Severe Storms

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1125 AM CDT Tue Sep 02 2025 Valid 021630Z - 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. ...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. ..Gleason/Lyons.. 09/02/2025 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1125 AM CDT Tue Sep 02 2025 Valid 021630Z - 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. ...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. ..Gleason/Lyons.. 09/02/2025 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1125 AM CDT Tue Sep 02 2025 Valid 021630Z - 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. ...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. ..Gleason/Lyons.. 09/02/2025 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1125 AM CDT Tue Sep 02 2025 Valid 021630Z - 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. ...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. ..Gleason/Lyons.. 09/02/2025 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1101 AM CDT Tue Sep 02 2025 Valid 021700Z - 031200Z The previous forecast largely remains on track with only minor adjustments made to account for recent convective trends. Through 15 UTC this morning, radar rainfall estimates and lightning data suggest a mix of wet and dry thunderstorms is ongoing across the Central Valley. Additional thunderstorm development remains likely through the evening hours across northern CA, northwest NV, and central OR. While 12 UTC guidance has captured the ongoing activity well, most solutions initialized with a notable warm/dry bias across northern CA and adjacent portions of OR/NV, suggesting that moisture quality may be slightly better than depicted by morning solutions. Additionally, mid/high-level cloud cover associated with the ongoing showers/thunderstorms will continue to spread north and may modulate diurnal heating/mixing to some degree over parts of northern CA/southern OR. These factors, coupled with forecast PWAT values between 0.6 to 0.8 inches, hint that a mix of dry/wet thunderstorms is probable for northern CA/southern OR with an increasing chance for dry lightning with north and eastward extent if/where storms can develop ahead of the approaching cloud cover. ..Moore.. 09/02/2025 .PREV DISCUSSION... /ISSUED 0155 AM CDT Tue Sep 02 2025/ ...Synopsis... A weak upper-level low will move northward across northern California into the Pacific Northwest today through D2/Wednesday, with increases in moisture and forcing leading to thunderstorm development. Precipitable water values will approach 0.60-0.90", decreasing with eastward extent across eastern Oregon/western Nevada. Faster storm motions around 15-20 kts will likely lead to a mix of wet/dry thunderstorms. New starts will be possible where little to no precipitation occurs, with ERCs around the 80th-90th percentile across portions of these regions. An isolated dry thunderstorm area was maintained with this outlook across portions of northern California into western Nevada an northward into central Oregon. ...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 1101 AM CDT Tue Sep 02 2025 Valid 021700Z - 031200Z The previous forecast largely remains on track with only minor adjustments made to account for recent convective trends. Through 15 UTC this morning, radar rainfall estimates and lightning data suggest a mix of wet and dry thunderstorms is ongoing across the Central Valley. Additional thunderstorm development remains likely through the evening hours across northern CA, northwest NV, and central OR. While 12 UTC guidance has captured the ongoing activity well, most solutions initialized with a notable warm/dry bias across northern CA and adjacent portions of OR/NV, suggesting that moisture quality may be slightly better than depicted by morning solutions. Additionally, mid/high-level cloud cover associated with the ongoing showers/thunderstorms will continue to spread north and may modulate diurnal heating/mixing to some degree over parts of northern CA/southern OR. These factors, coupled with forecast PWAT values between 0.6 to 0.8 inches, hint that a mix of dry/wet thunderstorms is probable for northern CA/southern OR with an increasing chance for dry lightning with north and eastward extent if/where storms can develop ahead of the approaching cloud cover. ..Moore.. 09/02/2025 .PREV DISCUSSION... /ISSUED 0155 AM CDT Tue Sep 02 2025/ ...Synopsis... A weak upper-level low will move northward across northern California into the Pacific Northwest today through D2/Wednesday, with increases in moisture and forcing leading to thunderstorm development. Precipitable water values will approach 0.60-0.90", decreasing with eastward extent across eastern Oregon/western Nevada. Faster storm motions around 15-20 kts will likely lead to a mix of wet/dry thunderstorms. New starts will be possible where little to no precipitation occurs, with ERCs around the 80th-90th percentile across portions of these regions. An isolated dry thunderstorm area was maintained with this outlook across portions of northern California into western Nevada an northward into central Oregon. ...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 1101 AM CDT Tue Sep 02 2025 Valid 021700Z - 031200Z The previous forecast largely remains on track with only minor adjustments made to account for recent convective trends. Through 15 UTC this morning, radar rainfall estimates and lightning data suggest a mix of wet and dry thunderstorms is ongoing across the Central Valley. Additional thunderstorm development remains likely through the evening hours across northern CA, northwest NV, and central OR. While 12 UTC guidance has captured the ongoing activity well, most solutions initialized with a notable warm/dry bias across northern CA and adjacent portions of OR/NV, suggesting that moisture quality may be slightly better than depicted by morning solutions. Additionally, mid/high-level cloud cover associated with the ongoing showers/thunderstorms will continue to spread north and may modulate diurnal heating/mixing to some degree over parts of northern CA/southern OR. These factors, coupled with forecast PWAT values between 0.6 to 0.8 inches, hint that a mix of dry/wet thunderstorms is probable for northern CA/southern OR with an increasing chance for dry lightning with north and eastward extent if/where storms can develop ahead of the approaching cloud cover. ..Moore.. 09/02/2025 .PREV DISCUSSION... /ISSUED 0155 AM CDT Tue Sep 02 2025/ ...Synopsis... A weak upper-level low will move northward across northern California into the Pacific Northwest today through D2/Wednesday, with increases in moisture and forcing leading to thunderstorm development. Precipitable water values will approach 0.60-0.90", decreasing with eastward extent across eastern Oregon/western Nevada. Faster storm motions around 15-20 kts will likely lead to a mix of wet/dry thunderstorms. New starts will be possible where little to no precipitation occurs, with ERCs around the 80th-90th percentile across portions of these regions. An isolated dry thunderstorm area was maintained with this outlook across portions of northern California into western Nevada an northward into central Oregon. ...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 1101 AM CDT Tue Sep 02 2025 Valid 021700Z - 031200Z The previous forecast largely remains on track with only minor adjustments made to account for recent convective trends. Through 15 UTC this morning, radar rainfall estimates and lightning data suggest a mix of wet and dry thunderstorms is ongoing across the Central Valley. Additional thunderstorm development remains likely through the evening hours across northern CA, northwest NV, and central OR. While 12 UTC guidance has captured the ongoing activity well, most solutions initialized with a notable warm/dry bias across northern CA and adjacent portions of OR/NV, suggesting that moisture quality may be slightly better than depicted by morning solutions. Additionally, mid/high-level cloud cover associated with the ongoing showers/thunderstorms will continue to spread north and may modulate diurnal heating/mixing to some degree over parts of northern CA/southern OR. These factors, coupled with forecast PWAT values between 0.6 to 0.8 inches, hint that a mix of dry/wet thunderstorms is probable for northern CA/southern OR with an increasing chance for dry lightning with north and eastward extent if/where storms can develop ahead of the approaching cloud cover. ..Moore.. 09/02/2025 .PREV DISCUSSION... /ISSUED 0155 AM CDT Tue Sep 02 2025/ ...Synopsis... A weak upper-level low will move northward across northern California into the Pacific Northwest today through D2/Wednesday, with increases in moisture and forcing leading to thunderstorm development. Precipitable water values will approach 0.60-0.90", decreasing with eastward extent across eastern Oregon/western Nevada. Faster storm motions around 15-20 kts will likely lead to a mix of wet/dry thunderstorms. New starts will be possible where little to no precipitation occurs, with ERCs around the 80th-90th percentile across portions of these regions. An isolated dry thunderstorm area was maintained with this outlook across portions of northern California into western Nevada an northward into central Oregon. ...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 1101 AM CDT Tue Sep 02 2025 Valid 021700Z - 031200Z The previous forecast largely remains on track with only minor adjustments made to account for recent convective trends. Through 15 UTC this morning, radar rainfall estimates and lightning data suggest a mix of wet and dry thunderstorms is ongoing across the Central Valley. Additional thunderstorm development remains likely through the evening hours across northern CA, northwest NV, and central OR. While 12 UTC guidance has captured the ongoing activity well, most solutions initialized with a notable warm/dry bias across northern CA and adjacent portions of OR/NV, suggesting that moisture quality may be slightly better than depicted by morning solutions. Additionally, mid/high-level cloud cover associated with the ongoing showers/thunderstorms will continue to spread north and may modulate diurnal heating/mixing to some degree over parts of northern CA/southern OR. These factors, coupled with forecast PWAT values between 0.6 to 0.8 inches, hint that a mix of dry/wet thunderstorms is probable for northern CA/southern OR with an increasing chance for dry lightning with north and eastward extent if/where storms can develop ahead of the approaching cloud cover. ..Moore.. 09/02/2025 .PREV DISCUSSION... /ISSUED 0155 AM CDT Tue Sep 02 2025/ ...Synopsis... A weak upper-level low will move northward across northern California into the Pacific Northwest today through D2/Wednesday, with increases in moisture and forcing leading to thunderstorm development. Precipitable water values will approach 0.60-0.90", decreasing with eastward extent across eastern Oregon/western Nevada. Faster storm motions around 15-20 kts will likely lead to a mix of wet/dry thunderstorms. New starts will be possible where little to no precipitation occurs, with ERCs around the 80th-90th percentile across portions of these regions. An isolated dry thunderstorm area was maintained with this outlook across portions of northern California into western Nevada an northward into central Oregon. ...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 1101 AM CDT Tue Sep 02 2025 Valid 021700Z - 031200Z The previous forecast largely remains on track with only minor adjustments made to account for recent convective trends. Through 15 UTC this morning, radar rainfall estimates and lightning data suggest a mix of wet and dry thunderstorms is ongoing across the Central Valley. Additional thunderstorm development remains likely through the evening hours across northern CA, northwest NV, and central OR. While 12 UTC guidance has captured the ongoing activity well, most solutions initialized with a notable warm/dry bias across northern CA and adjacent portions of OR/NV, suggesting that moisture quality may be slightly better than depicted by morning solutions. Additionally, mid/high-level cloud cover associated with the ongoing showers/thunderstorms will continue to spread north and may modulate diurnal heating/mixing to some degree over parts of northern CA/southern OR. These factors, coupled with forecast PWAT values between 0.6 to 0.8 inches, hint that a mix of dry/wet thunderstorms is probable for northern CA/southern OR with an increasing chance for dry lightning with north and eastward extent if/where storms can develop ahead of the approaching cloud cover. ..Moore.. 09/02/2025 .PREV DISCUSSION... /ISSUED 0155 AM CDT Tue Sep 02 2025/ ...Synopsis... A weak upper-level low will move northward across northern California into the Pacific Northwest today through D2/Wednesday, with increases in moisture and forcing leading to thunderstorm development. Precipitable water values will approach 0.60-0.90", decreasing with eastward extent across eastern Oregon/western Nevada. Faster storm motions around 15-20 kts will likely lead to a mix of wet/dry thunderstorms. New starts will be possible where little to no precipitation occurs, with ERCs around the 80th-90th percentile across portions of these regions. An isolated dry thunderstorm area was maintained with this outlook across portions of northern California into western Nevada an northward into central Oregon. ...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 1101 AM CDT Tue Sep 02 2025 Valid 021700Z - 031200Z The previous forecast largely remains on track with only minor adjustments made to account for recent convective trends. Through 15 UTC this morning, radar rainfall estimates and lightning data suggest a mix of wet and dry thunderstorms is ongoing across the Central Valley. Additional thunderstorm development remains likely through the evening hours across northern CA, northwest NV, and central OR. While 12 UTC guidance has captured the ongoing activity well, most solutions initialized with a notable warm/dry bias across northern CA and adjacent portions of OR/NV, suggesting that moisture quality may be slightly better than depicted by morning solutions. Additionally, mid/high-level cloud cover associated with the ongoing showers/thunderstorms will continue to spread north and may modulate diurnal heating/mixing to some degree over parts of northern CA/southern OR. These factors, coupled with forecast PWAT values between 0.6 to 0.8 inches, hint that a mix of dry/wet thunderstorms is probable for northern CA/southern OR with an increasing chance for dry lightning with north and eastward extent if/where storms can develop ahead of the approaching cloud cover. ..Moore.. 09/02/2025 .PREV DISCUSSION... /ISSUED 0155 AM CDT Tue Sep 02 2025/ ...Synopsis... A weak upper-level low will move northward across northern California into the Pacific Northwest today through D2/Wednesday, with increases in moisture and forcing leading to thunderstorm development. Precipitable water values will approach 0.60-0.90", decreasing with eastward extent across eastern Oregon/western Nevada. Faster storm motions around 15-20 kts will likely lead to a mix of wet/dry thunderstorms. New starts will be possible where little to no precipitation occurs, with ERCs around the 80th-90th percentile across portions of these regions. An isolated dry thunderstorm area was maintained with this outlook across portions of northern California into western Nevada an northward into central Oregon. ...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 1101 AM CDT Tue Sep 02 2025 Valid 021700Z - 031200Z The previous forecast largely remains on track with only minor adjustments made to account for recent convective trends. Through 15 UTC this morning, radar rainfall estimates and lightning data suggest a mix of wet and dry thunderstorms is ongoing across the Central Valley. Additional thunderstorm development remains likely through the evening hours across northern CA, northwest NV, and central OR. While 12 UTC guidance has captured the ongoing activity well, most solutions initialized with a notable warm/dry bias across northern CA and adjacent portions of OR/NV, suggesting that moisture quality may be slightly better than depicted by morning solutions. Additionally, mid/high-level cloud cover associated with the ongoing showers/thunderstorms will continue to spread north and may modulate diurnal heating/mixing to some degree over parts of northern CA/southern OR. These factors, coupled with forecast PWAT values between 0.6 to 0.8 inches, hint that a mix of dry/wet thunderstorms is probable for northern CA/southern OR with an increasing chance for dry lightning with north and eastward extent if/where storms can develop ahead of the approaching cloud cover. ..Moore.. 09/02/2025 .PREV DISCUSSION... /ISSUED 0155 AM CDT Tue Sep 02 2025/ ...Synopsis... A weak upper-level low will move northward across northern California into the Pacific Northwest today through D2/Wednesday, with increases in moisture and forcing leading to thunderstorm development. Precipitable water values will approach 0.60-0.90", decreasing with eastward extent across eastern Oregon/western Nevada. Faster storm motions around 15-20 kts will likely lead to a mix of wet/dry thunderstorms. New starts will be possible where little to no precipitation occurs, with ERCs around the 80th-90th percentile across portions of these regions. An isolated dry thunderstorm area was maintained with this outlook across portions of northern California into western Nevada an northward into central Oregon. ...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 1101 AM CDT Tue Sep 02 2025 Valid 021700Z - 031200Z The previous forecast largely remains on track with only minor adjustments made to account for recent convective trends. Through 15 UTC this morning, radar rainfall estimates and lightning data suggest a mix of wet and dry thunderstorms is ongoing across the Central Valley. Additional thunderstorm development remains likely through the evening hours across northern CA, northwest NV, and central OR. While 12 UTC guidance has captured the ongoing activity well, most solutions initialized with a notable warm/dry bias across northern CA and adjacent portions of OR/NV, suggesting that moisture quality may be slightly better than depicted by morning solutions. Additionally, mid/high-level cloud cover associated with the ongoing showers/thunderstorms will continue to spread north and may modulate diurnal heating/mixing to some degree over parts of northern CA/southern OR. These factors, coupled with forecast PWAT values between 0.6 to 0.8 inches, hint that a mix of dry/wet thunderstorms is probable for northern CA/southern OR with an increasing chance for dry lightning with north and eastward extent if/where storms can develop ahead of the approaching cloud cover. ..Moore.. 09/02/2025 .PREV DISCUSSION... /ISSUED 0155 AM CDT Tue Sep 02 2025/ ...Synopsis... A weak upper-level low will move northward across northern California into the Pacific Northwest today through D2/Wednesday, with increases in moisture and forcing leading to thunderstorm development. Precipitable water values will approach 0.60-0.90", decreasing with eastward extent across eastern Oregon/western Nevada. Faster storm motions around 15-20 kts will likely lead to a mix of wet/dry thunderstorms. New starts will be possible where little to no precipitation occurs, with ERCs around the 80th-90th percentile across portions of these regions. An isolated dry thunderstorm area was maintained with this outlook across portions of northern California into western Nevada an northward into central Oregon. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0733 AM CDT Tue Sep 02 2025 Valid 021300Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE UPPER MIDWEST... ...SUMMARY... Thunderstorms with potential for isolated severe wind gusts and marginally severe hail will be possible this afternoon into the early evening across parts of the Upper Midwest. ...Upper Midwest... An upper trough initially over central Canada will dig southeastward into the Upper Midwest/Lake Superior vicinity during the period. Showers and weak thunderstorms ongoing this morning over MN, aided by an MCV over northern MN, will gradually dissipate with differential heating/residual outflow arcing from southern MN west-northwestward towards the Dakotas/MN border by mid afternoon. A cold front initially over ND will advance southeastward into an adequately moist airmass, featuring surface dewpoints in the lower to mid 60s F ahead of it. Diurnal heating will likely yield moderate SBCAPE (1500-2000 J/kg) ahead of the front by mid-late afternoon. Model guidance is consistent in showing a band of scattered thunderstorms developing from the eastern half of SD into central MN by the mid-late afternoon. Upscale growth with higher storm coverage is expected from near the MN/SD border eastward into central and southern MN during the 22-02 UTC period. The stronger mid- and upper-level flow will likely lag behind the surface front and limit effective shear magnitudes (at or below 25 kt). However, a few organized multicells could be associated with isolated severe wind gusts and hail before this activity subsides during the early-mid evening. ..Smith/Bentley.. 09/02/2025 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0733 AM CDT Tue Sep 02 2025 Valid 021300Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE UPPER MIDWEST... ...SUMMARY... Thunderstorms with potential for isolated severe wind gusts and marginally severe hail will be possible this afternoon into the early evening across parts of the Upper Midwest. ...Upper Midwest... An upper trough initially over central Canada will dig southeastward into the Upper Midwest/Lake Superior vicinity during the period. Showers and weak thunderstorms ongoing this morning over MN, aided by an MCV over northern MN, will gradually dissipate with differential heating/residual outflow arcing from southern MN west-northwestward towards the Dakotas/MN border by mid afternoon. A cold front initially over ND will advance southeastward into an adequately moist airmass, featuring surface dewpoints in the lower to mid 60s F ahead of it. Diurnal heating will likely yield moderate SBCAPE (1500-2000 J/kg) ahead of the front by mid-late afternoon. Model guidance is consistent in showing a band of scattered thunderstorms developing from the eastern half of SD into central MN by the mid-late afternoon. Upscale growth with higher storm coverage is expected from near the MN/SD border eastward into central and southern MN during the 22-02 UTC period. The stronger mid- and upper-level flow will likely lag behind the surface front and limit effective shear magnitudes (at or below 25 kt). However, a few organized multicells could be associated with isolated severe wind gusts and hail before this activity subsides during the early-mid evening. ..Smith/Bentley.. 09/02/2025 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0733 AM CDT Tue Sep 02 2025 Valid 021300Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE UPPER MIDWEST... ...SUMMARY... Thunderstorms with potential for isolated severe wind gusts and marginally severe hail will be possible this afternoon into the early evening across parts of the Upper Midwest. ...Upper Midwest... An upper trough initially over central Canada will dig southeastward into the Upper Midwest/Lake Superior vicinity during the period. Showers and weak thunderstorms ongoing this morning over MN, aided by an MCV over northern MN, will gradually dissipate with differential heating/residual outflow arcing from southern MN west-northwestward towards the Dakotas/MN border by mid afternoon. A cold front initially over ND will advance southeastward into an adequately moist airmass, featuring surface dewpoints in the lower to mid 60s F ahead of it. Diurnal heating will likely yield moderate SBCAPE (1500-2000 J/kg) ahead of the front by mid-late afternoon. Model guidance is consistent in showing a band of scattered thunderstorms developing from the eastern half of SD into central MN by the mid-late afternoon. Upscale growth with higher storm coverage is expected from near the MN/SD border eastward into central and southern MN during the 22-02 UTC period. The stronger mid- and upper-level flow will likely lag behind the surface front and limit effective shear magnitudes (at or below 25 kt). However, a few organized multicells could be associated with isolated severe wind gusts and hail before this activity subsides during the early-mid evening. ..Smith/Bentley.. 09/02/2025 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0733 AM CDT Tue Sep 02 2025 Valid 021300Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE UPPER MIDWEST... ...SUMMARY... Thunderstorms with potential for isolated severe wind gusts and marginally severe hail will be possible this afternoon into the early evening across parts of the Upper Midwest. ...Upper Midwest... An upper trough initially over central Canada will dig southeastward into the Upper Midwest/Lake Superior vicinity during the period. Showers and weak thunderstorms ongoing this morning over MN, aided by an MCV over northern MN, will gradually dissipate with differential heating/residual outflow arcing from southern MN west-northwestward towards the Dakotas/MN border by mid afternoon. A cold front initially over ND will advance southeastward into an adequately moist airmass, featuring surface dewpoints in the lower to mid 60s F ahead of it. Diurnal heating will likely yield moderate SBCAPE (1500-2000 J/kg) ahead of the front by mid-late afternoon. Model guidance is consistent in showing a band of scattered thunderstorms developing from the eastern half of SD into central MN by the mid-late afternoon. Upscale growth with higher storm coverage is expected from near the MN/SD border eastward into central and southern MN during the 22-02 UTC period. The stronger mid- and upper-level flow will likely lag behind the surface front and limit effective shear magnitudes (at or below 25 kt). However, a few organized multicells could be associated with isolated severe wind gusts and hail before this activity subsides during the early-mid evening. ..Smith/Bentley.. 09/02/2025 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0733 AM CDT Tue Sep 02 2025 Valid 021300Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE UPPER MIDWEST... ...SUMMARY... Thunderstorms with potential for isolated severe wind gusts and marginally severe hail will be possible this afternoon into the early evening across parts of the Upper Midwest. ...Upper Midwest... An upper trough initially over central Canada will dig southeastward into the Upper Midwest/Lake Superior vicinity during the period. Showers and weak thunderstorms ongoing this morning over MN, aided by an MCV over northern MN, will gradually dissipate with differential heating/residual outflow arcing from southern MN west-northwestward towards the Dakotas/MN border by mid afternoon. A cold front initially over ND will advance southeastward into an adequately moist airmass, featuring surface dewpoints in the lower to mid 60s F ahead of it. Diurnal heating will likely yield moderate SBCAPE (1500-2000 J/kg) ahead of the front by mid-late afternoon. Model guidance is consistent in showing a band of scattered thunderstorms developing from the eastern half of SD into central MN by the mid-late afternoon. Upscale growth with higher storm coverage is expected from near the MN/SD border eastward into central and southern MN during the 22-02 UTC period. The stronger mid- and upper-level flow will likely lag behind the surface front and limit effective shear magnitudes (at or below 25 kt). However, a few organized multicells could be associated with isolated severe wind gusts and hail before this activity subsides during the early-mid evening. ..Smith/Bentley.. 09/02/2025 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0334 AM CDT Tue Sep 02 2025 Valid 051200Z - 101200Z ...DISCUSSION... A pronounced mid-level trough will progress across the Northeast late this week, ejecting into the Atlantic by the end of the weekend. Thereafter, a more progressive pattern will ensue, with multiple mid-level shortwave troughs poised to traverse the CONUS early into the middle of next week. Despite differences among medium-range guidance members, there is general agreement that a surface cold front will encounter seasonal low-level moisture across the eastern U.S. Days 4-5 (Friday-Saturday), promoting thunderstorm potential (some of which may be strong). However, any severe threat accompanying these storms is expected to be localized and isolated. Surface high pressure will then become established from the MS River Valley eastward, allowing for moisture return across the Plains states by next week. Nonetheless, overall forcing for ascent, along with buoyancy, are expected to be weak over the Plains next week, with severe potential currently appearing low. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0334 AM CDT Tue Sep 02 2025 Valid 051200Z - 101200Z ...DISCUSSION... A pronounced mid-level trough will progress across the Northeast late this week, ejecting into the Atlantic by the end of the weekend. Thereafter, a more progressive pattern will ensue, with multiple mid-level shortwave troughs poised to traverse the CONUS early into the middle of next week. Despite differences among medium-range guidance members, there is general agreement that a surface cold front will encounter seasonal low-level moisture across the eastern U.S. Days 4-5 (Friday-Saturday), promoting thunderstorm potential (some of which may be strong). However, any severe threat accompanying these storms is expected to be localized and isolated. Surface high pressure will then become established from the MS River Valley eastward, allowing for moisture return across the Plains states by next week. Nonetheless, overall forcing for ascent, along with buoyancy, are expected to be weak over the Plains next week, with severe potential currently appearing low. Read more