Severe Storms

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0322 PM CDT Tue Sep 02 2025 Valid 041200Z - 101200Z Fire weather potential appears limited across the country for the extended period. Medium to long-range guidance continues to show a gradual amplification of an upper wave over the central CONUS through late week with an unseasonably strong frontal intrusion into the Plains and Midwest. This will result in widespread below-normal temperatures and rain chances, though windy conditions will likely manifest across portions of the northern Plains on D3/Thursday. Across the West, persistent upper ridging will maintain warm and dry conditions across the Great Basin and Pacific Northwest. Weak gradient winds will mitigate most fire weather concerns through the remainder of the week. A gradual breakdown of the upper ridge will likely usher in cooler conditions for parts of the Northwest by early next week along with scattered rain chances. ...D3/Thursday - Northern Plains... Medium-range guidance shows strong consensus in 20-25 mph winds developing within a post-frontal air mass across eastern MT into the western Dakotas on Thursday afternoon. However, an influx of cooler air is expected to modulate RH reductions with most solutions/ensemble guidance suggesting RH values may fall into the 25-35% range. These marginal RH reductions, along with modest fuel dryness, should limit the overall fire weather threat, though a wind-driven concern could materialize if RH trends lower than anticipated and finer fuels can adequately dry. ..Moore.. 09/02/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0322 PM CDT Tue Sep 02 2025 Valid 041200Z - 101200Z Fire weather potential appears limited across the country for the extended period. Medium to long-range guidance continues to show a gradual amplification of an upper wave over the central CONUS through late week with an unseasonably strong frontal intrusion into the Plains and Midwest. This will result in widespread below-normal temperatures and rain chances, though windy conditions will likely manifest across portions of the northern Plains on D3/Thursday. Across the West, persistent upper ridging will maintain warm and dry conditions across the Great Basin and Pacific Northwest. Weak gradient winds will mitigate most fire weather concerns through the remainder of the week. A gradual breakdown of the upper ridge will likely usher in cooler conditions for parts of the Northwest by early next week along with scattered rain chances. ...D3/Thursday - Northern Plains... Medium-range guidance shows strong consensus in 20-25 mph winds developing within a post-frontal air mass across eastern MT into the western Dakotas on Thursday afternoon. However, an influx of cooler air is expected to modulate RH reductions with most solutions/ensemble guidance suggesting RH values may fall into the 25-35% range. These marginal RH reductions, along with modest fuel dryness, should limit the overall fire weather threat, though a wind-driven concern could materialize if RH trends lower than anticipated and finer fuels can adequately dry. ..Moore.. 09/02/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Tue Sep 02 2025 Valid 022000Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF EASTERN SOUTH DAKOTA INTO SOUTHERN/CENTRAL MINNESOTA AND FAR NORTHWESTERN WISCONSIN... ...SUMMARY... Thunderstorms capable of producing isolated severe wind gusts and marginally severe hail will be possible this afternoon and evening across parts of the northern Plains and Upper Midwest. ...20Z Update... No changes were made to the ongoing forecast. Strong to marginally severe storms still appear possible along a cold front in the northern Plains/Upper Midwest. See the previous discussion for additional details. ..Wendt.. 09/02/2025 .PREV DISCUSSION... /ISSUED 1125 AM CDT Tue Sep 02 2025/ ...Northern Plains/Upper Midwest... An upper trough over central Canada late this morning will dig southeastward towards the Upper Midwest/Lake Superior vicinity through the period. Showers and weak thunderstorms are ongoing over parts of central MN, aided by a remnant MCV over northern MN. This activity is forecast to further weaken this afternoon, with a residual outflow boundary arcing from southern MN west-northwestward towards the SD/MN border by mid afternoon. A cold front over ND will continue to advance southeastward into an adequately moist low-level airmass, with surface dewpoints generally in the lower to mid 60s. Filtered daytime heating away from this morning's convective cloud debris, along with modestly steepened mid-level lapse rates (reference 12Z ABR sounding), should aid in weak to locally moderate instability (MLCAPE around 1000-2000 J/kg) developing ahead of the front by mid to late afternoon. Latest model guidance remains consistent in showing isolated to scattered thunderstorms developing across roughly the eastern third of SD into central MN this afternoon along/near the cold front. There is considerable uncertainty regarding the degree of instability that will develop and related thunderstorm intensity given the widespread cloud cover in south-central MN. The stronger mid/upper-level flow associated with the upper trough over Canada will likely lag behind the surface front to some extent. This should limit effective bulk shear magnitudes (up to 20-30 kt). Even so, modestly organized multicells associated with isolated severe wind gusts and marginally severe hail appear possible, before this activity eventually subsides this evening with the loss of daytime heating. The Marginal Risk has been adjusted to account for the latest observational/short-term guidance trends. ...Lower Colorado River Valley... Compared to yesterday, modestly enhanced mid-level flow should trend more south-southeasterly today as a weak shortwave trough lifts northward from Baja California into the lower CO River Valley. Associated/ongoing showers and thunderstorms across southern CA should generally remain sub-severe through the morning as they track northwestward. In the wake of this activity, there is a fair amount of uncertainty regarding destabilization potential given scattered to widespread cloudiness over much of the lower CO River Valley. Wherever cloud breaks and heating can occur, steepening low-level lapse rates may support strong/gusty winds with any convection that can develop. Still, the potential for a focused area of severe gusts appears too low to include any probabilities at this time. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Tue Sep 02 2025 Valid 022000Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF EASTERN SOUTH DAKOTA INTO SOUTHERN/CENTRAL MINNESOTA AND FAR NORTHWESTERN WISCONSIN... ...SUMMARY... Thunderstorms capable of producing isolated severe wind gusts and marginally severe hail will be possible this afternoon and evening across parts of the northern Plains and Upper Midwest. ...20Z Update... No changes were made to the ongoing forecast. Strong to marginally severe storms still appear possible along a cold front in the northern Plains/Upper Midwest. See the previous discussion for additional details. ..Wendt.. 09/02/2025 .PREV DISCUSSION... /ISSUED 1125 AM CDT Tue Sep 02 2025/ ...Northern Plains/Upper Midwest... An upper trough over central Canada late this morning will dig southeastward towards the Upper Midwest/Lake Superior vicinity through the period. Showers and weak thunderstorms are ongoing over parts of central MN, aided by a remnant MCV over northern MN. This activity is forecast to further weaken this afternoon, with a residual outflow boundary arcing from southern MN west-northwestward towards the SD/MN border by mid afternoon. A cold front over ND will continue to advance southeastward into an adequately moist low-level airmass, with surface dewpoints generally in the lower to mid 60s. Filtered daytime heating away from this morning's convective cloud debris, along with modestly steepened mid-level lapse rates (reference 12Z ABR sounding), should aid in weak to locally moderate instability (MLCAPE around 1000-2000 J/kg) developing ahead of the front by mid to late afternoon. Latest model guidance remains consistent in showing isolated to scattered thunderstorms developing across roughly the eastern third of SD into central MN this afternoon along/near the cold front. There is considerable uncertainty regarding the degree of instability that will develop and related thunderstorm intensity given the widespread cloud cover in south-central MN. The stronger mid/upper-level flow associated with the upper trough over Canada will likely lag behind the surface front to some extent. This should limit effective bulk shear magnitudes (up to 20-30 kt). Even so, modestly organized multicells associated with isolated severe wind gusts and marginally severe hail appear possible, before this activity eventually subsides this evening with the loss of daytime heating. The Marginal Risk has been adjusted to account for the latest observational/short-term guidance trends. ...Lower Colorado River Valley... Compared to yesterday, modestly enhanced mid-level flow should trend more south-southeasterly today as a weak shortwave trough lifts northward from Baja California into the lower CO River Valley. Associated/ongoing showers and thunderstorms across southern CA should generally remain sub-severe through the morning as they track northwestward. In the wake of this activity, there is a fair amount of uncertainty regarding destabilization potential given scattered to widespread cloudiness over much of the lower CO River Valley. Wherever cloud breaks and heating can occur, steepening low-level lapse rates may support strong/gusty winds with any convection that can develop. Still, the potential for a focused area of severe gusts appears too low to include any probabilities at this time. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Tue Sep 02 2025 Valid 022000Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF EASTERN SOUTH DAKOTA INTO SOUTHERN/CENTRAL MINNESOTA AND FAR NORTHWESTERN WISCONSIN... ...SUMMARY... Thunderstorms capable of producing isolated severe wind gusts and marginally severe hail will be possible this afternoon and evening across parts of the northern Plains and Upper Midwest. ...20Z Update... No changes were made to the ongoing forecast. Strong to marginally severe storms still appear possible along a cold front in the northern Plains/Upper Midwest. See the previous discussion for additional details. ..Wendt.. 09/02/2025 .PREV DISCUSSION... /ISSUED 1125 AM CDT Tue Sep 02 2025/ ...Northern Plains/Upper Midwest... An upper trough over central Canada late this morning will dig southeastward towards the Upper Midwest/Lake Superior vicinity through the period. Showers and weak thunderstorms are ongoing over parts of central MN, aided by a remnant MCV over northern MN. This activity is forecast to further weaken this afternoon, with a residual outflow boundary arcing from southern MN west-northwestward towards the SD/MN border by mid afternoon. A cold front over ND will continue to advance southeastward into an adequately moist low-level airmass, with surface dewpoints generally in the lower to mid 60s. Filtered daytime heating away from this morning's convective cloud debris, along with modestly steepened mid-level lapse rates (reference 12Z ABR sounding), should aid in weak to locally moderate instability (MLCAPE around 1000-2000 J/kg) developing ahead of the front by mid to late afternoon. Latest model guidance remains consistent in showing isolated to scattered thunderstorms developing across roughly the eastern third of SD into central MN this afternoon along/near the cold front. There is considerable uncertainty regarding the degree of instability that will develop and related thunderstorm intensity given the widespread cloud cover in south-central MN. The stronger mid/upper-level flow associated with the upper trough over Canada will likely lag behind the surface front to some extent. This should limit effective bulk shear magnitudes (up to 20-30 kt). Even so, modestly organized multicells associated with isolated severe wind gusts and marginally severe hail appear possible, before this activity eventually subsides this evening with the loss of daytime heating. The Marginal Risk has been adjusted to account for the latest observational/short-term guidance trends. ...Lower Colorado River Valley... Compared to yesterday, modestly enhanced mid-level flow should trend more south-southeasterly today as a weak shortwave trough lifts northward from Baja California into the lower CO River Valley. Associated/ongoing showers and thunderstorms across southern CA should generally remain sub-severe through the morning as they track northwestward. In the wake of this activity, there is a fair amount of uncertainty regarding destabilization potential given scattered to widespread cloudiness over much of the lower CO River Valley. Wherever cloud breaks and heating can occur, steepening low-level lapse rates may support strong/gusty winds with any convection that can develop. Still, the potential for a focused area of severe gusts appears too low to include any probabilities at this time. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Tue Sep 02 2025 Valid 022000Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF EASTERN SOUTH DAKOTA INTO SOUTHERN/CENTRAL MINNESOTA AND FAR NORTHWESTERN WISCONSIN... ...SUMMARY... Thunderstorms capable of producing isolated severe wind gusts and marginally severe hail will be possible this afternoon and evening across parts of the northern Plains and Upper Midwest. ...20Z Update... No changes were made to the ongoing forecast. Strong to marginally severe storms still appear possible along a cold front in the northern Plains/Upper Midwest. See the previous discussion for additional details. ..Wendt.. 09/02/2025 .PREV DISCUSSION... /ISSUED 1125 AM CDT Tue Sep 02 2025/ ...Northern Plains/Upper Midwest... An upper trough over central Canada late this morning will dig southeastward towards the Upper Midwest/Lake Superior vicinity through the period. Showers and weak thunderstorms are ongoing over parts of central MN, aided by a remnant MCV over northern MN. This activity is forecast to further weaken this afternoon, with a residual outflow boundary arcing from southern MN west-northwestward towards the SD/MN border by mid afternoon. A cold front over ND will continue to advance southeastward into an adequately moist low-level airmass, with surface dewpoints generally in the lower to mid 60s. Filtered daytime heating away from this morning's convective cloud debris, along with modestly steepened mid-level lapse rates (reference 12Z ABR sounding), should aid in weak to locally moderate instability (MLCAPE around 1000-2000 J/kg) developing ahead of the front by mid to late afternoon. Latest model guidance remains consistent in showing isolated to scattered thunderstorms developing across roughly the eastern third of SD into central MN this afternoon along/near the cold front. There is considerable uncertainty regarding the degree of instability that will develop and related thunderstorm intensity given the widespread cloud cover in south-central MN. The stronger mid/upper-level flow associated with the upper trough over Canada will likely lag behind the surface front to some extent. This should limit effective bulk shear magnitudes (up to 20-30 kt). Even so, modestly organized multicells associated with isolated severe wind gusts and marginally severe hail appear possible, before this activity eventually subsides this evening with the loss of daytime heating. The Marginal Risk has been adjusted to account for the latest observational/short-term guidance trends. ...Lower Colorado River Valley... Compared to yesterday, modestly enhanced mid-level flow should trend more south-southeasterly today as a weak shortwave trough lifts northward from Baja California into the lower CO River Valley. Associated/ongoing showers and thunderstorms across southern CA should generally remain sub-severe through the morning as they track northwestward. In the wake of this activity, there is a fair amount of uncertainty regarding destabilization potential given scattered to widespread cloudiness over much of the lower CO River Valley. Wherever cloud breaks and heating can occur, steepening low-level lapse rates may support strong/gusty winds with any convection that can develop. Still, the potential for a focused area of severe gusts appears too low to include any probabilities at this time. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Tue Sep 02 2025 Valid 022000Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF EASTERN SOUTH DAKOTA INTO SOUTHERN/CENTRAL MINNESOTA AND FAR NORTHWESTERN WISCONSIN... ...SUMMARY... Thunderstorms capable of producing isolated severe wind gusts and marginally severe hail will be possible this afternoon and evening across parts of the northern Plains and Upper Midwest. ...20Z Update... No changes were made to the ongoing forecast. Strong to marginally severe storms still appear possible along a cold front in the northern Plains/Upper Midwest. See the previous discussion for additional details. ..Wendt.. 09/02/2025 .PREV DISCUSSION... /ISSUED 1125 AM CDT Tue Sep 02 2025/ ...Northern Plains/Upper Midwest... An upper trough over central Canada late this morning will dig southeastward towards the Upper Midwest/Lake Superior vicinity through the period. Showers and weak thunderstorms are ongoing over parts of central MN, aided by a remnant MCV over northern MN. This activity is forecast to further weaken this afternoon, with a residual outflow boundary arcing from southern MN west-northwestward towards the SD/MN border by mid afternoon. A cold front over ND will continue to advance southeastward into an adequately moist low-level airmass, with surface dewpoints generally in the lower to mid 60s. Filtered daytime heating away from this morning's convective cloud debris, along with modestly steepened mid-level lapse rates (reference 12Z ABR sounding), should aid in weak to locally moderate instability (MLCAPE around 1000-2000 J/kg) developing ahead of the front by mid to late afternoon. Latest model guidance remains consistent in showing isolated to scattered thunderstorms developing across roughly the eastern third of SD into central MN this afternoon along/near the cold front. There is considerable uncertainty regarding the degree of instability that will develop and related thunderstorm intensity given the widespread cloud cover in south-central MN. The stronger mid/upper-level flow associated with the upper trough over Canada will likely lag behind the surface front to some extent. This should limit effective bulk shear magnitudes (up to 20-30 kt). Even so, modestly organized multicells associated with isolated severe wind gusts and marginally severe hail appear possible, before this activity eventually subsides this evening with the loss of daytime heating. The Marginal Risk has been adjusted to account for the latest observational/short-term guidance trends. ...Lower Colorado River Valley... Compared to yesterday, modestly enhanced mid-level flow should trend more south-southeasterly today as a weak shortwave trough lifts northward from Baja California into the lower CO River Valley. Associated/ongoing showers and thunderstorms across southern CA should generally remain sub-severe through the morning as they track northwestward. In the wake of this activity, there is a fair amount of uncertainty regarding destabilization potential given scattered to widespread cloudiness over much of the lower CO River Valley. Wherever cloud breaks and heating can occur, steepening low-level lapse rates may support strong/gusty winds with any convection that can develop. Still, the potential for a focused area of severe gusts appears too low to include any probabilities at this time. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Tue Sep 02 2025 Valid 022000Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF EASTERN SOUTH DAKOTA INTO SOUTHERN/CENTRAL MINNESOTA AND FAR NORTHWESTERN WISCONSIN... ...SUMMARY... Thunderstorms capable of producing isolated severe wind gusts and marginally severe hail will be possible this afternoon and evening across parts of the northern Plains and Upper Midwest. ...20Z Update... No changes were made to the ongoing forecast. Strong to marginally severe storms still appear possible along a cold front in the northern Plains/Upper Midwest. See the previous discussion for additional details. ..Wendt.. 09/02/2025 .PREV DISCUSSION... /ISSUED 1125 AM CDT Tue Sep 02 2025/ ...Northern Plains/Upper Midwest... An upper trough over central Canada late this morning will dig southeastward towards the Upper Midwest/Lake Superior vicinity through the period. Showers and weak thunderstorms are ongoing over parts of central MN, aided by a remnant MCV over northern MN. This activity is forecast to further weaken this afternoon, with a residual outflow boundary arcing from southern MN west-northwestward towards the SD/MN border by mid afternoon. A cold front over ND will continue to advance southeastward into an adequately moist low-level airmass, with surface dewpoints generally in the lower to mid 60s. Filtered daytime heating away from this morning's convective cloud debris, along with modestly steepened mid-level lapse rates (reference 12Z ABR sounding), should aid in weak to locally moderate instability (MLCAPE around 1000-2000 J/kg) developing ahead of the front by mid to late afternoon. Latest model guidance remains consistent in showing isolated to scattered thunderstorms developing across roughly the eastern third of SD into central MN this afternoon along/near the cold front. There is considerable uncertainty regarding the degree of instability that will develop and related thunderstorm intensity given the widespread cloud cover in south-central MN. The stronger mid/upper-level flow associated with the upper trough over Canada will likely lag behind the surface front to some extent. This should limit effective bulk shear magnitudes (up to 20-30 kt). Even so, modestly organized multicells associated with isolated severe wind gusts and marginally severe hail appear possible, before this activity eventually subsides this evening with the loss of daytime heating. The Marginal Risk has been adjusted to account for the latest observational/short-term guidance trends. ...Lower Colorado River Valley... Compared to yesterday, modestly enhanced mid-level flow should trend more south-southeasterly today as a weak shortwave trough lifts northward from Baja California into the lower CO River Valley. Associated/ongoing showers and thunderstorms across southern CA should generally remain sub-severe through the morning as they track northwestward. In the wake of this activity, there is a fair amount of uncertainty regarding destabilization potential given scattered to widespread cloudiness over much of the lower CO River Valley. Wherever cloud breaks and heating can occur, steepening low-level lapse rates may support strong/gusty winds with any convection that can develop. Still, the potential for a focused area of severe gusts appears too low to include any probabilities at this time. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Tue Sep 02 2025 Valid 022000Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF EASTERN SOUTH DAKOTA INTO SOUTHERN/CENTRAL MINNESOTA AND FAR NORTHWESTERN WISCONSIN... ...SUMMARY... Thunderstorms capable of producing isolated severe wind gusts and marginally severe hail will be possible this afternoon and evening across parts of the northern Plains and Upper Midwest. ...20Z Update... No changes were made to the ongoing forecast. Strong to marginally severe storms still appear possible along a cold front in the northern Plains/Upper Midwest. See the previous discussion for additional details. ..Wendt.. 09/02/2025 .PREV DISCUSSION... /ISSUED 1125 AM CDT Tue Sep 02 2025/ ...Northern Plains/Upper Midwest... An upper trough over central Canada late this morning will dig southeastward towards the Upper Midwest/Lake Superior vicinity through the period. Showers and weak thunderstorms are ongoing over parts of central MN, aided by a remnant MCV over northern MN. This activity is forecast to further weaken this afternoon, with a residual outflow boundary arcing from southern MN west-northwestward towards the SD/MN border by mid afternoon. A cold front over ND will continue to advance southeastward into an adequately moist low-level airmass, with surface dewpoints generally in the lower to mid 60s. Filtered daytime heating away from this morning's convective cloud debris, along with modestly steepened mid-level lapse rates (reference 12Z ABR sounding), should aid in weak to locally moderate instability (MLCAPE around 1000-2000 J/kg) developing ahead of the front by mid to late afternoon. Latest model guidance remains consistent in showing isolated to scattered thunderstorms developing across roughly the eastern third of SD into central MN this afternoon along/near the cold front. There is considerable uncertainty regarding the degree of instability that will develop and related thunderstorm intensity given the widespread cloud cover in south-central MN. The stronger mid/upper-level flow associated with the upper trough over Canada will likely lag behind the surface front to some extent. This should limit effective bulk shear magnitudes (up to 20-30 kt). Even so, modestly organized multicells associated with isolated severe wind gusts and marginally severe hail appear possible, before this activity eventually subsides this evening with the loss of daytime heating. The Marginal Risk has been adjusted to account for the latest observational/short-term guidance trends. ...Lower Colorado River Valley... Compared to yesterday, modestly enhanced mid-level flow should trend more south-southeasterly today as a weak shortwave trough lifts northward from Baja California into the lower CO River Valley. Associated/ongoing showers and thunderstorms across southern CA should generally remain sub-severe through the morning as they track northwestward. In the wake of this activity, there is a fair amount of uncertainty regarding destabilization potential given scattered to widespread cloudiness over much of the lower CO River Valley. Wherever cloud breaks and heating can occur, steepening low-level lapse rates may support strong/gusty winds with any convection that can develop. Still, the potential for a focused area of severe gusts appears too low to include any probabilities at this time. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Tue Sep 02 2025 Valid 022000Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF EASTERN SOUTH DAKOTA INTO SOUTHERN/CENTRAL MINNESOTA AND FAR NORTHWESTERN WISCONSIN... ...SUMMARY... Thunderstorms capable of producing isolated severe wind gusts and marginally severe hail will be possible this afternoon and evening across parts of the northern Plains and Upper Midwest. ...20Z Update... No changes were made to the ongoing forecast. Strong to marginally severe storms still appear possible along a cold front in the northern Plains/Upper Midwest. See the previous discussion for additional details. ..Wendt.. 09/02/2025 .PREV DISCUSSION... /ISSUED 1125 AM CDT Tue Sep 02 2025/ ...Northern Plains/Upper Midwest... An upper trough over central Canada late this morning will dig southeastward towards the Upper Midwest/Lake Superior vicinity through the period. Showers and weak thunderstorms are ongoing over parts of central MN, aided by a remnant MCV over northern MN. This activity is forecast to further weaken this afternoon, with a residual outflow boundary arcing from southern MN west-northwestward towards the SD/MN border by mid afternoon. A cold front over ND will continue to advance southeastward into an adequately moist low-level airmass, with surface dewpoints generally in the lower to mid 60s. Filtered daytime heating away from this morning's convective cloud debris, along with modestly steepened mid-level lapse rates (reference 12Z ABR sounding), should aid in weak to locally moderate instability (MLCAPE around 1000-2000 J/kg) developing ahead of the front by mid to late afternoon. Latest model guidance remains consistent in showing isolated to scattered thunderstorms developing across roughly the eastern third of SD into central MN this afternoon along/near the cold front. There is considerable uncertainty regarding the degree of instability that will develop and related thunderstorm intensity given the widespread cloud cover in south-central MN. The stronger mid/upper-level flow associated with the upper trough over Canada will likely lag behind the surface front to some extent. This should limit effective bulk shear magnitudes (up to 20-30 kt). Even so, modestly organized multicells associated with isolated severe wind gusts and marginally severe hail appear possible, before this activity eventually subsides this evening with the loss of daytime heating. The Marginal Risk has been adjusted to account for the latest observational/short-term guidance trends. ...Lower Colorado River Valley... Compared to yesterday, modestly enhanced mid-level flow should trend more south-southeasterly today as a weak shortwave trough lifts northward from Baja California into the lower CO River Valley. Associated/ongoing showers and thunderstorms across southern CA should generally remain sub-severe through the morning as they track northwestward. In the wake of this activity, there is a fair amount of uncertainty regarding destabilization potential given scattered to widespread cloudiness over much of the lower CO River Valley. Wherever cloud breaks and heating can occur, steepening low-level lapse rates may support strong/gusty winds with any convection that can develop. Still, the potential for a focused area of severe gusts appears too low to include any probabilities at this time. Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 PM CDT Tue Sep 02 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THURSDAY IN A CORRIDOR FROM THE LEE OF THE ALLEGHENY MOUNTAINS INTO THE TENNESSEE VALLEY... ...SUMMARY... Scattered strong thunderstorms may impact a corridor from the lee of the Allegheny Mountains into the Tennessee Valley on Thursday, accompanied by a risk for potentially damaging wind gusts. ...Discussion... Models suggest that amplified large-scale mid-level troughing to the east of the Canadian/U.S. Rockies may continue to gradually consolidate during this period, becoming centered around a notable deepening and occluding cyclone across northern Ontario, to the west of James Bay. Around the southwestern periphery of this feature, a significant trailing short wave perturbation is forecast to dig across the northern U.S. Great Plains and Midwest through lower Great Lakes region, accompanied by a secondary surface cyclone and reinforcing cold intrusion from the lee of the northern Rockies through much of the central Great Plains and lower Missouri Valley by daybreak Friday. It appears that the occluding preceding front will progress east/southeast of the lower Great Lakes and Ohio Valley, before stalling and weakening, while seasonably high moisture content remains confined to a remnant preceding boundary across the southwestern Atlantic into southern Florida/southeastern Gulf Basin. ...Northern Mid Atlantic into Tennessee Valley... Aided by modestly steepening lower tropospheric lapse rates, it appears that residual boundary-layer moisture may become supportive of weak to modest destabilization, within at least a narrow pre-frontal corridor across the region during the day Thursday. This may include CAPE on the order of 500-1000 J/kg, in the presence of strengthening, but still modest, cyclonic west-southwesterly lower/mid-tropospheric flow, including 20-40+ kt in the 850-500 mb layer. It is possible that this environment may become conducive to at least widely scattered strong thunderstorm development capable of producing a few strong to potentially damaging wind gusts. ..Kerr.. 09/02/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 PM CDT Tue Sep 02 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THURSDAY IN A CORRIDOR FROM THE LEE OF THE ALLEGHENY MOUNTAINS INTO THE TENNESSEE VALLEY... ...SUMMARY... Scattered strong thunderstorms may impact a corridor from the lee of the Allegheny Mountains into the Tennessee Valley on Thursday, accompanied by a risk for potentially damaging wind gusts. ...Discussion... Models suggest that amplified large-scale mid-level troughing to the east of the Canadian/U.S. Rockies may continue to gradually consolidate during this period, becoming centered around a notable deepening and occluding cyclone across northern Ontario, to the west of James Bay. Around the southwestern periphery of this feature, a significant trailing short wave perturbation is forecast to dig across the northern U.S. Great Plains and Midwest through lower Great Lakes region, accompanied by a secondary surface cyclone and reinforcing cold intrusion from the lee of the northern Rockies through much of the central Great Plains and lower Missouri Valley by daybreak Friday. It appears that the occluding preceding front will progress east/southeast of the lower Great Lakes and Ohio Valley, before stalling and weakening, while seasonably high moisture content remains confined to a remnant preceding boundary across the southwestern Atlantic into southern Florida/southeastern Gulf Basin. ...Northern Mid Atlantic into Tennessee Valley... Aided by modestly steepening lower tropospheric lapse rates, it appears that residual boundary-layer moisture may become supportive of weak to modest destabilization, within at least a narrow pre-frontal corridor across the region during the day Thursday. This may include CAPE on the order of 500-1000 J/kg, in the presence of strengthening, but still modest, cyclonic west-southwesterly lower/mid-tropospheric flow, including 20-40+ kt in the 850-500 mb layer. It is possible that this environment may become conducive to at least widely scattered strong thunderstorm development capable of producing a few strong to potentially damaging wind gusts. ..Kerr.. 09/02/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 PM CDT Tue Sep 02 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THURSDAY IN A CORRIDOR FROM THE LEE OF THE ALLEGHENY MOUNTAINS INTO THE TENNESSEE VALLEY... ...SUMMARY... Scattered strong thunderstorms may impact a corridor from the lee of the Allegheny Mountains into the Tennessee Valley on Thursday, accompanied by a risk for potentially damaging wind gusts. ...Discussion... Models suggest that amplified large-scale mid-level troughing to the east of the Canadian/U.S. Rockies may continue to gradually consolidate during this period, becoming centered around a notable deepening and occluding cyclone across northern Ontario, to the west of James Bay. Around the southwestern periphery of this feature, a significant trailing short wave perturbation is forecast to dig across the northern U.S. Great Plains and Midwest through lower Great Lakes region, accompanied by a secondary surface cyclone and reinforcing cold intrusion from the lee of the northern Rockies through much of the central Great Plains and lower Missouri Valley by daybreak Friday. It appears that the occluding preceding front will progress east/southeast of the lower Great Lakes and Ohio Valley, before stalling and weakening, while seasonably high moisture content remains confined to a remnant preceding boundary across the southwestern Atlantic into southern Florida/southeastern Gulf Basin. ...Northern Mid Atlantic into Tennessee Valley... Aided by modestly steepening lower tropospheric lapse rates, it appears that residual boundary-layer moisture may become supportive of weak to modest destabilization, within at least a narrow pre-frontal corridor across the region during the day Thursday. This may include CAPE on the order of 500-1000 J/kg, in the presence of strengthening, but still modest, cyclonic west-southwesterly lower/mid-tropospheric flow, including 20-40+ kt in the 850-500 mb layer. It is possible that this environment may become conducive to at least widely scattered strong thunderstorm development capable of producing a few strong to potentially damaging wind gusts. ..Kerr.. 09/02/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 PM CDT Tue Sep 02 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THURSDAY IN A CORRIDOR FROM THE LEE OF THE ALLEGHENY MOUNTAINS INTO THE TENNESSEE VALLEY... ...SUMMARY... Scattered strong thunderstorms may impact a corridor from the lee of the Allegheny Mountains into the Tennessee Valley on Thursday, accompanied by a risk for potentially damaging wind gusts. ...Discussion... Models suggest that amplified large-scale mid-level troughing to the east of the Canadian/U.S. Rockies may continue to gradually consolidate during this period, becoming centered around a notable deepening and occluding cyclone across northern Ontario, to the west of James Bay. Around the southwestern periphery of this feature, a significant trailing short wave perturbation is forecast to dig across the northern U.S. Great Plains and Midwest through lower Great Lakes region, accompanied by a secondary surface cyclone and reinforcing cold intrusion from the lee of the northern Rockies through much of the central Great Plains and lower Missouri Valley by daybreak Friday. It appears that the occluding preceding front will progress east/southeast of the lower Great Lakes and Ohio Valley, before stalling and weakening, while seasonably high moisture content remains confined to a remnant preceding boundary across the southwestern Atlantic into southern Florida/southeastern Gulf Basin. ...Northern Mid Atlantic into Tennessee Valley... Aided by modestly steepening lower tropospheric lapse rates, it appears that residual boundary-layer moisture may become supportive of weak to modest destabilization, within at least a narrow pre-frontal corridor across the region during the day Thursday. This may include CAPE on the order of 500-1000 J/kg, in the presence of strengthening, but still modest, cyclonic west-southwesterly lower/mid-tropospheric flow, including 20-40+ kt in the 850-500 mb layer. It is possible that this environment may become conducive to at least widely scattered strong thunderstorm development capable of producing a few strong to potentially damaging wind gusts. ..Kerr.. 09/02/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 PM CDT Tue Sep 02 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THURSDAY IN A CORRIDOR FROM THE LEE OF THE ALLEGHENY MOUNTAINS INTO THE TENNESSEE VALLEY... ...SUMMARY... Scattered strong thunderstorms may impact a corridor from the lee of the Allegheny Mountains into the Tennessee Valley on Thursday, accompanied by a risk for potentially damaging wind gusts. ...Discussion... Models suggest that amplified large-scale mid-level troughing to the east of the Canadian/U.S. Rockies may continue to gradually consolidate during this period, becoming centered around a notable deepening and occluding cyclone across northern Ontario, to the west of James Bay. Around the southwestern periphery of this feature, a significant trailing short wave perturbation is forecast to dig across the northern U.S. Great Plains and Midwest through lower Great Lakes region, accompanied by a secondary surface cyclone and reinforcing cold intrusion from the lee of the northern Rockies through much of the central Great Plains and lower Missouri Valley by daybreak Friday. It appears that the occluding preceding front will progress east/southeast of the lower Great Lakes and Ohio Valley, before stalling and weakening, while seasonably high moisture content remains confined to a remnant preceding boundary across the southwestern Atlantic into southern Florida/southeastern Gulf Basin. ...Northern Mid Atlantic into Tennessee Valley... Aided by modestly steepening lower tropospheric lapse rates, it appears that residual boundary-layer moisture may become supportive of weak to modest destabilization, within at least a narrow pre-frontal corridor across the region during the day Thursday. This may include CAPE on the order of 500-1000 J/kg, in the presence of strengthening, but still modest, cyclonic west-southwesterly lower/mid-tropospheric flow, including 20-40+ kt in the 850-500 mb layer. It is possible that this environment may become conducive to at least widely scattered strong thunderstorm development capable of producing a few strong to potentially damaging wind gusts. ..Kerr.. 09/02/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 PM CDT Tue Sep 02 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THURSDAY IN A CORRIDOR FROM THE LEE OF THE ALLEGHENY MOUNTAINS INTO THE TENNESSEE VALLEY... ...SUMMARY... Scattered strong thunderstorms may impact a corridor from the lee of the Allegheny Mountains into the Tennessee Valley on Thursday, accompanied by a risk for potentially damaging wind gusts. ...Discussion... Models suggest that amplified large-scale mid-level troughing to the east of the Canadian/U.S. Rockies may continue to gradually consolidate during this period, becoming centered around a notable deepening and occluding cyclone across northern Ontario, to the west of James Bay. Around the southwestern periphery of this feature, a significant trailing short wave perturbation is forecast to dig across the northern U.S. Great Plains and Midwest through lower Great Lakes region, accompanied by a secondary surface cyclone and reinforcing cold intrusion from the lee of the northern Rockies through much of the central Great Plains and lower Missouri Valley by daybreak Friday. It appears that the occluding preceding front will progress east/southeast of the lower Great Lakes and Ohio Valley, before stalling and weakening, while seasonably high moisture content remains confined to a remnant preceding boundary across the southwestern Atlantic into southern Florida/southeastern Gulf Basin. ...Northern Mid Atlantic into Tennessee Valley... Aided by modestly steepening lower tropospheric lapse rates, it appears that residual boundary-layer moisture may become supportive of weak to modest destabilization, within at least a narrow pre-frontal corridor across the region during the day Thursday. This may include CAPE on the order of 500-1000 J/kg, in the presence of strengthening, but still modest, cyclonic west-southwesterly lower/mid-tropospheric flow, including 20-40+ kt in the 850-500 mb layer. It is possible that this environment may become conducive to at least widely scattered strong thunderstorm development capable of producing a few strong to potentially damaging wind gusts. ..Kerr.. 09/02/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 PM CDT Tue Sep 02 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THURSDAY IN A CORRIDOR FROM THE LEE OF THE ALLEGHENY MOUNTAINS INTO THE TENNESSEE VALLEY... ...SUMMARY... Scattered strong thunderstorms may impact a corridor from the lee of the Allegheny Mountains into the Tennessee Valley on Thursday, accompanied by a risk for potentially damaging wind gusts. ...Discussion... Models suggest that amplified large-scale mid-level troughing to the east of the Canadian/U.S. Rockies may continue to gradually consolidate during this period, becoming centered around a notable deepening and occluding cyclone across northern Ontario, to the west of James Bay. Around the southwestern periphery of this feature, a significant trailing short wave perturbation is forecast to dig across the northern U.S. Great Plains and Midwest through lower Great Lakes region, accompanied by a secondary surface cyclone and reinforcing cold intrusion from the lee of the northern Rockies through much of the central Great Plains and lower Missouri Valley by daybreak Friday. It appears that the occluding preceding front will progress east/southeast of the lower Great Lakes and Ohio Valley, before stalling and weakening, while seasonably high moisture content remains confined to a remnant preceding boundary across the southwestern Atlantic into southern Florida/southeastern Gulf Basin. ...Northern Mid Atlantic into Tennessee Valley... Aided by modestly steepening lower tropospheric lapse rates, it appears that residual boundary-layer moisture may become supportive of weak to modest destabilization, within at least a narrow pre-frontal corridor across the region during the day Thursday. This may include CAPE on the order of 500-1000 J/kg, in the presence of strengthening, but still modest, cyclonic west-southwesterly lower/mid-tropospheric flow, including 20-40+ kt in the 850-500 mb layer. It is possible that this environment may become conducive to at least widely scattered strong thunderstorm development capable of producing a few strong to potentially damaging wind gusts. ..Kerr.. 09/02/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 PM CDT Tue Sep 02 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THURSDAY IN A CORRIDOR FROM THE LEE OF THE ALLEGHENY MOUNTAINS INTO THE TENNESSEE VALLEY... ...SUMMARY... Scattered strong thunderstorms may impact a corridor from the lee of the Allegheny Mountains into the Tennessee Valley on Thursday, accompanied by a risk for potentially damaging wind gusts. ...Discussion... Models suggest that amplified large-scale mid-level troughing to the east of the Canadian/U.S. Rockies may continue to gradually consolidate during this period, becoming centered around a notable deepening and occluding cyclone across northern Ontario, to the west of James Bay. Around the southwestern periphery of this feature, a significant trailing short wave perturbation is forecast to dig across the northern U.S. Great Plains and Midwest through lower Great Lakes region, accompanied by a secondary surface cyclone and reinforcing cold intrusion from the lee of the northern Rockies through much of the central Great Plains and lower Missouri Valley by daybreak Friday. It appears that the occluding preceding front will progress east/southeast of the lower Great Lakes and Ohio Valley, before stalling and weakening, while seasonably high moisture content remains confined to a remnant preceding boundary across the southwestern Atlantic into southern Florida/southeastern Gulf Basin. ...Northern Mid Atlantic into Tennessee Valley... Aided by modestly steepening lower tropospheric lapse rates, it appears that residual boundary-layer moisture may become supportive of weak to modest destabilization, within at least a narrow pre-frontal corridor across the region during the day Thursday. This may include CAPE on the order of 500-1000 J/kg, in the presence of strengthening, but still modest, cyclonic west-southwesterly lower/mid-tropospheric flow, including 20-40+ kt in the 850-500 mb layer. It is possible that this environment may become conducive to at least widely scattered strong thunderstorm development capable of producing a few strong to potentially damaging wind gusts. ..Kerr.. 09/02/2025 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0135 PM CDT Tue Sep 02 2025 Valid 031200Z - 041200Z Latest guidance continues to show the potential for isolated to widely scattered thunderstorms on Wednesday across northern CA into OR and adjacent portions of far northwest NV as an upper wave (currently along the central CA coast) lifts northward. Thunderstorms may be ongoing at the start of the forecast period before a second round develops by late afternoon. High-res guidance hints at cloud cover during the day that may hinder diurnal heating and destabilization to some degree, and PWAT values near 0.75 inches may support swaths of wetting rainfall with the more intense convection (as hinted by some CAM solutions). However, antecedent dry conditions within the lowest 2-3 km AGL should modulate rainfall totals to some degree, and will support the potential for dry lightning strikes - especially with weaker, more isolated storms. With dry fuels already in place and ongoing fires noted across the region, the potential for dry-lightning/thunderstorm driven fire concerns remains sufficiently high to maintain ongoing highlights despite some forecast concerns. ..Moore.. 09/02/2025 .PREV DISCUSSION... /ISSUED 0156 AM CDT Tue Sep 02 2025/ ...Synopsis... As the upper-level low continues to shift northward through D2/Wednesday, the isolated dry thunderstorms chances will continue across northern California into central Oregon, southern Washington, and western Idaho. Storm motions will decrease but coverage and moisture may also decrease with more isolated lingering activity expected. An isolated dry thunderstorm area was maintained with this outlook to cover this potential. ...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 0135 PM CDT Tue Sep 02 2025 Valid 031200Z - 041200Z Latest guidance continues to show the potential for isolated to widely scattered thunderstorms on Wednesday across northern CA into OR and adjacent portions of far northwest NV as an upper wave (currently along the central CA coast) lifts northward. Thunderstorms may be ongoing at the start of the forecast period before a second round develops by late afternoon. High-res guidance hints at cloud cover during the day that may hinder diurnal heating and destabilization to some degree, and PWAT values near 0.75 inches may support swaths of wetting rainfall with the more intense convection (as hinted by some CAM solutions). However, antecedent dry conditions within the lowest 2-3 km AGL should modulate rainfall totals to some degree, and will support the potential for dry lightning strikes - especially with weaker, more isolated storms. With dry fuels already in place and ongoing fires noted across the region, the potential for dry-lightning/thunderstorm driven fire concerns remains sufficiently high to maintain ongoing highlights despite some forecast concerns. ..Moore.. 09/02/2025 .PREV DISCUSSION... /ISSUED 0156 AM CDT Tue Sep 02 2025/ ...Synopsis... As the upper-level low continues to shift northward through D2/Wednesday, the isolated dry thunderstorms chances will continue across northern California into central Oregon, southern Washington, and western Idaho. Storm motions will decrease but coverage and moisture may also decrease with more isolated lingering activity expected. An isolated dry thunderstorm area was maintained with this outlook to cover this potential. ...Please see www.spc.noaa.gov/fire for graphic product... Read more