevel low will exist across Ontario, with multiple lobes of vorticity rotating around the low. One such vorticity lobe/shortwave trough will move east across the Great Lakes bringing with it increasing ascent across portions of the eastern US. At the surface, a cold front associated with the midlevel shortwave trough will stretch through the Plains east-northeast into the lower Great Lakes at the start of the forecast period. This cold front will make slow progress southward across the Plains and faster progress east across the eastern Great Lakes region. ... East Tennessee northward into Upstate New York ... Seasonable moisture will be in place across the region ahead of the advancing surface cold front. Diurnal heating of this airmass should result in pockets of most-unstable CAPE up to 1500 J/kg to develop by early afternoon across southern portions of the region to perhaps 750 J/kg across northern portions of the area. Thunderstorms, or their remnants, ongoing across portions of eastern Ohio and western Pennsylvania at the start of the period, should weaken/dissipate through the morning as they move east. These showers/storms or their outflow may provide potential foci for thunderstorm development/intensification during the afternoon. To the west, increasing large scale ascent associated with the shortwave trough and low-level convergence along the surface cold front should support additional bands of thunderstorms. The best thermodynamics will reside across Tennessee and adjacent areas, with the best deep-layer shear displaced to the north across northern Pennsylvania and New York. However, the joint distribution of forecast profiles of shear and buoyancy should favor thunderstorm organization into small multicell clusters or small linear segments, with the strongest of these capable of some damaging wind potential. ..Marsh.. 09/03/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1253 AM CDT Wed Sep 03 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN TENNESSEE NORTHWARD INTO NORTHERN NEW YORK... ...SUMMARY... Scattered strong thunderstorms may impact a corridor from east Tennessee northward to the US-Canadian border across northern New York on Thursday, accompanied by a risk for potentially damaging wind gusts. ... Synopsis ... A highly amplified midlevel pattern will continue through Thursday/Day-2 as a large ridge pushes north through western Canada and a downstream trough persists across much of the eastern United States. Within this amplified pattern, a seasonably cold midlevel low will exist across Ontario, with multiple lobes of vorticity rotating around the low. One such vorticity lobe/shortwave trough will move east across the Great Lakes bringing with it increasing ascent across portions of the eastern US. At the surface, a cold front associated with the midlevel shortwave trough will stretch through the Plains east-northeast into the lower Great Lakes at the start of the forecast period. This cold front will make slow progress southward across the Plains and faster progress east across the eastern Great Lakes region. ... East Tennessee northward into Upstate New York ... Seasonable moisture will be in place across the region ahead of the advancing surface cold front. Diurnal heating of this airmass should result in pockets of most-unstable CAPE up to 1500 J/kg to develop by early afternoon across southern portions of the region to perhaps 750 J/kg across northern portions of the area. Thunderstorms, or their remnants, ongoing across portions of eastern Ohio and western Pennsylvania at the start of the period, should weaken/dissipate through the morning as they move east. These showers/storms or their outflow may provide potential foci for thunderstorm development/intensification during the afternoon. To the west, increasing large scale ascent associated with the shortwave trough and low-level convergence along the surface cold front should support additional bands of thunderstorms. The best thermodynamics will reside across Tennessee and adjacent areas, with the best deep-layer shear displaced to the north across northern Pennsylvania and New York. However, the joint distribution of forecast profiles of shear and buoyancy should favor thunderstorm organization into small multicell clusters or small linear segments, with the strongest of these capable of some damaging wind potential. ..Marsh.. 09/03/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1253 AM CDT Wed Sep 03 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN TENNESSEE NORTHWARD INTO NORTHERN NEW YORK... ...SUMMARY... Scattered strong thunderstorms may impact a corridor from east Tennessee northward to the US-Canadian border across northern New York on Thursday, accompanied by a risk for potentially damaging wind gusts. ... Synopsis ... A highly amplified midlevel pattern will continue through Thursday/Day-2 as a large ridge pushes north through western Canada and a downstream trough persists across much of the eastern United States. Within this amplified pattern, a seasonably cold midlevel low will exist across Ontario, with multiple lobes of vorticity rotating around the low. One such vorticity lobe/shortwave trough will move east across the Great Lakes bringing with it increasing ascent across portions of the eastern US. At the surface, a cold front associated with the midlevel shortwave trough will stretch through the Plains east-northeast into the lower Great Lakes at the start of the forecast period. This cold front will make slow progress southward across the Plains and faster progress east across the eastern Great Lakes region. ... East Tennessee northward into Upstate New York ... Seasonable moisture will be in place across the region ahead of the advancing surface cold front. Diurnal heating of this airmass should result in pockets of most-unstable CAPE up to 1500 J/kg to develop by early afternoon across southern portions of the region to perhaps 750 J/kg across northern portions of the area. Thunderstorms, or their remnants, ongoing across portions of eastern Ohio and western Pennsylvania at the start of the period, should weaken/dissipate through the morning as they move east. These showers/storms or their outflow may provide potential foci for thunderstorm development/intensification during the afternoon. To the west, increasing large scale ascent associated with the shortwave trough and low-level convergence along the surface cold front should support additional bands of thunderstorms. The best thermodynamics will reside across Tennessee and adjacent areas, with the best deep-layer shear displaced to the north across northern Pennsylvania and New York. However, the joint distribution of forecast profiles of shear and buoyancy should favor thunderstorm organization into small multicell clusters or small linear segments, with the strongest of these capable of some damaging wind potential. ..Marsh.. 09/03/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1253 AM CDT Wed Sep 03 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN TENNESSEE NORTHWARD INTO NORTHERN NEW YORK... ...SUMMARY... Scattered strong thunderstorms may impact a corridor from east Tennessee northward to the US-Canadian border across northern New York on Thursday, accompanied by a risk for potentially damaging wind gusts. ... Synopsis ... A highly amplified midlevel pattern will continue through Thursday/Day-2 as a large ridge pushes north through western Canada and a downstream trough persists across much of the eastern United States. Within this amplified pattern, a seasonably cold midlevel low will exist across Ontario, with multiple lobes of vorticity rotating around the low. One such vorticity lobe/shortwave trough will move east across the Great Lakes bringing with it increasing ascent across portions of the eastern US. At the surface, a cold front associated with the midlevel shortwave trough will stretch through the Plains east-northeast into the lower Great Lakes at the start of the forecast period. This cold front will make slow progress southward across the Plains and faster progress east across the eastern Great Lakes region. ... East Tennessee northward into Upstate New York ... Seasonable moisture will be in place across the region ahead of the advancing surface cold front. Diurnal heating of this airmass should result in pockets of most-unstable CAPE up to 1500 J/kg to develop by early afternoon across southern portions of the region to perhaps 750 J/kg across northern portions of the area. Thunderstorms, or their remnants, ongoing across portions of eastern Ohio and western Pennsylvania at the start of the period, should weaken/dissipate through the morning as they move east. These showers/storms or their outflow may provide potential foci for thunderstorm development/intensification during the afternoon. To the west, increasing large scale ascent associated with the shortwave trough and low-level convergence along the surface cold front should support additional bands of thunderstorms. The best thermodynamics will reside across Tennessee and adjacent areas, with the best deep-layer shear displaced to the north across northern Pennsylvania and New York. However, the joint distribution of forecast profiles of shear and buoyancy should favor thunderstorm organization into small multicell clusters or small linear segments, with the strongest of these capable of some damaging wind potential. ..Marsh.. 09/03/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1253 AM CDT Wed Sep 03 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN TENNESSEE NORTHWARD INTO NORTHERN NEW YORK... ...SUMMARY... Scattered strong thunderstorms may impact a corridor from east Tennessee northward to the US-Canadian border across northern New York on Thursday, accompanied by a risk for potentially damaging wind gusts. ... Synopsis ... A highly amplified midlevel pattern will continue through Thursday/Day-2 as a large ridge pushes north through western Canada and a downstream trough persists across much of the eastern United States. Within this amplified pattern, a seasonably cold midlevel low will exist across Ontario, with multiple lobes of vorticity rotating around the low. One such vorticity lobe/shortwave trough will move east across the Great Lakes bringing with it increasing ascent across portions of the eastern US. At the surface, a cold front associated with the midlevel shortwave trough will stretch through the Plains east-northeast into the lower Great Lakes at the start of the forecast period. This cold front will make slow progress southward across the Plains and faster progress east across the eastern Great Lakes region. ... East Tennessee northward into Upstate New York ... Seasonable moisture will be in place across the region ahead of the advancing surface cold front. Diurnal heating of this airmass should result in pockets of most-unstable CAPE up to 1500 J/kg to develop by early afternoon across southern portions of the region to perhaps 750 J/kg across northern portions of the area. Thunderstorms, or their remnants, ongoing across portions of eastern Ohio and western Pennsylvania at the start of the period, should weaken/dissipate through the morning as they move east. These showers/storms or their outflow may provide potential foci for thunderstorm development/intensification during the afternoon. To the west, increasing large scale ascent associated with the shortwave trough and low-level convergence along the surface cold front should support additional bands of thunderstorms. The best thermodynamics will reside across Tennessee and adjacent areas, with the best deep-layer shear displaced to the north across northern Pennsylvania and New York. However, the joint distribution of forecast profiles of shear and buoyancy should favor thunderstorm organization into small multicell clusters or small linear segments, with the strongest of these capable of some damaging wind potential. ..Marsh.. 09/03/2025 Read more