Aggregator

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

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

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

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

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

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

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

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1155 PM CDT Sat Jul 19 2025 Valid 211200Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS MONDAY INTO MONDAY NIGHT ACROSS PARTS OF THE NORTHERN GREAT PLAINS AND TENNESSEE VALLEY INTO SOUTH ATLANTIC SEABOARD... ...SUMMARY... Strong thunderstorm development may pose at least some risk for severe wind and hail across parts of the northern Great Plains and parts of the Southeast Monday into Monday night. ...Synopsis... Models continue to indicate at least some shearing of mid-level troughing initially across the Pacific Northwest at the outset of the period, between fairly prominent and persistent lower latitude ridging encompassing much of the interior U.S. and stronger higher latitude ridging centered over the northeastern Pacific. However, one short wave impulse embedded within the troughing may maintain fairly vigorous strength while slowly accelerating northeastward into the mountains of western Montana. Downstream of this perturbation, the interior U.S. ridging may tend to build a bit further northeastward across parts of the northern U.S. Great Plains and Upper Midwest/adjacent Great Lakes vicinity, in the wake of significant mid-level troughing progressing offshore of the northern U.S. and Canadian Atlantic coast. Another significant trough and embedded mid-level low emerging from the northwestern Canadian Arctic latitudes is forecast to slowly turn east of the Northwest Territories toward Hudson Bay. In lower levels, it appears that a cold front associated with the higher latitude perturbation may advance through the Canadian Prairies, but remain north of the international border through this period. A preceding cold front may progress slowly southward through portions of the southern Mid Atlantic, while stalling across parts of the lower Ohio into middle Mississippi Valleys and weakening across the middle Missouri Valley/northern Great Plains. ...Northern Great Plains... Beneath a plume of warm and capping elevated mixed-layer air, models indicate that a seasonably moist boundary layer will again become characterized by moderate to large potential instability across parts of the middle Missouri Valley and adjacent Great Plains. The NAM has been more aggressive in recent runs with boundary-layer moistening on northeasterly to easterly low-level flow into deepening surface troughing across central and southeastern Montana. However, aside from the higher terrain of central Montana, downstream of the short wave impulse emerging from the Pacific Northwest, forcing for ascent to support convective development remains a bit unclear across much of the remainder of the northern Great Plains, given the inhibition associated with the elevated mixed-layer air. There does appear an increasing signal that a subtle short wave impulse, migrating around the western/northwestern periphery of the stronger mid-level ridging, may contribute to scattered vigorous high-based thunderstorm development within the drier and more deeply mixed environment across parts of eastern Wyoming and northeastern Colorado. This activity may pose a risk for severe hail and wind while tending to advect across and northeast/east of the higher plains late Monday afternoon and evening. Otherwise, locally enhanced low-level convergence during and shortly after peak heating might weaken inhibition sufficiently to support isolated supercell development within the seasonably moist/higher CAPE environment, with various model output continuing to indicate one possible focus across parts of central or north central South Dakota. ...Tennessee Valley into southern Atlantic Seaboard... Even as the lead cold front continues to advance south of the stronger westerlies, destabilization along and ahead of it may become conducive to scattered upscale growing thunderstorm activity posing a risk for potentially damaging wind gusts by late Monday afternoon into early evening. Based on model output, it still appears possible that this could be aided by a remnant convectively generated or enhanced perturbation emerging from the lower Ohio Valley. ..Kerr.. 07/20/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1155 PM CDT Sat Jul 19 2025 Valid 211200Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS MONDAY INTO MONDAY NIGHT ACROSS PARTS OF THE NORTHERN GREAT PLAINS AND TENNESSEE VALLEY INTO SOUTH ATLANTIC SEABOARD... ...SUMMARY... Strong thunderstorm development may pose at least some risk for severe wind and hail across parts of the northern Great Plains and parts of the Southeast Monday into Monday night. ...Synopsis... Models continue to indicate at least some shearing of mid-level troughing initially across the Pacific Northwest at the outset of the period, between fairly prominent and persistent lower latitude ridging encompassing much of the interior U.S. and stronger higher latitude ridging centered over the northeastern Pacific. However, one short wave impulse embedded within the troughing may maintain fairly vigorous strength while slowly accelerating northeastward into the mountains of western Montana. Downstream of this perturbation, the interior U.S. ridging may tend to build a bit further northeastward across parts of the northern U.S. Great Plains and Upper Midwest/adjacent Great Lakes vicinity, in the wake of significant mid-level troughing progressing offshore of the northern U.S. and Canadian Atlantic coast. Another significant trough and embedded mid-level low emerging from the northwestern Canadian Arctic latitudes is forecast to slowly turn east of the Northwest Territories toward Hudson Bay. In lower levels, it appears that a cold front associated with the higher latitude perturbation may advance through the Canadian Prairies, but remain north of the international border through this period. A preceding cold front may progress slowly southward through portions of the southern Mid Atlantic, while stalling across parts of the lower Ohio into middle Mississippi Valleys and weakening across the middle Missouri Valley/northern Great Plains. ...Northern Great Plains... Beneath a plume of warm and capping elevated mixed-layer air, models indicate that a seasonably moist boundary layer will again become characterized by moderate to large potential instability across parts of the middle Missouri Valley and adjacent Great Plains. The NAM has been more aggressive in recent runs with boundary-layer moistening on northeasterly to easterly low-level flow into deepening surface troughing across central and southeastern Montana. However, aside from the higher terrain of central Montana, downstream of the short wave impulse emerging from the Pacific Northwest, forcing for ascent to support convective development remains a bit unclear across much of the remainder of the northern Great Plains, given the inhibition associated with the elevated mixed-layer air. There does appear an increasing signal that a subtle short wave impulse, migrating around the western/northwestern periphery of the stronger mid-level ridging, may contribute to scattered vigorous high-based thunderstorm development within the drier and more deeply mixed environment across parts of eastern Wyoming and northeastern Colorado. This activity may pose a risk for severe hail and wind while tending to advect across and northeast/east of the higher plains late Monday afternoon and evening. Otherwise, locally enhanced low-level convergence during and shortly after peak heating might weaken inhibition sufficiently to support isolated supercell development within the seasonably moist/higher CAPE environment, with various model output continuing to indicate one possible focus across parts of central or north central South Dakota. ...Tennessee Valley into southern Atlantic Seaboard... Even as the lead cold front continues to advance south of the stronger westerlies, destabilization along and ahead of it may become conducive to scattered upscale growing thunderstorm activity posing a risk for potentially damaging wind gusts by late Monday afternoon into early evening. Based on model output, it still appears possible that this could be aided by a remnant convectively generated or enhanced perturbation emerging from the lower Ohio Valley. ..Kerr.. 07/20/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1155 PM CDT Sat Jul 19 2025 Valid 211200Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS MONDAY INTO MONDAY NIGHT ACROSS PARTS OF THE NORTHERN GREAT PLAINS AND TENNESSEE VALLEY INTO SOUTH ATLANTIC SEABOARD... ...SUMMARY... Strong thunderstorm development may pose at least some risk for severe wind and hail across parts of the northern Great Plains and parts of the Southeast Monday into Monday night. ...Synopsis... Models continue to indicate at least some shearing of mid-level troughing initially across the Pacific Northwest at the outset of the period, between fairly prominent and persistent lower latitude ridging encompassing much of the interior U.S. and stronger higher latitude ridging centered over the northeastern Pacific. However, one short wave impulse embedded within the troughing may maintain fairly vigorous strength while slowly accelerating northeastward into the mountains of western Montana. Downstream of this perturbation, the interior U.S. ridging may tend to build a bit further northeastward across parts of the northern U.S. Great Plains and Upper Midwest/adjacent Great Lakes vicinity, in the wake of significant mid-level troughing progressing offshore of the northern U.S. and Canadian Atlantic coast. Another significant trough and embedded mid-level low emerging from the northwestern Canadian Arctic latitudes is forecast to slowly turn east of the Northwest Territories toward Hudson Bay. In lower levels, it appears that a cold front associated with the higher latitude perturbation may advance through the Canadian Prairies, but remain north of the international border through this period. A preceding cold front may progress slowly southward through portions of the southern Mid Atlantic, while stalling across parts of the lower Ohio into middle Mississippi Valleys and weakening across the middle Missouri Valley/northern Great Plains. ...Northern Great Plains... Beneath a plume of warm and capping elevated mixed-layer air, models indicate that a seasonably moist boundary layer will again become characterized by moderate to large potential instability across parts of the middle Missouri Valley and adjacent Great Plains. The NAM has been more aggressive in recent runs with boundary-layer moistening on northeasterly to easterly low-level flow into deepening surface troughing across central and southeastern Montana. However, aside from the higher terrain of central Montana, downstream of the short wave impulse emerging from the Pacific Northwest, forcing for ascent to support convective development remains a bit unclear across much of the remainder of the northern Great Plains, given the inhibition associated with the elevated mixed-layer air. There does appear an increasing signal that a subtle short wave impulse, migrating around the western/northwestern periphery of the stronger mid-level ridging, may contribute to scattered vigorous high-based thunderstorm development within the drier and more deeply mixed environment across parts of eastern Wyoming and northeastern Colorado. This activity may pose a risk for severe hail and wind while tending to advect across and northeast/east of the higher plains late Monday afternoon and evening. Otherwise, locally enhanced low-level convergence during and shortly after peak heating might weaken inhibition sufficiently to support isolated supercell development within the seasonably moist/higher CAPE environment, with various model output continuing to indicate one possible focus across parts of central or north central South Dakota. ...Tennessee Valley into southern Atlantic Seaboard... Even as the lead cold front continues to advance south of the stronger westerlies, destabilization along and ahead of it may become conducive to scattered upscale growing thunderstorm activity posing a risk for potentially damaging wind gusts by late Monday afternoon into early evening. Based on model output, it still appears possible that this could be aided by a remnant convectively generated or enhanced perturbation emerging from the lower Ohio Valley. ..Kerr.. 07/20/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1155 PM CDT Sat Jul 19 2025 Valid 211200Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS MONDAY INTO MONDAY NIGHT ACROSS PARTS OF THE NORTHERN GREAT PLAINS AND TENNESSEE VALLEY INTO SOUTH ATLANTIC SEABOARD... ...SUMMARY... Strong thunderstorm development may pose at least some risk for severe wind and hail across parts of the northern Great Plains and parts of the Southeast Monday into Monday night. ...Synopsis... Models continue to indicate at least some shearing of mid-level troughing initially across the Pacific Northwest at the outset of the period, between fairly prominent and persistent lower latitude ridging encompassing much of the interior U.S. and stronger higher latitude ridging centered over the northeastern Pacific. However, one short wave impulse embedded within the troughing may maintain fairly vigorous strength while slowly accelerating northeastward into the mountains of western Montana. Downstream of this perturbation, the interior U.S. ridging may tend to build a bit further northeastward across parts of the northern U.S. Great Plains and Upper Midwest/adjacent Great Lakes vicinity, in the wake of significant mid-level troughing progressing offshore of the northern U.S. and Canadian Atlantic coast. Another significant trough and embedded mid-level low emerging from the northwestern Canadian Arctic latitudes is forecast to slowly turn east of the Northwest Territories toward Hudson Bay. In lower levels, it appears that a cold front associated with the higher latitude perturbation may advance through the Canadian Prairies, but remain north of the international border through this period. A preceding cold front may progress slowly southward through portions of the southern Mid Atlantic, while stalling across parts of the lower Ohio into middle Mississippi Valleys and weakening across the middle Missouri Valley/northern Great Plains. ...Northern Great Plains... Beneath a plume of warm and capping elevated mixed-layer air, models indicate that a seasonably moist boundary layer will again become characterized by moderate to large potential instability across parts of the middle Missouri Valley and adjacent Great Plains. The NAM has been more aggressive in recent runs with boundary-layer moistening on northeasterly to easterly low-level flow into deepening surface troughing across central and southeastern Montana. However, aside from the higher terrain of central Montana, downstream of the short wave impulse emerging from the Pacific Northwest, forcing for ascent to support convective development remains a bit unclear across much of the remainder of the northern Great Plains, given the inhibition associated with the elevated mixed-layer air. There does appear an increasing signal that a subtle short wave impulse, migrating around the western/northwestern periphery of the stronger mid-level ridging, may contribute to scattered vigorous high-based thunderstorm development within the drier and more deeply mixed environment across parts of eastern Wyoming and northeastern Colorado. This activity may pose a risk for severe hail and wind while tending to advect across and northeast/east of the higher plains late Monday afternoon and evening. Otherwise, locally enhanced low-level convergence during and shortly after peak heating might weaken inhibition sufficiently to support isolated supercell development within the seasonably moist/higher CAPE environment, with various model output continuing to indicate one possible focus across parts of central or north central South Dakota. ...Tennessee Valley into southern Atlantic Seaboard... Even as the lead cold front continues to advance south of the stronger westerlies, destabilization along and ahead of it may become conducive to scattered upscale growing thunderstorm activity posing a risk for potentially damaging wind gusts by late Monday afternoon into early evening. Based on model output, it still appears possible that this could be aided by a remnant convectively generated or enhanced perturbation emerging from the lower Ohio Valley. ..Kerr.. 07/20/2025 Read more

MD 1733 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR SOUTHERN IOWA...EXTREME NORTHEAST MISSOURI...WEST-CENTRAL ILLINOIS
Mesoscale Discussion 1733 NWS Storm Prediction Center Norman OK 1139 PM CDT Sat Jul 19 2025 Areas affected...Southern Iowa...extreme northeast Missouri...west-central Illinois Concerning...Severe potential...Watch possible Valid 200439Z - 200645Z Probability of Watch Issuance...40 percent SUMMARY...A small cluster of thunderstorms will pose a risk for isolated large hail and strong wind gusts. Should these storms show signs of becoming better organized, then watch issuance would be possible. DISCUSSION...A small cluster of thunderstorms has recently intensified over south-central Iowa in the vicinity of an east-west frontal boundary. Latest objective analysis shows this area within a zone of low-level warm advection, and also within the right entrance region of an upper-level jet maximum. Strong instability (MUCAPE in excess of 2500 J/kg) and around 40 kts of westerly shear will provide a favorable environment for some continued severe hail and wind threat, with some non-zero tornado potential in the vicinity of the boundary. The primary uncertainty is the degree of organization that would result in more than an isolated severe threat. Latest hi-res guidance remains varied regarding near-term forecasts for these storms, although the potential does exist for increased organization over the next few hours. Were this to occur, then watch issuance would be possible. Convective trends will be monitored closely. ..Bunting/Hart.. 07/20/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LSX...DVN...DMX...EAX... LAT...LON 40989426 41229306 41189216 40949158 40719122 40539107 40309107 40259185 40319296 40449388 40789428 40989426 MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 95 MPH MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1259 AM CDT Sun Jul 20 2025 Valid 201200Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE NORTHEAST...MIDWEST...OHIO VALLEY...AND NORTHERN PLAINS... ...SUMMARY... Strong to severe storms appear most likely later today into this evening across parts of the Northeast, Midwest and Ohio Valley, and northern Plains. ...Northeast... A deep upper-level trough over parts of Quebec and Ontario will dig southeastward through the day today. As this occurs, cooling aloft and increasing mid/upper-level flow is expected from northern parts of the Mid Atlantic into New England. Midlevel lapse rates will generally remain weak, but diurnal heating of a moist airmass will result in MLCAPE increasing to 1000-1500 J/kg along/ahead of a cold front. Scattered storm development is expected along/ahead of the front this afternoon, with effective shear of 35-45 kt sufficient for storm organization. A few supercells will be possible initially, with a threat for locally damaging wind, isolated hail, and possibly a tornado. With time, some storm clustering is possible, which could lead to locally more concentrated areas of wind damage. Some severe threat could linger into the early evening for near-coastal areas, before storms move offshore. ...Parts of the Mid MS and OH Valleys... Despite warm temperatures aloft, heating of a very moist airmass will support MLCAPE increasing into the 2000-3000 J/kg range this afternoon across parts of the mid MS and OH Valleys, near/south of a remnant surface boundary and any convective outflows. Modestly enhanced west-northwesterly mid/upper flow will conditionally support organized storm potential, though evolution of storms through the day and evening across the region remains somewhat uncertain. An MCS (or its remnant) may move from parts of IL/IN toward parts of the upper OH Valley through the day. Some reintensification of this system, and/or development along its trailing outflow, will be possible during the afternoon, with steepening low-level lapse rates and large PW supporting localized downbursts and damaging outflow winds. Additional development will be possible farther west near the outflow-influenced surface boundary, which could result in development of organized cells/clusters capable of damaging wind. Deep-layer shear will be marginally supportive of supercells, and some threat for hail and a tornado cannot be ruled out with any sustained supercells. Some severe threat could linger into tonight, as modest low-level warm advection helps to regenerate storms near and north of the effective surface boundary. ...Northern/central Plains... A mid/upper-level trough will remain in place over the Northwest and northern Rockies today. A surface trough will extend from eastern MT into the central High Plains this afternoon. East of the surface trough, a surface boundary initially draped across parts of NE/KS will attempt to lift north as a warm front, in the wake of early morning convection. Details regarding storm development and evolution remain rather uncertain across the region, but most guidance suggests at least isolated storm development will be possible near the surface trough and near/north of the effective warm front sometime this afternoon or evening. Effective shear of 40+ kt will support initial supercell development, with a threat of hail, isolated severe gusts, and possibly a tornado. Outflow consolidation could lead to some clustering and upscale growth, which would tend to move southeastward with a continued threat of at least localized severe gusts and isolated hail into tonight. ..Dean/Wendt.. 07/20/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1259 AM CDT Sun Jul 20 2025 Valid 201200Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE NORTHEAST...MIDWEST...OHIO VALLEY...AND NORTHERN PLAINS... ...SUMMARY... Strong to severe storms appear most likely later today into this evening across parts of the Northeast, Midwest and Ohio Valley, and northern Plains. ...Northeast... A deep upper-level trough over parts of Quebec and Ontario will dig southeastward through the day today. As this occurs, cooling aloft and increasing mid/upper-level flow is expected from northern parts of the Mid Atlantic into New England. Midlevel lapse rates will generally remain weak, but diurnal heating of a moist airmass will result in MLCAPE increasing to 1000-1500 J/kg along/ahead of a cold front. Scattered storm development is expected along/ahead of the front this afternoon, with effective shear of 35-45 kt sufficient for storm organization. A few supercells will be possible initially, with a threat for locally damaging wind, isolated hail, and possibly a tornado. With time, some storm clustering is possible, which could lead to locally more concentrated areas of wind damage. Some severe threat could linger into the early evening for near-coastal areas, before storms move offshore. ...Parts of the Mid MS and OH Valleys... Despite warm temperatures aloft, heating of a very moist airmass will support MLCAPE increasing into the 2000-3000 J/kg range this afternoon across parts of the mid MS and OH Valleys, near/south of a remnant surface boundary and any convective outflows. Modestly enhanced west-northwesterly mid/upper flow will conditionally support organized storm potential, though evolution of storms through the day and evening across the region remains somewhat uncertain. An MCS (or its remnant) may move from parts of IL/IN toward parts of the upper OH Valley through the day. Some reintensification of this system, and/or development along its trailing outflow, will be possible during the afternoon, with steepening low-level lapse rates and large PW supporting localized downbursts and damaging outflow winds. Additional development will be possible farther west near the outflow-influenced surface boundary, which could result in development of organized cells/clusters capable of damaging wind. Deep-layer shear will be marginally supportive of supercells, and some threat for hail and a tornado cannot be ruled out with any sustained supercells. Some severe threat could linger into tonight, as modest low-level warm advection helps to regenerate storms near and north of the effective surface boundary. ...Northern/central Plains... A mid/upper-level trough will remain in place over the Northwest and northern Rockies today. A surface trough will extend from eastern MT into the central High Plains this afternoon. East of the surface trough, a surface boundary initially draped across parts of NE/KS will attempt to lift north as a warm front, in the wake of early morning convection. Details regarding storm development and evolution remain rather uncertain across the region, but most guidance suggests at least isolated storm development will be possible near the surface trough and near/north of the effective warm front sometime this afternoon or evening. Effective shear of 40+ kt will support initial supercell development, with a threat of hail, isolated severe gusts, and possibly a tornado. Outflow consolidation could lead to some clustering and upscale growth, which would tend to move southeastward with a continued threat of at least localized severe gusts and isolated hail into tonight. ..Dean/Wendt.. 07/20/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1259 AM CDT Sun Jul 20 2025 Valid 201200Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE NORTHEAST...MIDWEST...OHIO VALLEY...AND NORTHERN PLAINS... ...SUMMARY... Strong to severe storms appear most likely later today into this evening across parts of the Northeast, Midwest and Ohio Valley, and northern Plains. ...Northeast... A deep upper-level trough over parts of Quebec and Ontario will dig southeastward through the day today. As this occurs, cooling aloft and increasing mid/upper-level flow is expected from northern parts of the Mid Atlantic into New England. Midlevel lapse rates will generally remain weak, but diurnal heating of a moist airmass will result in MLCAPE increasing to 1000-1500 J/kg along/ahead of a cold front. Scattered storm development is expected along/ahead of the front this afternoon, with effective shear of 35-45 kt sufficient for storm organization. A few supercells will be possible initially, with a threat for locally damaging wind, isolated hail, and possibly a tornado. With time, some storm clustering is possible, which could lead to locally more concentrated areas of wind damage. Some severe threat could linger into the early evening for near-coastal areas, before storms move offshore. ...Parts of the Mid MS and OH Valleys... Despite warm temperatures aloft, heating of a very moist airmass will support MLCAPE increasing into the 2000-3000 J/kg range this afternoon across parts of the mid MS and OH Valleys, near/south of a remnant surface boundary and any convective outflows. Modestly enhanced west-northwesterly mid/upper flow will conditionally support organized storm potential, though evolution of storms through the day and evening across the region remains somewhat uncertain. An MCS (or its remnant) may move from parts of IL/IN toward parts of the upper OH Valley through the day. Some reintensification of this system, and/or development along its trailing outflow, will be possible during the afternoon, with steepening low-level lapse rates and large PW supporting localized downbursts and damaging outflow winds. Additional development will be possible farther west near the outflow-influenced surface boundary, which could result in development of organized cells/clusters capable of damaging wind. Deep-layer shear will be marginally supportive of supercells, and some threat for hail and a tornado cannot be ruled out with any sustained supercells. Some severe threat could linger into tonight, as modest low-level warm advection helps to regenerate storms near and north of the effective surface boundary. ...Northern/central Plains... A mid/upper-level trough will remain in place over the Northwest and northern Rockies today. A surface trough will extend from eastern MT into the central High Plains this afternoon. East of the surface trough, a surface boundary initially draped across parts of NE/KS will attempt to lift north as a warm front, in the wake of early morning convection. Details regarding storm development and evolution remain rather uncertain across the region, but most guidance suggests at least isolated storm development will be possible near the surface trough and near/north of the effective warm front sometime this afternoon or evening. Effective shear of 40+ kt will support initial supercell development, with a threat of hail, isolated severe gusts, and possibly a tornado. Outflow consolidation could lead to some clustering and upscale growth, which would tend to move southeastward with a continued threat of at least localized severe gusts and isolated hail into tonight. ..Dean/Wendt.. 07/20/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1259 AM CDT Sun Jul 20 2025 Valid 201200Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE NORTHEAST...MIDWEST...OHIO VALLEY...AND NORTHERN PLAINS... ...SUMMARY... Strong to severe storms appear most likely later today into this evening across parts of the Northeast, Midwest and Ohio Valley, and northern Plains. ...Northeast... A deep upper-level trough over parts of Quebec and Ontario will dig southeastward through the day today. As this occurs, cooling aloft and increasing mid/upper-level flow is expected from northern parts of the Mid Atlantic into New England. Midlevel lapse rates will generally remain weak, but diurnal heating of a moist airmass will result in MLCAPE increasing to 1000-1500 J/kg along/ahead of a cold front. Scattered storm development is expected along/ahead of the front this afternoon, with effective shear of 35-45 kt sufficient for storm organization. A few supercells will be possible initially, with a threat for locally damaging wind, isolated hail, and possibly a tornado. With time, some storm clustering is possible, which could lead to locally more concentrated areas of wind damage. Some severe threat could linger into the early evening for near-coastal areas, before storms move offshore. ...Parts of the Mid MS and OH Valleys... Despite warm temperatures aloft, heating of a very moist airmass will support MLCAPE increasing into the 2000-3000 J/kg range this afternoon across parts of the mid MS and OH Valleys, near/south of a remnant surface boundary and any convective outflows. Modestly enhanced west-northwesterly mid/upper flow will conditionally support organized storm potential, though evolution of storms through the day and evening across the region remains somewhat uncertain. An MCS (or its remnant) may move from parts of IL/IN toward parts of the upper OH Valley through the day. Some reintensification of this system, and/or development along its trailing outflow, will be possible during the afternoon, with steepening low-level lapse rates and large PW supporting localized downbursts and damaging outflow winds. Additional development will be possible farther west near the outflow-influenced surface boundary, which could result in development of organized cells/clusters capable of damaging wind. Deep-layer shear will be marginally supportive of supercells, and some threat for hail and a tornado cannot be ruled out with any sustained supercells. Some severe threat could linger into tonight, as modest low-level warm advection helps to regenerate storms near and north of the effective surface boundary. ...Northern/central Plains... A mid/upper-level trough will remain in place over the Northwest and northern Rockies today. A surface trough will extend from eastern MT into the central High Plains this afternoon. East of the surface trough, a surface boundary initially draped across parts of NE/KS will attempt to lift north as a warm front, in the wake of early morning convection. Details regarding storm development and evolution remain rather uncertain across the region, but most guidance suggests at least isolated storm development will be possible near the surface trough and near/north of the effective warm front sometime this afternoon or evening. Effective shear of 40+ kt will support initial supercell development, with a threat of hail, isolated severe gusts, and possibly a tornado. Outflow consolidation could lead to some clustering and upscale growth, which would tend to move southeastward with a continued threat of at least localized severe gusts and isolated hail into tonight. ..Dean/Wendt.. 07/20/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1259 AM CDT Sun Jul 20 2025 Valid 201200Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE NORTHEAST...MIDWEST...OHIO VALLEY...AND NORTHERN PLAINS... ...SUMMARY... Strong to severe storms appear most likely later today into this evening across parts of the Northeast, Midwest and Ohio Valley, and northern Plains. ...Northeast... A deep upper-level trough over parts of Quebec and Ontario will dig southeastward through the day today. As this occurs, cooling aloft and increasing mid/upper-level flow is expected from northern parts of the Mid Atlantic into New England. Midlevel lapse rates will generally remain weak, but diurnal heating of a moist airmass will result in MLCAPE increasing to 1000-1500 J/kg along/ahead of a cold front. Scattered storm development is expected along/ahead of the front this afternoon, with effective shear of 35-45 kt sufficient for storm organization. A few supercells will be possible initially, with a threat for locally damaging wind, isolated hail, and possibly a tornado. With time, some storm clustering is possible, which could lead to locally more concentrated areas of wind damage. Some severe threat could linger into the early evening for near-coastal areas, before storms move offshore. ...Parts of the Mid MS and OH Valleys... Despite warm temperatures aloft, heating of a very moist airmass will support MLCAPE increasing into the 2000-3000 J/kg range this afternoon across parts of the mid MS and OH Valleys, near/south of a remnant surface boundary and any convective outflows. Modestly enhanced west-northwesterly mid/upper flow will conditionally support organized storm potential, though evolution of storms through the day and evening across the region remains somewhat uncertain. An MCS (or its remnant) may move from parts of IL/IN toward parts of the upper OH Valley through the day. Some reintensification of this system, and/or development along its trailing outflow, will be possible during the afternoon, with steepening low-level lapse rates and large PW supporting localized downbursts and damaging outflow winds. Additional development will be possible farther west near the outflow-influenced surface boundary, which could result in development of organized cells/clusters capable of damaging wind. Deep-layer shear will be marginally supportive of supercells, and some threat for hail and a tornado cannot be ruled out with any sustained supercells. Some severe threat could linger into tonight, as modest low-level warm advection helps to regenerate storms near and north of the effective surface boundary. ...Northern/central Plains... A mid/upper-level trough will remain in place over the Northwest and northern Rockies today. A surface trough will extend from eastern MT into the central High Plains this afternoon. East of the surface trough, a surface boundary initially draped across parts of NE/KS will attempt to lift north as a warm front, in the wake of early morning convection. Details regarding storm development and evolution remain rather uncertain across the region, but most guidance suggests at least isolated storm development will be possible near the surface trough and near/north of the effective warm front sometime this afternoon or evening. Effective shear of 40+ kt will support initial supercell development, with a threat of hail, isolated severe gusts, and possibly a tornado. Outflow consolidation could lead to some clustering and upscale growth, which would tend to move southeastward with a continued threat of at least localized severe gusts and isolated hail into tonight. ..Dean/Wendt.. 07/20/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1259 AM CDT Sun Jul 20 2025 Valid 201200Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE NORTHEAST...MIDWEST...OHIO VALLEY...AND NORTHERN PLAINS... ...SUMMARY... Strong to severe storms appear most likely later today into this evening across parts of the Northeast, Midwest and Ohio Valley, and northern Plains. ...Northeast... A deep upper-level trough over parts of Quebec and Ontario will dig southeastward through the day today. As this occurs, cooling aloft and increasing mid/upper-level flow is expected from northern parts of the Mid Atlantic into New England. Midlevel lapse rates will generally remain weak, but diurnal heating of a moist airmass will result in MLCAPE increasing to 1000-1500 J/kg along/ahead of a cold front. Scattered storm development is expected along/ahead of the front this afternoon, with effective shear of 35-45 kt sufficient for storm organization. A few supercells will be possible initially, with a threat for locally damaging wind, isolated hail, and possibly a tornado. With time, some storm clustering is possible, which could lead to locally more concentrated areas of wind damage. Some severe threat could linger into the early evening for near-coastal areas, before storms move offshore. ...Parts of the Mid MS and OH Valleys... Despite warm temperatures aloft, heating of a very moist airmass will support MLCAPE increasing into the 2000-3000 J/kg range this afternoon across parts of the mid MS and OH Valleys, near/south of a remnant surface boundary and any convective outflows. Modestly enhanced west-northwesterly mid/upper flow will conditionally support organized storm potential, though evolution of storms through the day and evening across the region remains somewhat uncertain. An MCS (or its remnant) may move from parts of IL/IN toward parts of the upper OH Valley through the day. Some reintensification of this system, and/or development along its trailing outflow, will be possible during the afternoon, with steepening low-level lapse rates and large PW supporting localized downbursts and damaging outflow winds. Additional development will be possible farther west near the outflow-influenced surface boundary, which could result in development of organized cells/clusters capable of damaging wind. Deep-layer shear will be marginally supportive of supercells, and some threat for hail and a tornado cannot be ruled out with any sustained supercells. Some severe threat could linger into tonight, as modest low-level warm advection helps to regenerate storms near and north of the effective surface boundary. ...Northern/central Plains... A mid/upper-level trough will remain in place over the Northwest and northern Rockies today. A surface trough will extend from eastern MT into the central High Plains this afternoon. East of the surface trough, a surface boundary initially draped across parts of NE/KS will attempt to lift north as a warm front, in the wake of early morning convection. Details regarding storm development and evolution remain rather uncertain across the region, but most guidance suggests at least isolated storm development will be possible near the surface trough and near/north of the effective warm front sometime this afternoon or evening. Effective shear of 40+ kt will support initial supercell development, with a threat of hail, isolated severe gusts, and possibly a tornado. Outflow consolidation could lead to some clustering and upscale growth, which would tend to move southeastward with a continued threat of at least localized severe gusts and isolated hail into tonight. ..Dean/Wendt.. 07/20/2025 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1249 AM CDT Sun Jul 20 2025 Valid 211200Z - 221200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF NORTHWEST NEVADA... ...Synopsis... The upper-level trough in the Northwest will continue to dig southward through the day on Monday. Some increase in the mid-level jet is expected to occur from northwest Nevada into the northern Rockies. A surface low will deepen in the northern Great Basin. ...Central/northern Great Basin into western Wyoming... A broad area of elevated fire weather conditions are expected across these regions. Surface winds will reach 15-20 mph in most locations, though areas of higher speeds are possible in terrain-favored areas. Single digit RH is possible in parts of central/northern Nevada, but 15-20% will be more common elsewhere. Critical conditions are expected along the Sierra Front in northwest Nevada. Here, the mid-level jet will enhance winds aloft during the afternoon. While the surface low will not be overly deep, the combination of these factors will support winds around 20 mph near the terrain. Gusts to around 30 mph are also possible. There is some potential for high level clouds to limit RH reductions. Even with some of these marginal factors, wind speeds should be sufficient to promote rapid fire spread in fuels that are very dry (ERCs above 90th percentile). ..Wendt.. 07/20/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more