Severe Storms

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0255 PM CDT Mon Jul 21 2025 Valid 212000Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN PLAINS... ...SUMMARY... Severe thunderstorms capable of producing large hail, severe gusts, and perhaps a tornado or two will be possible late this afternoon into tonight across parts of the northern Plains. ...20Z Update... The previous forecast remains on track, and only minor adjustments were made with this update. In the northern Plains, the Slight risk was expanded eastward in portions of ND, driven by 15-percent wind probabilities. The latest model guidance is in relatively good agreement, depicting an eastward-moving cluster of storms through the early morning hours -- aided by a strengthening low-level jet and convectively augmented midlevel impulse. Farther south, the Marginal risk was expanded slightly southward across central KS. Here, continued diurnal heating/destabilization amid rich boundary-layer moisture and steep lapse rates will favor severe wind gusts with any storm clusters that evolve through this evening. ..Weinman.. 07/21/2025 .PREV DISCUSSION... /ISSUED 1132 AM CDT Mon Jul 21 2025/ ...Northern Plains into the Upper Midwest... Water-vapor imagery shows a mid-level trough progressing eastward across the Pacific Northwest towards the northern Rockies. A lead mid-level vorticity max rotating through the base of the trough is forecast to pivot east-northeastward from north-central ID into MT by the early evening. In the low levels, a stationary frontal zone extends from near the NE/SD border west-northwestward to near the ID/WY/MT border with an easterly component to the low-level flow being maintained across eastern into central portions of MT. A moisture plume protrudes northwestward along and north of this boundary with a reservoir of 70s F dewpoints over NE to lower 60s in southeast MT (850-mb dewpoints around 16 deg C per objective analysis). A notable capping inversion will likely inhibit storm development until mid afternoon and the initial storm activity will likely focus near higher terrain and over southern MT. Steep mid-level lapse rates and 30-45 kt southwesterly 500-mb flow will support supercells with large to very large hail accompanying these storms from near the Black Hills into southern MT. A tornado risk may develop where locally backed flow in the presence of smaller temperature-dewpoint spreads could evolve near the boundary. Upscale growth into one or more clusters or an MCS seems plausible this evening into the overnight as storms move/develop east into the Dakotas. ...Central Plains... No change was made to the previous forecast for the Central Plains region. Much of the central Plains will remain capped today, as the upper ridge and warm temperatures aloft exert their influence. A surface trough is expected to extend southward across the central High Plains this afternoon, and a remnant MCV related to earlier convection should move eastward along/near the NE/KS border. Both of these features may aid in at least isolated thunderstorm development this afternoon, in the presence of moderate to strong instability amid modest deep-layer shear. Isolated severe hail and wind gusts may occur with any of the more robust cores that can develop and be maintained in an otherwise weak forcing regime. ...Tennessee Valley into the Southeast... Midday visible-satellite imagery shows an agitated cumulus field from southern GA northwestward into the southern Appalachians and Cumberland Plateau. 12 UTC raobs from Jacksonville, Atlanta, and Charleston showed PW in excess of 2 inches, signifying a very moist, deep troposphere. Surface temperatures will continue to warm into the 90s F, thereby steepening 0-2 km lapse rates. As storms develop, some of the stronger water-loaded downdrafts may yield a threat for localized 50-65 mph gusts and pockets of wind damage. This activity will likely diminish by the evening. Read more

No Mesoscale Discussions are in effect as of Mon Jul 21 20:00:02 UTC 2025.

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0226 PM CDT Mon Jul 21 2025 Valid 231200Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE UPPER MISSISSIPPI VALLEY TO UPPER GREAT LAKES REGION... ...SUMMARY... A few organizing clusters of storms posing a risk for severe wind and perhaps some hail are possible across parts of the Upper Midwest into adjacent Great Lakes region Wednesday through Wednesday night. ...Discussion... An upper ridge will exist over the eastern CONUS, with a belt of moderate winds aloft from the upper MS Valley and Great Lakes. A surface trough will extend roughly from Lake Superior southwestward into NE, with rich moisture to the south and east. Storms are likely to be ongoing over the upper Great Lakes region early on Wednesday, supported by southwest winds at 850 mb within a theta-e plume. Some of this early activity could product strong wind gusts. Behind this activity, destabilization will occur near the surface trough, and new development is likely during the late afternoon from MN into SD and NE. With only subtle features aloft, this activity will likely develop into clusters of storms with east/southeastward propagation and attendant outflow/severe gust threat. Otherwise, isolated severe cells with hail will be possible over the High Plains over southeast MT, eastern WY and CO, as moisture backs westward into the steeper lapse rate environment. Longer hodographs over MT/WY could support a supercell or two, and this area will be monitored for higher probabilities in later outlooks. ..Jewell.. 07/21/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0226 PM CDT Mon Jul 21 2025 Valid 231200Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE UPPER MISSISSIPPI VALLEY TO UPPER GREAT LAKES REGION... ...SUMMARY... A few organizing clusters of storms posing a risk for severe wind and perhaps some hail are possible across parts of the Upper Midwest into adjacent Great Lakes region Wednesday through Wednesday night. ...Discussion... An upper ridge will exist over the eastern CONUS, with a belt of moderate winds aloft from the upper MS Valley and Great Lakes. A surface trough will extend roughly from Lake Superior southwestward into NE, with rich moisture to the south and east. Storms are likely to be ongoing over the upper Great Lakes region early on Wednesday, supported by southwest winds at 850 mb within a theta-e plume. Some of this early activity could product strong wind gusts. Behind this activity, destabilization will occur near the surface trough, and new development is likely during the late afternoon from MN into SD and NE. With only subtle features aloft, this activity will likely develop into clusters of storms with east/southeastward propagation and attendant outflow/severe gust threat. Otherwise, isolated severe cells with hail will be possible over the High Plains over southeast MT, eastern WY and CO, as moisture backs westward into the steeper lapse rate environment. Longer hodographs over MT/WY could support a supercell or two, and this area will be monitored for higher probabilities in later outlooks. ..Jewell.. 07/21/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0226 PM CDT Mon Jul 21 2025 Valid 231200Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE UPPER MISSISSIPPI VALLEY TO UPPER GREAT LAKES REGION... ...SUMMARY... A few organizing clusters of storms posing a risk for severe wind and perhaps some hail are possible across parts of the Upper Midwest into adjacent Great Lakes region Wednesday through Wednesday night. ...Discussion... An upper ridge will exist over the eastern CONUS, with a belt of moderate winds aloft from the upper MS Valley and Great Lakes. A surface trough will extend roughly from Lake Superior southwestward into NE, with rich moisture to the south and east. Storms are likely to be ongoing over the upper Great Lakes region early on Wednesday, supported by southwest winds at 850 mb within a theta-e plume. Some of this early activity could product strong wind gusts. Behind this activity, destabilization will occur near the surface trough, and new development is likely during the late afternoon from MN into SD and NE. With only subtle features aloft, this activity will likely develop into clusters of storms with east/southeastward propagation and attendant outflow/severe gust threat. Otherwise, isolated severe cells with hail will be possible over the High Plains over southeast MT, eastern WY and CO, as moisture backs westward into the steeper lapse rate environment. Longer hodographs over MT/WY could support a supercell or two, and this area will be monitored for higher probabilities in later outlooks. ..Jewell.. 07/21/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0226 PM CDT Mon Jul 21 2025 Valid 231200Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE UPPER MISSISSIPPI VALLEY TO UPPER GREAT LAKES REGION... ...SUMMARY... A few organizing clusters of storms posing a risk for severe wind and perhaps some hail are possible across parts of the Upper Midwest into adjacent Great Lakes region Wednesday through Wednesday night. ...Discussion... An upper ridge will exist over the eastern CONUS, with a belt of moderate winds aloft from the upper MS Valley and Great Lakes. A surface trough will extend roughly from Lake Superior southwestward into NE, with rich moisture to the south and east. Storms are likely to be ongoing over the upper Great Lakes region early on Wednesday, supported by southwest winds at 850 mb within a theta-e plume. Some of this early activity could product strong wind gusts. Behind this activity, destabilization will occur near the surface trough, and new development is likely during the late afternoon from MN into SD and NE. With only subtle features aloft, this activity will likely develop into clusters of storms with east/southeastward propagation and attendant outflow/severe gust threat. Otherwise, isolated severe cells with hail will be possible over the High Plains over southeast MT, eastern WY and CO, as moisture backs westward into the steeper lapse rate environment. Longer hodographs over MT/WY could support a supercell or two, and this area will be monitored for higher probabilities in later outlooks. ..Jewell.. 07/21/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0226 PM CDT Mon Jul 21 2025 Valid 231200Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE UPPER MISSISSIPPI VALLEY TO UPPER GREAT LAKES REGION... ...SUMMARY... A few organizing clusters of storms posing a risk for severe wind and perhaps some hail are possible across parts of the Upper Midwest into adjacent Great Lakes region Wednesday through Wednesday night. ...Discussion... An upper ridge will exist over the eastern CONUS, with a belt of moderate winds aloft from the upper MS Valley and Great Lakes. A surface trough will extend roughly from Lake Superior southwestward into NE, with rich moisture to the south and east. Storms are likely to be ongoing over the upper Great Lakes region early on Wednesday, supported by southwest winds at 850 mb within a theta-e plume. Some of this early activity could product strong wind gusts. Behind this activity, destabilization will occur near the surface trough, and new development is likely during the late afternoon from MN into SD and NE. With only subtle features aloft, this activity will likely develop into clusters of storms with east/southeastward propagation and attendant outflow/severe gust threat. Otherwise, isolated severe cells with hail will be possible over the High Plains over southeast MT, eastern WY and CO, as moisture backs westward into the steeper lapse rate environment. Longer hodographs over MT/WY could support a supercell or two, and this area will be monitored for higher probabilities in later outlooks. ..Jewell.. 07/21/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0226 PM CDT Mon Jul 21 2025 Valid 231200Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE UPPER MISSISSIPPI VALLEY TO UPPER GREAT LAKES REGION... ...SUMMARY... A few organizing clusters of storms posing a risk for severe wind and perhaps some hail are possible across parts of the Upper Midwest into adjacent Great Lakes region Wednesday through Wednesday night. ...Discussion... An upper ridge will exist over the eastern CONUS, with a belt of moderate winds aloft from the upper MS Valley and Great Lakes. A surface trough will extend roughly from Lake Superior southwestward into NE, with rich moisture to the south and east. Storms are likely to be ongoing over the upper Great Lakes region early on Wednesday, supported by southwest winds at 850 mb within a theta-e plume. Some of this early activity could product strong wind gusts. Behind this activity, destabilization will occur near the surface trough, and new development is likely during the late afternoon from MN into SD and NE. With only subtle features aloft, this activity will likely develop into clusters of storms with east/southeastward propagation and attendant outflow/severe gust threat. Otherwise, isolated severe cells with hail will be possible over the High Plains over southeast MT, eastern WY and CO, as moisture backs westward into the steeper lapse rate environment. Longer hodographs over MT/WY could support a supercell or two, and this area will be monitored for higher probabilities in later outlooks. ..Jewell.. 07/21/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0226 PM CDT Mon Jul 21 2025 Valid 231200Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE UPPER MISSISSIPPI VALLEY TO UPPER GREAT LAKES REGION... ...SUMMARY... A few organizing clusters of storms posing a risk for severe wind and perhaps some hail are possible across parts of the Upper Midwest into adjacent Great Lakes region Wednesday through Wednesday night. ...Discussion... An upper ridge will exist over the eastern CONUS, with a belt of moderate winds aloft from the upper MS Valley and Great Lakes. A surface trough will extend roughly from Lake Superior southwestward into NE, with rich moisture to the south and east. Storms are likely to be ongoing over the upper Great Lakes region early on Wednesday, supported by southwest winds at 850 mb within a theta-e plume. Some of this early activity could product strong wind gusts. Behind this activity, destabilization will occur near the surface trough, and new development is likely during the late afternoon from MN into SD and NE. With only subtle features aloft, this activity will likely develop into clusters of storms with east/southeastward propagation and attendant outflow/severe gust threat. Otherwise, isolated severe cells with hail will be possible over the High Plains over southeast MT, eastern WY and CO, as moisture backs westward into the steeper lapse rate environment. Longer hodographs over MT/WY could support a supercell or two, and this area will be monitored for higher probabilities in later outlooks. ..Jewell.. 07/21/2025 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0217 PM CDT Mon Jul 21 2025 Valid 221200Z - 231200Z No changes are needed to the D2 Fire Weather Outlook. ..Thornton.. 07/21/2025 .PREV DISCUSSION... /ISSUED 0201 AM CDT Mon Jul 21 2025/ ...Synopsis... The upper-level trough in the Northwest will become more diffuse on Tuesday. Mid-level winds will slacken across the Great Basin. A weak surface trough/boundary will remain in northern Nevada. ...Southern/central Nevada... While surface winds will generally be weaker than previous days, the surface pressure gradient near the boundary will support 15-20 mph in portions of southern/central Nevada. RH of 15-20% appears possible during the afternoon. Area fuels remain dry enough to support elevated fire weather conditions. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0217 PM CDT Mon Jul 21 2025 Valid 221200Z - 231200Z No changes are needed to the D2 Fire Weather Outlook. ..Thornton.. 07/21/2025 .PREV DISCUSSION... /ISSUED 0201 AM CDT Mon Jul 21 2025/ ...Synopsis... The upper-level trough in the Northwest will become more diffuse on Tuesday. Mid-level winds will slacken across the Great Basin. A weak surface trough/boundary will remain in northern Nevada. ...Southern/central Nevada... While surface winds will generally be weaker than previous days, the surface pressure gradient near the boundary will support 15-20 mph in portions of southern/central Nevada. RH of 15-20% appears possible during the afternoon. Area fuels remain dry enough to support elevated fire weather conditions. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0217 PM CDT Mon Jul 21 2025 Valid 221200Z - 231200Z No changes are needed to the D2 Fire Weather Outlook. ..Thornton.. 07/21/2025 .PREV DISCUSSION... /ISSUED 0201 AM CDT Mon Jul 21 2025/ ...Synopsis... The upper-level trough in the Northwest will become more diffuse on Tuesday. Mid-level winds will slacken across the Great Basin. A weak surface trough/boundary will remain in northern Nevada. ...Southern/central Nevada... While surface winds will generally be weaker than previous days, the surface pressure gradient near the boundary will support 15-20 mph in portions of southern/central Nevada. RH of 15-20% appears possible during the afternoon. Area fuels remain dry enough to support elevated fire weather conditions. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0217 PM CDT Mon Jul 21 2025 Valid 221200Z - 231200Z No changes are needed to the D2 Fire Weather Outlook. ..Thornton.. 07/21/2025 .PREV DISCUSSION... /ISSUED 0201 AM CDT Mon Jul 21 2025/ ...Synopsis... The upper-level trough in the Northwest will become more diffuse on Tuesday. Mid-level winds will slacken across the Great Basin. A weak surface trough/boundary will remain in northern Nevada. ...Southern/central Nevada... While surface winds will generally be weaker than previous days, the surface pressure gradient near the boundary will support 15-20 mph in portions of southern/central Nevada. RH of 15-20% appears possible during the afternoon. Area fuels remain dry enough to support elevated fire weather conditions. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0217 PM CDT Mon Jul 21 2025 Valid 221200Z - 231200Z No changes are needed to the D2 Fire Weather Outlook. ..Thornton.. 07/21/2025 .PREV DISCUSSION... /ISSUED 0201 AM CDT Mon Jul 21 2025/ ...Synopsis... The upper-level trough in the Northwest will become more diffuse on Tuesday. Mid-level winds will slacken across the Great Basin. A weak surface trough/boundary will remain in northern Nevada. ...Southern/central Nevada... While surface winds will generally be weaker than previous days, the surface pressure gradient near the boundary will support 15-20 mph in portions of southern/central Nevada. RH of 15-20% appears possible during the afternoon. Area fuels remain dry enough to support elevated fire weather conditions. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0217 PM CDT Mon Jul 21 2025 Valid 221200Z - 231200Z No changes are needed to the D2 Fire Weather Outlook. ..Thornton.. 07/21/2025 .PREV DISCUSSION... /ISSUED 0201 AM CDT Mon Jul 21 2025/ ...Synopsis... The upper-level trough in the Northwest will become more diffuse on Tuesday. Mid-level winds will slacken across the Great Basin. A weak surface trough/boundary will remain in northern Nevada. ...Southern/central Nevada... While surface winds will generally be weaker than previous days, the surface pressure gradient near the boundary will support 15-20 mph in portions of southern/central Nevada. RH of 15-20% appears possible during the afternoon. Area fuels remain dry enough to support elevated fire weather conditions. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0217 PM CDT Mon Jul 21 2025 Valid 221200Z - 231200Z No changes are needed to the D2 Fire Weather Outlook. ..Thornton.. 07/21/2025 .PREV DISCUSSION... /ISSUED 0201 AM CDT Mon Jul 21 2025/ ...Synopsis... The upper-level trough in the Northwest will become more diffuse on Tuesday. Mid-level winds will slacken across the Great Basin. A weak surface trough/boundary will remain in northern Nevada. ...Southern/central Nevada... While surface winds will generally be weaker than previous days, the surface pressure gradient near the boundary will support 15-20 mph in portions of southern/central Nevada. RH of 15-20% appears possible during the afternoon. Area fuels remain dry enough to support elevated fire weather conditions. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0217 PM CDT Mon Jul 21 2025 Valid 221200Z - 231200Z No changes are needed to the D2 Fire Weather Outlook. ..Thornton.. 07/21/2025 .PREV DISCUSSION... /ISSUED 0201 AM CDT Mon Jul 21 2025/ ...Synopsis... The upper-level trough in the Northwest will become more diffuse on Tuesday. Mid-level winds will slacken across the Great Basin. A weak surface trough/boundary will remain in northern Nevada. ...Southern/central Nevada... While surface winds will generally be weaker than previous days, the surface pressure gradient near the boundary will support 15-20 mph in portions of southern/central Nevada. RH of 15-20% appears possible during the afternoon. Area fuels remain dry enough to support elevated fire weather conditions. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0732 AM CDT Mon Jul 21 2025 Valid 211300Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN PLAINS... ...SUMMARY... Severe thunderstorms capable of producing large hail, severe gusts, and perhaps a tornado or two will be possible today and tonight across parts of the northern Plains. Additional isolated strong to severe storms may occur across portions of the central Plains. ...Northern Plains into the Upper Midwest... A long-lived and compact MCS has advanced into parts of west-central MN this morning. This convection is on the northern periphery of meaningful low-level moisture and related instability. It should generally weaken over the next few hours while it tracks southeastward over southern MN as a low-level jet gradually lessens. But in the short term, it may still be capable of producing occasional strong to severe wind gusts. Behind this activity, a moist and rather unstable airmass will exist across the northern Plains along and south of a convectively reinforced front that should become oriented generally east-west along the ND/SD border by late this afternoon. Large-scale ascent across the northern Plains will likely be weak for much of the day, as upper ridging remains prominent over the central CONUS. Even so, there are indications that a weak mid-level perturbation emanating from upper troughing over the Pacific Northwest should overspread the northern Rockies and adjacent High Plains of central/eastern MT by mid/late afternoon as ample daytime heating of a slowly moistening low-level airmass occurs. A belt of enhanced west-southwesterly mid-level flow will accompany this feature, supporting ample veering/strengthening of the wind profile with height through mid/upper levels. Related strong deep-layer shear of 40-50+ kt will easily support supercells with initial development off the Bighorns given the presence of at least moderate instability across the High Plains. Large hail will be possible with these supercells this afternoon, followed by an increasing severe wind threat with time this evening/overnight into parts of the Dakotas as convection potentially grows upscale, and where ample MUCAPE and strong deep-layer shear will be present along/north of the surface boundary. The development of elevated supercells also appears possible across parts of the Dakotas late tonight as a low-level jet gradually strengthens, with a related threat for at least isolated severe hail if they occur. ...Central Plains... Much of the central Plains will remain capped today, as the upper ridge and warm temperatures aloft exert their influence. A surface trough is expected to extend southward across the central High Plains this afternoon, and a remnant MCV related to earlier convection should move eastward along/near the NE/KS border. Both of these features may aid in at least isolated thunderstorm development this afternoon, in the presence of moderate to strong instability amid modest deep-layer shear. Isolated severe hail and wind gusts may occur with any of the more robust cores that can develop and be maintained in an otherwise weak forcing regime. The Marginal Risk has been expanded southward a little to include more of northern KS and southeast NE, where strong to severe convection may develop later today in close proximity to the MCV. ...Tennessee Valley into the Southeast... A weak MCV related to ongoing convection across MO and southern IL this morning will track southeastward across the TN Valley and vicinity through this afternoon. Modest west-northwesterly flow should be in place today across parts of the OH/TN Valleys into the Southeast. This may support loosely organized multicells and pulse thunderstorms today, as mostly sunny conditions aid in the development of moderate to locally strong instability this afternoon. While deep-layer shear is forecast to remain weak, some of this convection may still be capable of producing strong to locally damaging winds. Parts of these regions may be considered for inclusion in a Marginal Risk in a later outlook update, pending additional observational/model trends. ..Gleason/Bentley.. 07/21/2025 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0353 AM CDT Mon Jul 21 2025 Valid 241200Z - 291200Z ...DISCUSSION... Medium-range models indicate that mid-level ridging, initially centered over the Ohio Valley, will weaken late this work week through next weekend, as flow undergoes substantive amplification upstream. This appears likely to include a significant short wave trough digging southeast of the Aleutians, accompanied by lower/mid-tropospheric cyclogenesis across the northeastern Pacific. Part of a higher latitude blocking pattern, little subsequent movement of this cyclone is forecast through early next week, as an expansive, prominent mid-level ridge also evolves in the downstream lower latitudes, across much of the Intermountain West, Rockies and Great Plains into mid and lower Mississippi Valley. However, as a notable mid-level low continues slowly east of Hudson Bay, across northern Quebec and Newfoundland and Labrador, a belt of seasonably strong westerly mid/upper flow may be maintained across Ontario and Quebec this Thursday through Friday. Along the favorably sheared southern fringe of this regime, seasonably moist low-level air advecting ahead of a stalled to southward advancing frontal zone may contribute to sufficient destabilization for the evolution of organizing thunderstorm clusters capable of producing swaths of damaging wind gusts. The extent to which this may impact U.S. portions of the Great Lakes into New England remains unclear. It might not be out of the question that a similar type regime could evolve beneath developing northwesterly mid-level flow, from the North Dakota/Minnesota international border area into the Upper Midwest/Great Lakes late next weekend into early next week. Current guidance is still suggestive that this is a lower probability, but this could be due to the low predictability of the pertinent features at this extended range. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0353 AM CDT Mon Jul 21 2025 Valid 241200Z - 291200Z ...DISCUSSION... Medium-range models indicate that mid-level ridging, initially centered over the Ohio Valley, will weaken late this work week through next weekend, as flow undergoes substantive amplification upstream. This appears likely to include a significant short wave trough digging southeast of the Aleutians, accompanied by lower/mid-tropospheric cyclogenesis across the northeastern Pacific. Part of a higher latitude blocking pattern, little subsequent movement of this cyclone is forecast through early next week, as an expansive, prominent mid-level ridge also evolves in the downstream lower latitudes, across much of the Intermountain West, Rockies and Great Plains into mid and lower Mississippi Valley. However, as a notable mid-level low continues slowly east of Hudson Bay, across northern Quebec and Newfoundland and Labrador, a belt of seasonably strong westerly mid/upper flow may be maintained across Ontario and Quebec this Thursday through Friday. Along the favorably sheared southern fringe of this regime, seasonably moist low-level air advecting ahead of a stalled to southward advancing frontal zone may contribute to sufficient destabilization for the evolution of organizing thunderstorm clusters capable of producing swaths of damaging wind gusts. The extent to which this may impact U.S. portions of the Great Lakes into New England remains unclear. It might not be out of the question that a similar type regime could evolve beneath developing northwesterly mid-level flow, from the North Dakota/Minnesota international border area into the Upper Midwest/Great Lakes late next weekend into early next week. Current guidance is still suggestive that this is a lower probability, but this could be due to the low predictability of the pertinent features at this extended range. Read more