Severe Storms

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 PM CDT Wed Sep 03 2025 Valid 051200Z - 061200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... A couple strong thunderstorms will be possible from the Ohio/Tennessee Valleys to the southern Plains and across parts of Oregon on Friday, though the potential for organized severe storms appears low. ...Discussion... A broad midlevel trough centered on the Great Lakes region will shift slightly eastward through the period, as a midlevel speed maximum advances east-northeastward from the Great Lakes into Quebec. A related surface low will track northeastward from Ontario into Quebec, while a cold front extents southwestward across the OH Valley to a separate surface low in the southern Great Plains. Given a slow east-southeastward motion of the front and large-scale forcing for ascent lagging behind, thunderstorms may tend to be anafrontal. However, if any thunderstorms can develop along/immediately ahead of the front from the OH/TN Valleys into the southern Plains, ample moisture/buoyancy and around 30 kt of midlevel west-southwesterly flow would conditionally support a couple strong/loosely organized storms. Farther west, a midlevel trough will approach the Pacific Northwest through the period. Related forcing for ascent will promote scattered thunderstorms across OR. Moderately enhanced midlevel flow and steep deep-layer lapse rates may promote a couple strong storms capable of producing locally strong wind gusts. ..Weinman.. 09/03/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 PM CDT Wed Sep 03 2025 Valid 051200Z - 061200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... A couple strong thunderstorms will be possible from the Ohio/Tennessee Valleys to the southern Plains and across parts of Oregon on Friday, though the potential for organized severe storms appears low. ...Discussion... A broad midlevel trough centered on the Great Lakes region will shift slightly eastward through the period, as a midlevel speed maximum advances east-northeastward from the Great Lakes into Quebec. A related surface low will track northeastward from Ontario into Quebec, while a cold front extents southwestward across the OH Valley to a separate surface low in the southern Great Plains. Given a slow east-southeastward motion of the front and large-scale forcing for ascent lagging behind, thunderstorms may tend to be anafrontal. However, if any thunderstorms can develop along/immediately ahead of the front from the OH/TN Valleys into the southern Plains, ample moisture/buoyancy and around 30 kt of midlevel west-southwesterly flow would conditionally support a couple strong/loosely organized storms. Farther west, a midlevel trough will approach the Pacific Northwest through the period. Related forcing for ascent will promote scattered thunderstorms across OR. Moderately enhanced midlevel flow and steep deep-layer lapse rates may promote a couple strong storms capable of producing locally strong wind gusts. ..Weinman.. 09/03/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 PM CDT Wed Sep 03 2025 Valid 051200Z - 061200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... A couple strong thunderstorms will be possible from the Ohio/Tennessee Valleys to the southern Plains and across parts of Oregon on Friday, though the potential for organized severe storms appears low. ...Discussion... A broad midlevel trough centered on the Great Lakes region will shift slightly eastward through the period, as a midlevel speed maximum advances east-northeastward from the Great Lakes into Quebec. A related surface low will track northeastward from Ontario into Quebec, while a cold front extents southwestward across the OH Valley to a separate surface low in the southern Great Plains. Given a slow east-southeastward motion of the front and large-scale forcing for ascent lagging behind, thunderstorms may tend to be anafrontal. However, if any thunderstorms can develop along/immediately ahead of the front from the OH/TN Valleys into the southern Plains, ample moisture/buoyancy and around 30 kt of midlevel west-southwesterly flow would conditionally support a couple strong/loosely organized storms. Farther west, a midlevel trough will approach the Pacific Northwest through the period. Related forcing for ascent will promote scattered thunderstorms across OR. Moderately enhanced midlevel flow and steep deep-layer lapse rates may promote a couple strong storms capable of producing locally strong wind gusts. ..Weinman.. 09/03/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 PM CDT Wed Sep 03 2025 Valid 051200Z - 061200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... A couple strong thunderstorms will be possible from the Ohio/Tennessee Valleys to the southern Plains and across parts of Oregon on Friday, though the potential for organized severe storms appears low. ...Discussion... A broad midlevel trough centered on the Great Lakes region will shift slightly eastward through the period, as a midlevel speed maximum advances east-northeastward from the Great Lakes into Quebec. A related surface low will track northeastward from Ontario into Quebec, while a cold front extents southwestward across the OH Valley to a separate surface low in the southern Great Plains. Given a slow east-southeastward motion of the front and large-scale forcing for ascent lagging behind, thunderstorms may tend to be anafrontal. However, if any thunderstorms can develop along/immediately ahead of the front from the OH/TN Valleys into the southern Plains, ample moisture/buoyancy and around 30 kt of midlevel west-southwesterly flow would conditionally support a couple strong/loosely organized storms. Farther west, a midlevel trough will approach the Pacific Northwest through the period. Related forcing for ascent will promote scattered thunderstorms across OR. Moderately enhanced midlevel flow and steep deep-layer lapse rates may promote a couple strong storms capable of producing locally strong wind gusts. ..Weinman.. 09/03/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 PM CDT Wed Sep 03 2025 Valid 051200Z - 061200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... A couple strong thunderstorms will be possible from the Ohio/Tennessee Valleys to the southern Plains and across parts of Oregon on Friday, though the potential for organized severe storms appears low. ...Discussion... A broad midlevel trough centered on the Great Lakes region will shift slightly eastward through the period, as a midlevel speed maximum advances east-northeastward from the Great Lakes into Quebec. A related surface low will track northeastward from Ontario into Quebec, while a cold front extents southwestward across the OH Valley to a separate surface low in the southern Great Plains. Given a slow east-southeastward motion of the front and large-scale forcing for ascent lagging behind, thunderstorms may tend to be anafrontal. However, if any thunderstorms can develop along/immediately ahead of the front from the OH/TN Valleys into the southern Plains, ample moisture/buoyancy and around 30 kt of midlevel west-southwesterly flow would conditionally support a couple strong/loosely organized storms. Farther west, a midlevel trough will approach the Pacific Northwest through the period. Related forcing for ascent will promote scattered thunderstorms across OR. Moderately enhanced midlevel flow and steep deep-layer lapse rates may promote a couple strong storms capable of producing locally strong wind gusts. ..Weinman.. 09/03/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 PM CDT Wed Sep 03 2025 Valid 051200Z - 061200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... A couple strong thunderstorms will be possible from the Ohio/Tennessee Valleys to the southern Plains and across parts of Oregon on Friday, though the potential for organized severe storms appears low. ...Discussion... A broad midlevel trough centered on the Great Lakes region will shift slightly eastward through the period, as a midlevel speed maximum advances east-northeastward from the Great Lakes into Quebec. A related surface low will track northeastward from Ontario into Quebec, while a cold front extents southwestward across the OH Valley to a separate surface low in the southern Great Plains. Given a slow east-southeastward motion of the front and large-scale forcing for ascent lagging behind, thunderstorms may tend to be anafrontal. However, if any thunderstorms can develop along/immediately ahead of the front from the OH/TN Valleys into the southern Plains, ample moisture/buoyancy and around 30 kt of midlevel west-southwesterly flow would conditionally support a couple strong/loosely organized storms. Farther west, a midlevel trough will approach the Pacific Northwest through the period. Related forcing for ascent will promote scattered thunderstorms across OR. Moderately enhanced midlevel flow and steep deep-layer lapse rates may promote a couple strong storms capable of producing locally strong wind gusts. ..Weinman.. 09/03/2025 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1231 PM CDT Wed Sep 03 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE TENNESSEE VALLEY AND SOUTHERN APPALACHIANS NORTHWARD INTO NEW YORK... ...SUMMARY... Scattered strong thunderstorms capable of producing locally damaging wind gusts may impact a corridor from the Tennessee Valley and southern Appalachians northward through northern New York on Thursday. ...Synopsis... A deep/vertically stacked low pressure system will retrograde slightly westward over Ontario through the forecast period, while broad large-scale troughing encompasses much of the eastern CONUS. An embedded midlevel trough will track eastward across the Lower Great Lakes during the day, while a related cold front extending from NY south-southwestward along the Appalachians moves gradually eastward. ...TN Valley and Southern Appalachians northward into NY... Despite poor midlevel lapse rates, diurnal heating amid middle/upper 50 to lower 60s dewpoints will result in a corridor of weak to locally moderate surface-based buoyancy ahead of the front during the afternoon. Scattered thunderstorms are expected along/ahead of the front, where 30-40 kt of effective shear will promote loosely organized multicell clusters and line segments. The stronger storm clusters will be capable of producing locally damaging wind gusts through the afternoon. ...Northern Plains... On the backside of the large-scale trough, a robust midlevel speed maximum will move into the northern Plains during the day. Strong forcing for ascent and cold temperatures aloft will support isolated thunderstorms. While deep-layer shear will be sufficient for organized storms, the post-frontal nature of this activity should limit the overall severe risk. ..Weinman.. 09/03/2025 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1231 PM CDT Wed Sep 03 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE TENNESSEE VALLEY AND SOUTHERN APPALACHIANS NORTHWARD INTO NEW YORK... ...SUMMARY... Scattered strong thunderstorms capable of producing locally damaging wind gusts may impact a corridor from the Tennessee Valley and southern Appalachians northward through northern New York on Thursday. ...Synopsis... A deep/vertically stacked low pressure system will retrograde slightly westward over Ontario through the forecast period, while broad large-scale troughing encompasses much of the eastern CONUS. An embedded midlevel trough will track eastward across the Lower Great Lakes during the day, while a related cold front extending from NY south-southwestward along the Appalachians moves gradually eastward. ...TN Valley and Southern Appalachians northward into NY... Despite poor midlevel lapse rates, diurnal heating amid middle/upper 50 to lower 60s dewpoints will result in a corridor of weak to locally moderate surface-based buoyancy ahead of the front during the afternoon. Scattered thunderstorms are expected along/ahead of the front, where 30-40 kt of effective shear will promote loosely organized multicell clusters and line segments. The stronger storm clusters will be capable of producing locally damaging wind gusts through the afternoon. ...Northern Plains... On the backside of the large-scale trough, a robust midlevel speed maximum will move into the northern Plains during the day. Strong forcing for ascent and cold temperatures aloft will support isolated thunderstorms. While deep-layer shear will be sufficient for organized storms, the post-frontal nature of this activity should limit the overall severe risk. ..Weinman.. 09/03/2025 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1231 PM CDT Wed Sep 03 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE TENNESSEE VALLEY AND SOUTHERN APPALACHIANS NORTHWARD INTO NEW YORK... ...SUMMARY... Scattered strong thunderstorms capable of producing locally damaging wind gusts may impact a corridor from the Tennessee Valley and southern Appalachians northward through northern New York on Thursday. ...Synopsis... A deep/vertically stacked low pressure system will retrograde slightly westward over Ontario through the forecast period, while broad large-scale troughing encompasses much of the eastern CONUS. An embedded midlevel trough will track eastward across the Lower Great Lakes during the day, while a related cold front extending from NY south-southwestward along the Appalachians moves gradually eastward. ...TN Valley and Southern Appalachians northward into NY... Despite poor midlevel lapse rates, diurnal heating amid middle/upper 50 to lower 60s dewpoints will result in a corridor of weak to locally moderate surface-based buoyancy ahead of the front during the afternoon. Scattered thunderstorms are expected along/ahead of the front, where 30-40 kt of effective shear will promote loosely organized multicell clusters and line segments. The stronger storm clusters will be capable of producing locally damaging wind gusts through the afternoon. ...Northern Plains... On the backside of the large-scale trough, a robust midlevel speed maximum will move into the northern Plains during the day. Strong forcing for ascent and cold temperatures aloft will support isolated thunderstorms. While deep-layer shear will be sufficient for organized storms, the post-frontal nature of this activity should limit the overall severe risk. ..Weinman.. 09/03/2025 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1231 PM CDT Wed Sep 03 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE TENNESSEE VALLEY AND SOUTHERN APPALACHIANS NORTHWARD INTO NEW YORK... ...SUMMARY... Scattered strong thunderstorms capable of producing locally damaging wind gusts may impact a corridor from the Tennessee Valley and southern Appalachians northward through northern New York on Thursday. ...Synopsis... A deep/vertically stacked low pressure system will retrograde slightly westward over Ontario through the forecast period, while broad large-scale troughing encompasses much of the eastern CONUS. An embedded midlevel trough will track eastward across the Lower Great Lakes during the day, while a related cold front extending from NY south-southwestward along the Appalachians moves gradually eastward. ...TN Valley and Southern Appalachians northward into NY... Despite poor midlevel lapse rates, diurnal heating amid middle/upper 50 to lower 60s dewpoints will result in a corridor of weak to locally moderate surface-based buoyancy ahead of the front during the afternoon. Scattered thunderstorms are expected along/ahead of the front, where 30-40 kt of effective shear will promote loosely organized multicell clusters and line segments. The stronger storm clusters will be capable of producing locally damaging wind gusts through the afternoon. ...Northern Plains... On the backside of the large-scale trough, a robust midlevel speed maximum will move into the northern Plains during the day. Strong forcing for ascent and cold temperatures aloft will support isolated thunderstorms. While deep-layer shear will be sufficient for organized storms, the post-frontal nature of this activity should limit the overall severe risk. ..Weinman.. 09/03/2025 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1231 PM CDT Wed Sep 03 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE TENNESSEE VALLEY AND SOUTHERN APPALACHIANS NORTHWARD INTO NEW YORK... ...SUMMARY... Scattered strong thunderstorms capable of producing locally damaging wind gusts may impact a corridor from the Tennessee Valley and southern Appalachians northward through northern New York on Thursday. ...Synopsis... A deep/vertically stacked low pressure system will retrograde slightly westward over Ontario through the forecast period, while broad large-scale troughing encompasses much of the eastern CONUS. An embedded midlevel trough will track eastward across the Lower Great Lakes during the day, while a related cold front extending from NY south-southwestward along the Appalachians moves gradually eastward. ...TN Valley and Southern Appalachians northward into NY... Despite poor midlevel lapse rates, diurnal heating amid middle/upper 50 to lower 60s dewpoints will result in a corridor of weak to locally moderate surface-based buoyancy ahead of the front during the afternoon. Scattered thunderstorms are expected along/ahead of the front, where 30-40 kt of effective shear will promote loosely organized multicell clusters and line segments. The stronger storm clusters will be capable of producing locally damaging wind gusts through the afternoon. ...Northern Plains... On the backside of the large-scale trough, a robust midlevel speed maximum will move into the northern Plains during the day. Strong forcing for ascent and cold temperatures aloft will support isolated thunderstorms. While deep-layer shear will be sufficient for organized storms, the post-frontal nature of this activity should limit the overall severe risk. ..Weinman.. 09/03/2025 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1231 PM CDT Wed Sep 03 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE TENNESSEE VALLEY AND SOUTHERN APPALACHIANS NORTHWARD INTO NEW YORK... ...SUMMARY... Scattered strong thunderstorms capable of producing locally damaging wind gusts may impact a corridor from the Tennessee Valley and southern Appalachians northward through northern New York on Thursday. ...Synopsis... A deep/vertically stacked low pressure system will retrograde slightly westward over Ontario through the forecast period, while broad large-scale troughing encompasses much of the eastern CONUS. An embedded midlevel trough will track eastward across the Lower Great Lakes during the day, while a related cold front extending from NY south-southwestward along the Appalachians moves gradually eastward. ...TN Valley and Southern Appalachians northward into NY... Despite poor midlevel lapse rates, diurnal heating amid middle/upper 50 to lower 60s dewpoints will result in a corridor of weak to locally moderate surface-based buoyancy ahead of the front during the afternoon. Scattered thunderstorms are expected along/ahead of the front, where 30-40 kt of effective shear will promote loosely organized multicell clusters and line segments. The stronger storm clusters will be capable of producing locally damaging wind gusts through the afternoon. ...Northern Plains... On the backside of the large-scale trough, a robust midlevel speed maximum will move into the northern Plains during the day. Strong forcing for ascent and cold temperatures aloft will support isolated thunderstorms. While deep-layer shear will be sufficient for organized storms, the post-frontal nature of this activity should limit the overall severe risk. ..Weinman.. 09/03/2025 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1231 PM CDT Wed Sep 03 2025 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE TENNESSEE VALLEY AND SOUTHERN APPALACHIANS NORTHWARD INTO NEW YORK... ...SUMMARY... Scattered strong thunderstorms capable of producing locally damaging wind gusts may impact a corridor from the Tennessee Valley and southern Appalachians northward through northern New York on Thursday. ...Synopsis... A deep/vertically stacked low pressure system will retrograde slightly westward over Ontario through the forecast period, while broad large-scale troughing encompasses much of the eastern CONUS. An embedded midlevel trough will track eastward across the Lower Great Lakes during the day, while a related cold front extending from NY south-southwestward along the Appalachians moves gradually eastward. ...TN Valley and Southern Appalachians northward into NY... Despite poor midlevel lapse rates, diurnal heating amid middle/upper 50 to lower 60s dewpoints will result in a corridor of weak to locally moderate surface-based buoyancy ahead of the front during the afternoon. Scattered thunderstorms are expected along/ahead of the front, where 30-40 kt of effective shear will promote loosely organized multicell clusters and line segments. The stronger storm clusters will be capable of producing locally damaging wind gusts through the afternoon. ...Northern Plains... On the backside of the large-scale trough, a robust midlevel speed maximum will move into the northern Plains during the day. Strong forcing for ascent and cold temperatures aloft will support isolated thunderstorms. While deep-layer shear will be sufficient for organized storms, the post-frontal nature of this activity should limit the overall severe risk. ..Weinman.. 09/03/2025 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1155 AM CDT Wed Sep 03 2025 Valid 031700Z - 041200Z An upper-level trough supporting ongoing convection across the northern Sierra Nevada will promote expanding showers and thunderstorms across northern CA as well as the Cascades and south-central OR later this afternoon. Additional lightning ignitions are possible, particularly in drier, heavier fuels along the Shasta Siskiyous and Cascades. The northeast extent of dry thunderstorm highlights was trimmed across portions of central OR as well as the northern Sacramento Valley area, supported by latest CAM and ensemble model guidance. ..Williams.. 09/03/2025 .PREV DISCUSSION... /ISSUED 0149 AM CDT Wed Sep 03 2025/ ...Synopsis... A weak upper-level trough will continue to move northward across northern California into the Pacific Northwest on Wednesday. Lift associated with this feature will promote isolated to scattered thunderstorm activity. Thunderstorms will likely be ongoing at the beginning of the period with a second round developing by the afternoon. Overall, a mix of wet/dry thunderstorms is expected across the driest fuels in northern California, far western Nevada, and central Oregon. While locally higher totals will be possible in the strongest storms, ensemble guidance generally shows < 0.10" across much of this region. New lightning starts were reported on Tuesday in these areas, with rainfall amounts 0.10-0.25". An isolated dry thunderstorm area was maintained with this outlook to support this potential. ...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 1155 AM CDT Wed Sep 03 2025 Valid 031700Z - 041200Z An upper-level trough supporting ongoing convection across the northern Sierra Nevada will promote expanding showers and thunderstorms across northern CA as well as the Cascades and south-central OR later this afternoon. Additional lightning ignitions are possible, particularly in drier, heavier fuels along the Shasta Siskiyous and Cascades. The northeast extent of dry thunderstorm highlights was trimmed across portions of central OR as well as the northern Sacramento Valley area, supported by latest CAM and ensemble model guidance. ..Williams.. 09/03/2025 .PREV DISCUSSION... /ISSUED 0149 AM CDT Wed Sep 03 2025/ ...Synopsis... A weak upper-level trough will continue to move northward across northern California into the Pacific Northwest on Wednesday. Lift associated with this feature will promote isolated to scattered thunderstorm activity. Thunderstorms will likely be ongoing at the beginning of the period with a second round developing by the afternoon. Overall, a mix of wet/dry thunderstorms is expected across the driest fuels in northern California, far western Nevada, and central Oregon. While locally higher totals will be possible in the strongest storms, ensemble guidance generally shows < 0.10" across much of this region. New lightning starts were reported on Tuesday in these areas, with rainfall amounts 0.10-0.25". An isolated dry thunderstorm area was maintained with this outlook to support this potential. ...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 1155 AM CDT Wed Sep 03 2025 Valid 031700Z - 041200Z An upper-level trough supporting ongoing convection across the northern Sierra Nevada will promote expanding showers and thunderstorms across northern CA as well as the Cascades and south-central OR later this afternoon. Additional lightning ignitions are possible, particularly in drier, heavier fuels along the Shasta Siskiyous and Cascades. The northeast extent of dry thunderstorm highlights was trimmed across portions of central OR as well as the northern Sacramento Valley area, supported by latest CAM and ensemble model guidance. ..Williams.. 09/03/2025 .PREV DISCUSSION... /ISSUED 0149 AM CDT Wed Sep 03 2025/ ...Synopsis... A weak upper-level trough will continue to move northward across northern California into the Pacific Northwest on Wednesday. Lift associated with this feature will promote isolated to scattered thunderstorm activity. Thunderstorms will likely be ongoing at the beginning of the period with a second round developing by the afternoon. Overall, a mix of wet/dry thunderstorms is expected across the driest fuels in northern California, far western Nevada, and central Oregon. While locally higher totals will be possible in the strongest storms, ensemble guidance generally shows < 0.10" across much of this region. New lightning starts were reported on Tuesday in these areas, with rainfall amounts 0.10-0.25". An isolated dry thunderstorm area was maintained with this outlook to support this potential. ...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 1155 AM CDT Wed Sep 03 2025 Valid 031700Z - 041200Z An upper-level trough supporting ongoing convection across the northern Sierra Nevada will promote expanding showers and thunderstorms across northern CA as well as the Cascades and south-central OR later this afternoon. Additional lightning ignitions are possible, particularly in drier, heavier fuels along the Shasta Siskiyous and Cascades. The northeast extent of dry thunderstorm highlights was trimmed across portions of central OR as well as the northern Sacramento Valley area, supported by latest CAM and ensemble model guidance. ..Williams.. 09/03/2025 .PREV DISCUSSION... /ISSUED 0149 AM CDT Wed Sep 03 2025/ ...Synopsis... A weak upper-level trough will continue to move northward across northern California into the Pacific Northwest on Wednesday. Lift associated with this feature will promote isolated to scattered thunderstorm activity. Thunderstorms will likely be ongoing at the beginning of the period with a second round developing by the afternoon. Overall, a mix of wet/dry thunderstorms is expected across the driest fuels in northern California, far western Nevada, and central Oregon. While locally higher totals will be possible in the strongest storms, ensemble guidance generally shows < 0.10" across much of this region. New lightning starts were reported on Tuesday in these areas, with rainfall amounts 0.10-0.25". An isolated dry thunderstorm area was maintained with this outlook to support this potential. ...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 1155 AM CDT Wed Sep 03 2025 Valid 031700Z - 041200Z An upper-level trough supporting ongoing convection across the northern Sierra Nevada will promote expanding showers and thunderstorms across northern CA as well as the Cascades and south-central OR later this afternoon. Additional lightning ignitions are possible, particularly in drier, heavier fuels along the Shasta Siskiyous and Cascades. The northeast extent of dry thunderstorm highlights was trimmed across portions of central OR as well as the northern Sacramento Valley area, supported by latest CAM and ensemble model guidance. ..Williams.. 09/03/2025 .PREV DISCUSSION... /ISSUED 0149 AM CDT Wed Sep 03 2025/ ...Synopsis... A weak upper-level trough will continue to move northward across northern California into the Pacific Northwest on Wednesday. Lift associated with this feature will promote isolated to scattered thunderstorm activity. Thunderstorms will likely be ongoing at the beginning of the period with a second round developing by the afternoon. Overall, a mix of wet/dry thunderstorms is expected across the driest fuels in northern California, far western Nevada, and central Oregon. While locally higher totals will be possible in the strongest storms, ensemble guidance generally shows < 0.10" across much of this region. New lightning starts were reported on Tuesday in these areas, with rainfall amounts 0.10-0.25". An isolated dry thunderstorm area was maintained with this outlook to support this potential. ...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 1155 AM CDT Wed Sep 03 2025 Valid 031700Z - 041200Z An upper-level trough supporting ongoing convection across the northern Sierra Nevada will promote expanding showers and thunderstorms across northern CA as well as the Cascades and south-central OR later this afternoon. Additional lightning ignitions are possible, particularly in drier, heavier fuels along the Shasta Siskiyous and Cascades. The northeast extent of dry thunderstorm highlights was trimmed across portions of central OR as well as the northern Sacramento Valley area, supported by latest CAM and ensemble model guidance. ..Williams.. 09/03/2025 .PREV DISCUSSION... /ISSUED 0149 AM CDT Wed Sep 03 2025/ ...Synopsis... A weak upper-level trough will continue to move northward across northern California into the Pacific Northwest on Wednesday. Lift associated with this feature will promote isolated to scattered thunderstorm activity. Thunderstorms will likely be ongoing at the beginning of the period with a second round developing by the afternoon. Overall, a mix of wet/dry thunderstorms is expected across the driest fuels in northern California, far western Nevada, and central Oregon. While locally higher totals will be possible in the strongest storms, ensemble guidance generally shows < 0.10" across much of this region. New lightning starts were reported on Tuesday in these areas, with rainfall amounts 0.10-0.25". An isolated dry thunderstorm area was maintained with this outlook to support this potential. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1128 AM CDT Wed Sep 03 2025 Valid 031630Z - 041200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL PLAINS AND LOWER MISSOURI VALLEY... ...SUMMARY... Scattered thunderstorms capable of producing large to very large hail and severe wind gusts should occur this afternoon and evening across parts of the central Plains and lower Missouri Valley. ...Central Plains into the Lower Missouri Valley... A mid-level shortwave trough over southern SD/eastern NE will continue to advance quickly southeastward today as a large-scale upper-level low moves from western ON to near Lake Superior through the period. The shortwave trough is forecast to reach the lower MO Valley by late afternoon, with an attendant belt of moderately strong northwesterly mid/high-level flow overspreading the central Plains into the mid MS Valley. At the surface, a cold front will advance southward across parts of the central Plains and lower MO Valley, with generally low to mid 60s surface dewpoints present ahead of the boundary. Diurnal heating of this airmass will contribute to moderate instability (MLCAPE around 1000-2000 J/kg) by mid afternoon across central/eastern KS, with weaker instability forecast with eastward extent into MO. As convective inhibition gradually erodes near the front, scattered thunderstorms will likely develop along its length from central KS into the lower MO Valley during the 20-00Z period. Around 35-55 kt of northwesterly flow in the 500-250 mb layer will yield similar values of effective bulk shear, which will support organized updrafts. A few supercells will probably evolve across central/eastern KS and perhaps into western MO, where the main risk will be large to very large hail given steep lapse rates aloft and favorable shear. Severe wind gusts will also be possible with these supercells, or any small clusters/bowing segments that can develop where low-level lapse rates are steepest (mainly KS into northwest OK and parts of the OK/TX Panhandles). Some severe threat should persist into the evening as multiple small clusters move southward into southern KS and adjacent portions of far northern OK and southwest MO, before they eventually weaken as convective inhibition increases with nocturnal cooling. ...Great Lakes/Midwest... Additional thunderstorms should develop this afternoon along/near the cold front across parts of Lower MI into central IL. Poor lapse rates aloft and limited low-level moisture (reference 12Z soundings from APX and ILX) will likely temper the degree of instability that can develop, even with diurnal heating. While occasional strong/gusty winds appear possible with thunderstorms that spread east-southeastward this afternoon and evening, the overall severe threat should remain fairly limited. ..Gleason/Lyons.. 09/03/2025 Read more