Severe Storms

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sun Jul 20 2025 Valid 201630Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE NORTHERN AND CENTRAL PLAINS...OHIO VALLEY...AND PARTS OF THE NORTHEAST... ...SUMMARY... Severe thunderstorms appear most likely this afternoon into this evening across parts of the Northeast, portions of the northern and central Plains, and perhaps the Ohio Valley. ...Synopsis... A mid-level trough will amplify across the Northeast today with increasing mid-level flow ahead of an approaching jet streak. A low-amplitude ridge will build somewhat across the Upper Midwest. Farther west, mid-level flow will strengthen across the northern Rockies into the northern Plains as a trough amplifies on the Pacific Northwest coast. ...Northeast... Weak to moderate instability is forecast to develop across the Northeast through mid afternoon as the airmass continues to destabilize. Midday surface analysis indicates temperatures are warming into the 80s with dewpoints in the upper 60s to lower 70s. As the cold front advances east into this uncapped airmass, scattered thunderstorms should develop. Shear of 30 to 35 knots and relatively long/straight hodographs will support the potential for supercells. Weak mid-level lapse rates will be the primary limiting factor for large hail, but the overall favorable shear with strong venting aloft and potential supercells may support some isolated large hail. Damaging wind gusts will be the primary threat, both from initial cells and also from any clusters which develop. Any stronger clusters with bowing segments could support a better organized damaging wind swath. The greatest wind damage threat will likely exist from western Massachusetts to far southern Maine. ...Southeast MT into the Dakotas and Central Plains... Lee troughing is forecast to extend southward from eastern MT into the central High Plains near and south of the westerlies confined to the northern tier of states. Elevated weak thunderstorm activity along the ND/SD border may continue but considerable uncertainty exists whether these storms will intensify and pose a severe risk this afternoon. Meanwhile, farther west, moist low levels arc from southeast MT southeastward through west-central SD and south into NE/northwest KS. Strong heating will contribute to a moderate to very unstable airmass from the central Plains states into eastern MT. Easterly low-level flow beneath 30-40 kt 500 mb flow in southeast MT will support organized storms, including supercell potential. Isolated to scattered storms are forecast to develop and spread east into the Dakotas. Other isolated to widely scattered storms are possible from SD southward into NE/CO/KS border vicinity late this afternoon into the evening. Large to very large hail will be possible with any supercells that develop within this general region. However, the severe wind threat may increase by this evening and become the main threat as storms congeal into one or more clusters or MCS. ...Ohio Valley... Visible-satellite/radar composite shows an elongated area of showers/thunderstorms from northern MO east into western OH in conjunction with an MCV moving east from IL into IN. Additional storm development along the composite front/trailing outflow boundary is expected, but timing of this storm activity remains unclear. Nonetheless, differential heating along the baroclinic zone will yield 2000 to 3000 J/kg MLCAPE amidst moderate effective shear (25-35 kt). A few clusters are forecast to eventually evolve later this afternoon into the evening with the stronger storms capable primarily of a wind-damage threat. ..Smith/Halbert.. 07/20/2025 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sun Jul 20 2025 Valid 201630Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE NORTHERN AND CENTRAL PLAINS...OHIO VALLEY...AND PARTS OF THE NORTHEAST... ...SUMMARY... Severe thunderstorms appear most likely this afternoon into this evening across parts of the Northeast, portions of the northern and central Plains, and perhaps the Ohio Valley. ...Synopsis... A mid-level trough will amplify across the Northeast today with increasing mid-level flow ahead of an approaching jet streak. A low-amplitude ridge will build somewhat across the Upper Midwest. Farther west, mid-level flow will strengthen across the northern Rockies into the northern Plains as a trough amplifies on the Pacific Northwest coast. ...Northeast... Weak to moderate instability is forecast to develop across the Northeast through mid afternoon as the airmass continues to destabilize. Midday surface analysis indicates temperatures are warming into the 80s with dewpoints in the upper 60s to lower 70s. As the cold front advances east into this uncapped airmass, scattered thunderstorms should develop. Shear of 30 to 35 knots and relatively long/straight hodographs will support the potential for supercells. Weak mid-level lapse rates will be the primary limiting factor for large hail, but the overall favorable shear with strong venting aloft and potential supercells may support some isolated large hail. Damaging wind gusts will be the primary threat, both from initial cells and also from any clusters which develop. Any stronger clusters with bowing segments could support a better organized damaging wind swath. The greatest wind damage threat will likely exist from western Massachusetts to far southern Maine. ...Southeast MT into the Dakotas and Central Plains... Lee troughing is forecast to extend southward from eastern MT into the central High Plains near and south of the westerlies confined to the northern tier of states. Elevated weak thunderstorm activity along the ND/SD border may continue but considerable uncertainty exists whether these storms will intensify and pose a severe risk this afternoon. Meanwhile, farther west, moist low levels arc from southeast MT southeastward through west-central SD and south into NE/northwest KS. Strong heating will contribute to a moderate to very unstable airmass from the central Plains states into eastern MT. Easterly low-level flow beneath 30-40 kt 500 mb flow in southeast MT will support organized storms, including supercell potential. Isolated to scattered storms are forecast to develop and spread east into the Dakotas. Other isolated to widely scattered storms are possible from SD southward into NE/CO/KS border vicinity late this afternoon into the evening. Large to very large hail will be possible with any supercells that develop within this general region. However, the severe wind threat may increase by this evening and become the main threat as storms congeal into one or more clusters or MCS. ...Ohio Valley... Visible-satellite/radar composite shows an elongated area of showers/thunderstorms from northern MO east into western OH in conjunction with an MCV moving east from IL into IN. Additional storm development along the composite front/trailing outflow boundary is expected, but timing of this storm activity remains unclear. Nonetheless, differential heating along the baroclinic zone will yield 2000 to 3000 J/kg MLCAPE amidst moderate effective shear (25-35 kt). A few clusters are forecast to eventually evolve later this afternoon into the evening with the stronger storms capable primarily of a wind-damage threat. ..Smith/Halbert.. 07/20/2025 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sun Jul 20 2025 Valid 201630Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE NORTHERN AND CENTRAL PLAINS...OHIO VALLEY...AND PARTS OF THE NORTHEAST... ...SUMMARY... Severe thunderstorms appear most likely this afternoon into this evening across parts of the Northeast, portions of the northern and central Plains, and perhaps the Ohio Valley. ...Synopsis... A mid-level trough will amplify across the Northeast today with increasing mid-level flow ahead of an approaching jet streak. A low-amplitude ridge will build somewhat across the Upper Midwest. Farther west, mid-level flow will strengthen across the northern Rockies into the northern Plains as a trough amplifies on the Pacific Northwest coast. ...Northeast... Weak to moderate instability is forecast to develop across the Northeast through mid afternoon as the airmass continues to destabilize. Midday surface analysis indicates temperatures are warming into the 80s with dewpoints in the upper 60s to lower 70s. As the cold front advances east into this uncapped airmass, scattered thunderstorms should develop. Shear of 30 to 35 knots and relatively long/straight hodographs will support the potential for supercells. Weak mid-level lapse rates will be the primary limiting factor for large hail, but the overall favorable shear with strong venting aloft and potential supercells may support some isolated large hail. Damaging wind gusts will be the primary threat, both from initial cells and also from any clusters which develop. Any stronger clusters with bowing segments could support a better organized damaging wind swath. The greatest wind damage threat will likely exist from western Massachusetts to far southern Maine. ...Southeast MT into the Dakotas and Central Plains... Lee troughing is forecast to extend southward from eastern MT into the central High Plains near and south of the westerlies confined to the northern tier of states. Elevated weak thunderstorm activity along the ND/SD border may continue but considerable uncertainty exists whether these storms will intensify and pose a severe risk this afternoon. Meanwhile, farther west, moist low levels arc from southeast MT southeastward through west-central SD and south into NE/northwest KS. Strong heating will contribute to a moderate to very unstable airmass from the central Plains states into eastern MT. Easterly low-level flow beneath 30-40 kt 500 mb flow in southeast MT will support organized storms, including supercell potential. Isolated to scattered storms are forecast to develop and spread east into the Dakotas. Other isolated to widely scattered storms are possible from SD southward into NE/CO/KS border vicinity late this afternoon into the evening. Large to very large hail will be possible with any supercells that develop within this general region. However, the severe wind threat may increase by this evening and become the main threat as storms congeal into one or more clusters or MCS. ...Ohio Valley... Visible-satellite/radar composite shows an elongated area of showers/thunderstorms from northern MO east into western OH in conjunction with an MCV moving east from IL into IN. Additional storm development along the composite front/trailing outflow boundary is expected, but timing of this storm activity remains unclear. Nonetheless, differential heating along the baroclinic zone will yield 2000 to 3000 J/kg MLCAPE amidst moderate effective shear (25-35 kt). A few clusters are forecast to eventually evolve later this afternoon into the evening with the stronger storms capable primarily of a wind-damage threat. ..Smith/Halbert.. 07/20/2025 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sun Jul 20 2025 Valid 201630Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE NORTHERN AND CENTRAL PLAINS...OHIO VALLEY...AND PARTS OF THE NORTHEAST... ...SUMMARY... Severe thunderstorms appear most likely this afternoon into this evening across parts of the Northeast, portions of the northern and central Plains, and perhaps the Ohio Valley. ...Synopsis... A mid-level trough will amplify across the Northeast today with increasing mid-level flow ahead of an approaching jet streak. A low-amplitude ridge will build somewhat across the Upper Midwest. Farther west, mid-level flow will strengthen across the northern Rockies into the northern Plains as a trough amplifies on the Pacific Northwest coast. ...Northeast... Weak to moderate instability is forecast to develop across the Northeast through mid afternoon as the airmass continues to destabilize. Midday surface analysis indicates temperatures are warming into the 80s with dewpoints in the upper 60s to lower 70s. As the cold front advances east into this uncapped airmass, scattered thunderstorms should develop. Shear of 30 to 35 knots and relatively long/straight hodographs will support the potential for supercells. Weak mid-level lapse rates will be the primary limiting factor for large hail, but the overall favorable shear with strong venting aloft and potential supercells may support some isolated large hail. Damaging wind gusts will be the primary threat, both from initial cells and also from any clusters which develop. Any stronger clusters with bowing segments could support a better organized damaging wind swath. The greatest wind damage threat will likely exist from western Massachusetts to far southern Maine. ...Southeast MT into the Dakotas and Central Plains... Lee troughing is forecast to extend southward from eastern MT into the central High Plains near and south of the westerlies confined to the northern tier of states. Elevated weak thunderstorm activity along the ND/SD border may continue but considerable uncertainty exists whether these storms will intensify and pose a severe risk this afternoon. Meanwhile, farther west, moist low levels arc from southeast MT southeastward through west-central SD and south into NE/northwest KS. Strong heating will contribute to a moderate to very unstable airmass from the central Plains states into eastern MT. Easterly low-level flow beneath 30-40 kt 500 mb flow in southeast MT will support organized storms, including supercell potential. Isolated to scattered storms are forecast to develop and spread east into the Dakotas. Other isolated to widely scattered storms are possible from SD southward into NE/CO/KS border vicinity late this afternoon into the evening. Large to very large hail will be possible with any supercells that develop within this general region. However, the severe wind threat may increase by this evening and become the main threat as storms congeal into one or more clusters or MCS. ...Ohio Valley... Visible-satellite/radar composite shows an elongated area of showers/thunderstorms from northern MO east into western OH in conjunction with an MCV moving east from IL into IN. Additional storm development along the composite front/trailing outflow boundary is expected, but timing of this storm activity remains unclear. Nonetheless, differential heating along the baroclinic zone will yield 2000 to 3000 J/kg MLCAPE amidst moderate effective shear (25-35 kt). A few clusters are forecast to eventually evolve later this afternoon into the evening with the stronger storms capable primarily of a wind-damage threat. ..Smith/Halbert.. 07/20/2025 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sun Jul 20 2025 Valid 201630Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE NORTHERN AND CENTRAL PLAINS...OHIO VALLEY...AND PARTS OF THE NORTHEAST... ...SUMMARY... Severe thunderstorms appear most likely this afternoon into this evening across parts of the Northeast, portions of the northern and central Plains, and perhaps the Ohio Valley. ...Synopsis... A mid-level trough will amplify across the Northeast today with increasing mid-level flow ahead of an approaching jet streak. A low-amplitude ridge will build somewhat across the Upper Midwest. Farther west, mid-level flow will strengthen across the northern Rockies into the northern Plains as a trough amplifies on the Pacific Northwest coast. ...Northeast... Weak to moderate instability is forecast to develop across the Northeast through mid afternoon as the airmass continues to destabilize. Midday surface analysis indicates temperatures are warming into the 80s with dewpoints in the upper 60s to lower 70s. As the cold front advances east into this uncapped airmass, scattered thunderstorms should develop. Shear of 30 to 35 knots and relatively long/straight hodographs will support the potential for supercells. Weak mid-level lapse rates will be the primary limiting factor for large hail, but the overall favorable shear with strong venting aloft and potential supercells may support some isolated large hail. Damaging wind gusts will be the primary threat, both from initial cells and also from any clusters which develop. Any stronger clusters with bowing segments could support a better organized damaging wind swath. The greatest wind damage threat will likely exist from western Massachusetts to far southern Maine. ...Southeast MT into the Dakotas and Central Plains... Lee troughing is forecast to extend southward from eastern MT into the central High Plains near and south of the westerlies confined to the northern tier of states. Elevated weak thunderstorm activity along the ND/SD border may continue but considerable uncertainty exists whether these storms will intensify and pose a severe risk this afternoon. Meanwhile, farther west, moist low levels arc from southeast MT southeastward through west-central SD and south into NE/northwest KS. Strong heating will contribute to a moderate to very unstable airmass from the central Plains states into eastern MT. Easterly low-level flow beneath 30-40 kt 500 mb flow in southeast MT will support organized storms, including supercell potential. Isolated to scattered storms are forecast to develop and spread east into the Dakotas. Other isolated to widely scattered storms are possible from SD southward into NE/CO/KS border vicinity late this afternoon into the evening. Large to very large hail will be possible with any supercells that develop within this general region. However, the severe wind threat may increase by this evening and become the main threat as storms congeal into one or more clusters or MCS. ...Ohio Valley... Visible-satellite/radar composite shows an elongated area of showers/thunderstorms from northern MO east into western OH in conjunction with an MCV moving east from IL into IN. Additional storm development along the composite front/trailing outflow boundary is expected, but timing of this storm activity remains unclear. Nonetheless, differential heating along the baroclinic zone will yield 2000 to 3000 J/kg MLCAPE amidst moderate effective shear (25-35 kt). A few clusters are forecast to eventually evolve later this afternoon into the evening with the stronger storms capable primarily of a wind-damage threat. ..Smith/Halbert.. 07/20/2025 Read more

MD 1735 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PORTIONS OF FAR EAST-CENTRAL IL INTO CENTRAL IN
Mesoscale Discussion 1735 NWS Storm Prediction Center Norman OK 0735 AM CDT Sun Jul 20 2025 Areas affected...Portions of far east-central IL into central IN Concerning...Severe potential...Watch possible Valid 201235Z - 201430Z Probability of Watch Issuance...40 percent SUMMARY...A small complex of thunderstorms may pose a gradually increasing threat for damaging winds over the next few hours. Watch issuance is possible later this morning if this activity can intensify. DISCUSSION...Thunderstorms are ongoing this morning across parts of central IL, aided by modest west-southwesterly low-level warm advection and a low-amplitude mid-level perturbation. This convection should continue to track generally east-southeastward this morning across parts of central IN along an instability gradient evident in latest mesoanalysis. While low/mid-level flow is not overly strong, recent VWPs from KILX/KIND do show some strengthening with height through mid levels. Resultant 25-30 kt of effective bulk shear should continue to support some updraft organization, with a recent supercell structure noted with a thunderstorm near the IL/IN border. If a small bowing cluster can become established as some recent high-resolution guidance suggests, then a greater threat for scattered severe/damaging winds may be realized across parts of central IN later this morning as the boundary layer gradually destabilizes with filtered daytime heating. While not immediately likely, Severe Thunderstorm Watch issuance may eventually be needed if the ongoing activity can intensify. ..Gleason.. 07/20/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...IWX...IND...LOT...ILX... LAT...LON 40298835 40788789 40538657 40198532 39768532 39428551 39398622 39488703 39878799 40298835 MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 95 MPH MOST PROBABLE PEAK WIND GUST...55-70 MPH Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0728 AM CDT Sun Jul 20 2025 Valid 201300Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE NORTHEAST...MIDWEST...OHIO VALLEY...AND NORTHERN PLAINS... ...SUMMARY... Strong to severe storms appear most likely later today into this evening across parts of the Northeast, Midwest and Ohio Valley, and northern Plains. ...Synopsis... A mid-level trough will amplify across the Northeast today with increasing mid-level flow ahead of an approaching jet streak. A low-amplitude ridge will build somewhat across the Upper Midwest. Farther west, mid-level flow will strengthen across the northern Rockies into the northern Plains as a trough amplifies on the Pacific Northwest coast. As of 12Z, an elongated frontal zone exists from the Northeast to the Ohio Valley/southern Great Lakes and into the northern Plains. Ongoing thunderstorms are present across the eastern Great Lakes, the Midwest, and the northern Plains. This is correlated with the stronger ascent and the areas with the greatest severe weather potential today. ...Northeast... Weak to moderate instability is forecast to develop across the Northeast today as temperatures warm into the 80s with dewpoints in the upper 60s, and as mid-level temperatures gradually cool through the day. As the cold front advances east into this uncapped airmass, scattered thunderstorms should develop. Shear of 30 to 35 knots and relatively long/straight hodographs will support the potential for supercells. Weak mid-level lapse rates will be the primary limiting factor for large hail, but the overall favorable shear with strong venting aloft and potential supercells may support some isolated large hail. Damaging wind gusts will be the primary threat, both from initial cells and also from any clusters which develop. Any stronger clusters with bowing segments could support a better organized damaging wind swath. The greatest wind damage threat will likely exist from western Massachusetts to far southern Maine. ...Ohio Valley... A large mass of thunderstorms continues east across eastern Iowa and northern Illinois this morning. Heating is anticipated south and east of this activity which should result in an increasing severe weather threat by late morning to early afternoon. It remains unclear whether the afternoon severe threat may materialize out of ongoing thunderstorm activity, or from additional storm development along the front or the outflow boundary associated with these storms. Nonetheless, 1000 to 1500 J/kg MLCAPE and effective shear of 35 to 40 knots will support an organized severe weather threat including the potential for supercells. Despite the supercell mode, the hail threat should remain minimal given the weak mid-level lapse rates and warm mid-level temperatures with high freezing levels. Damaging wind gusts will be the primary threat from these storms with the greatest threat from central Indiana to southwest Ohio and northern Kentucky. ...Northern Plains... Weak lee troughing is forecast in the western Nebraska vicinity today as moderate mid-level flow overspreads the northern Plains. A dryline will extend southward from this surface low into the central High Plains. Isolated storms are possible along this boundary this afternoon/evening. Moderate destabilization is forecast across central South Dakota and vicinity as low-level moisture is advected westward to the north of the surface low. Diurnal thunderstorm activity is forecast to be relatively isolated along the dryline with perhaps slightly greater coverage across eastern Minnesota amid cooler temperatures aloft. However, the ongoing cluster of storms across North Dakota is forecast to linger as isentropic ascent is maintained through the day. Eventual upscale growth and a southeastward movement along the instability gradient is anticipated. RAP forecast soundings show an environment favorable for large hail initially with any supercells which develop. However, the severe wind threat may increase by this evening as storms congeal into a MCS with potential linear, bowing segments. ..Bentley/Gleason.. 07/20/2025 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0728 AM CDT Sun Jul 20 2025 Valid 201300Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE NORTHEAST...MIDWEST...OHIO VALLEY...AND NORTHERN PLAINS... ...SUMMARY... Strong to severe storms appear most likely later today into this evening across parts of the Northeast, Midwest and Ohio Valley, and northern Plains. ...Synopsis... A mid-level trough will amplify across the Northeast today with increasing mid-level flow ahead of an approaching jet streak. A low-amplitude ridge will build somewhat across the Upper Midwest. Farther west, mid-level flow will strengthen across the northern Rockies into the northern Plains as a trough amplifies on the Pacific Northwest coast. As of 12Z, an elongated frontal zone exists from the Northeast to the Ohio Valley/southern Great Lakes and into the northern Plains. Ongoing thunderstorms are present across the eastern Great Lakes, the Midwest, and the northern Plains. This is correlated with the stronger ascent and the areas with the greatest severe weather potential today. ...Northeast... Weak to moderate instability is forecast to develop across the Northeast today as temperatures warm into the 80s with dewpoints in the upper 60s, and as mid-level temperatures gradually cool through the day. As the cold front advances east into this uncapped airmass, scattered thunderstorms should develop. Shear of 30 to 35 knots and relatively long/straight hodographs will support the potential for supercells. Weak mid-level lapse rates will be the primary limiting factor for large hail, but the overall favorable shear with strong venting aloft and potential supercells may support some isolated large hail. Damaging wind gusts will be the primary threat, both from initial cells and also from any clusters which develop. Any stronger clusters with bowing segments could support a better organized damaging wind swath. The greatest wind damage threat will likely exist from western Massachusetts to far southern Maine. ...Ohio Valley... A large mass of thunderstorms continues east across eastern Iowa and northern Illinois this morning. Heating is anticipated south and east of this activity which should result in an increasing severe weather threat by late morning to early afternoon. It remains unclear whether the afternoon severe threat may materialize out of ongoing thunderstorm activity, or from additional storm development along the front or the outflow boundary associated with these storms. Nonetheless, 1000 to 1500 J/kg MLCAPE and effective shear of 35 to 40 knots will support an organized severe weather threat including the potential for supercells. Despite the supercell mode, the hail threat should remain minimal given the weak mid-level lapse rates and warm mid-level temperatures with high freezing levels. Damaging wind gusts will be the primary threat from these storms with the greatest threat from central Indiana to southwest Ohio and northern Kentucky. ...Northern Plains... Weak lee troughing is forecast in the western Nebraska vicinity today as moderate mid-level flow overspreads the northern Plains. A dryline will extend southward from this surface low into the central High Plains. Isolated storms are possible along this boundary this afternoon/evening. Moderate destabilization is forecast across central South Dakota and vicinity as low-level moisture is advected westward to the north of the surface low. Diurnal thunderstorm activity is forecast to be relatively isolated along the dryline with perhaps slightly greater coverage across eastern Minnesota amid cooler temperatures aloft. However, the ongoing cluster of storms across North Dakota is forecast to linger as isentropic ascent is maintained through the day. Eventual upscale growth and a southeastward movement along the instability gradient is anticipated. RAP forecast soundings show an environment favorable for large hail initially with any supercells which develop. However, the severe wind threat may increase by this evening as storms congeal into a MCS with potential linear, bowing segments. ..Bentley/Gleason.. 07/20/2025 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0728 AM CDT Sun Jul 20 2025 Valid 201300Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE NORTHEAST...MIDWEST...OHIO VALLEY...AND NORTHERN PLAINS... ...SUMMARY... Strong to severe storms appear most likely later today into this evening across parts of the Northeast, Midwest and Ohio Valley, and northern Plains. ...Synopsis... A mid-level trough will amplify across the Northeast today with increasing mid-level flow ahead of an approaching jet streak. A low-amplitude ridge will build somewhat across the Upper Midwest. Farther west, mid-level flow will strengthen across the northern Rockies into the northern Plains as a trough amplifies on the Pacific Northwest coast. As of 12Z, an elongated frontal zone exists from the Northeast to the Ohio Valley/southern Great Lakes and into the northern Plains. Ongoing thunderstorms are present across the eastern Great Lakes, the Midwest, and the northern Plains. This is correlated with the stronger ascent and the areas with the greatest severe weather potential today. ...Northeast... Weak to moderate instability is forecast to develop across the Northeast today as temperatures warm into the 80s with dewpoints in the upper 60s, and as mid-level temperatures gradually cool through the day. As the cold front advances east into this uncapped airmass, scattered thunderstorms should develop. Shear of 30 to 35 knots and relatively long/straight hodographs will support the potential for supercells. Weak mid-level lapse rates will be the primary limiting factor for large hail, but the overall favorable shear with strong venting aloft and potential supercells may support some isolated large hail. Damaging wind gusts will be the primary threat, both from initial cells and also from any clusters which develop. Any stronger clusters with bowing segments could support a better organized damaging wind swath. The greatest wind damage threat will likely exist from western Massachusetts to far southern Maine. ...Ohio Valley... A large mass of thunderstorms continues east across eastern Iowa and northern Illinois this morning. Heating is anticipated south and east of this activity which should result in an increasing severe weather threat by late morning to early afternoon. It remains unclear whether the afternoon severe threat may materialize out of ongoing thunderstorm activity, or from additional storm development along the front or the outflow boundary associated with these storms. Nonetheless, 1000 to 1500 J/kg MLCAPE and effective shear of 35 to 40 knots will support an organized severe weather threat including the potential for supercells. Despite the supercell mode, the hail threat should remain minimal given the weak mid-level lapse rates and warm mid-level temperatures with high freezing levels. Damaging wind gusts will be the primary threat from these storms with the greatest threat from central Indiana to southwest Ohio and northern Kentucky. ...Northern Plains... Weak lee troughing is forecast in the western Nebraska vicinity today as moderate mid-level flow overspreads the northern Plains. A dryline will extend southward from this surface low into the central High Plains. Isolated storms are possible along this boundary this afternoon/evening. Moderate destabilization is forecast across central South Dakota and vicinity as low-level moisture is advected westward to the north of the surface low. Diurnal thunderstorm activity is forecast to be relatively isolated along the dryline with perhaps slightly greater coverage across eastern Minnesota amid cooler temperatures aloft. However, the ongoing cluster of storms across North Dakota is forecast to linger as isentropic ascent is maintained through the day. Eventual upscale growth and a southeastward movement along the instability gradient is anticipated. RAP forecast soundings show an environment favorable for large hail initially with any supercells which develop. However, the severe wind threat may increase by this evening as storms congeal into a MCS with potential linear, bowing segments. ..Bentley/Gleason.. 07/20/2025 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0728 AM CDT Sun Jul 20 2025 Valid 201300Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE NORTHEAST...MIDWEST...OHIO VALLEY...AND NORTHERN PLAINS... ...SUMMARY... Strong to severe storms appear most likely later today into this evening across parts of the Northeast, Midwest and Ohio Valley, and northern Plains. ...Synopsis... A mid-level trough will amplify across the Northeast today with increasing mid-level flow ahead of an approaching jet streak. A low-amplitude ridge will build somewhat across the Upper Midwest. Farther west, mid-level flow will strengthen across the northern Rockies into the northern Plains as a trough amplifies on the Pacific Northwest coast. As of 12Z, an elongated frontal zone exists from the Northeast to the Ohio Valley/southern Great Lakes and into the northern Plains. Ongoing thunderstorms are present across the eastern Great Lakes, the Midwest, and the northern Plains. This is correlated with the stronger ascent and the areas with the greatest severe weather potential today. ...Northeast... Weak to moderate instability is forecast to develop across the Northeast today as temperatures warm into the 80s with dewpoints in the upper 60s, and as mid-level temperatures gradually cool through the day. As the cold front advances east into this uncapped airmass, scattered thunderstorms should develop. Shear of 30 to 35 knots and relatively long/straight hodographs will support the potential for supercells. Weak mid-level lapse rates will be the primary limiting factor for large hail, but the overall favorable shear with strong venting aloft and potential supercells may support some isolated large hail. Damaging wind gusts will be the primary threat, both from initial cells and also from any clusters which develop. Any stronger clusters with bowing segments could support a better organized damaging wind swath. The greatest wind damage threat will likely exist from western Massachusetts to far southern Maine. ...Ohio Valley... A large mass of thunderstorms continues east across eastern Iowa and northern Illinois this morning. Heating is anticipated south and east of this activity which should result in an increasing severe weather threat by late morning to early afternoon. It remains unclear whether the afternoon severe threat may materialize out of ongoing thunderstorm activity, or from additional storm development along the front or the outflow boundary associated with these storms. Nonetheless, 1000 to 1500 J/kg MLCAPE and effective shear of 35 to 40 knots will support an organized severe weather threat including the potential for supercells. Despite the supercell mode, the hail threat should remain minimal given the weak mid-level lapse rates and warm mid-level temperatures with high freezing levels. Damaging wind gusts will be the primary threat from these storms with the greatest threat from central Indiana to southwest Ohio and northern Kentucky. ...Northern Plains... Weak lee troughing is forecast in the western Nebraska vicinity today as moderate mid-level flow overspreads the northern Plains. A dryline will extend southward from this surface low into the central High Plains. Isolated storms are possible along this boundary this afternoon/evening. Moderate destabilization is forecast across central South Dakota and vicinity as low-level moisture is advected westward to the north of the surface low. Diurnal thunderstorm activity is forecast to be relatively isolated along the dryline with perhaps slightly greater coverage across eastern Minnesota amid cooler temperatures aloft. However, the ongoing cluster of storms across North Dakota is forecast to linger as isentropic ascent is maintained through the day. Eventual upscale growth and a southeastward movement along the instability gradient is anticipated. RAP forecast soundings show an environment favorable for large hail initially with any supercells which develop. However, the severe wind threat may increase by this evening as storms congeal into a MCS with potential linear, bowing segments. ..Bentley/Gleason.. 07/20/2025 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0728 AM CDT Sun Jul 20 2025 Valid 201300Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE NORTHEAST...MIDWEST...OHIO VALLEY...AND NORTHERN PLAINS... ...SUMMARY... Strong to severe storms appear most likely later today into this evening across parts of the Northeast, Midwest and Ohio Valley, and northern Plains. ...Synopsis... A mid-level trough will amplify across the Northeast today with increasing mid-level flow ahead of an approaching jet streak. A low-amplitude ridge will build somewhat across the Upper Midwest. Farther west, mid-level flow will strengthen across the northern Rockies into the northern Plains as a trough amplifies on the Pacific Northwest coast. As of 12Z, an elongated frontal zone exists from the Northeast to the Ohio Valley/southern Great Lakes and into the northern Plains. Ongoing thunderstorms are present across the eastern Great Lakes, the Midwest, and the northern Plains. This is correlated with the stronger ascent and the areas with the greatest severe weather potential today. ...Northeast... Weak to moderate instability is forecast to develop across the Northeast today as temperatures warm into the 80s with dewpoints in the upper 60s, and as mid-level temperatures gradually cool through the day. As the cold front advances east into this uncapped airmass, scattered thunderstorms should develop. Shear of 30 to 35 knots and relatively long/straight hodographs will support the potential for supercells. Weak mid-level lapse rates will be the primary limiting factor for large hail, but the overall favorable shear with strong venting aloft and potential supercells may support some isolated large hail. Damaging wind gusts will be the primary threat, both from initial cells and also from any clusters which develop. Any stronger clusters with bowing segments could support a better organized damaging wind swath. The greatest wind damage threat will likely exist from western Massachusetts to far southern Maine. ...Ohio Valley... A large mass of thunderstorms continues east across eastern Iowa and northern Illinois this morning. Heating is anticipated south and east of this activity which should result in an increasing severe weather threat by late morning to early afternoon. It remains unclear whether the afternoon severe threat may materialize out of ongoing thunderstorm activity, or from additional storm development along the front or the outflow boundary associated with these storms. Nonetheless, 1000 to 1500 J/kg MLCAPE and effective shear of 35 to 40 knots will support an organized severe weather threat including the potential for supercells. Despite the supercell mode, the hail threat should remain minimal given the weak mid-level lapse rates and warm mid-level temperatures with high freezing levels. Damaging wind gusts will be the primary threat from these storms with the greatest threat from central Indiana to southwest Ohio and northern Kentucky. ...Northern Plains... Weak lee troughing is forecast in the western Nebraska vicinity today as moderate mid-level flow overspreads the northern Plains. A dryline will extend southward from this surface low into the central High Plains. Isolated storms are possible along this boundary this afternoon/evening. Moderate destabilization is forecast across central South Dakota and vicinity as low-level moisture is advected westward to the north of the surface low. Diurnal thunderstorm activity is forecast to be relatively isolated along the dryline with perhaps slightly greater coverage across eastern Minnesota amid cooler temperatures aloft. However, the ongoing cluster of storms across North Dakota is forecast to linger as isentropic ascent is maintained through the day. Eventual upscale growth and a southeastward movement along the instability gradient is anticipated. RAP forecast soundings show an environment favorable for large hail initially with any supercells which develop. However, the severe wind threat may increase by this evening as storms congeal into a MCS with potential linear, bowing segments. ..Bentley/Gleason.. 07/20/2025 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0728 AM CDT Sun Jul 20 2025 Valid 201300Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE NORTHEAST...MIDWEST...OHIO VALLEY...AND NORTHERN PLAINS... ...SUMMARY... Strong to severe storms appear most likely later today into this evening across parts of the Northeast, Midwest and Ohio Valley, and northern Plains. ...Synopsis... A mid-level trough will amplify across the Northeast today with increasing mid-level flow ahead of an approaching jet streak. A low-amplitude ridge will build somewhat across the Upper Midwest. Farther west, mid-level flow will strengthen across the northern Rockies into the northern Plains as a trough amplifies on the Pacific Northwest coast. As of 12Z, an elongated frontal zone exists from the Northeast to the Ohio Valley/southern Great Lakes and into the northern Plains. Ongoing thunderstorms are present across the eastern Great Lakes, the Midwest, and the northern Plains. This is correlated with the stronger ascent and the areas with the greatest severe weather potential today. ...Northeast... Weak to moderate instability is forecast to develop across the Northeast today as temperatures warm into the 80s with dewpoints in the upper 60s, and as mid-level temperatures gradually cool through the day. As the cold front advances east into this uncapped airmass, scattered thunderstorms should develop. Shear of 30 to 35 knots and relatively long/straight hodographs will support the potential for supercells. Weak mid-level lapse rates will be the primary limiting factor for large hail, but the overall favorable shear with strong venting aloft and potential supercells may support some isolated large hail. Damaging wind gusts will be the primary threat, both from initial cells and also from any clusters which develop. Any stronger clusters with bowing segments could support a better organized damaging wind swath. The greatest wind damage threat will likely exist from western Massachusetts to far southern Maine. ...Ohio Valley... A large mass of thunderstorms continues east across eastern Iowa and northern Illinois this morning. Heating is anticipated south and east of this activity which should result in an increasing severe weather threat by late morning to early afternoon. It remains unclear whether the afternoon severe threat may materialize out of ongoing thunderstorm activity, or from additional storm development along the front or the outflow boundary associated with these storms. Nonetheless, 1000 to 1500 J/kg MLCAPE and effective shear of 35 to 40 knots will support an organized severe weather threat including the potential for supercells. Despite the supercell mode, the hail threat should remain minimal given the weak mid-level lapse rates and warm mid-level temperatures with high freezing levels. Damaging wind gusts will be the primary threat from these storms with the greatest threat from central Indiana to southwest Ohio and northern Kentucky. ...Northern Plains... Weak lee troughing is forecast in the western Nebraska vicinity today as moderate mid-level flow overspreads the northern Plains. A dryline will extend southward from this surface low into the central High Plains. Isolated storms are possible along this boundary this afternoon/evening. Moderate destabilization is forecast across central South Dakota and vicinity as low-level moisture is advected westward to the north of the surface low. Diurnal thunderstorm activity is forecast to be relatively isolated along the dryline with perhaps slightly greater coverage across eastern Minnesota amid cooler temperatures aloft. However, the ongoing cluster of storms across North Dakota is forecast to linger as isentropic ascent is maintained through the day. Eventual upscale growth and a southeastward movement along the instability gradient is anticipated. RAP forecast soundings show an environment favorable for large hail initially with any supercells which develop. However, the severe wind threat may increase by this evening as storms congeal into a MCS with potential linear, bowing segments. ..Bentley/Gleason.. 07/20/2025 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0345 AM CDT Sun Jul 20 2025 Valid 231200Z - 281200Z ...DISCUSSION... The latest medium-range output offers little change from prior runs concerning the general large-scale pattern evolution during the middle to latter portion of the coming work week. It still appears that a fairly significant mid-level low currently emerging from the northwestern Canadian Arctic latitudes will slowly progress across and east-southeast of the Hudson Bay vicinity, to the north of an increasingly prominent mid-level high evolving across the Ohio Valley. As this contributes to a belt of strengthening westerly to northwesterly flow between the two features, it appears that low-level moistening in a corridor beneath the southern periphery of this regime will support substantive destabilization, and increasing potential for organized strong to severe thunderstorm development. The extent to which this corridor evolves south of the international border, across parts of the Upper Midwest and adjacent Great Lakes region toward the St. Lawrence Valley/New England remains at least a bit unclear. Adding to this uncertainty, forcing for this potential convective development will be largely associated with sub-synoptic perturbations with low predictability at this extended time frame. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0345 AM CDT Sun Jul 20 2025 Valid 231200Z - 281200Z ...DISCUSSION... The latest medium-range output offers little change from prior runs concerning the general large-scale pattern evolution during the middle to latter portion of the coming work week. It still appears that a fairly significant mid-level low currently emerging from the northwestern Canadian Arctic latitudes will slowly progress across and east-southeast of the Hudson Bay vicinity, to the north of an increasingly prominent mid-level high evolving across the Ohio Valley. As this contributes to a belt of strengthening westerly to northwesterly flow between the two features, it appears that low-level moistening in a corridor beneath the southern periphery of this regime will support substantive destabilization, and increasing potential for organized strong to severe thunderstorm development. The extent to which this corridor evolves south of the international border, across parts of the Upper Midwest and adjacent Great Lakes region toward the St. Lawrence Valley/New England remains at least a bit unclear. Adding to this uncertainty, forcing for this potential convective development will be largely associated with sub-synoptic perturbations with low predictability at this extended time frame. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0345 AM CDT Sun Jul 20 2025 Valid 231200Z - 281200Z ...DISCUSSION... The latest medium-range output offers little change from prior runs concerning the general large-scale pattern evolution during the middle to latter portion of the coming work week. It still appears that a fairly significant mid-level low currently emerging from the northwestern Canadian Arctic latitudes will slowly progress across and east-southeast of the Hudson Bay vicinity, to the north of an increasingly prominent mid-level high evolving across the Ohio Valley. As this contributes to a belt of strengthening westerly to northwesterly flow between the two features, it appears that low-level moistening in a corridor beneath the southern periphery of this regime will support substantive destabilization, and increasing potential for organized strong to severe thunderstorm development. The extent to which this corridor evolves south of the international border, across parts of the Upper Midwest and adjacent Great Lakes region toward the St. Lawrence Valley/New England remains at least a bit unclear. Adding to this uncertainty, forcing for this potential convective development will be largely associated with sub-synoptic perturbations with low predictability at this extended time frame. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0345 AM CDT Sun Jul 20 2025 Valid 231200Z - 281200Z ...DISCUSSION... The latest medium-range output offers little change from prior runs concerning the general large-scale pattern evolution during the middle to latter portion of the coming work week. It still appears that a fairly significant mid-level low currently emerging from the northwestern Canadian Arctic latitudes will slowly progress across and east-southeast of the Hudson Bay vicinity, to the north of an increasingly prominent mid-level high evolving across the Ohio Valley. As this contributes to a belt of strengthening westerly to northwesterly flow between the two features, it appears that low-level moistening in a corridor beneath the southern periphery of this regime will support substantive destabilization, and increasing potential for organized strong to severe thunderstorm development. The extent to which this corridor evolves south of the international border, across parts of the Upper Midwest and adjacent Great Lakes region toward the St. Lawrence Valley/New England remains at least a bit unclear. Adding to this uncertainty, forcing for this potential convective development will be largely associated with sub-synoptic perturbations with low predictability at this extended time frame. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0345 AM CDT Sun Jul 20 2025 Valid 231200Z - 281200Z ...DISCUSSION... The latest medium-range output offers little change from prior runs concerning the general large-scale pattern evolution during the middle to latter portion of the coming work week. It still appears that a fairly significant mid-level low currently emerging from the northwestern Canadian Arctic latitudes will slowly progress across and east-southeast of the Hudson Bay vicinity, to the north of an increasingly prominent mid-level high evolving across the Ohio Valley. As this contributes to a belt of strengthening westerly to northwesterly flow between the two features, it appears that low-level moistening in a corridor beneath the southern periphery of this regime will support substantive destabilization, and increasing potential for organized strong to severe thunderstorm development. The extent to which this corridor evolves south of the international border, across parts of the Upper Midwest and adjacent Great Lakes region toward the St. Lawrence Valley/New England remains at least a bit unclear. Adding to this uncertainty, forcing for this potential convective development will be largely associated with sub-synoptic perturbations with low predictability at this extended time frame. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook CORR 1 NWS Storm Prediction Center Norman OK 0235 AM CDT Sun Jul 20 2025 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TUESDAY INTO TUESDAY NIGHT ACROSS PARTS OF WESTERN UPPER MICHIGAN...NORTHWESTERN WISCONSIN...MINNESOTA...SOUTHEASTERN NORTH DAKOTA...SOUTH DAKOTA...MUCH OF NEBRASKA AND PARTS OF SOUTHEASTERN MONTANA...NORTHEASTERN WYOMING AND NORTHEASTERN COLORADO... CORRECTED A POINT ON THE CATEGORICAL THUNDER LINE OVER THE LAKE HURON VICINITY ...SUMMARY... Scattered strong thunderstorm development may impact parts of the northern Great Plains into the Upper Midwest Tuesday into Tuesday night, and pose at least some risk for severe wind and hail. ...Discussion... Models indicate that a center of higher mid-level heights may become increasingly prominent across the middle Mississippi/lower Ohio Valley region during this period, within persistent ridging encompassing much of the interior U.S. Modest, anticyclonic flow around the northern periphery of this feature is likely to be maintained across the northern Great Basin, Rockies and Great Plains through the Great Lakes and adjacent portions of Ontario and Quebec. It appears that ridging will also remain prominent across much of the northeastern Pacific, though it may begin to undergo some suppression. Weak mid-level troughing is likely to linger between the ridging across the Pacific coast vicinity, with one embedded short wave impulse forecast to accelerate northeast of the mountains of western Montana. It appears that this will trail a significant mid-level low continuing to slowly migrate east of the Canadian Northwest Territories toward Hudson Bay, but there is spread among the various models concerning this. The stronger perturbation will be accompanied by a modest surface cyclone, with a trailing cold front forecast to advance across the international border into the northern Great Plains late Tuesday into Tuesday night. ...Northern Great Plains into Upper Midwest... Beneath the mid-level ridging, insolation within a seasonably moist boundary-layer appears likely to once again contribute to moderate to large potential instability across parts of the middle Missouri Valley and adjacent Great Plains, within modestly deep pre-frontal surface troughing. This low-level moisture is forecast to advect northeastward toward the Upper Midwest late Tuesday through Tuesday night, beneath thermodynamic profiles characterized by generally steep lapse rates, but with warm, capping layers aloft. Near the southern periphery of a belt of strengthening southwesterly mid-level flow, the environment is likely to become at least conditionally supportive of organized thunderstorm development, including supercells and upscale growing clusters. However, south of the international border, forcing for ascent to support thunderstorm development is likely to mostly be linked to subtle perturbations progressing around the northern periphery of the mid-level ridging, which remain uncertain at this time. There does appear a general consensus for increasing thunderstorm development across parts of Minnesota into Wisconsin, particularly Tuesday night. But this may be largely rooted in lower/mid-tropospheric warm advection, above a stable boundary-layer, and within relatively warm thermodynamic profiles, where the extent of the potential for severe wind and hail is still unclear. ..Kerr.. 07/20/2025 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook CORR 1 NWS Storm Prediction Center Norman OK 0235 AM CDT Sun Jul 20 2025 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TUESDAY INTO TUESDAY NIGHT ACROSS PARTS OF WESTERN UPPER MICHIGAN...NORTHWESTERN WISCONSIN...MINNESOTA...SOUTHEASTERN NORTH DAKOTA...SOUTH DAKOTA...MUCH OF NEBRASKA AND PARTS OF SOUTHEASTERN MONTANA...NORTHEASTERN WYOMING AND NORTHEASTERN COLORADO... CORRECTED A POINT ON THE CATEGORICAL THUNDER LINE OVER THE LAKE HURON VICINITY ...SUMMARY... Scattered strong thunderstorm development may impact parts of the northern Great Plains into the Upper Midwest Tuesday into Tuesday night, and pose at least some risk for severe wind and hail. ...Discussion... Models indicate that a center of higher mid-level heights may become increasingly prominent across the middle Mississippi/lower Ohio Valley region during this period, within persistent ridging encompassing much of the interior U.S. Modest, anticyclonic flow around the northern periphery of this feature is likely to be maintained across the northern Great Basin, Rockies and Great Plains through the Great Lakes and adjacent portions of Ontario and Quebec. It appears that ridging will also remain prominent across much of the northeastern Pacific, though it may begin to undergo some suppression. Weak mid-level troughing is likely to linger between the ridging across the Pacific coast vicinity, with one embedded short wave impulse forecast to accelerate northeast of the mountains of western Montana. It appears that this will trail a significant mid-level low continuing to slowly migrate east of the Canadian Northwest Territories toward Hudson Bay, but there is spread among the various models concerning this. The stronger perturbation will be accompanied by a modest surface cyclone, with a trailing cold front forecast to advance across the international border into the northern Great Plains late Tuesday into Tuesday night. ...Northern Great Plains into Upper Midwest... Beneath the mid-level ridging, insolation within a seasonably moist boundary-layer appears likely to once again contribute to moderate to large potential instability across parts of the middle Missouri Valley and adjacent Great Plains, within modestly deep pre-frontal surface troughing. This low-level moisture is forecast to advect northeastward toward the Upper Midwest late Tuesday through Tuesday night, beneath thermodynamic profiles characterized by generally steep lapse rates, but with warm, capping layers aloft. Near the southern periphery of a belt of strengthening southwesterly mid-level flow, the environment is likely to become at least conditionally supportive of organized thunderstorm development, including supercells and upscale growing clusters. However, south of the international border, forcing for ascent to support thunderstorm development is likely to mostly be linked to subtle perturbations progressing around the northern periphery of the mid-level ridging, which remain uncertain at this time. There does appear a general consensus for increasing thunderstorm development across parts of Minnesota into Wisconsin, particularly Tuesday night. But this may be largely rooted in lower/mid-tropospheric warm advection, above a stable boundary-layer, and within relatively warm thermodynamic profiles, where the extent of the potential for severe wind and hail is still unclear. ..Kerr.. 07/20/2025 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook CORR 1 NWS Storm Prediction Center Norman OK 0235 AM CDT Sun Jul 20 2025 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TUESDAY INTO TUESDAY NIGHT ACROSS PARTS OF WESTERN UPPER MICHIGAN...NORTHWESTERN WISCONSIN...MINNESOTA...SOUTHEASTERN NORTH DAKOTA...SOUTH DAKOTA...MUCH OF NEBRASKA AND PARTS OF SOUTHEASTERN MONTANA...NORTHEASTERN WYOMING AND NORTHEASTERN COLORADO... CORRECTED A POINT ON THE CATEGORICAL THUNDER LINE OVER THE LAKE HURON VICINITY ...SUMMARY... Scattered strong thunderstorm development may impact parts of the northern Great Plains into the Upper Midwest Tuesday into Tuesday night, and pose at least some risk for severe wind and hail. ...Discussion... Models indicate that a center of higher mid-level heights may become increasingly prominent across the middle Mississippi/lower Ohio Valley region during this period, within persistent ridging encompassing much of the interior U.S. Modest, anticyclonic flow around the northern periphery of this feature is likely to be maintained across the northern Great Basin, Rockies and Great Plains through the Great Lakes and adjacent portions of Ontario and Quebec. It appears that ridging will also remain prominent across much of the northeastern Pacific, though it may begin to undergo some suppression. Weak mid-level troughing is likely to linger between the ridging across the Pacific coast vicinity, with one embedded short wave impulse forecast to accelerate northeast of the mountains of western Montana. It appears that this will trail a significant mid-level low continuing to slowly migrate east of the Canadian Northwest Territories toward Hudson Bay, but there is spread among the various models concerning this. The stronger perturbation will be accompanied by a modest surface cyclone, with a trailing cold front forecast to advance across the international border into the northern Great Plains late Tuesday into Tuesday night. ...Northern Great Plains into Upper Midwest... Beneath the mid-level ridging, insolation within a seasonably moist boundary-layer appears likely to once again contribute to moderate to large potential instability across parts of the middle Missouri Valley and adjacent Great Plains, within modestly deep pre-frontal surface troughing. This low-level moisture is forecast to advect northeastward toward the Upper Midwest late Tuesday through Tuesday night, beneath thermodynamic profiles characterized by generally steep lapse rates, but with warm, capping layers aloft. Near the southern periphery of a belt of strengthening southwesterly mid-level flow, the environment is likely to become at least conditionally supportive of organized thunderstorm development, including supercells and upscale growing clusters. However, south of the international border, forcing for ascent to support thunderstorm development is likely to mostly be linked to subtle perturbations progressing around the northern periphery of the mid-level ridging, which remain uncertain at this time. There does appear a general consensus for increasing thunderstorm development across parts of Minnesota into Wisconsin, particularly Tuesday night. But this may be largely rooted in lower/mid-tropospheric warm advection, above a stable boundary-layer, and within relatively warm thermodynamic profiles, where the extent of the potential for severe wind and hail is still unclear. ..Kerr.. 07/20/2025 Read more