Severe Storms

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1118 AM CDT Mon Sep 02 2024 Valid 021630Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE INTERIOR PACIFIC NORTHWEST INTO THE NORTHERN GREAT BASIN/ROCKIES... ...SUMMARY... Isolated to scattered thunderstorms across the northern Great Basin and parts of the interior Pacific Northwest may be capable of occasional strong to severe wind gusts this afternoon and evening. ...Interior Pacific Northwest into the Northern Great Basin/Rockies... Water-vapor imagery this morning shows a closed low near the northern CA/southern OR coast. This upper feature will move east through OR and be situated along the OR/ID border by daybreak Tuesday. A belt of stronger flow (30-50 kt 500-mb winds) will move through the base of the larger-scale mid-level trough and overspread northern NV into southwestern ID and eastern OR this afternoon into the early evening. Large-scale ascent associated with the upper disturbance and the development of weak buoyancy (mainly via heating), will facilitate the development of isolated to scattered high-based thunderstorms beginning later this afternoon and persisting into the evening. Forecast soundings show large surface temperature-dewpoint spreads (50 degrees F) with 9+ degrees C lapse rates into the mid levels and a dry sub-cloud layer. Evaporative cooling of the more intense downdrafts will probably yield a risk for isolated 60-70 mph gusts before weakening later this evening. ..Smith/Squitieri.. 09/02/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1118 AM CDT Mon Sep 02 2024 Valid 021630Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE INTERIOR PACIFIC NORTHWEST INTO THE NORTHERN GREAT BASIN/ROCKIES... ...SUMMARY... Isolated to scattered thunderstorms across the northern Great Basin and parts of the interior Pacific Northwest may be capable of occasional strong to severe wind gusts this afternoon and evening. ...Interior Pacific Northwest into the Northern Great Basin/Rockies... Water-vapor imagery this morning shows a closed low near the northern CA/southern OR coast. This upper feature will move east through OR and be situated along the OR/ID border by daybreak Tuesday. A belt of stronger flow (30-50 kt 500-mb winds) will move through the base of the larger-scale mid-level trough and overspread northern NV into southwestern ID and eastern OR this afternoon into the early evening. Large-scale ascent associated with the upper disturbance and the development of weak buoyancy (mainly via heating), will facilitate the development of isolated to scattered high-based thunderstorms beginning later this afternoon and persisting into the evening. Forecast soundings show large surface temperature-dewpoint spreads (50 degrees F) with 9+ degrees C lapse rates into the mid levels and a dry sub-cloud layer. Evaporative cooling of the more intense downdrafts will probably yield a risk for isolated 60-70 mph gusts before weakening later this evening. ..Smith/Squitieri.. 09/02/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1118 AM CDT Mon Sep 02 2024 Valid 021630Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE INTERIOR PACIFIC NORTHWEST INTO THE NORTHERN GREAT BASIN/ROCKIES... ...SUMMARY... Isolated to scattered thunderstorms across the northern Great Basin and parts of the interior Pacific Northwest may be capable of occasional strong to severe wind gusts this afternoon and evening. ...Interior Pacific Northwest into the Northern Great Basin/Rockies... Water-vapor imagery this morning shows a closed low near the northern CA/southern OR coast. This upper feature will move east through OR and be situated along the OR/ID border by daybreak Tuesday. A belt of stronger flow (30-50 kt 500-mb winds) will move through the base of the larger-scale mid-level trough and overspread northern NV into southwestern ID and eastern OR this afternoon into the early evening. Large-scale ascent associated with the upper disturbance and the development of weak buoyancy (mainly via heating), will facilitate the development of isolated to scattered high-based thunderstorms beginning later this afternoon and persisting into the evening. Forecast soundings show large surface temperature-dewpoint spreads (50 degrees F) with 9+ degrees C lapse rates into the mid levels and a dry sub-cloud layer. Evaporative cooling of the more intense downdrafts will probably yield a risk for isolated 60-70 mph gusts before weakening later this evening. ..Smith/Squitieri.. 09/02/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1118 AM CDT Mon Sep 02 2024 Valid 021630Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE INTERIOR PACIFIC NORTHWEST INTO THE NORTHERN GREAT BASIN/ROCKIES... ...SUMMARY... Isolated to scattered thunderstorms across the northern Great Basin and parts of the interior Pacific Northwest may be capable of occasional strong to severe wind gusts this afternoon and evening. ...Interior Pacific Northwest into the Northern Great Basin/Rockies... Water-vapor imagery this morning shows a closed low near the northern CA/southern OR coast. This upper feature will move east through OR and be situated along the OR/ID border by daybreak Tuesday. A belt of stronger flow (30-50 kt 500-mb winds) will move through the base of the larger-scale mid-level trough and overspread northern NV into southwestern ID and eastern OR this afternoon into the early evening. Large-scale ascent associated with the upper disturbance and the development of weak buoyancy (mainly via heating), will facilitate the development of isolated to scattered high-based thunderstorms beginning later this afternoon and persisting into the evening. Forecast soundings show large surface temperature-dewpoint spreads (50 degrees F) with 9+ degrees C lapse rates into the mid levels and a dry sub-cloud layer. Evaporative cooling of the more intense downdrafts will probably yield a risk for isolated 60-70 mph gusts before weakening later this evening. ..Smith/Squitieri.. 09/02/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1118 AM CDT Mon Sep 02 2024 Valid 021630Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE INTERIOR PACIFIC NORTHWEST INTO THE NORTHERN GREAT BASIN/ROCKIES... ...SUMMARY... Isolated to scattered thunderstorms across the northern Great Basin and parts of the interior Pacific Northwest may be capable of occasional strong to severe wind gusts this afternoon and evening. ...Interior Pacific Northwest into the Northern Great Basin/Rockies... Water-vapor imagery this morning shows a closed low near the northern CA/southern OR coast. This upper feature will move east through OR and be situated along the OR/ID border by daybreak Tuesday. A belt of stronger flow (30-50 kt 500-mb winds) will move through the base of the larger-scale mid-level trough and overspread northern NV into southwestern ID and eastern OR this afternoon into the early evening. Large-scale ascent associated with the upper disturbance and the development of weak buoyancy (mainly via heating), will facilitate the development of isolated to scattered high-based thunderstorms beginning later this afternoon and persisting into the evening. Forecast soundings show large surface temperature-dewpoint spreads (50 degrees F) with 9+ degrees C lapse rates into the mid levels and a dry sub-cloud layer. Evaporative cooling of the more intense downdrafts will probably yield a risk for isolated 60-70 mph gusts before weakening later this evening. ..Smith/Squitieri.. 09/02/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1118 AM CDT Mon Sep 02 2024 Valid 021630Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE INTERIOR PACIFIC NORTHWEST INTO THE NORTHERN GREAT BASIN/ROCKIES... ...SUMMARY... Isolated to scattered thunderstorms across the northern Great Basin and parts of the interior Pacific Northwest may be capable of occasional strong to severe wind gusts this afternoon and evening. ...Interior Pacific Northwest into the Northern Great Basin/Rockies... Water-vapor imagery this morning shows a closed low near the northern CA/southern OR coast. This upper feature will move east through OR and be situated along the OR/ID border by daybreak Tuesday. A belt of stronger flow (30-50 kt 500-mb winds) will move through the base of the larger-scale mid-level trough and overspread northern NV into southwestern ID and eastern OR this afternoon into the early evening. Large-scale ascent associated with the upper disturbance and the development of weak buoyancy (mainly via heating), will facilitate the development of isolated to scattered high-based thunderstorms beginning later this afternoon and persisting into the evening. Forecast soundings show large surface temperature-dewpoint spreads (50 degrees F) with 9+ degrees C lapse rates into the mid levels and a dry sub-cloud layer. Evaporative cooling of the more intense downdrafts will probably yield a risk for isolated 60-70 mph gusts before weakening later this evening. ..Smith/Squitieri.. 09/02/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0738 AM CDT Mon Sep 02 2024 Valid 021300Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE INTERIOR PACIFIC NORTHWEST INTO THE NORTHERN GREAT BASIN/ROCKIES... ...SUMMARY... Isolated to scattered thunderstorms across the northern Great Basin and parts of the interior Pacific Northwest may be capable of occasional strong to severe wind gusts this afternoon and evening. ...Interior Pacific Northwest into the Northern Great Basin/Rockies... A closed upper low approaching the northern CA and OR Coast will continue eastward today across the Pacific Northwest and northern Great Basin. Associated 35-50 kt mid-level south-southwesterlies will overspread these regions through the afternoon and evening. Large-scale ascent attendant to the upper low has already encouraged weak, elevated convection this morning across pats of eastern OR and vicinity. Current expectations are for additional showers and thunderstorms to develop later this afternoon as daytime heating occurs, mainly across parts of central/eastern OR into ID and northern NV/northwest UT. This convection will likely be rather high-based (LCLs around 3-4 km AGL), as latest surface observations and area 12Z soundings show very limited low-level moisture, and total PWAT values generally 0.5-0.7 inches. Even with rather weak buoyancy forecast across much of this area, a deeply mixed boundary layer should encourage efficient evaporative cooling of convective downdrafts. An isolated risk for strong/gusty winds approaching and occasionally exceeding severe levels remains apparent with this high-based convection as it spreads generally north-northeastward through the afternoon/evening before eventually weakening. ..Gleason/Leitman.. 09/02/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0738 AM CDT Mon Sep 02 2024 Valid 021300Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE INTERIOR PACIFIC NORTHWEST INTO THE NORTHERN GREAT BASIN/ROCKIES... ...SUMMARY... Isolated to scattered thunderstorms across the northern Great Basin and parts of the interior Pacific Northwest may be capable of occasional strong to severe wind gusts this afternoon and evening. ...Interior Pacific Northwest into the Northern Great Basin/Rockies... A closed upper low approaching the northern CA and OR Coast will continue eastward today across the Pacific Northwest and northern Great Basin. Associated 35-50 kt mid-level south-southwesterlies will overspread these regions through the afternoon and evening. Large-scale ascent attendant to the upper low has already encouraged weak, elevated convection this morning across pats of eastern OR and vicinity. Current expectations are for additional showers and thunderstorms to develop later this afternoon as daytime heating occurs, mainly across parts of central/eastern OR into ID and northern NV/northwest UT. This convection will likely be rather high-based (LCLs around 3-4 km AGL), as latest surface observations and area 12Z soundings show very limited low-level moisture, and total PWAT values generally 0.5-0.7 inches. Even with rather weak buoyancy forecast across much of this area, a deeply mixed boundary layer should encourage efficient evaporative cooling of convective downdrafts. An isolated risk for strong/gusty winds approaching and occasionally exceeding severe levels remains apparent with this high-based convection as it spreads generally north-northeastward through the afternoon/evening before eventually weakening. ..Gleason/Leitman.. 09/02/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0738 AM CDT Mon Sep 02 2024 Valid 021300Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE INTERIOR PACIFIC NORTHWEST INTO THE NORTHERN GREAT BASIN/ROCKIES... ...SUMMARY... Isolated to scattered thunderstorms across the northern Great Basin and parts of the interior Pacific Northwest may be capable of occasional strong to severe wind gusts this afternoon and evening. ...Interior Pacific Northwest into the Northern Great Basin/Rockies... A closed upper low approaching the northern CA and OR Coast will continue eastward today across the Pacific Northwest and northern Great Basin. Associated 35-50 kt mid-level south-southwesterlies will overspread these regions through the afternoon and evening. Large-scale ascent attendant to the upper low has already encouraged weak, elevated convection this morning across pats of eastern OR and vicinity. Current expectations are for additional showers and thunderstorms to develop later this afternoon as daytime heating occurs, mainly across parts of central/eastern OR into ID and northern NV/northwest UT. This convection will likely be rather high-based (LCLs around 3-4 km AGL), as latest surface observations and area 12Z soundings show very limited low-level moisture, and total PWAT values generally 0.5-0.7 inches. Even with rather weak buoyancy forecast across much of this area, a deeply mixed boundary layer should encourage efficient evaporative cooling of convective downdrafts. An isolated risk for strong/gusty winds approaching and occasionally exceeding severe levels remains apparent with this high-based convection as it spreads generally north-northeastward through the afternoon/evening before eventually weakening. ..Gleason/Leitman.. 09/02/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0738 AM CDT Mon Sep 02 2024 Valid 021300Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE INTERIOR PACIFIC NORTHWEST INTO THE NORTHERN GREAT BASIN/ROCKIES... ...SUMMARY... Isolated to scattered thunderstorms across the northern Great Basin and parts of the interior Pacific Northwest may be capable of occasional strong to severe wind gusts this afternoon and evening. ...Interior Pacific Northwest into the Northern Great Basin/Rockies... A closed upper low approaching the northern CA and OR Coast will continue eastward today across the Pacific Northwest and northern Great Basin. Associated 35-50 kt mid-level south-southwesterlies will overspread these regions through the afternoon and evening. Large-scale ascent attendant to the upper low has already encouraged weak, elevated convection this morning across pats of eastern OR and vicinity. Current expectations are for additional showers and thunderstorms to develop later this afternoon as daytime heating occurs, mainly across parts of central/eastern OR into ID and northern NV/northwest UT. This convection will likely be rather high-based (LCLs around 3-4 km AGL), as latest surface observations and area 12Z soundings show very limited low-level moisture, and total PWAT values generally 0.5-0.7 inches. Even with rather weak buoyancy forecast across much of this area, a deeply mixed boundary layer should encourage efficient evaporative cooling of convective downdrafts. An isolated risk for strong/gusty winds approaching and occasionally exceeding severe levels remains apparent with this high-based convection as it spreads generally north-northeastward through the afternoon/evening before eventually weakening. ..Gleason/Leitman.. 09/02/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0738 AM CDT Mon Sep 02 2024 Valid 021300Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE INTERIOR PACIFIC NORTHWEST INTO THE NORTHERN GREAT BASIN/ROCKIES... ...SUMMARY... Isolated to scattered thunderstorms across the northern Great Basin and parts of the interior Pacific Northwest may be capable of occasional strong to severe wind gusts this afternoon and evening. ...Interior Pacific Northwest into the Northern Great Basin/Rockies... A closed upper low approaching the northern CA and OR Coast will continue eastward today across the Pacific Northwest and northern Great Basin. Associated 35-50 kt mid-level south-southwesterlies will overspread these regions through the afternoon and evening. Large-scale ascent attendant to the upper low has already encouraged weak, elevated convection this morning across pats of eastern OR and vicinity. Current expectations are for additional showers and thunderstorms to develop later this afternoon as daytime heating occurs, mainly across parts of central/eastern OR into ID and northern NV/northwest UT. This convection will likely be rather high-based (LCLs around 3-4 km AGL), as latest surface observations and area 12Z soundings show very limited low-level moisture, and total PWAT values generally 0.5-0.7 inches. Even with rather weak buoyancy forecast across much of this area, a deeply mixed boundary layer should encourage efficient evaporative cooling of convective downdrafts. An isolated risk for strong/gusty winds approaching and occasionally exceeding severe levels remains apparent with this high-based convection as it spreads generally north-northeastward through the afternoon/evening before eventually weakening. ..Gleason/Leitman.. 09/02/2024 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Mon Sep 02 2024 Valid 051200Z - 101200Z ...DISCUSSION... Global models have come into a bit better agreement with each other, through late next week, with respect to their handling of the large-scale features. Day 4 (Thursday), the upper trough crossing central portions of Canada and the north-central U.S. is progged to continue digging southeastward -- reaching a roughly upper Mississippi Valley to Mid-Missouri Valley position by Friday morning. As this occurs, a corresponding eastward/southward advance of a surface cold front will occur, crossing the Upper Great Lakes/Upper Midwest and drifting as far south as the central Plains overnight. Preceding the front, limited low-level moisture is expected, with Gulf moisture remaining restricted to the southern-tier states. Thus, while a few strong/severe storms may evolve within a southern Upper Great Lakes to central Plains corridor, potential for a more widespread severe event appears limited at this time. Day 5 (Friday), a continued southeastward advance/amplification of the upper trough is anticipated, shifting across the Great Lakes and Midwest through the day, and with cyclonic flow surrounding the trough to encompass the entire eastern half of the country by Saturday morning. The associated cold front -- crossing the central U.S. through the day, is expected to reach a Lower Great Lakes to Lower Mississippi Valley to Texas position overnight. Meanwhile, the height falls associated with this trough into the southeastern U.S. may support frontal wave development along the remnant baroclinic zone likely to be lingering over the northern Gulf/Gulf Coast area. While still uncertain, this low may shift across the Southeast Friday, reaching the eastern Carolinas vicinity by Sunday morning. While it is not out of the question that -- with this front/low marking the northward extent of tropical low-level air, that low-end severe risk could evolve overnight. However, this scenario is uncertain, and would seem likely to remain limited in terms of significance. Day 6, some negative tilt of the upper trough is expected as it advances across the Midwest and Lower Great Lakes area, with models suggesting evolution into a closed low over the eastern Ontario vicinity with time. Meanwhile, the advancing cold front is progged to begin to overtake the remnant baroclinic zone and frontal wave, with the combined front to linger near -- and eventually move off -- the Atlantic Seaboard as the frontal low moves toward/into southern New England overnight. Again, some severe potential may manifest ahead of the consolidating surface front, but at this time, models suggest that destabilization will remain largely just offshore. By Sunday (Day 7) and continuing through the end of the period, model divergence increases -- with evolution/positioning of the deepening closed low over eastern NOAM, and -- as a result, the upstream flow pattern over the western half of the country. Overall severe risk would appear to be low overall however, with general ridging likely over the western half of the country. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Mon Sep 02 2024 Valid 051200Z - 101200Z ...DISCUSSION... Global models have come into a bit better agreement with each other, through late next week, with respect to their handling of the large-scale features. Day 4 (Thursday), the upper trough crossing central portions of Canada and the north-central U.S. is progged to continue digging southeastward -- reaching a roughly upper Mississippi Valley to Mid-Missouri Valley position by Friday morning. As this occurs, a corresponding eastward/southward advance of a surface cold front will occur, crossing the Upper Great Lakes/Upper Midwest and drifting as far south as the central Plains overnight. Preceding the front, limited low-level moisture is expected, with Gulf moisture remaining restricted to the southern-tier states. Thus, while a few strong/severe storms may evolve within a southern Upper Great Lakes to central Plains corridor, potential for a more widespread severe event appears limited at this time. Day 5 (Friday), a continued southeastward advance/amplification of the upper trough is anticipated, shifting across the Great Lakes and Midwest through the day, and with cyclonic flow surrounding the trough to encompass the entire eastern half of the country by Saturday morning. The associated cold front -- crossing the central U.S. through the day, is expected to reach a Lower Great Lakes to Lower Mississippi Valley to Texas position overnight. Meanwhile, the height falls associated with this trough into the southeastern U.S. may support frontal wave development along the remnant baroclinic zone likely to be lingering over the northern Gulf/Gulf Coast area. While still uncertain, this low may shift across the Southeast Friday, reaching the eastern Carolinas vicinity by Sunday morning. While it is not out of the question that -- with this front/low marking the northward extent of tropical low-level air, that low-end severe risk could evolve overnight. However, this scenario is uncertain, and would seem likely to remain limited in terms of significance. Day 6, some negative tilt of the upper trough is expected as it advances across the Midwest and Lower Great Lakes area, with models suggesting evolution into a closed low over the eastern Ontario vicinity with time. Meanwhile, the advancing cold front is progged to begin to overtake the remnant baroclinic zone and frontal wave, with the combined front to linger near -- and eventually move off -- the Atlantic Seaboard as the frontal low moves toward/into southern New England overnight. Again, some severe potential may manifest ahead of the consolidating surface front, but at this time, models suggest that destabilization will remain largely just offshore. By Sunday (Day 7) and continuing through the end of the period, model divergence increases -- with evolution/positioning of the deepening closed low over eastern NOAM, and -- as a result, the upstream flow pattern over the western half of the country. Overall severe risk would appear to be low overall however, with general ridging likely over the western half of the country. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Mon Sep 02 2024 Valid 051200Z - 101200Z ...DISCUSSION... Global models have come into a bit better agreement with each other, through late next week, with respect to their handling of the large-scale features. Day 4 (Thursday), the upper trough crossing central portions of Canada and the north-central U.S. is progged to continue digging southeastward -- reaching a roughly upper Mississippi Valley to Mid-Missouri Valley position by Friday morning. As this occurs, a corresponding eastward/southward advance of a surface cold front will occur, crossing the Upper Great Lakes/Upper Midwest and drifting as far south as the central Plains overnight. Preceding the front, limited low-level moisture is expected, with Gulf moisture remaining restricted to the southern-tier states. Thus, while a few strong/severe storms may evolve within a southern Upper Great Lakes to central Plains corridor, potential for a more widespread severe event appears limited at this time. Day 5 (Friday), a continued southeastward advance/amplification of the upper trough is anticipated, shifting across the Great Lakes and Midwest through the day, and with cyclonic flow surrounding the trough to encompass the entire eastern half of the country by Saturday morning. The associated cold front -- crossing the central U.S. through the day, is expected to reach a Lower Great Lakes to Lower Mississippi Valley to Texas position overnight. Meanwhile, the height falls associated with this trough into the southeastern U.S. may support frontal wave development along the remnant baroclinic zone likely to be lingering over the northern Gulf/Gulf Coast area. While still uncertain, this low may shift across the Southeast Friday, reaching the eastern Carolinas vicinity by Sunday morning. While it is not out of the question that -- with this front/low marking the northward extent of tropical low-level air, that low-end severe risk could evolve overnight. However, this scenario is uncertain, and would seem likely to remain limited in terms of significance. Day 6, some negative tilt of the upper trough is expected as it advances across the Midwest and Lower Great Lakes area, with models suggesting evolution into a closed low over the eastern Ontario vicinity with time. Meanwhile, the advancing cold front is progged to begin to overtake the remnant baroclinic zone and frontal wave, with the combined front to linger near -- and eventually move off -- the Atlantic Seaboard as the frontal low moves toward/into southern New England overnight. Again, some severe potential may manifest ahead of the consolidating surface front, but at this time, models suggest that destabilization will remain largely just offshore. By Sunday (Day 7) and continuing through the end of the period, model divergence increases -- with evolution/positioning of the deepening closed low over eastern NOAM, and -- as a result, the upstream flow pattern over the western half of the country. Overall severe risk would appear to be low overall however, with general ridging likely over the western half of the country. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Mon Sep 02 2024 Valid 051200Z - 101200Z ...DISCUSSION... Global models have come into a bit better agreement with each other, through late next week, with respect to their handling of the large-scale features. Day 4 (Thursday), the upper trough crossing central portions of Canada and the north-central U.S. is progged to continue digging southeastward -- reaching a roughly upper Mississippi Valley to Mid-Missouri Valley position by Friday morning. As this occurs, a corresponding eastward/southward advance of a surface cold front will occur, crossing the Upper Great Lakes/Upper Midwest and drifting as far south as the central Plains overnight. Preceding the front, limited low-level moisture is expected, with Gulf moisture remaining restricted to the southern-tier states. Thus, while a few strong/severe storms may evolve within a southern Upper Great Lakes to central Plains corridor, potential for a more widespread severe event appears limited at this time. Day 5 (Friday), a continued southeastward advance/amplification of the upper trough is anticipated, shifting across the Great Lakes and Midwest through the day, and with cyclonic flow surrounding the trough to encompass the entire eastern half of the country by Saturday morning. The associated cold front -- crossing the central U.S. through the day, is expected to reach a Lower Great Lakes to Lower Mississippi Valley to Texas position overnight. Meanwhile, the height falls associated with this trough into the southeastern U.S. may support frontal wave development along the remnant baroclinic zone likely to be lingering over the northern Gulf/Gulf Coast area. While still uncertain, this low may shift across the Southeast Friday, reaching the eastern Carolinas vicinity by Sunday morning. While it is not out of the question that -- with this front/low marking the northward extent of tropical low-level air, that low-end severe risk could evolve overnight. However, this scenario is uncertain, and would seem likely to remain limited in terms of significance. Day 6, some negative tilt of the upper trough is expected as it advances across the Midwest and Lower Great Lakes area, with models suggesting evolution into a closed low over the eastern Ontario vicinity with time. Meanwhile, the advancing cold front is progged to begin to overtake the remnant baroclinic zone and frontal wave, with the combined front to linger near -- and eventually move off -- the Atlantic Seaboard as the frontal low moves toward/into southern New England overnight. Again, some severe potential may manifest ahead of the consolidating surface front, but at this time, models suggest that destabilization will remain largely just offshore. By Sunday (Day 7) and continuing through the end of the period, model divergence increases -- with evolution/positioning of the deepening closed low over eastern NOAM, and -- as a result, the upstream flow pattern over the western half of the country. Overall severe risk would appear to be low overall however, with general ridging likely over the western half of the country. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Mon Sep 02 2024 Valid 051200Z - 101200Z ...DISCUSSION... Global models have come into a bit better agreement with each other, through late next week, with respect to their handling of the large-scale features. Day 4 (Thursday), the upper trough crossing central portions of Canada and the north-central U.S. is progged to continue digging southeastward -- reaching a roughly upper Mississippi Valley to Mid-Missouri Valley position by Friday morning. As this occurs, a corresponding eastward/southward advance of a surface cold front will occur, crossing the Upper Great Lakes/Upper Midwest and drifting as far south as the central Plains overnight. Preceding the front, limited low-level moisture is expected, with Gulf moisture remaining restricted to the southern-tier states. Thus, while a few strong/severe storms may evolve within a southern Upper Great Lakes to central Plains corridor, potential for a more widespread severe event appears limited at this time. Day 5 (Friday), a continued southeastward advance/amplification of the upper trough is anticipated, shifting across the Great Lakes and Midwest through the day, and with cyclonic flow surrounding the trough to encompass the entire eastern half of the country by Saturday morning. The associated cold front -- crossing the central U.S. through the day, is expected to reach a Lower Great Lakes to Lower Mississippi Valley to Texas position overnight. Meanwhile, the height falls associated with this trough into the southeastern U.S. may support frontal wave development along the remnant baroclinic zone likely to be lingering over the northern Gulf/Gulf Coast area. While still uncertain, this low may shift across the Southeast Friday, reaching the eastern Carolinas vicinity by Sunday morning. While it is not out of the question that -- with this front/low marking the northward extent of tropical low-level air, that low-end severe risk could evolve overnight. However, this scenario is uncertain, and would seem likely to remain limited in terms of significance. Day 6, some negative tilt of the upper trough is expected as it advances across the Midwest and Lower Great Lakes area, with models suggesting evolution into a closed low over the eastern Ontario vicinity with time. Meanwhile, the advancing cold front is progged to begin to overtake the remnant baroclinic zone and frontal wave, with the combined front to linger near -- and eventually move off -- the Atlantic Seaboard as the frontal low moves toward/into southern New England overnight. Again, some severe potential may manifest ahead of the consolidating surface front, but at this time, models suggest that destabilization will remain largely just offshore. By Sunday (Day 7) and continuing through the end of the period, model divergence increases -- with evolution/positioning of the deepening closed low over eastern NOAM, and -- as a result, the upstream flow pattern over the western half of the country. Overall severe risk would appear to be low overall however, with general ridging likely over the western half of the country. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Mon Sep 02 2024 Valid 051200Z - 101200Z ...DISCUSSION... Global models have come into a bit better agreement with each other, through late next week, with respect to their handling of the large-scale features. Day 4 (Thursday), the upper trough crossing central portions of Canada and the north-central U.S. is progged to continue digging southeastward -- reaching a roughly upper Mississippi Valley to Mid-Missouri Valley position by Friday morning. As this occurs, a corresponding eastward/southward advance of a surface cold front will occur, crossing the Upper Great Lakes/Upper Midwest and drifting as far south as the central Plains overnight. Preceding the front, limited low-level moisture is expected, with Gulf moisture remaining restricted to the southern-tier states. Thus, while a few strong/severe storms may evolve within a southern Upper Great Lakes to central Plains corridor, potential for a more widespread severe event appears limited at this time. Day 5 (Friday), a continued southeastward advance/amplification of the upper trough is anticipated, shifting across the Great Lakes and Midwest through the day, and with cyclonic flow surrounding the trough to encompass the entire eastern half of the country by Saturday morning. The associated cold front -- crossing the central U.S. through the day, is expected to reach a Lower Great Lakes to Lower Mississippi Valley to Texas position overnight. Meanwhile, the height falls associated with this trough into the southeastern U.S. may support frontal wave development along the remnant baroclinic zone likely to be lingering over the northern Gulf/Gulf Coast area. While still uncertain, this low may shift across the Southeast Friday, reaching the eastern Carolinas vicinity by Sunday morning. While it is not out of the question that -- with this front/low marking the northward extent of tropical low-level air, that low-end severe risk could evolve overnight. However, this scenario is uncertain, and would seem likely to remain limited in terms of significance. Day 6, some negative tilt of the upper trough is expected as it advances across the Midwest and Lower Great Lakes area, with models suggesting evolution into a closed low over the eastern Ontario vicinity with time. Meanwhile, the advancing cold front is progged to begin to overtake the remnant baroclinic zone and frontal wave, with the combined front to linger near -- and eventually move off -- the Atlantic Seaboard as the frontal low moves toward/into southern New England overnight. Again, some severe potential may manifest ahead of the consolidating surface front, but at this time, models suggest that destabilization will remain largely just offshore. By Sunday (Day 7) and continuing through the end of the period, model divergence increases -- with evolution/positioning of the deepening closed low over eastern NOAM, and -- as a result, the upstream flow pattern over the western half of the country. Overall severe risk would appear to be low overall however, with general ridging likely over the western half of the country. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 AM CDT Mon Sep 02 2024 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTH-CENTRAL U.S. AND INTO THE ROCKIES... ...SUMMARY... Risk for isolated strong to severe storms -- capable of producing gusty/locally damaging winds -- will be possible from parts of Montana/Wyoming/Colorado into the northern Plains Wednesday/Wednesday night. Marginal hail with stronger storms may also occur across the northern Plains region. ...Synopsis... The main upper feature of interest with respect to convective/local severe risk will be a short-wave trough initially situated from the northern Intermountain region to the Great Basin. As this feature advances eastward toward -- and eventually into -- the northern and central Plains, it is expected to gradually phase with larger-scale trough digging southeastward into the Canadian Prairie. This will result in slow amplification of the upper pattern over Canada and the adjacent northern half of the U.S. through Thursday morning. At the surface, a baroclinic zone is forecast to linger in the vicinity of the Gulf Coast/northern Gulf of Mexico, at the southern fringe of a drier Continental airmass represented by a large area of high pressure over the eastern and into the central states. Meanwhile, a second cold front -- ahead of the evolving northern U.S. upper trough -- will shift eastward across the northern Plains and southward into the central Plains through the period. By Thursday morning, the front should extend from Minnesota southwestward to the Far West Texas vicinity. ...Northern Plains into parts of Montana/Wyoming/Colorado... Diurnal heating in the wake of the advancing cold front/beneath the upper trough will result in modest destabilization across portions of Montana/Wyoming/Colorado during the afternoon -- resulting in development of isolated thunderstorms. With a belt of moderate mid-level west-southwesterlies supporting locally stronger updrafts, and a deep mixed layer suggesting some evaporative enhancement potential in the sub-cloud layer, a few instances of strong/severe outflow winds are expected. Farther east, destabilization near/ahead of the advancing from should support isolated storm by late afternoon, and continuing into the evening hours. With shear becoming sufficient for organized updrafts, a few stronger storms during the afternoon and evening should prove capable of producing strong/gusty winds and marginal hail, before nocturnally weakening. ..Goss.. 09/02/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 AM CDT Mon Sep 02 2024 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTH-CENTRAL U.S. AND INTO THE ROCKIES... ...SUMMARY... Risk for isolated strong to severe storms -- capable of producing gusty/locally damaging winds -- will be possible from parts of Montana/Wyoming/Colorado into the northern Plains Wednesday/Wednesday night. Marginal hail with stronger storms may also occur across the northern Plains region. ...Synopsis... The main upper feature of interest with respect to convective/local severe risk will be a short-wave trough initially situated from the northern Intermountain region to the Great Basin. As this feature advances eastward toward -- and eventually into -- the northern and central Plains, it is expected to gradually phase with larger-scale trough digging southeastward into the Canadian Prairie. This will result in slow amplification of the upper pattern over Canada and the adjacent northern half of the U.S. through Thursday morning. At the surface, a baroclinic zone is forecast to linger in the vicinity of the Gulf Coast/northern Gulf of Mexico, at the southern fringe of a drier Continental airmass represented by a large area of high pressure over the eastern and into the central states. Meanwhile, a second cold front -- ahead of the evolving northern U.S. upper trough -- will shift eastward across the northern Plains and southward into the central Plains through the period. By Thursday morning, the front should extend from Minnesota southwestward to the Far West Texas vicinity. ...Northern Plains into parts of Montana/Wyoming/Colorado... Diurnal heating in the wake of the advancing cold front/beneath the upper trough will result in modest destabilization across portions of Montana/Wyoming/Colorado during the afternoon -- resulting in development of isolated thunderstorms. With a belt of moderate mid-level west-southwesterlies supporting locally stronger updrafts, and a deep mixed layer suggesting some evaporative enhancement potential in the sub-cloud layer, a few instances of strong/severe outflow winds are expected. Farther east, destabilization near/ahead of the advancing from should support isolated storm by late afternoon, and continuing into the evening hours. With shear becoming sufficient for organized updrafts, a few stronger storms during the afternoon and evening should prove capable of producing strong/gusty winds and marginal hail, before nocturnally weakening. ..Goss.. 09/02/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 AM CDT Mon Sep 02 2024 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTH-CENTRAL U.S. AND INTO THE ROCKIES... ...SUMMARY... Risk for isolated strong to severe storms -- capable of producing gusty/locally damaging winds -- will be possible from parts of Montana/Wyoming/Colorado into the northern Plains Wednesday/Wednesday night. Marginal hail with stronger storms may also occur across the northern Plains region. ...Synopsis... The main upper feature of interest with respect to convective/local severe risk will be a short-wave trough initially situated from the northern Intermountain region to the Great Basin. As this feature advances eastward toward -- and eventually into -- the northern and central Plains, it is expected to gradually phase with larger-scale trough digging southeastward into the Canadian Prairie. This will result in slow amplification of the upper pattern over Canada and the adjacent northern half of the U.S. through Thursday morning. At the surface, a baroclinic zone is forecast to linger in the vicinity of the Gulf Coast/northern Gulf of Mexico, at the southern fringe of a drier Continental airmass represented by a large area of high pressure over the eastern and into the central states. Meanwhile, a second cold front -- ahead of the evolving northern U.S. upper trough -- will shift eastward across the northern Plains and southward into the central Plains through the period. By Thursday morning, the front should extend from Minnesota southwestward to the Far West Texas vicinity. ...Northern Plains into parts of Montana/Wyoming/Colorado... Diurnal heating in the wake of the advancing cold front/beneath the upper trough will result in modest destabilization across portions of Montana/Wyoming/Colorado during the afternoon -- resulting in development of isolated thunderstorms. With a belt of moderate mid-level west-southwesterlies supporting locally stronger updrafts, and a deep mixed layer suggesting some evaporative enhancement potential in the sub-cloud layer, a few instances of strong/severe outflow winds are expected. Farther east, destabilization near/ahead of the advancing from should support isolated storm by late afternoon, and continuing into the evening hours. With shear becoming sufficient for organized updrafts, a few stronger storms during the afternoon and evening should prove capable of producing strong/gusty winds and marginal hail, before nocturnally weakening. ..Goss.. 09/02/2024 Read more