Severe Storms

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0157 AM CDT Thu Aug 21 2025 Valid 221200Z - 231200Z ...Synopsis... As the upper ridge persist over the West, several subtropical perturbations will arrive from the south, ushering in another surge of monsoon moisture. Isolated thunderstorms are likely across the southern Sierra and into parts of the Great Basin Friday. With very warm surface temperatures and dry sub-cloud layers, little wetting rainfall is expected. This should allow for isolated dry lightning atop receptive fuel mainly over portions of California and Nevada where fuels are most receptive. Some localized dry and breezy winds may also occur outside of the thunderstorms over the central great Basin Friday. Over the southern Great Basin and Southwest, higher PWATs near 1 inch are expected. Isolated to widely scattered thunderstorms are likely through the afternoon. However, a wetter storm mode is more probable across northern Arizona, southern Utah and western Colorado, where fuels are also less receptive. ...California... Isolated thunderstorms are likely in portions of southern California mountains and over the Mojave. A wetter mode is expected with max PWATs near 1.2 to 1.3 inches and little in the way of steering flow. However, cloud bases are likely to be over 3-km with a hot/dry sub-cloud layer limiting some precipitation efficiency. Sporadic dry strikes re possible given the degree of extreme heat and dry fuels but coverage is not expected to reach 10% or greater. Additionally, very hot, dry and unstable conditions may support plume dominated fire behavior with existing large fires. ..Lyons.. 08/21/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0156 AM CDT Thu Aug 21 2025 Valid 211200Z - 221200Z ...Synopsis... A strong ridge of high pressure will remain in place over much of the west today and tonight. Beneath the ridge, hot conditions are expected with near record high temperatures. Additionally, monsoon moisture will move northward along the western edge of the ridge supporting shower and thunderstorm chances across portions of the West. ...Great Basin and northern Rockies... At the nose of the monsoon surge, PWAT values are likely to be between 0.5-0.8" with a dry sub-cloud layer and steep low-level lapse rates over portions of Nevada, into Idaho and Wyoming. Storm development is expected along the higher terrain and near a stalled/weakening cold front by early afternoon. Despite slower storm motions and isolated coverage, little wetting rainfall is expected from any of these storms. This should support isolated dry thunderstorm potential with dry fuels in place. Elsewhere, localized dry and breezy conditions are possible over parts of the Snake River Plain, southern Great Basin and northern Colorado this afternoon. While occasional gusts to 15-20 mph overlapping with low RH cannot be ruled out, the coverage of elevated fire-weather potential should remain low/localized. ...California... In addition to the risk for very isolated thunderstorms, hot, dry and unstable conditions are expected across much of the west and southern CA. Locally breezy winds are possible near a thermal trough with very warm temperatures expected over much of the West. Steep mid-level lapse rates and very weak buoyancy could also support some plume dominated fire growth and pyroconvection near large active fires. ..Lyons.. 08/21/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0156 AM CDT Thu Aug 21 2025 Valid 211200Z - 221200Z ...Synopsis... A strong ridge of high pressure will remain in place over much of the west today and tonight. Beneath the ridge, hot conditions are expected with near record high temperatures. Additionally, monsoon moisture will move northward along the western edge of the ridge supporting shower and thunderstorm chances across portions of the West. ...Great Basin and northern Rockies... At the nose of the monsoon surge, PWAT values are likely to be between 0.5-0.8" with a dry sub-cloud layer and steep low-level lapse rates over portions of Nevada, into Idaho and Wyoming. Storm development is expected along the higher terrain and near a stalled/weakening cold front by early afternoon. Despite slower storm motions and isolated coverage, little wetting rainfall is expected from any of these storms. This should support isolated dry thunderstorm potential with dry fuels in place. Elsewhere, localized dry and breezy conditions are possible over parts of the Snake River Plain, southern Great Basin and northern Colorado this afternoon. While occasional gusts to 15-20 mph overlapping with low RH cannot be ruled out, the coverage of elevated fire-weather potential should remain low/localized. ...California... In addition to the risk for very isolated thunderstorms, hot, dry and unstable conditions are expected across much of the west and southern CA. Locally breezy winds are possible near a thermal trough with very warm temperatures expected over much of the West. Steep mid-level lapse rates and very weak buoyancy could also support some plume dominated fire growth and pyroconvection near large active fires. ..Lyons.. 08/21/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0156 AM CDT Thu Aug 21 2025 Valid 211200Z - 221200Z ...Synopsis... A strong ridge of high pressure will remain in place over much of the west today and tonight. Beneath the ridge, hot conditions are expected with near record high temperatures. Additionally, monsoon moisture will move northward along the western edge of the ridge supporting shower and thunderstorm chances across portions of the West. ...Great Basin and northern Rockies... At the nose of the monsoon surge, PWAT values are likely to be between 0.5-0.8" with a dry sub-cloud layer and steep low-level lapse rates over portions of Nevada, into Idaho and Wyoming. Storm development is expected along the higher terrain and near a stalled/weakening cold front by early afternoon. Despite slower storm motions and isolated coverage, little wetting rainfall is expected from any of these storms. This should support isolated dry thunderstorm potential with dry fuels in place. Elsewhere, localized dry and breezy conditions are possible over parts of the Snake River Plain, southern Great Basin and northern Colorado this afternoon. While occasional gusts to 15-20 mph overlapping with low RH cannot be ruled out, the coverage of elevated fire-weather potential should remain low/localized. ...California... In addition to the risk for very isolated thunderstorms, hot, dry and unstable conditions are expected across much of the west and southern CA. Locally breezy winds are possible near a thermal trough with very warm temperatures expected over much of the West. Steep mid-level lapse rates and very weak buoyancy could also support some plume dominated fire growth and pyroconvection near large active fires. ..Lyons.. 08/21/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0156 AM CDT Thu Aug 21 2025 Valid 211200Z - 221200Z ...Synopsis... A strong ridge of high pressure will remain in place over much of the west today and tonight. Beneath the ridge, hot conditions are expected with near record high temperatures. Additionally, monsoon moisture will move northward along the western edge of the ridge supporting shower and thunderstorm chances across portions of the West. ...Great Basin and northern Rockies... At the nose of the monsoon surge, PWAT values are likely to be between 0.5-0.8" with a dry sub-cloud layer and steep low-level lapse rates over portions of Nevada, into Idaho and Wyoming. Storm development is expected along the higher terrain and near a stalled/weakening cold front by early afternoon. Despite slower storm motions and isolated coverage, little wetting rainfall is expected from any of these storms. This should support isolated dry thunderstorm potential with dry fuels in place. Elsewhere, localized dry and breezy conditions are possible over parts of the Snake River Plain, southern Great Basin and northern Colorado this afternoon. While occasional gusts to 15-20 mph overlapping with low RH cannot be ruled out, the coverage of elevated fire-weather potential should remain low/localized. ...California... In addition to the risk for very isolated thunderstorms, hot, dry and unstable conditions are expected across much of the west and southern CA. Locally breezy winds are possible near a thermal trough with very warm temperatures expected over much of the West. Steep mid-level lapse rates and very weak buoyancy could also support some plume dominated fire growth and pyroconvection near large active fires. ..Lyons.. 08/21/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0156 AM CDT Thu Aug 21 2025 Valid 211200Z - 221200Z ...Synopsis... A strong ridge of high pressure will remain in place over much of the west today and tonight. Beneath the ridge, hot conditions are expected with near record high temperatures. Additionally, monsoon moisture will move northward along the western edge of the ridge supporting shower and thunderstorm chances across portions of the West. ...Great Basin and northern Rockies... At the nose of the monsoon surge, PWAT values are likely to be between 0.5-0.8" with a dry sub-cloud layer and steep low-level lapse rates over portions of Nevada, into Idaho and Wyoming. Storm development is expected along the higher terrain and near a stalled/weakening cold front by early afternoon. Despite slower storm motions and isolated coverage, little wetting rainfall is expected from any of these storms. This should support isolated dry thunderstorm potential with dry fuels in place. Elsewhere, localized dry and breezy conditions are possible over parts of the Snake River Plain, southern Great Basin and northern Colorado this afternoon. While occasional gusts to 15-20 mph overlapping with low RH cannot be ruled out, the coverage of elevated fire-weather potential should remain low/localized. ...California... In addition to the risk for very isolated thunderstorms, hot, dry and unstable conditions are expected across much of the west and southern CA. Locally breezy winds are possible near a thermal trough with very warm temperatures expected over much of the West. Steep mid-level lapse rates and very weak buoyancy could also support some plume dominated fire growth and pyroconvection near large active fires. ..Lyons.. 08/21/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1258 AM CDT Thu Aug 21 2025 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE CENTRAL/NORTHERN HIGH PLAINS INTO THE UPPER MIDWEST... ...SUMMARY... Strong to locally severe thunderstorms are possible Friday from parts of the central and northern High Plains into the Upper Midwest. ...Northern/central High Plains into the Upper Midwest... A mid/upper-level cyclone and attendant surface low is forecast to move eastward across parts of MB and northwest ON Friday. An outflow-influenced surface boundary may drift southeastward across the central Plains into the Upper Midwest during the day, while a strong trailing cold front begins to move across the Dakotas and northern MN. The greatest relative confidence in diurnal storm development is within the post-frontal regime across parts of eastern WY/CO. Steep midlevel lapse rates, moderate buoyancy, and relatively elongated hodographs will support potential for strong to potential severe storm development, initially near the higher terrain. Isolated hail and locally gusty winds could accompany the strongest cells. While uncertain, there is some potential for storm clustering during the evening, which could result in some severe potential spreading into parts of western NE and perhaps northwest KS Friday night. Farther east, confidence is low regarding the details of convective evolution from central/eastern NE/SD into the Upper Midwest. In general, a zone of moderate buoyancy, with MLCAPE of 1000-2000 J/kg (locally higher), is expected to develop by afternoon near/north of the leading surface boundary, and ahead of the trailing cold front. Gradually strengthening midlevel flow is forecast to provide modestly favorable effective shear (25-35 kt). There may be some potential for early-day convection to intensify as it moves through a destabilizing environment during the afternoon. Otherwise, isolated to widely scattered storm development will be possible during the afternoon/evening within the zone of favorable moisture/instability, with a threat of locally damaging gusts and isolated hail. ...Arizona... Similar to D1/Thursday, scattered storm development will be possible Friday afternoon across higher terrain areas of AZ, with easterly flow potentially steering storms (or at least their remnant outflows) into the lower deserts with time. Isolated damaging wind cannot be ruled out with this activity, given the presence of a hot and well-mixed environment, though it remains uncertain if more substantial storm clustering and outflow consolidation will evolve during the evening. ..Dean.. 08/21/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1258 AM CDT Thu Aug 21 2025 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE CENTRAL/NORTHERN HIGH PLAINS INTO THE UPPER MIDWEST... ...SUMMARY... Strong to locally severe thunderstorms are possible Friday from parts of the central and northern High Plains into the Upper Midwest. ...Northern/central High Plains into the Upper Midwest... A mid/upper-level cyclone and attendant surface low is forecast to move eastward across parts of MB and northwest ON Friday. An outflow-influenced surface boundary may drift southeastward across the central Plains into the Upper Midwest during the day, while a strong trailing cold front begins to move across the Dakotas and northern MN. The greatest relative confidence in diurnal storm development is within the post-frontal regime across parts of eastern WY/CO. Steep midlevel lapse rates, moderate buoyancy, and relatively elongated hodographs will support potential for strong to potential severe storm development, initially near the higher terrain. Isolated hail and locally gusty winds could accompany the strongest cells. While uncertain, there is some potential for storm clustering during the evening, which could result in some severe potential spreading into parts of western NE and perhaps northwest KS Friday night. Farther east, confidence is low regarding the details of convective evolution from central/eastern NE/SD into the Upper Midwest. In general, a zone of moderate buoyancy, with MLCAPE of 1000-2000 J/kg (locally higher), is expected to develop by afternoon near/north of the leading surface boundary, and ahead of the trailing cold front. Gradually strengthening midlevel flow is forecast to provide modestly favorable effective shear (25-35 kt). There may be some potential for early-day convection to intensify as it moves through a destabilizing environment during the afternoon. Otherwise, isolated to widely scattered storm development will be possible during the afternoon/evening within the zone of favorable moisture/instability, with a threat of locally damaging gusts and isolated hail. ...Arizona... Similar to D1/Thursday, scattered storm development will be possible Friday afternoon across higher terrain areas of AZ, with easterly flow potentially steering storms (or at least their remnant outflows) into the lower deserts with time. Isolated damaging wind cannot be ruled out with this activity, given the presence of a hot and well-mixed environment, though it remains uncertain if more substantial storm clustering and outflow consolidation will evolve during the evening. ..Dean.. 08/21/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1258 AM CDT Thu Aug 21 2025 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE CENTRAL/NORTHERN HIGH PLAINS INTO THE UPPER MIDWEST... ...SUMMARY... Strong to locally severe thunderstorms are possible Friday from parts of the central and northern High Plains into the Upper Midwest. ...Northern/central High Plains into the Upper Midwest... A mid/upper-level cyclone and attendant surface low is forecast to move eastward across parts of MB and northwest ON Friday. An outflow-influenced surface boundary may drift southeastward across the central Plains into the Upper Midwest during the day, while a strong trailing cold front begins to move across the Dakotas and northern MN. The greatest relative confidence in diurnal storm development is within the post-frontal regime across parts of eastern WY/CO. Steep midlevel lapse rates, moderate buoyancy, and relatively elongated hodographs will support potential for strong to potential severe storm development, initially near the higher terrain. Isolated hail and locally gusty winds could accompany the strongest cells. While uncertain, there is some potential for storm clustering during the evening, which could result in some severe potential spreading into parts of western NE and perhaps northwest KS Friday night. Farther east, confidence is low regarding the details of convective evolution from central/eastern NE/SD into the Upper Midwest. In general, a zone of moderate buoyancy, with MLCAPE of 1000-2000 J/kg (locally higher), is expected to develop by afternoon near/north of the leading surface boundary, and ahead of the trailing cold front. Gradually strengthening midlevel flow is forecast to provide modestly favorable effective shear (25-35 kt). There may be some potential for early-day convection to intensify as it moves through a destabilizing environment during the afternoon. Otherwise, isolated to widely scattered storm development will be possible during the afternoon/evening within the zone of favorable moisture/instability, with a threat of locally damaging gusts and isolated hail. ...Arizona... Similar to D1/Thursday, scattered storm development will be possible Friday afternoon across higher terrain areas of AZ, with easterly flow potentially steering storms (or at least their remnant outflows) into the lower deserts with time. Isolated damaging wind cannot be ruled out with this activity, given the presence of a hot and well-mixed environment, though it remains uncertain if more substantial storm clustering and outflow consolidation will evolve during the evening. ..Dean.. 08/21/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1258 AM CDT Thu Aug 21 2025 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE CENTRAL/NORTHERN HIGH PLAINS INTO THE UPPER MIDWEST... ...SUMMARY... Strong to locally severe thunderstorms are possible Friday from parts of the central and northern High Plains into the Upper Midwest. ...Northern/central High Plains into the Upper Midwest... A mid/upper-level cyclone and attendant surface low is forecast to move eastward across parts of MB and northwest ON Friday. An outflow-influenced surface boundary may drift southeastward across the central Plains into the Upper Midwest during the day, while a strong trailing cold front begins to move across the Dakotas and northern MN. The greatest relative confidence in diurnal storm development is within the post-frontal regime across parts of eastern WY/CO. Steep midlevel lapse rates, moderate buoyancy, and relatively elongated hodographs will support potential for strong to potential severe storm development, initially near the higher terrain. Isolated hail and locally gusty winds could accompany the strongest cells. While uncertain, there is some potential for storm clustering during the evening, which could result in some severe potential spreading into parts of western NE and perhaps northwest KS Friday night. Farther east, confidence is low regarding the details of convective evolution from central/eastern NE/SD into the Upper Midwest. In general, a zone of moderate buoyancy, with MLCAPE of 1000-2000 J/kg (locally higher), is expected to develop by afternoon near/north of the leading surface boundary, and ahead of the trailing cold front. Gradually strengthening midlevel flow is forecast to provide modestly favorable effective shear (25-35 kt). There may be some potential for early-day convection to intensify as it moves through a destabilizing environment during the afternoon. Otherwise, isolated to widely scattered storm development will be possible during the afternoon/evening within the zone of favorable moisture/instability, with a threat of locally damaging gusts and isolated hail. ...Arizona... Similar to D1/Thursday, scattered storm development will be possible Friday afternoon across higher terrain areas of AZ, with easterly flow potentially steering storms (or at least their remnant outflows) into the lower deserts with time. Isolated damaging wind cannot be ruled out with this activity, given the presence of a hot and well-mixed environment, though it remains uncertain if more substantial storm clustering and outflow consolidation will evolve during the evening. ..Dean.. 08/21/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1258 AM CDT Thu Aug 21 2025 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE CENTRAL/NORTHERN HIGH PLAINS INTO THE UPPER MIDWEST... ...SUMMARY... Strong to locally severe thunderstorms are possible Friday from parts of the central and northern High Plains into the Upper Midwest. ...Northern/central High Plains into the Upper Midwest... A mid/upper-level cyclone and attendant surface low is forecast to move eastward across parts of MB and northwest ON Friday. An outflow-influenced surface boundary may drift southeastward across the central Plains into the Upper Midwest during the day, while a strong trailing cold front begins to move across the Dakotas and northern MN. The greatest relative confidence in diurnal storm development is within the post-frontal regime across parts of eastern WY/CO. Steep midlevel lapse rates, moderate buoyancy, and relatively elongated hodographs will support potential for strong to potential severe storm development, initially near the higher terrain. Isolated hail and locally gusty winds could accompany the strongest cells. While uncertain, there is some potential for storm clustering during the evening, which could result in some severe potential spreading into parts of western NE and perhaps northwest KS Friday night. Farther east, confidence is low regarding the details of convective evolution from central/eastern NE/SD into the Upper Midwest. In general, a zone of moderate buoyancy, with MLCAPE of 1000-2000 J/kg (locally higher), is expected to develop by afternoon near/north of the leading surface boundary, and ahead of the trailing cold front. Gradually strengthening midlevel flow is forecast to provide modestly favorable effective shear (25-35 kt). There may be some potential for early-day convection to intensify as it moves through a destabilizing environment during the afternoon. Otherwise, isolated to widely scattered storm development will be possible during the afternoon/evening within the zone of favorable moisture/instability, with a threat of locally damaging gusts and isolated hail. ...Arizona... Similar to D1/Thursday, scattered storm development will be possible Friday afternoon across higher terrain areas of AZ, with easterly flow potentially steering storms (or at least their remnant outflows) into the lower deserts with time. Isolated damaging wind cannot be ruled out with this activity, given the presence of a hot and well-mixed environment, though it remains uncertain if more substantial storm clustering and outflow consolidation will evolve during the evening. ..Dean.. 08/21/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1240 AM CDT Thu Aug 21 2025 Valid 211200Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN PLAINS INTO MINNESOTA... ...SUMMARY... Isolated severe thunderstorms are possible across portions of the northern Plains into Minnesota later this afternoon and evening. Severe gusts and hail are the primary concern. ...Northern Plains/Minnesota... Northern Plains upper ridge will flatten considerably during the day1 period as heights fall ahead of a digging upper trough. Early this morning, water-vapor imagery depicts the short wave along the BC/AB border. This feature is forecast to advance into eastern SK by 22/00z before it advances to the SK/MB border by the end of the period. While the primary large-scale forcing will be noted north of the international border, high-level diffluent flow will be noted across the eastern Dakotas/Minnesota - coincident with the front that will be draped across this region at peak heating. Latest model guidance suggests a plume of steep low-level lapse rates will extend across the central Plains into south central SD where surface temperatures are expected to soar through the mid 90s. The majority of CAM guidance struggles to develop more than isolated convection along the surface front - possibly due to the aforementioned weak large-scale ascent. In addition, LLJ does not strengthen appreciably ahead of the boundary, and this also supports isolated coverage. Notably, during the overnight hours, robust convection may develop within a weak warm advection zone across eastern SD into southwest MN - possibly in response to a bit more forcing along the southern fringe of the digging upper trough after 06z. Wind/hail will be the primary threats with both the late-afternoon and overnight convection. Isolated storm coverage favors MRGL Risk at this time. Upstream, surface front will trail across the southern Black Hills into central WY by peak heating. Northeast upslope flow should encourage convection to develop across the higher terrain by late afternoon. While forecast buoyancy is not expected to be particularly strong, adequate deep-layer shear will prove supportive of organized updrafts that could generate hail/wind. ..Darrow/Lyons.. 08/21/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1240 AM CDT Thu Aug 21 2025 Valid 211200Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN PLAINS INTO MINNESOTA... ...SUMMARY... Isolated severe thunderstorms are possible across portions of the northern Plains into Minnesota later this afternoon and evening. Severe gusts and hail are the primary concern. ...Northern Plains/Minnesota... Northern Plains upper ridge will flatten considerably during the day1 period as heights fall ahead of a digging upper trough. Early this morning, water-vapor imagery depicts the short wave along the BC/AB border. This feature is forecast to advance into eastern SK by 22/00z before it advances to the SK/MB border by the end of the period. While the primary large-scale forcing will be noted north of the international border, high-level diffluent flow will be noted across the eastern Dakotas/Minnesota - coincident with the front that will be draped across this region at peak heating. Latest model guidance suggests a plume of steep low-level lapse rates will extend across the central Plains into south central SD where surface temperatures are expected to soar through the mid 90s. The majority of CAM guidance struggles to develop more than isolated convection along the surface front - possibly due to the aforementioned weak large-scale ascent. In addition, LLJ does not strengthen appreciably ahead of the boundary, and this also supports isolated coverage. Notably, during the overnight hours, robust convection may develop within a weak warm advection zone across eastern SD into southwest MN - possibly in response to a bit more forcing along the southern fringe of the digging upper trough after 06z. Wind/hail will be the primary threats with both the late-afternoon and overnight convection. Isolated storm coverage favors MRGL Risk at this time. Upstream, surface front will trail across the southern Black Hills into central WY by peak heating. Northeast upslope flow should encourage convection to develop across the higher terrain by late afternoon. While forecast buoyancy is not expected to be particularly strong, adequate deep-layer shear will prove supportive of organized updrafts that could generate hail/wind. ..Darrow/Lyons.. 08/21/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1240 AM CDT Thu Aug 21 2025 Valid 211200Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN PLAINS INTO MINNESOTA... ...SUMMARY... Isolated severe thunderstorms are possible across portions of the northern Plains into Minnesota later this afternoon and evening. Severe gusts and hail are the primary concern. ...Northern Plains/Minnesota... Northern Plains upper ridge will flatten considerably during the day1 period as heights fall ahead of a digging upper trough. Early this morning, water-vapor imagery depicts the short wave along the BC/AB border. This feature is forecast to advance into eastern SK by 22/00z before it advances to the SK/MB border by the end of the period. While the primary large-scale forcing will be noted north of the international border, high-level diffluent flow will be noted across the eastern Dakotas/Minnesota - coincident with the front that will be draped across this region at peak heating. Latest model guidance suggests a plume of steep low-level lapse rates will extend across the central Plains into south central SD where surface temperatures are expected to soar through the mid 90s. The majority of CAM guidance struggles to develop more than isolated convection along the surface front - possibly due to the aforementioned weak large-scale ascent. In addition, LLJ does not strengthen appreciably ahead of the boundary, and this also supports isolated coverage. Notably, during the overnight hours, robust convection may develop within a weak warm advection zone across eastern SD into southwest MN - possibly in response to a bit more forcing along the southern fringe of the digging upper trough after 06z. Wind/hail will be the primary threats with both the late-afternoon and overnight convection. Isolated storm coverage favors MRGL Risk at this time. Upstream, surface front will trail across the southern Black Hills into central WY by peak heating. Northeast upslope flow should encourage convection to develop across the higher terrain by late afternoon. While forecast buoyancy is not expected to be particularly strong, adequate deep-layer shear will prove supportive of organized updrafts that could generate hail/wind. ..Darrow/Lyons.. 08/21/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1240 AM CDT Thu Aug 21 2025 Valid 211200Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN PLAINS INTO MINNESOTA... ...SUMMARY... Isolated severe thunderstorms are possible across portions of the northern Plains into Minnesota later this afternoon and evening. Severe gusts and hail are the primary concern. ...Northern Plains/Minnesota... Northern Plains upper ridge will flatten considerably during the day1 period as heights fall ahead of a digging upper trough. Early this morning, water-vapor imagery depicts the short wave along the BC/AB border. This feature is forecast to advance into eastern SK by 22/00z before it advances to the SK/MB border by the end of the period. While the primary large-scale forcing will be noted north of the international border, high-level diffluent flow will be noted across the eastern Dakotas/Minnesota - coincident with the front that will be draped across this region at peak heating. Latest model guidance suggests a plume of steep low-level lapse rates will extend across the central Plains into south central SD where surface temperatures are expected to soar through the mid 90s. The majority of CAM guidance struggles to develop more than isolated convection along the surface front - possibly due to the aforementioned weak large-scale ascent. In addition, LLJ does not strengthen appreciably ahead of the boundary, and this also supports isolated coverage. Notably, during the overnight hours, robust convection may develop within a weak warm advection zone across eastern SD into southwest MN - possibly in response to a bit more forcing along the southern fringe of the digging upper trough after 06z. Wind/hail will be the primary threats with both the late-afternoon and overnight convection. Isolated storm coverage favors MRGL Risk at this time. Upstream, surface front will trail across the southern Black Hills into central WY by peak heating. Northeast upslope flow should encourage convection to develop across the higher terrain by late afternoon. While forecast buoyancy is not expected to be particularly strong, adequate deep-layer shear will prove supportive of organized updrafts that could generate hail/wind. ..Darrow/Lyons.. 08/21/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1240 AM CDT Thu Aug 21 2025 Valid 211200Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN PLAINS INTO MINNESOTA... ...SUMMARY... Isolated severe thunderstorms are possible across portions of the northern Plains into Minnesota later this afternoon and evening. Severe gusts and hail are the primary concern. ...Northern Plains/Minnesota... Northern Plains upper ridge will flatten considerably during the day1 period as heights fall ahead of a digging upper trough. Early this morning, water-vapor imagery depicts the short wave along the BC/AB border. This feature is forecast to advance into eastern SK by 22/00z before it advances to the SK/MB border by the end of the period. While the primary large-scale forcing will be noted north of the international border, high-level diffluent flow will be noted across the eastern Dakotas/Minnesota - coincident with the front that will be draped across this region at peak heating. Latest model guidance suggests a plume of steep low-level lapse rates will extend across the central Plains into south central SD where surface temperatures are expected to soar through the mid 90s. The majority of CAM guidance struggles to develop more than isolated convection along the surface front - possibly due to the aforementioned weak large-scale ascent. In addition, LLJ does not strengthen appreciably ahead of the boundary, and this also supports isolated coverage. Notably, during the overnight hours, robust convection may develop within a weak warm advection zone across eastern SD into southwest MN - possibly in response to a bit more forcing along the southern fringe of the digging upper trough after 06z. Wind/hail will be the primary threats with both the late-afternoon and overnight convection. Isolated storm coverage favors MRGL Risk at this time. Upstream, surface front will trail across the southern Black Hills into central WY by peak heating. Northeast upslope flow should encourage convection to develop across the higher terrain by late afternoon. While forecast buoyancy is not expected to be particularly strong, adequate deep-layer shear will prove supportive of organized updrafts that could generate hail/wind. ..Darrow/Lyons.. 08/21/2025 Read more

MD 1997 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF NORTH-CENTRAL INTO NORTHEASTERN MONTANA
Mesoscale Discussion 1997 NWS Storm Prediction Center Norman OK 0702 PM CDT Wed Aug 20 2025 Areas affected...portions of north-central into northeastern Montana Concerning...Severe potential...Watch unlikely Valid 210002Z - 210230Z Probability of Watch Issuance...20 percent SUMMARY...Isolated supercells should persist across portions of north-central into northeastern Montana over the next few hours, accompanied by a severe hail and wind threat. DISCUSSION...Two dominant, discrete supercells have materialized over the past few hours, with severe gusts reported and MRMS mosaic MESH data suggesting hail over 1.5 inches in diameter occurring. These storms are rapidly progressing eastward amid strong mid- to upper-level flow associated with a 300 mb jet streak. 40 kts of effective bulk shear is present, and is coinciding with 1000-1500 J/kg MLCAPE, driven mainly by 8.5+ C/km mid-level lapse rates. Given this environment, supercells should continue eastward for at least a few more hours, with severe gusts potentially reaching 75 mph, along with 1.5+ inch diameter hail. Despite the severe conditions associated with these storms, the severe threat should remain isolated and localized, given the low coverage of storms. As such, a WW issuance is not currently anticipated. ..Squitieri/Mosier.. 08/21/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...GGW...TFX... LAT...LON 47150948 47330982 47670998 48460990 48840937 48960660 48640613 48210595 47650610 47230650 47070722 47080819 47090889 47150948 MOST PROBABLE PEAK WIND GUST...65-80 MPH MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0739 PM CDT Wed Aug 20 2025 Valid 210100Z - 211200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF CENTRAL MONTANA INTO NORTHERN NORTH DAKOTA AND ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY... ...SUMMARY... Isolated severe thunderstorms are possible from central Montana into northern North Dakota tonight. A few wind gusts may also be noted with storms over the lower Mississippi Valley early this evening. ...01z Update... Early-evening water-vapor imagery depicts an upper trough extending across southeast BC into the northern Rockies. This feature is forecast to advance to near the AB/SK border by the end of the period, with modest mid-level height falls expected across northeast MT into ND. As 500mb speed max strengthens over southern SK later tonight some increase in LLJ should be noted across western ND - just ahead of the progressive surface front. Isolated robust convection has developed ahead of the short wave from southwest SK into central MT. This activity may continue to generate gusty winds and hail, but new updrafts are expected downstream across western ND with time. Vis imagery suggests high-based updrafts are deepening across southeast MT into southwest ND, and isolated severe may ultimately evolve along the northern edge of this steep lapse rate plume, immediately ahead of the front. Boundary-layer heating was instrumental in scattered-widespread convection across the northern Gulf States this afternoon. While considerable convective overturning has occurred, a pocket of modest instability persists across much of LA. Cluster of strong-locally severe thunderstorms will drift south across this region over the next several hours. Boundary-layer cooling will negate updraft intensity by mid evening. ..Darrow.. 08/21/2025 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0739 PM CDT Wed Aug 20 2025 Valid 210100Z - 211200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF CENTRAL MONTANA INTO NORTHERN NORTH DAKOTA AND ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY... ...SUMMARY... Isolated severe thunderstorms are possible from central Montana into northern North Dakota tonight. A few wind gusts may also be noted with storms over the lower Mississippi Valley early this evening. ...01z Update... Early-evening water-vapor imagery depicts an upper trough extending across southeast BC into the northern Rockies. This feature is forecast to advance to near the AB/SK border by the end of the period, with modest mid-level height falls expected across northeast MT into ND. As 500mb speed max strengthens over southern SK later tonight some increase in LLJ should be noted across western ND - just ahead of the progressive surface front. Isolated robust convection has developed ahead of the short wave from southwest SK into central MT. This activity may continue to generate gusty winds and hail, but new updrafts are expected downstream across western ND with time. Vis imagery suggests high-based updrafts are deepening across southeast MT into southwest ND, and isolated severe may ultimately evolve along the northern edge of this steep lapse rate plume, immediately ahead of the front. Boundary-layer heating was instrumental in scattered-widespread convection across the northern Gulf States this afternoon. While considerable convective overturning has occurred, a pocket of modest instability persists across much of LA. Cluster of strong-locally severe thunderstorms will drift south across this region over the next several hours. Boundary-layer cooling will negate updraft intensity by mid evening. ..Darrow.. 08/21/2025 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0739 PM CDT Wed Aug 20 2025 Valid 210100Z - 211200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF CENTRAL MONTANA INTO NORTHERN NORTH DAKOTA AND ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY... ...SUMMARY... Isolated severe thunderstorms are possible from central Montana into northern North Dakota tonight. A few wind gusts may also be noted with storms over the lower Mississippi Valley early this evening. ...01z Update... Early-evening water-vapor imagery depicts an upper trough extending across southeast BC into the northern Rockies. This feature is forecast to advance to near the AB/SK border by the end of the period, with modest mid-level height falls expected across northeast MT into ND. As 500mb speed max strengthens over southern SK later tonight some increase in LLJ should be noted across western ND - just ahead of the progressive surface front. Isolated robust convection has developed ahead of the short wave from southwest SK into central MT. This activity may continue to generate gusty winds and hail, but new updrafts are expected downstream across western ND with time. Vis imagery suggests high-based updrafts are deepening across southeast MT into southwest ND, and isolated severe may ultimately evolve along the northern edge of this steep lapse rate plume, immediately ahead of the front. Boundary-layer heating was instrumental in scattered-widespread convection across the northern Gulf States this afternoon. While considerable convective overturning has occurred, a pocket of modest instability persists across much of LA. Cluster of strong-locally severe thunderstorms will drift south across this region over the next several hours. Boundary-layer cooling will negate updraft intensity by mid evening. ..Darrow.. 08/21/2025 Read more