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SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0239 PM CDT Sun Jul 20 2025 Valid 202000Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE CENTRAL INTO NORTHERN PLAINS...PARTS OF THE 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. ...20Z Update... The primary change made to the Day 1 outlook was to add 5 percent tornado probabilities across south-central SD into north-central NE. Here, a cluster of supercells is expected to develop along a diffuse warm-frontal boundary, where directional low-level shear will be present. Up to 200 m2/s2 effective SRH in this region may support the development of a tornado in addition to severe winds and very large hail, given 2500-4000 J/kg MLCAPE by evening. Consideration was also given to remove Slight risk and 2 percent tornado probabilities over the OH Valley given remnant cloud cover and overall lack of upper support to foster an organized severe threat. However, on the immediate southern periphery of this cloud deck resides an axis of overlapping 2000+ MLCAPE and 30+ kts of effective bulk shear. Should storms manage to develop, especially before nocturnal cooling commences, a conditional risk for scattered damaging gusts or a brief tornado would exist, so 15 percent severe wind/2 percent tornado probabilities have been maintained. Otherwise, the previous forecast (see below) remains on track. ..Squitieri.. 07/20/2025 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sun Jul 20 2025/ ...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. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0239 PM CDT Sun Jul 20 2025 Valid 202000Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE CENTRAL INTO NORTHERN PLAINS...PARTS OF THE 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. ...20Z Update... The primary change made to the Day 1 outlook was to add 5 percent tornado probabilities across south-central SD into north-central NE. Here, a cluster of supercells is expected to develop along a diffuse warm-frontal boundary, where directional low-level shear will be present. Up to 200 m2/s2 effective SRH in this region may support the development of a tornado in addition to severe winds and very large hail, given 2500-4000 J/kg MLCAPE by evening. Consideration was also given to remove Slight risk and 2 percent tornado probabilities over the OH Valley given remnant cloud cover and overall lack of upper support to foster an organized severe threat. However, on the immediate southern periphery of this cloud deck resides an axis of overlapping 2000+ MLCAPE and 30+ kts of effective bulk shear. Should storms manage to develop, especially before nocturnal cooling commences, a conditional risk for scattered damaging gusts or a brief tornado would exist, so 15 percent severe wind/2 percent tornado probabilities have been maintained. Otherwise, the previous forecast (see below) remains on track. ..Squitieri.. 07/20/2025 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sun Jul 20 2025/ ...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. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0239 PM CDT Sun Jul 20 2025 Valid 202000Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE CENTRAL INTO NORTHERN PLAINS...PARTS OF THE 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. ...20Z Update... The primary change made to the Day 1 outlook was to add 5 percent tornado probabilities across south-central SD into north-central NE. Here, a cluster of supercells is expected to develop along a diffuse warm-frontal boundary, where directional low-level shear will be present. Up to 200 m2/s2 effective SRH in this region may support the development of a tornado in addition to severe winds and very large hail, given 2500-4000 J/kg MLCAPE by evening. Consideration was also given to remove Slight risk and 2 percent tornado probabilities over the OH Valley given remnant cloud cover and overall lack of upper support to foster an organized severe threat. However, on the immediate southern periphery of this cloud deck resides an axis of overlapping 2000+ MLCAPE and 30+ kts of effective bulk shear. Should storms manage to develop, especially before nocturnal cooling commences, a conditional risk for scattered damaging gusts or a brief tornado would exist, so 15 percent severe wind/2 percent tornado probabilities have been maintained. Otherwise, the previous forecast (see below) remains on track. ..Squitieri.. 07/20/2025 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sun Jul 20 2025/ ...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. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0239 PM CDT Sun Jul 20 2025 Valid 202000Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE CENTRAL INTO NORTHERN PLAINS...PARTS OF THE 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. ...20Z Update... The primary change made to the Day 1 outlook was to add 5 percent tornado probabilities across south-central SD into north-central NE. Here, a cluster of supercells is expected to develop along a diffuse warm-frontal boundary, where directional low-level shear will be present. Up to 200 m2/s2 effective SRH in this region may support the development of a tornado in addition to severe winds and very large hail, given 2500-4000 J/kg MLCAPE by evening. Consideration was also given to remove Slight risk and 2 percent tornado probabilities over the OH Valley given remnant cloud cover and overall lack of upper support to foster an organized severe threat. However, on the immediate southern periphery of this cloud deck resides an axis of overlapping 2000+ MLCAPE and 30+ kts of effective bulk shear. Should storms manage to develop, especially before nocturnal cooling commences, a conditional risk for scattered damaging gusts or a brief tornado would exist, so 15 percent severe wind/2 percent tornado probabilities have been maintained. Otherwise, the previous forecast (see below) remains on track. ..Squitieri.. 07/20/2025 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sun Jul 20 2025/ ...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. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0239 PM CDT Sun Jul 20 2025 Valid 202000Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE CENTRAL INTO NORTHERN PLAINS...PARTS OF THE 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. ...20Z Update... The primary change made to the Day 1 outlook was to add 5 percent tornado probabilities across south-central SD into north-central NE. Here, a cluster of supercells is expected to develop along a diffuse warm-frontal boundary, where directional low-level shear will be present. Up to 200 m2/s2 effective SRH in this region may support the development of a tornado in addition to severe winds and very large hail, given 2500-4000 J/kg MLCAPE by evening. Consideration was also given to remove Slight risk and 2 percent tornado probabilities over the OH Valley given remnant cloud cover and overall lack of upper support to foster an organized severe threat. However, on the immediate southern periphery of this cloud deck resides an axis of overlapping 2000+ MLCAPE and 30+ kts of effective bulk shear. Should storms manage to develop, especially before nocturnal cooling commences, a conditional risk for scattered damaging gusts or a brief tornado would exist, so 15 percent severe wind/2 percent tornado probabilities have been maintained. Otherwise, the previous forecast (see below) remains on track. ..Squitieri.. 07/20/2025 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sun Jul 20 2025/ ...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. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0239 PM CDT Sun Jul 20 2025 Valid 202000Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE CENTRAL INTO NORTHERN PLAINS...PARTS OF THE 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. ...20Z Update... The primary change made to the Day 1 outlook was to add 5 percent tornado probabilities across south-central SD into north-central NE. Here, a cluster of supercells is expected to develop along a diffuse warm-frontal boundary, where directional low-level shear will be present. Up to 200 m2/s2 effective SRH in this region may support the development of a tornado in addition to severe winds and very large hail, given 2500-4000 J/kg MLCAPE by evening. Consideration was also given to remove Slight risk and 2 percent tornado probabilities over the OH Valley given remnant cloud cover and overall lack of upper support to foster an organized severe threat. However, on the immediate southern periphery of this cloud deck resides an axis of overlapping 2000+ MLCAPE and 30+ kts of effective bulk shear. Should storms manage to develop, especially before nocturnal cooling commences, a conditional risk for scattered damaging gusts or a brief tornado would exist, so 15 percent severe wind/2 percent tornado probabilities have been maintained. Otherwise, the previous forecast (see below) remains on track. ..Squitieri.. 07/20/2025 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sun Jul 20 2025/ ...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. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0239 PM CDT Sun Jul 20 2025 Valid 202000Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE CENTRAL INTO NORTHERN PLAINS...PARTS OF THE 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. ...20Z Update... The primary change made to the Day 1 outlook was to add 5 percent tornado probabilities across south-central SD into north-central NE. Here, a cluster of supercells is expected to develop along a diffuse warm-frontal boundary, where directional low-level shear will be present. Up to 200 m2/s2 effective SRH in this region may support the development of a tornado in addition to severe winds and very large hail, given 2500-4000 J/kg MLCAPE by evening. Consideration was also given to remove Slight risk and 2 percent tornado probabilities over the OH Valley given remnant cloud cover and overall lack of upper support to foster an organized severe threat. However, on the immediate southern periphery of this cloud deck resides an axis of overlapping 2000+ MLCAPE and 30+ kts of effective bulk shear. Should storms manage to develop, especially before nocturnal cooling commences, a conditional risk for scattered damaging gusts or a brief tornado would exist, so 15 percent severe wind/2 percent tornado probabilities have been maintained. Otherwise, the previous forecast (see below) remains on track. ..Squitieri.. 07/20/2025 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sun Jul 20 2025/ ...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. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0239 PM CDT Sun Jul 20 2025 Valid 202000Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE CENTRAL INTO NORTHERN PLAINS...PARTS OF THE 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. ...20Z Update... The primary change made to the Day 1 outlook was to add 5 percent tornado probabilities across south-central SD into north-central NE. Here, a cluster of supercells is expected to develop along a diffuse warm-frontal boundary, where directional low-level shear will be present. Up to 200 m2/s2 effective SRH in this region may support the development of a tornado in addition to severe winds and very large hail, given 2500-4000 J/kg MLCAPE by evening. Consideration was also given to remove Slight risk and 2 percent tornado probabilities over the OH Valley given remnant cloud cover and overall lack of upper support to foster an organized severe threat. However, on the immediate southern periphery of this cloud deck resides an axis of overlapping 2000+ MLCAPE and 30+ kts of effective bulk shear. Should storms manage to develop, especially before nocturnal cooling commences, a conditional risk for scattered damaging gusts or a brief tornado would exist, so 15 percent severe wind/2 percent tornado probabilities have been maintained. Otherwise, the previous forecast (see below) remains on track. ..Squitieri.. 07/20/2025 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sun Jul 20 2025/ ...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. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0239 PM CDT Sun Jul 20 2025 Valid 202000Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE CENTRAL INTO NORTHERN PLAINS...PARTS OF THE 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. ...20Z Update... The primary change made to the Day 1 outlook was to add 5 percent tornado probabilities across south-central SD into north-central NE. Here, a cluster of supercells is expected to develop along a diffuse warm-frontal boundary, where directional low-level shear will be present. Up to 200 m2/s2 effective SRH in this region may support the development of a tornado in addition to severe winds and very large hail, given 2500-4000 J/kg MLCAPE by evening. Consideration was also given to remove Slight risk and 2 percent tornado probabilities over the OH Valley given remnant cloud cover and overall lack of upper support to foster an organized severe threat. However, on the immediate southern periphery of this cloud deck resides an axis of overlapping 2000+ MLCAPE and 30+ kts of effective bulk shear. Should storms manage to develop, especially before nocturnal cooling commences, a conditional risk for scattered damaging gusts or a brief tornado would exist, so 15 percent severe wind/2 percent tornado probabilities have been maintained. Otherwise, the previous forecast (see below) remains on track. ..Squitieri.. 07/20/2025 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sun Jul 20 2025/ ...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. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0239 PM CDT Sun Jul 20 2025 Valid 202000Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE CENTRAL INTO NORTHERN PLAINS...PARTS OF THE 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. ...20Z Update... The primary change made to the Day 1 outlook was to add 5 percent tornado probabilities across south-central SD into north-central NE. Here, a cluster of supercells is expected to develop along a diffuse warm-frontal boundary, where directional low-level shear will be present. Up to 200 m2/s2 effective SRH in this region may support the development of a tornado in addition to severe winds and very large hail, given 2500-4000 J/kg MLCAPE by evening. Consideration was also given to remove Slight risk and 2 percent tornado probabilities over the OH Valley given remnant cloud cover and overall lack of upper support to foster an organized severe threat. However, on the immediate southern periphery of this cloud deck resides an axis of overlapping 2000+ MLCAPE and 30+ kts of effective bulk shear. Should storms manage to develop, especially before nocturnal cooling commences, a conditional risk for scattered damaging gusts or a brief tornado would exist, so 15 percent severe wind/2 percent tornado probabilities have been maintained. Otherwise, the previous forecast (see below) remains on track. ..Squitieri.. 07/20/2025 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sun Jul 20 2025/ ...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. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0239 PM CDT Sun Jul 20 2025 Valid 202000Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE CENTRAL INTO NORTHERN PLAINS...PARTS OF THE 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. ...20Z Update... The primary change made to the Day 1 outlook was to add 5 percent tornado probabilities across south-central SD into north-central NE. Here, a cluster of supercells is expected to develop along a diffuse warm-frontal boundary, where directional low-level shear will be present. Up to 200 m2/s2 effective SRH in this region may support the development of a tornado in addition to severe winds and very large hail, given 2500-4000 J/kg MLCAPE by evening. Consideration was also given to remove Slight risk and 2 percent tornado probabilities over the OH Valley given remnant cloud cover and overall lack of upper support to foster an organized severe threat. However, on the immediate southern periphery of this cloud deck resides an axis of overlapping 2000+ MLCAPE and 30+ kts of effective bulk shear. Should storms manage to develop, especially before nocturnal cooling commences, a conditional risk for scattered damaging gusts or a brief tornado would exist, so 15 percent severe wind/2 percent tornado probabilities have been maintained. Otherwise, the previous forecast (see below) remains on track. ..Squitieri.. 07/20/2025 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sun Jul 20 2025/ ...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. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0239 PM CDT Sun Jul 20 2025 Valid 202000Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE CENTRAL INTO NORTHERN PLAINS...PARTS OF THE 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. ...20Z Update... The primary change made to the Day 1 outlook was to add 5 percent tornado probabilities across south-central SD into north-central NE. Here, a cluster of supercells is expected to develop along a diffuse warm-frontal boundary, where directional low-level shear will be present. Up to 200 m2/s2 effective SRH in this region may support the development of a tornado in addition to severe winds and very large hail, given 2500-4000 J/kg MLCAPE by evening. Consideration was also given to remove Slight risk and 2 percent tornado probabilities over the OH Valley given remnant cloud cover and overall lack of upper support to foster an organized severe threat. However, on the immediate southern periphery of this cloud deck resides an axis of overlapping 2000+ MLCAPE and 30+ kts of effective bulk shear. Should storms manage to develop, especially before nocturnal cooling commences, a conditional risk for scattered damaging gusts or a brief tornado would exist, so 15 percent severe wind/2 percent tornado probabilities have been maintained. Otherwise, the previous forecast (see below) remains on track. ..Squitieri.. 07/20/2025 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sun Jul 20 2025/ ...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. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0239 PM CDT Sun Jul 20 2025 Valid 202000Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE CENTRAL INTO NORTHERN PLAINS...PARTS OF THE 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. ...20Z Update... The primary change made to the Day 1 outlook was to add 5 percent tornado probabilities across south-central SD into north-central NE. Here, a cluster of supercells is expected to develop along a diffuse warm-frontal boundary, where directional low-level shear will be present. Up to 200 m2/s2 effective SRH in this region may support the development of a tornado in addition to severe winds and very large hail, given 2500-4000 J/kg MLCAPE by evening. Consideration was also given to remove Slight risk and 2 percent tornado probabilities over the OH Valley given remnant cloud cover and overall lack of upper support to foster an organized severe threat. However, on the immediate southern periphery of this cloud deck resides an axis of overlapping 2000+ MLCAPE and 30+ kts of effective bulk shear. Should storms manage to develop, especially before nocturnal cooling commences, a conditional risk for scattered damaging gusts or a brief tornado would exist, so 15 percent severe wind/2 percent tornado probabilities have been maintained. Otherwise, the previous forecast (see below) remains on track. ..Squitieri.. 07/20/2025 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sun Jul 20 2025/ ...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. Read more

MD 1736 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PORTIONS OF EASTERN PENNSYLVANIA INTO NEW JERSEY...SOUTHERN NEW YORK...AND WESTERN PORTIONS OF NEW ENGLAND
Mesoscale Discussion 1736 NWS Storm Prediction Center Norman OK 0101 PM CDT Sun Jul 20 2025 Areas affected...Portions of eastern Pennsylvania into New Jersey...southern New York...and western portions of New England Concerning...Severe potential...Watch possible Valid 201801Z - 202000Z Probability of Watch Issuance...60 percent SUMMARY...Scattered severe thunderstorms, primarily capable of damaging wind gusts, are anticipated this afternoon and into the evening across portions of New England into eastern Pennsylvania, southern New York, and New Jersey. Though there is some uncertainty in the degree of convective organization and evolution, a severe thunderstorm watch could be warranted later this afternoon. DISCUSSION...Satellite and radar trends show convection developing across PA into NY in an environment characterized by moderate buoyancy (~1000-1500 J/kg MLCAPE) and strong deep-layer shear (40-45 kt 0-6km). Though deep convection has yet to form, it is anticipated that as daytime heating and mixing continues, the environment will support strong, organized thunderstorm updrafts. Given long, straight hodographs and appreciable 0-1 km lapse rates approaching 8 C/km, along with seasonably high precipitable water content approaching 2.00 inches, the primary threat will be for damaging straight-line winds of 55-70 MPH within thunderstorm downdrafts. Hail or a brief tornado cannot be ruled out with any stronger, isolated organized convection that occurs, though low-level shear and mid-level lapse rates do not suggest that they are likely at this time. A severe thunderstorm watch may be needed later this afternoon as convective trends continue to be monitored. ..Halbert/Smith.. 07/20/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...GYX...BOX...BTV...OKX...ALY...PHI...BGM... LAT...LON 42977429 43247363 43327321 43377270 43217212 42927176 42517159 41997157 41567178 41257213 40967271 40687355 40577420 40477470 40647520 40957580 41247601 41777616 41997617 42027613 42467539 42707483 42757473 42977429 MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 95 MPH MOST PROBABLE PEAK WIND GUST...55-70 MPH MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN Read more

No watches are valid as of Sun Jul 20 19:45:01 UTC 2025.

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 PM CDT Sun Jul 20 2025 Valid 221200Z - 231200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE UPPER MIDWEST... ...SUMMARY... Scattered strong/severe thunderstorms may impact parts of the northern Great Plains into the Upper Midwest Tuesday into Tuesday night, posing a risk for severe wind and hail. Damaging thunderstorm wind gusts are also possible across parts of the Southeast. ...Northern Plains to the Upper Midwest... Along the northwestern periphery of an expansive midlevel ridge centered on Mid MS Valley, moderate west-southwesterly midlevel flow will be in place from the northern Plains to the Upper Midwest -- downstream of a persistent midlevel trough over the Northwest. Several embedded impulses should advance through the belt of west-southwesterlies, while a surface low moves slowly eastward across the Dakotas. Downstream of the surface low, middle/upper 70s dewpoints beneath a steep midlevel lapse rate plume will contribute to a corridor of extreme surface-based buoyancy along a warm-front type feature draped across the Upper Midwest. While subtle forcing for ascent and potential early-day convection cast uncertainty on the overall convective scenario here, a broad/strong low-level jet (and related warm-air advection), the extreme buoyancy, and strong deep-layer shear will support robust/organized storms capable of producing swaths of severe wind and hail. Farther west over eastern MT into the Dakotas, subtle midlevel height falls atop seasonably rich boundary-layer moisture will also favor strong to severe storms, with a risk of severe wind gusts and large hail. ...Southeast... A very high PW air mass will be in place across the Southeast, where diurnal heating will contribute to moderate surface-based buoyancy. As a weak cold front impinges on this air mass during the afternoon, modestly enhanced midlevel northerly flow will support loosely organized storm clusters capable of producing damaging winds. ..Weinman.. 07/20/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 PM CDT Sun Jul 20 2025 Valid 221200Z - 231200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE UPPER MIDWEST... ...SUMMARY... Scattered strong/severe thunderstorms may impact parts of the northern Great Plains into the Upper Midwest Tuesday into Tuesday night, posing a risk for severe wind and hail. Damaging thunderstorm wind gusts are also possible across parts of the Southeast. ...Northern Plains to the Upper Midwest... Along the northwestern periphery of an expansive midlevel ridge centered on Mid MS Valley, moderate west-southwesterly midlevel flow will be in place from the northern Plains to the Upper Midwest -- downstream of a persistent midlevel trough over the Northwest. Several embedded impulses should advance through the belt of west-southwesterlies, while a surface low moves slowly eastward across the Dakotas. Downstream of the surface low, middle/upper 70s dewpoints beneath a steep midlevel lapse rate plume will contribute to a corridor of extreme surface-based buoyancy along a warm-front type feature draped across the Upper Midwest. While subtle forcing for ascent and potential early-day convection cast uncertainty on the overall convective scenario here, a broad/strong low-level jet (and related warm-air advection), the extreme buoyancy, and strong deep-layer shear will support robust/organized storms capable of producing swaths of severe wind and hail. Farther west over eastern MT into the Dakotas, subtle midlevel height falls atop seasonably rich boundary-layer moisture will also favor strong to severe storms, with a risk of severe wind gusts and large hail. ...Southeast... A very high PW air mass will be in place across the Southeast, where diurnal heating will contribute to moderate surface-based buoyancy. As a weak cold front impinges on this air mass during the afternoon, modestly enhanced midlevel northerly flow will support loosely organized storm clusters capable of producing damaging winds. ..Weinman.. 07/20/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 PM CDT Sun Jul 20 2025 Valid 221200Z - 231200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE UPPER MIDWEST... ...SUMMARY... Scattered strong/severe thunderstorms may impact parts of the northern Great Plains into the Upper Midwest Tuesday into Tuesday night, posing a risk for severe wind and hail. Damaging thunderstorm wind gusts are also possible across parts of the Southeast. ...Northern Plains to the Upper Midwest... Along the northwestern periphery of an expansive midlevel ridge centered on Mid MS Valley, moderate west-southwesterly midlevel flow will be in place from the northern Plains to the Upper Midwest -- downstream of a persistent midlevel trough over the Northwest. Several embedded impulses should advance through the belt of west-southwesterlies, while a surface low moves slowly eastward across the Dakotas. Downstream of the surface low, middle/upper 70s dewpoints beneath a steep midlevel lapse rate plume will contribute to a corridor of extreme surface-based buoyancy along a warm-front type feature draped across the Upper Midwest. While subtle forcing for ascent and potential early-day convection cast uncertainty on the overall convective scenario here, a broad/strong low-level jet (and related warm-air advection), the extreme buoyancy, and strong deep-layer shear will support robust/organized storms capable of producing swaths of severe wind and hail. Farther west over eastern MT into the Dakotas, subtle midlevel height falls atop seasonably rich boundary-layer moisture will also favor strong to severe storms, with a risk of severe wind gusts and large hail. ...Southeast... A very high PW air mass will be in place across the Southeast, where diurnal heating will contribute to moderate surface-based buoyancy. As a weak cold front impinges on this air mass during the afternoon, modestly enhanced midlevel northerly flow will support loosely organized storm clusters capable of producing damaging winds. ..Weinman.. 07/20/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 PM CDT Sun Jul 20 2025 Valid 221200Z - 231200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE UPPER MIDWEST... ...SUMMARY... Scattered strong/severe thunderstorms may impact parts of the northern Great Plains into the Upper Midwest Tuesday into Tuesday night, posing a risk for severe wind and hail. Damaging thunderstorm wind gusts are also possible across parts of the Southeast. ...Northern Plains to the Upper Midwest... Along the northwestern periphery of an expansive midlevel ridge centered on Mid MS Valley, moderate west-southwesterly midlevel flow will be in place from the northern Plains to the Upper Midwest -- downstream of a persistent midlevel trough over the Northwest. Several embedded impulses should advance through the belt of west-southwesterlies, while a surface low moves slowly eastward across the Dakotas. Downstream of the surface low, middle/upper 70s dewpoints beneath a steep midlevel lapse rate plume will contribute to a corridor of extreme surface-based buoyancy along a warm-front type feature draped across the Upper Midwest. While subtle forcing for ascent and potential early-day convection cast uncertainty on the overall convective scenario here, a broad/strong low-level jet (and related warm-air advection), the extreme buoyancy, and strong deep-layer shear will support robust/organized storms capable of producing swaths of severe wind and hail. Farther west over eastern MT into the Dakotas, subtle midlevel height falls atop seasonably rich boundary-layer moisture will also favor strong to severe storms, with a risk of severe wind gusts and large hail. ...Southeast... A very high PW air mass will be in place across the Southeast, where diurnal heating will contribute to moderate surface-based buoyancy. As a weak cold front impinges on this air mass during the afternoon, modestly enhanced midlevel northerly flow will support loosely organized storm clusters capable of producing damaging winds. ..Weinman.. 07/20/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 PM CDT Sun Jul 20 2025 Valid 221200Z - 231200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE UPPER MIDWEST... ...SUMMARY... Scattered strong/severe thunderstorms may impact parts of the northern Great Plains into the Upper Midwest Tuesday into Tuesday night, posing a risk for severe wind and hail. Damaging thunderstorm wind gusts are also possible across parts of the Southeast. ...Northern Plains to the Upper Midwest... Along the northwestern periphery of an expansive midlevel ridge centered on Mid MS Valley, moderate west-southwesterly midlevel flow will be in place from the northern Plains to the Upper Midwest -- downstream of a persistent midlevel trough over the Northwest. Several embedded impulses should advance through the belt of west-southwesterlies, while a surface low moves slowly eastward across the Dakotas. Downstream of the surface low, middle/upper 70s dewpoints beneath a steep midlevel lapse rate plume will contribute to a corridor of extreme surface-based buoyancy along a warm-front type feature draped across the Upper Midwest. While subtle forcing for ascent and potential early-day convection cast uncertainty on the overall convective scenario here, a broad/strong low-level jet (and related warm-air advection), the extreme buoyancy, and strong deep-layer shear will support robust/organized storms capable of producing swaths of severe wind and hail. Farther west over eastern MT into the Dakotas, subtle midlevel height falls atop seasonably rich boundary-layer moisture will also favor strong to severe storms, with a risk of severe wind gusts and large hail. ...Southeast... A very high PW air mass will be in place across the Southeast, where diurnal heating will contribute to moderate surface-based buoyancy. As a weak cold front impinges on this air mass during the afternoon, modestly enhanced midlevel northerly flow will support loosely organized storm clusters capable of producing damaging winds. ..Weinman.. 07/20/2025 Read more