Severe Storms

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook CORR 1 NWS Storm Prediction Center Norman OK 0804 PM CDT Sat Jun 21 2025 Valid 220100Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NEW YORK AND NEW ENGLAND... CORRECTED FOR FLIPPED THUNDER LINE IN SOUTHEAST ...SUMMARY... Thunderstorms associated with severe wind gusts and hail will be possible tonight across New York and New England. Isolated severe storms will also be possible across parts of the Great Lakes and the central to northern Plains. ...Northeast/New York/Great Lakes... Latest water vapor imagery has a belt of strong anticyclonic flow located from the upper Mississippi Valley into the Great Lakes and Northeast. A ridge-riding mid-level shortwave trough is located over Ontario. At the surface, a moist airmass is in place from New York into western New England, where surface dewpoints are in the lower to mid 60s F. The low-level moisture will contribute to continued destabilization across the region, in the form of elevated instability, this evening into tonight. As the shortwave trough moves southeastward toward the Northeast, low-level flow will markedly strengthen. In response, convective coverage is expected to increase, and a line of thunderstorms appears likely to develop late this evening. This line is forecast to move southeastward across New York and western New England from late evening into the overnight period. Overnight, RAP forecast soundings ahead of the line in northern New York have a low-level temperature inversion, with MUCAPE in the 1500 to 2000 J/kg range. Effective shear is forecast to be around 40 knots. This should be favorable for a severe threat. Although much of the line could be elevated, isolated large hail and severe gusts will still be possible, mainly with the more intense component of the line. The line is expected to move through the western New England and the Hudson River Valley late tonight, approaching southern New England toward 12Z. ...Central Plains... Southwest mid-level flow is in place across much of the central Plains early this evening. At the surface, a moist airmass is located over much of the High Plains, with surface dewpoints mostly in the 60s F. In response to low-level warm advection, isolated to scattered thunderstorms will likely develop along the western edge of this moist airmass. This convection is expected to move northeastward across Nebraska and southeastern South Dakota this evening. In addition to moderate instability, mid-level lapse rates are very steep. This, combined with moderate deep-layer shear, will likely support a marginal severe threat. Hail and isolated severe gusts will be possible. ...Northern High Plains... A mid-level trough, evident on water vapor imagery, will move northeastward into the northern High Plains tonight. Ahead of the trough, a post-frontal airmass is in place with the western edge of a moist airmass located over the western Dakotas. As large-scale ascent increases across the northern High Plains later tonight, scattered thunderstorm development is expected. These storms will move northeastward across eastern Montana and western North Dakota, mainly after midnight. Weak to moderate instability, combined with steep lapse rates and moderate deep-layer shear should support a marginal severe threat. Hail and a few severe gusts will be possible. ..Broyles.. 06/22/2025 Read more

No watches are valid as of Sat Jun 21 22:34:01 UTC 2025.

No Mesoscale Discussions are in effect as of Sat Jun 21 22:34:01 UTC 2025.

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0319 PM CDT Sat Jun 21 2025 Valid 231200Z - 291200Z Periods of Elevated to near Critical fire weather conditions are possible early next week as weak troughing remains across the western US through the period. A high amplitude ridge building across the eastern US will bring very warm temperatures and drying across much of the central/southern Plains into the East before precipitation potential returns late in the period. ...Day 3-4/Monday-Tuesday... An upper-level trough will persist over the western U.S. D3/Monday and D4/Tuesday, with occasional daytime elevated winds across portions of the Upper Colorado River Basin and northern Arizona. This will extend as far north as southeastern Wyoming on D4/Tuesday as an upper-level jet streak traverses the northern Rockies. Dry and breezy conditions will persist, with dry fuels aiding in increased wildfire spread potential. ...Day 5-8/Wednesday-Saturday... The upper-level low will weaken by mid-week with winds becoming more localized terrain driven breezes. A series of shortwaves late in the period may bring an increase in winds across the Snake River Plain in Idaho, with potential for highlights to be included if confidence increases. ...Dry Thunderstorms... Moisture will steadily increase into western New Mexico and southern Arizona as early as Day 3/Monday and D4/Tuesday. Dry thunderstorm threats may increase on the periphery of this deeper moisture but confidence remains low on coverage, precluding introduction of dry thunderstorm probabilities at this time. ..Thornton.. 06/21/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0319 PM CDT Sat Jun 21 2025 Valid 231200Z - 291200Z Periods of Elevated to near Critical fire weather conditions are possible early next week as weak troughing remains across the western US through the period. A high amplitude ridge building across the eastern US will bring very warm temperatures and drying across much of the central/southern Plains into the East before precipitation potential returns late in the period. ...Day 3-4/Monday-Tuesday... An upper-level trough will persist over the western U.S. D3/Monday and D4/Tuesday, with occasional daytime elevated winds across portions of the Upper Colorado River Basin and northern Arizona. This will extend as far north as southeastern Wyoming on D4/Tuesday as an upper-level jet streak traverses the northern Rockies. Dry and breezy conditions will persist, with dry fuels aiding in increased wildfire spread potential. ...Day 5-8/Wednesday-Saturday... The upper-level low will weaken by mid-week with winds becoming more localized terrain driven breezes. A series of shortwaves late in the period may bring an increase in winds across the Snake River Plain in Idaho, with potential for highlights to be included if confidence increases. ...Dry Thunderstorms... Moisture will steadily increase into western New Mexico and southern Arizona as early as Day 3/Monday and D4/Tuesday. Dry thunderstorm threats may increase on the periphery of this deeper moisture but confidence remains low on coverage, precluding introduction of dry thunderstorm probabilities at this time. ..Thornton.. 06/21/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0319 PM CDT Sat Jun 21 2025 Valid 231200Z - 291200Z Periods of Elevated to near Critical fire weather conditions are possible early next week as weak troughing remains across the western US through the period. A high amplitude ridge building across the eastern US will bring very warm temperatures and drying across much of the central/southern Plains into the East before precipitation potential returns late in the period. ...Day 3-4/Monday-Tuesday... An upper-level trough will persist over the western U.S. D3/Monday and D4/Tuesday, with occasional daytime elevated winds across portions of the Upper Colorado River Basin and northern Arizona. This will extend as far north as southeastern Wyoming on D4/Tuesday as an upper-level jet streak traverses the northern Rockies. Dry and breezy conditions will persist, with dry fuels aiding in increased wildfire spread potential. ...Day 5-8/Wednesday-Saturday... The upper-level low will weaken by mid-week with winds becoming more localized terrain driven breezes. A series of shortwaves late in the period may bring an increase in winds across the Snake River Plain in Idaho, with potential for highlights to be included if confidence increases. ...Dry Thunderstorms... Moisture will steadily increase into western New Mexico and southern Arizona as early as Day 3/Monday and D4/Tuesday. Dry thunderstorm threats may increase on the periphery of this deeper moisture but confidence remains low on coverage, precluding introduction of dry thunderstorm probabilities at this time. ..Thornton.. 06/21/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0319 PM CDT Sat Jun 21 2025 Valid 231200Z - 291200Z Periods of Elevated to near Critical fire weather conditions are possible early next week as weak troughing remains across the western US through the period. A high amplitude ridge building across the eastern US will bring very warm temperatures and drying across much of the central/southern Plains into the East before precipitation potential returns late in the period. ...Day 3-4/Monday-Tuesday... An upper-level trough will persist over the western U.S. D3/Monday and D4/Tuesday, with occasional daytime elevated winds across portions of the Upper Colorado River Basin and northern Arizona. This will extend as far north as southeastern Wyoming on D4/Tuesday as an upper-level jet streak traverses the northern Rockies. Dry and breezy conditions will persist, with dry fuels aiding in increased wildfire spread potential. ...Day 5-8/Wednesday-Saturday... The upper-level low will weaken by mid-week with winds becoming more localized terrain driven breezes. A series of shortwaves late in the period may bring an increase in winds across the Snake River Plain in Idaho, with potential for highlights to be included if confidence increases. ...Dry Thunderstorms... Moisture will steadily increase into western New Mexico and southern Arizona as early as Day 3/Monday and D4/Tuesday. Dry thunderstorm threats may increase on the periphery of this deeper moisture but confidence remains low on coverage, precluding introduction of dry thunderstorm probabilities at this time. ..Thornton.. 06/21/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0319 PM CDT Sat Jun 21 2025 Valid 231200Z - 291200Z Periods of Elevated to near Critical fire weather conditions are possible early next week as weak troughing remains across the western US through the period. A high amplitude ridge building across the eastern US will bring very warm temperatures and drying across much of the central/southern Plains into the East before precipitation potential returns late in the period. ...Day 3-4/Monday-Tuesday... An upper-level trough will persist over the western U.S. D3/Monday and D4/Tuesday, with occasional daytime elevated winds across portions of the Upper Colorado River Basin and northern Arizona. This will extend as far north as southeastern Wyoming on D4/Tuesday as an upper-level jet streak traverses the northern Rockies. Dry and breezy conditions will persist, with dry fuels aiding in increased wildfire spread potential. ...Day 5-8/Wednesday-Saturday... The upper-level low will weaken by mid-week with winds becoming more localized terrain driven breezes. A series of shortwaves late in the period may bring an increase in winds across the Snake River Plain in Idaho, with potential for highlights to be included if confidence increases. ...Dry Thunderstorms... Moisture will steadily increase into western New Mexico and southern Arizona as early as Day 3/Monday and D4/Tuesday. Dry thunderstorm threats may increase on the periphery of this deeper moisture but confidence remains low on coverage, precluding introduction of dry thunderstorm probabilities at this time. ..Thornton.. 06/21/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0319 PM CDT Sat Jun 21 2025 Valid 231200Z - 291200Z Periods of Elevated to near Critical fire weather conditions are possible early next week as weak troughing remains across the western US through the period. A high amplitude ridge building across the eastern US will bring very warm temperatures and drying across much of the central/southern Plains into the East before precipitation potential returns late in the period. ...Day 3-4/Monday-Tuesday... An upper-level trough will persist over the western U.S. D3/Monday and D4/Tuesday, with occasional daytime elevated winds across portions of the Upper Colorado River Basin and northern Arizona. This will extend as far north as southeastern Wyoming on D4/Tuesday as an upper-level jet streak traverses the northern Rockies. Dry and breezy conditions will persist, with dry fuels aiding in increased wildfire spread potential. ...Day 5-8/Wednesday-Saturday... The upper-level low will weaken by mid-week with winds becoming more localized terrain driven breezes. A series of shortwaves late in the period may bring an increase in winds across the Snake River Plain in Idaho, with potential for highlights to be included if confidence increases. ...Dry Thunderstorms... Moisture will steadily increase into western New Mexico and southern Arizona as early as Day 3/Monday and D4/Tuesday. Dry thunderstorm threats may increase on the periphery of this deeper moisture but confidence remains low on coverage, precluding introduction of dry thunderstorm probabilities at this time. ..Thornton.. 06/21/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0319 PM CDT Sat Jun 21 2025 Valid 231200Z - 291200Z Periods of Elevated to near Critical fire weather conditions are possible early next week as weak troughing remains across the western US through the period. A high amplitude ridge building across the eastern US will bring very warm temperatures and drying across much of the central/southern Plains into the East before precipitation potential returns late in the period. ...Day 3-4/Monday-Tuesday... An upper-level trough will persist over the western U.S. D3/Monday and D4/Tuesday, with occasional daytime elevated winds across portions of the Upper Colorado River Basin and northern Arizona. This will extend as far north as southeastern Wyoming on D4/Tuesday as an upper-level jet streak traverses the northern Rockies. Dry and breezy conditions will persist, with dry fuels aiding in increased wildfire spread potential. ...Day 5-8/Wednesday-Saturday... The upper-level low will weaken by mid-week with winds becoming more localized terrain driven breezes. A series of shortwaves late in the period may bring an increase in winds across the Snake River Plain in Idaho, with potential for highlights to be included if confidence increases. ...Dry Thunderstorms... Moisture will steadily increase into western New Mexico and southern Arizona as early as Day 3/Monday and D4/Tuesday. Dry thunderstorm threats may increase on the periphery of this deeper moisture but confidence remains low on coverage, precluding introduction of dry thunderstorm probabilities at this time. ..Thornton.. 06/21/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0319 PM CDT Sat Jun 21 2025 Valid 231200Z - 291200Z Periods of Elevated to near Critical fire weather conditions are possible early next week as weak troughing remains across the western US through the period. A high amplitude ridge building across the eastern US will bring very warm temperatures and drying across much of the central/southern Plains into the East before precipitation potential returns late in the period. ...Day 3-4/Monday-Tuesday... An upper-level trough will persist over the western U.S. D3/Monday and D4/Tuesday, with occasional daytime elevated winds across portions of the Upper Colorado River Basin and northern Arizona. This will extend as far north as southeastern Wyoming on D4/Tuesday as an upper-level jet streak traverses the northern Rockies. Dry and breezy conditions will persist, with dry fuels aiding in increased wildfire spread potential. ...Day 5-8/Wednesday-Saturday... The upper-level low will weaken by mid-week with winds becoming more localized terrain driven breezes. A series of shortwaves late in the period may bring an increase in winds across the Snake River Plain in Idaho, with potential for highlights to be included if confidence increases. ...Dry Thunderstorms... Moisture will steadily increase into western New Mexico and southern Arizona as early as Day 3/Monday and D4/Tuesday. Dry thunderstorm threats may increase on the periphery of this deeper moisture but confidence remains low on coverage, precluding introduction of dry thunderstorm probabilities at this time. ..Thornton.. 06/21/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Sat Jun 21 2025 Valid 212000Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF NORTHERN NEW YORK...VERMONT AND NEW HAMPSHIRE... ...SUMMARY... Thunderstorms associated with severe wind gusts and hail will be possible tonight across New York and New England. Isolated severe storms will also be possible across portions of the Great Lakes, the northern High Plains and Middle Missouri Valley. ...20z Update... Minimal changes were made to the prior valid outlook. Thus far, strong convection across the Great Lakes region has remained on the Canadian side of the border. Continued heating and weak mid-level ascent overspreading a trailing composite front/lake breeze boundary may eventually support scattered storm development over the UP of Michigan this afternoon/evening. Isolated damaging gusts and some hail are possible with moderate CAPE and vertical shear. These storms should grow upscale across the lakes and through southern Ontario, reaching western New England late tonight as an MCS. This MCS may pose a risk for damaging gusts late tonight. Have adjusted the eastern edge of the Slight and Marginal Risk areas for the latest hi-res guidance. Otherwise the outlook remains unchanged, see the previous discussion. ..Lyons.. 06/21/2025 .PREV DISCUSSION... /ISSUED 1149 AM CDT Sat Jun 21 2025/ ...Great Lakes... Strong/intermittently severe thunderstorms continue across the northern Lower Peninsula of Michigan this morning, associated with the long-lived severe MCS that moved across the northern Plains/upper Midwest Friday afternoon and night. Although the immediate downstream environment is only slowly warming due to the presence of mid/high-level clouds, some slow destabilization is occurring. This will maintain at least some continued risk for a strong/severe storm through early afternoon across northern Lower MI and adjacent waters of Lake Huron. Across the MI Upper Peninsula, a warm front is expected to sharpen across this area, along with rising heights in the wake of the convectively-augmented vorticity maximum now moving through southern Ontario. Heating of a very moist boundary layer will result in strong to extreme instability (MLCAPE in excess of 3000 J/kg), however the presence of a pronounced cap should suppress storms during the afternoon. As a modest low-level jet strengthens this evening, isolated elevated severe storms will be possible on the immediate cool side of the front, within an environment supportive of organized storms including supercells. Large hail and damaging winds will be possible. ...NY into Western New England... Thunderstorms moving across Lake Huron/southwestern Ontario at 16z will continue east, and most morning CAM guidance suggests storms will remain west of western NY. Of greater concern will be the potential for storms to move into northern NY/western New England late tonight ahead of a southeast-moving cold front, where modest destabilization and strong deep-layer shear will support storm organization. Morning hi-res guidance supports a loosely organized linear structure, and perhaps supercells with an attendant risk for strong winds and severe hail late tonight. The Level 2/Slight Risk has been expanded east into northern VT based on this expectation. ...Eastern MT into Western ND... Isolated thunderstorms have weakened over eastern MT this morning, with additional isolated redevelopment possible this afternoon and tonight as ascent associated with minor perturbations within southwest mid-level flow moves across the area. Modest instability and strong deep-layer shear will support updraft organization and a risk for severe hail and/or damaging gusts. ...Central NE/SD/ND into the Upper Midwest... Surface low currently over central SD is expected to move little this afternoon, with low-level moisture advection throughout the warm sector east of this low. Air mass recovery/modification following the overnight MCS is expected, and this will contribute to a sharpening warm-frontal zone. Strong to extreme buoyancy (i.e. MLCAPE greater from 3000 to 5000 J/kg) is expected by this evening along this warm front from the ND/SD border vicinity eastward through central MN into northern WI. Some low-level convergence is anticipated in this region, but height rises will occur within the large-scale environment. Additionally, warm mid-level temperatures (16 to 17 deg C at 700 mb) are expected, capping the airmass to deep convection this afternoon. Isolated thunderstorm development will be possible mainly this evening as a low-level jet strengthens, with a risk for severe wind and isolated hail. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Sat Jun 21 2025 Valid 212000Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF NORTHERN NEW YORK...VERMONT AND NEW HAMPSHIRE... ...SUMMARY... Thunderstorms associated with severe wind gusts and hail will be possible tonight across New York and New England. Isolated severe storms will also be possible across portions of the Great Lakes, the northern High Plains and Middle Missouri Valley. ...20z Update... Minimal changes were made to the prior valid outlook. Thus far, strong convection across the Great Lakes region has remained on the Canadian side of the border. Continued heating and weak mid-level ascent overspreading a trailing composite front/lake breeze boundary may eventually support scattered storm development over the UP of Michigan this afternoon/evening. Isolated damaging gusts and some hail are possible with moderate CAPE and vertical shear. These storms should grow upscale across the lakes and through southern Ontario, reaching western New England late tonight as an MCS. This MCS may pose a risk for damaging gusts late tonight. Have adjusted the eastern edge of the Slight and Marginal Risk areas for the latest hi-res guidance. Otherwise the outlook remains unchanged, see the previous discussion. ..Lyons.. 06/21/2025 .PREV DISCUSSION... /ISSUED 1149 AM CDT Sat Jun 21 2025/ ...Great Lakes... Strong/intermittently severe thunderstorms continue across the northern Lower Peninsula of Michigan this morning, associated with the long-lived severe MCS that moved across the northern Plains/upper Midwest Friday afternoon and night. Although the immediate downstream environment is only slowly warming due to the presence of mid/high-level clouds, some slow destabilization is occurring. This will maintain at least some continued risk for a strong/severe storm through early afternoon across northern Lower MI and adjacent waters of Lake Huron. Across the MI Upper Peninsula, a warm front is expected to sharpen across this area, along with rising heights in the wake of the convectively-augmented vorticity maximum now moving through southern Ontario. Heating of a very moist boundary layer will result in strong to extreme instability (MLCAPE in excess of 3000 J/kg), however the presence of a pronounced cap should suppress storms during the afternoon. As a modest low-level jet strengthens this evening, isolated elevated severe storms will be possible on the immediate cool side of the front, within an environment supportive of organized storms including supercells. Large hail and damaging winds will be possible. ...NY into Western New England... Thunderstorms moving across Lake Huron/southwestern Ontario at 16z will continue east, and most morning CAM guidance suggests storms will remain west of western NY. Of greater concern will be the potential for storms to move into northern NY/western New England late tonight ahead of a southeast-moving cold front, where modest destabilization and strong deep-layer shear will support storm organization. Morning hi-res guidance supports a loosely organized linear structure, and perhaps supercells with an attendant risk for strong winds and severe hail late tonight. The Level 2/Slight Risk has been expanded east into northern VT based on this expectation. ...Eastern MT into Western ND... Isolated thunderstorms have weakened over eastern MT this morning, with additional isolated redevelopment possible this afternoon and tonight as ascent associated with minor perturbations within southwest mid-level flow moves across the area. Modest instability and strong deep-layer shear will support updraft organization and a risk for severe hail and/or damaging gusts. ...Central NE/SD/ND into the Upper Midwest... Surface low currently over central SD is expected to move little this afternoon, with low-level moisture advection throughout the warm sector east of this low. Air mass recovery/modification following the overnight MCS is expected, and this will contribute to a sharpening warm-frontal zone. Strong to extreme buoyancy (i.e. MLCAPE greater from 3000 to 5000 J/kg) is expected by this evening along this warm front from the ND/SD border vicinity eastward through central MN into northern WI. Some low-level convergence is anticipated in this region, but height rises will occur within the large-scale environment. Additionally, warm mid-level temperatures (16 to 17 deg C at 700 mb) are expected, capping the airmass to deep convection this afternoon. Isolated thunderstorm development will be possible mainly this evening as a low-level jet strengthens, with a risk for severe wind and isolated hail. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Sat Jun 21 2025 Valid 212000Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF NORTHERN NEW YORK...VERMONT AND NEW HAMPSHIRE... ...SUMMARY... Thunderstorms associated with severe wind gusts and hail will be possible tonight across New York and New England. Isolated severe storms will also be possible across portions of the Great Lakes, the northern High Plains and Middle Missouri Valley. ...20z Update... Minimal changes were made to the prior valid outlook. Thus far, strong convection across the Great Lakes region has remained on the Canadian side of the border. Continued heating and weak mid-level ascent overspreading a trailing composite front/lake breeze boundary may eventually support scattered storm development over the UP of Michigan this afternoon/evening. Isolated damaging gusts and some hail are possible with moderate CAPE and vertical shear. These storms should grow upscale across the lakes and through southern Ontario, reaching western New England late tonight as an MCS. This MCS may pose a risk for damaging gusts late tonight. Have adjusted the eastern edge of the Slight and Marginal Risk areas for the latest hi-res guidance. Otherwise the outlook remains unchanged, see the previous discussion. ..Lyons.. 06/21/2025 .PREV DISCUSSION... /ISSUED 1149 AM CDT Sat Jun 21 2025/ ...Great Lakes... Strong/intermittently severe thunderstorms continue across the northern Lower Peninsula of Michigan this morning, associated with the long-lived severe MCS that moved across the northern Plains/upper Midwest Friday afternoon and night. Although the immediate downstream environment is only slowly warming due to the presence of mid/high-level clouds, some slow destabilization is occurring. This will maintain at least some continued risk for a strong/severe storm through early afternoon across northern Lower MI and adjacent waters of Lake Huron. Across the MI Upper Peninsula, a warm front is expected to sharpen across this area, along with rising heights in the wake of the convectively-augmented vorticity maximum now moving through southern Ontario. Heating of a very moist boundary layer will result in strong to extreme instability (MLCAPE in excess of 3000 J/kg), however the presence of a pronounced cap should suppress storms during the afternoon. As a modest low-level jet strengthens this evening, isolated elevated severe storms will be possible on the immediate cool side of the front, within an environment supportive of organized storms including supercells. Large hail and damaging winds will be possible. ...NY into Western New England... Thunderstorms moving across Lake Huron/southwestern Ontario at 16z will continue east, and most morning CAM guidance suggests storms will remain west of western NY. Of greater concern will be the potential for storms to move into northern NY/western New England late tonight ahead of a southeast-moving cold front, where modest destabilization and strong deep-layer shear will support storm organization. Morning hi-res guidance supports a loosely organized linear structure, and perhaps supercells with an attendant risk for strong winds and severe hail late tonight. The Level 2/Slight Risk has been expanded east into northern VT based on this expectation. ...Eastern MT into Western ND... Isolated thunderstorms have weakened over eastern MT this morning, with additional isolated redevelopment possible this afternoon and tonight as ascent associated with minor perturbations within southwest mid-level flow moves across the area. Modest instability and strong deep-layer shear will support updraft organization and a risk for severe hail and/or damaging gusts. ...Central NE/SD/ND into the Upper Midwest... Surface low currently over central SD is expected to move little this afternoon, with low-level moisture advection throughout the warm sector east of this low. Air mass recovery/modification following the overnight MCS is expected, and this will contribute to a sharpening warm-frontal zone. Strong to extreme buoyancy (i.e. MLCAPE greater from 3000 to 5000 J/kg) is expected by this evening along this warm front from the ND/SD border vicinity eastward through central MN into northern WI. Some low-level convergence is anticipated in this region, but height rises will occur within the large-scale environment. Additionally, warm mid-level temperatures (16 to 17 deg C at 700 mb) are expected, capping the airmass to deep convection this afternoon. Isolated thunderstorm development will be possible mainly this evening as a low-level jet strengthens, with a risk for severe wind and isolated hail. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Sat Jun 21 2025 Valid 212000Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF NORTHERN NEW YORK...VERMONT AND NEW HAMPSHIRE... ...SUMMARY... Thunderstorms associated with severe wind gusts and hail will be possible tonight across New York and New England. Isolated severe storms will also be possible across portions of the Great Lakes, the northern High Plains and Middle Missouri Valley. ...20z Update... Minimal changes were made to the prior valid outlook. Thus far, strong convection across the Great Lakes region has remained on the Canadian side of the border. Continued heating and weak mid-level ascent overspreading a trailing composite front/lake breeze boundary may eventually support scattered storm development over the UP of Michigan this afternoon/evening. Isolated damaging gusts and some hail are possible with moderate CAPE and vertical shear. These storms should grow upscale across the lakes and through southern Ontario, reaching western New England late tonight as an MCS. This MCS may pose a risk for damaging gusts late tonight. Have adjusted the eastern edge of the Slight and Marginal Risk areas for the latest hi-res guidance. Otherwise the outlook remains unchanged, see the previous discussion. ..Lyons.. 06/21/2025 .PREV DISCUSSION... /ISSUED 1149 AM CDT Sat Jun 21 2025/ ...Great Lakes... Strong/intermittently severe thunderstorms continue across the northern Lower Peninsula of Michigan this morning, associated with the long-lived severe MCS that moved across the northern Plains/upper Midwest Friday afternoon and night. Although the immediate downstream environment is only slowly warming due to the presence of mid/high-level clouds, some slow destabilization is occurring. This will maintain at least some continued risk for a strong/severe storm through early afternoon across northern Lower MI and adjacent waters of Lake Huron. Across the MI Upper Peninsula, a warm front is expected to sharpen across this area, along with rising heights in the wake of the convectively-augmented vorticity maximum now moving through southern Ontario. Heating of a very moist boundary layer will result in strong to extreme instability (MLCAPE in excess of 3000 J/kg), however the presence of a pronounced cap should suppress storms during the afternoon. As a modest low-level jet strengthens this evening, isolated elevated severe storms will be possible on the immediate cool side of the front, within an environment supportive of organized storms including supercells. Large hail and damaging winds will be possible. ...NY into Western New England... Thunderstorms moving across Lake Huron/southwestern Ontario at 16z will continue east, and most morning CAM guidance suggests storms will remain west of western NY. Of greater concern will be the potential for storms to move into northern NY/western New England late tonight ahead of a southeast-moving cold front, where modest destabilization and strong deep-layer shear will support storm organization. Morning hi-res guidance supports a loosely organized linear structure, and perhaps supercells with an attendant risk for strong winds and severe hail late tonight. The Level 2/Slight Risk has been expanded east into northern VT based on this expectation. ...Eastern MT into Western ND... Isolated thunderstorms have weakened over eastern MT this morning, with additional isolated redevelopment possible this afternoon and tonight as ascent associated with minor perturbations within southwest mid-level flow moves across the area. Modest instability and strong deep-layer shear will support updraft organization and a risk for severe hail and/or damaging gusts. ...Central NE/SD/ND into the Upper Midwest... Surface low currently over central SD is expected to move little this afternoon, with low-level moisture advection throughout the warm sector east of this low. Air mass recovery/modification following the overnight MCS is expected, and this will contribute to a sharpening warm-frontal zone. Strong to extreme buoyancy (i.e. MLCAPE greater from 3000 to 5000 J/kg) is expected by this evening along this warm front from the ND/SD border vicinity eastward through central MN into northern WI. Some low-level convergence is anticipated in this region, but height rises will occur within the large-scale environment. Additionally, warm mid-level temperatures (16 to 17 deg C at 700 mb) are expected, capping the airmass to deep convection this afternoon. Isolated thunderstorm development will be possible mainly this evening as a low-level jet strengthens, with a risk for severe wind and isolated hail. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Sat Jun 21 2025 Valid 212000Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF NORTHERN NEW YORK...VERMONT AND NEW HAMPSHIRE... ...SUMMARY... Thunderstorms associated with severe wind gusts and hail will be possible tonight across New York and New England. Isolated severe storms will also be possible across portions of the Great Lakes, the northern High Plains and Middle Missouri Valley. ...20z Update... Minimal changes were made to the prior valid outlook. Thus far, strong convection across the Great Lakes region has remained on the Canadian side of the border. Continued heating and weak mid-level ascent overspreading a trailing composite front/lake breeze boundary may eventually support scattered storm development over the UP of Michigan this afternoon/evening. Isolated damaging gusts and some hail are possible with moderate CAPE and vertical shear. These storms should grow upscale across the lakes and through southern Ontario, reaching western New England late tonight as an MCS. This MCS may pose a risk for damaging gusts late tonight. Have adjusted the eastern edge of the Slight and Marginal Risk areas for the latest hi-res guidance. Otherwise the outlook remains unchanged, see the previous discussion. ..Lyons.. 06/21/2025 .PREV DISCUSSION... /ISSUED 1149 AM CDT Sat Jun 21 2025/ ...Great Lakes... Strong/intermittently severe thunderstorms continue across the northern Lower Peninsula of Michigan this morning, associated with the long-lived severe MCS that moved across the northern Plains/upper Midwest Friday afternoon and night. Although the immediate downstream environment is only slowly warming due to the presence of mid/high-level clouds, some slow destabilization is occurring. This will maintain at least some continued risk for a strong/severe storm through early afternoon across northern Lower MI and adjacent waters of Lake Huron. Across the MI Upper Peninsula, a warm front is expected to sharpen across this area, along with rising heights in the wake of the convectively-augmented vorticity maximum now moving through southern Ontario. Heating of a very moist boundary layer will result in strong to extreme instability (MLCAPE in excess of 3000 J/kg), however the presence of a pronounced cap should suppress storms during the afternoon. As a modest low-level jet strengthens this evening, isolated elevated severe storms will be possible on the immediate cool side of the front, within an environment supportive of organized storms including supercells. Large hail and damaging winds will be possible. ...NY into Western New England... Thunderstorms moving across Lake Huron/southwestern Ontario at 16z will continue east, and most morning CAM guidance suggests storms will remain west of western NY. Of greater concern will be the potential for storms to move into northern NY/western New England late tonight ahead of a southeast-moving cold front, where modest destabilization and strong deep-layer shear will support storm organization. Morning hi-res guidance supports a loosely organized linear structure, and perhaps supercells with an attendant risk for strong winds and severe hail late tonight. The Level 2/Slight Risk has been expanded east into northern VT based on this expectation. ...Eastern MT into Western ND... Isolated thunderstorms have weakened over eastern MT this morning, with additional isolated redevelopment possible this afternoon and tonight as ascent associated with minor perturbations within southwest mid-level flow moves across the area. Modest instability and strong deep-layer shear will support updraft organization and a risk for severe hail and/or damaging gusts. ...Central NE/SD/ND into the Upper Midwest... Surface low currently over central SD is expected to move little this afternoon, with low-level moisture advection throughout the warm sector east of this low. Air mass recovery/modification following the overnight MCS is expected, and this will contribute to a sharpening warm-frontal zone. Strong to extreme buoyancy (i.e. MLCAPE greater from 3000 to 5000 J/kg) is expected by this evening along this warm front from the ND/SD border vicinity eastward through central MN into northern WI. Some low-level convergence is anticipated in this region, but height rises will occur within the large-scale environment. Additionally, warm mid-level temperatures (16 to 17 deg C at 700 mb) are expected, capping the airmass to deep convection this afternoon. Isolated thunderstorm development will be possible mainly this evening as a low-level jet strengthens, with a risk for severe wind and isolated hail. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Sat Jun 21 2025 Valid 212000Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF NORTHERN NEW YORK...VERMONT AND NEW HAMPSHIRE... ...SUMMARY... Thunderstorms associated with severe wind gusts and hail will be possible tonight across New York and New England. Isolated severe storms will also be possible across portions of the Great Lakes, the northern High Plains and Middle Missouri Valley. ...20z Update... Minimal changes were made to the prior valid outlook. Thus far, strong convection across the Great Lakes region has remained on the Canadian side of the border. Continued heating and weak mid-level ascent overspreading a trailing composite front/lake breeze boundary may eventually support scattered storm development over the UP of Michigan this afternoon/evening. Isolated damaging gusts and some hail are possible with moderate CAPE and vertical shear. These storms should grow upscale across the lakes and through southern Ontario, reaching western New England late tonight as an MCS. This MCS may pose a risk for damaging gusts late tonight. Have adjusted the eastern edge of the Slight and Marginal Risk areas for the latest hi-res guidance. Otherwise the outlook remains unchanged, see the previous discussion. ..Lyons.. 06/21/2025 .PREV DISCUSSION... /ISSUED 1149 AM CDT Sat Jun 21 2025/ ...Great Lakes... Strong/intermittently severe thunderstorms continue across the northern Lower Peninsula of Michigan this morning, associated with the long-lived severe MCS that moved across the northern Plains/upper Midwest Friday afternoon and night. Although the immediate downstream environment is only slowly warming due to the presence of mid/high-level clouds, some slow destabilization is occurring. This will maintain at least some continued risk for a strong/severe storm through early afternoon across northern Lower MI and adjacent waters of Lake Huron. Across the MI Upper Peninsula, a warm front is expected to sharpen across this area, along with rising heights in the wake of the convectively-augmented vorticity maximum now moving through southern Ontario. Heating of a very moist boundary layer will result in strong to extreme instability (MLCAPE in excess of 3000 J/kg), however the presence of a pronounced cap should suppress storms during the afternoon. As a modest low-level jet strengthens this evening, isolated elevated severe storms will be possible on the immediate cool side of the front, within an environment supportive of organized storms including supercells. Large hail and damaging winds will be possible. ...NY into Western New England... Thunderstorms moving across Lake Huron/southwestern Ontario at 16z will continue east, and most morning CAM guidance suggests storms will remain west of western NY. Of greater concern will be the potential for storms to move into northern NY/western New England late tonight ahead of a southeast-moving cold front, where modest destabilization and strong deep-layer shear will support storm organization. Morning hi-res guidance supports a loosely organized linear structure, and perhaps supercells with an attendant risk for strong winds and severe hail late tonight. The Level 2/Slight Risk has been expanded east into northern VT based on this expectation. ...Eastern MT into Western ND... Isolated thunderstorms have weakened over eastern MT this morning, with additional isolated redevelopment possible this afternoon and tonight as ascent associated with minor perturbations within southwest mid-level flow moves across the area. Modest instability and strong deep-layer shear will support updraft organization and a risk for severe hail and/or damaging gusts. ...Central NE/SD/ND into the Upper Midwest... Surface low currently over central SD is expected to move little this afternoon, with low-level moisture advection throughout the warm sector east of this low. Air mass recovery/modification following the overnight MCS is expected, and this will contribute to a sharpening warm-frontal zone. Strong to extreme buoyancy (i.e. MLCAPE greater from 3000 to 5000 J/kg) is expected by this evening along this warm front from the ND/SD border vicinity eastward through central MN into northern WI. Some low-level convergence is anticipated in this region, but height rises will occur within the large-scale environment. Additionally, warm mid-level temperatures (16 to 17 deg C at 700 mb) are expected, capping the airmass to deep convection this afternoon. Isolated thunderstorm development will be possible mainly this evening as a low-level jet strengthens, with a risk for severe wind and isolated hail. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Sat Jun 21 2025 Valid 212000Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF NORTHERN NEW YORK...VERMONT AND NEW HAMPSHIRE... ...SUMMARY... Thunderstorms associated with severe wind gusts and hail will be possible tonight across New York and New England. Isolated severe storms will also be possible across portions of the Great Lakes, the northern High Plains and Middle Missouri Valley. ...20z Update... Minimal changes were made to the prior valid outlook. Thus far, strong convection across the Great Lakes region has remained on the Canadian side of the border. Continued heating and weak mid-level ascent overspreading a trailing composite front/lake breeze boundary may eventually support scattered storm development over the UP of Michigan this afternoon/evening. Isolated damaging gusts and some hail are possible with moderate CAPE and vertical shear. These storms should grow upscale across the lakes and through southern Ontario, reaching western New England late tonight as an MCS. This MCS may pose a risk for damaging gusts late tonight. Have adjusted the eastern edge of the Slight and Marginal Risk areas for the latest hi-res guidance. Otherwise the outlook remains unchanged, see the previous discussion. ..Lyons.. 06/21/2025 .PREV DISCUSSION... /ISSUED 1149 AM CDT Sat Jun 21 2025/ ...Great Lakes... Strong/intermittently severe thunderstorms continue across the northern Lower Peninsula of Michigan this morning, associated with the long-lived severe MCS that moved across the northern Plains/upper Midwest Friday afternoon and night. Although the immediate downstream environment is only slowly warming due to the presence of mid/high-level clouds, some slow destabilization is occurring. This will maintain at least some continued risk for a strong/severe storm through early afternoon across northern Lower MI and adjacent waters of Lake Huron. Across the MI Upper Peninsula, a warm front is expected to sharpen across this area, along with rising heights in the wake of the convectively-augmented vorticity maximum now moving through southern Ontario. Heating of a very moist boundary layer will result in strong to extreme instability (MLCAPE in excess of 3000 J/kg), however the presence of a pronounced cap should suppress storms during the afternoon. As a modest low-level jet strengthens this evening, isolated elevated severe storms will be possible on the immediate cool side of the front, within an environment supportive of organized storms including supercells. Large hail and damaging winds will be possible. ...NY into Western New England... Thunderstorms moving across Lake Huron/southwestern Ontario at 16z will continue east, and most morning CAM guidance suggests storms will remain west of western NY. Of greater concern will be the potential for storms to move into northern NY/western New England late tonight ahead of a southeast-moving cold front, where modest destabilization and strong deep-layer shear will support storm organization. Morning hi-res guidance supports a loosely organized linear structure, and perhaps supercells with an attendant risk for strong winds and severe hail late tonight. The Level 2/Slight Risk has been expanded east into northern VT based on this expectation. ...Eastern MT into Western ND... Isolated thunderstorms have weakened over eastern MT this morning, with additional isolated redevelopment possible this afternoon and tonight as ascent associated with minor perturbations within southwest mid-level flow moves across the area. Modest instability and strong deep-layer shear will support updraft organization and a risk for severe hail and/or damaging gusts. ...Central NE/SD/ND into the Upper Midwest... Surface low currently over central SD is expected to move little this afternoon, with low-level moisture advection throughout the warm sector east of this low. Air mass recovery/modification following the overnight MCS is expected, and this will contribute to a sharpening warm-frontal zone. Strong to extreme buoyancy (i.e. MLCAPE greater from 3000 to 5000 J/kg) is expected by this evening along this warm front from the ND/SD border vicinity eastward through central MN into northern WI. Some low-level convergence is anticipated in this region, but height rises will occur within the large-scale environment. Additionally, warm mid-level temperatures (16 to 17 deg C at 700 mb) are expected, capping the airmass to deep convection this afternoon. Isolated thunderstorm development will be possible mainly this evening as a low-level jet strengthens, with a risk for severe wind and isolated hail. Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0214 PM CDT Sat Jun 21 2025 Valid 231200Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE GREAT LAKES... ...SUMMARY... Strong to potentially severe storms may develop on Monday, from parts of the Great Lakes into the central Plains. ...Synopsis... Broad mid-level troughing across the western U.S., as well as upper ridging across the eastern CONUS, will remain in place Monday. The embedded mid-level shortwave trough and associated surface low over the northern U.S. on Day 2 (Sunday) will eject into Ontario on Monday. As such, overall synoptic ascent will decrease across the northern/central CONUS through the period. Nonetheless, surface lee troughing and a trailing frontal boundary will serve as the impetus for thunderstorm development across parts of the Great Lakes into the central Plains, where adequate buoyancy will support strong to potentially severe thunderstorms. ...Great Lakes/Upper Midwest... Thunderstorm development is likely along or immediately ahead of the frontal boundary by Monday afternoon. Deep-layer flow/shear will be oriented roughly parallel to the surface boundary, encouraging mainly multicellular/linear structures. 30 kts of effective bulk shear will be in place, amid 2000 J/kg MLCAPE, driven by 7 C/km mid-level lapse rates atop 70 F surface dewpoints. As such, the more robust, longer-lived storms may support a few instances of severe wind and/or hail. ...Portions of the central Plains... Thunderstorms may develop immediately along the surface boundary, as well as behind the front across the central Plains by afternoon peak heating. Deep-layer shear will be weaker here compared to the Great Lakes, though low-level lapse rates may be steeper (i.e. over 8.5 C/km), yielding MLCAPE values at least in the 2000-3000 J/kg range. As such, any of the more intense pulse cellular or multicellular storms that develop may produce few severe gusts. ...New England... Strong to locally extreme buoyancy, driven by a residual EML, will meander over the Mid Atlantic to New England on Monday as a surface anticyclone and associated upper ridge remains in place. Upper support is lacking for appreciable thunderstorm development. Some of the latest guidance suggests that strong thunderstorm potential will be confined to the periphery of the upper ridge over central Quebec. However, thunderstorm probabilities have been maintained given the possibility of a trailing stray storm over southern Quebec potentially impinging on northern New England. ..Squitieri.. 06/21/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0214 PM CDT Sat Jun 21 2025 Valid 231200Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE GREAT LAKES... ...SUMMARY... Strong to potentially severe storms may develop on Monday, from parts of the Great Lakes into the central Plains. ...Synopsis... Broad mid-level troughing across the western U.S., as well as upper ridging across the eastern CONUS, will remain in place Monday. The embedded mid-level shortwave trough and associated surface low over the northern U.S. on Day 2 (Sunday) will eject into Ontario on Monday. As such, overall synoptic ascent will decrease across the northern/central CONUS through the period. Nonetheless, surface lee troughing and a trailing frontal boundary will serve as the impetus for thunderstorm development across parts of the Great Lakes into the central Plains, where adequate buoyancy will support strong to potentially severe thunderstorms. ...Great Lakes/Upper Midwest... Thunderstorm development is likely along or immediately ahead of the frontal boundary by Monday afternoon. Deep-layer flow/shear will be oriented roughly parallel to the surface boundary, encouraging mainly multicellular/linear structures. 30 kts of effective bulk shear will be in place, amid 2000 J/kg MLCAPE, driven by 7 C/km mid-level lapse rates atop 70 F surface dewpoints. As such, the more robust, longer-lived storms may support a few instances of severe wind and/or hail. ...Portions of the central Plains... Thunderstorms may develop immediately along the surface boundary, as well as behind the front across the central Plains by afternoon peak heating. Deep-layer shear will be weaker here compared to the Great Lakes, though low-level lapse rates may be steeper (i.e. over 8.5 C/km), yielding MLCAPE values at least in the 2000-3000 J/kg range. As such, any of the more intense pulse cellular or multicellular storms that develop may produce few severe gusts. ...New England... Strong to locally extreme buoyancy, driven by a residual EML, will meander over the Mid Atlantic to New England on Monday as a surface anticyclone and associated upper ridge remains in place. Upper support is lacking for appreciable thunderstorm development. Some of the latest guidance suggests that strong thunderstorm potential will be confined to the periphery of the upper ridge over central Quebec. However, thunderstorm probabilities have been maintained given the possibility of a trailing stray storm over southern Quebec potentially impinging on northern New England. ..Squitieri.. 06/21/2025 Read more