Severe Storms

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 AM CDT Thu Aug 21 2025 Valid 231200Z - 241200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorm potential currently appears low on Saturday. ...Parts of the Midwest/Lower Great Lakes into the south-central Plains... A mid/upper-level trough is forecast to gradually amplify across the north-central and eastern CONUS Saturday. A cold front will continue moving southeastward across parts of the Great Lakes/Midwest into the south-central Plains. Midlevel lapse rates along/ahead of the front will generally be weak, but low-level moisture will be sufficient for moderate buoyancy by afternoon. The strongest deep-layer flow/shear will located across parts of the central Great Lakes, but the convective signal in most guidance is rather sparse across this area, likely due to limited frontal convergence and very dry air aloft. The 00Z NAM is a notable outlier, depicting both a much slower front, and more substantial development along/ahead of the front during the afternoon and evening. Severe probabilities may eventually be needed if trends end up supporting more robust convection along/ahead of the front across the Midwest and Great Lakes. Farther southwest, isolated to widely scattered storms will be possible across parts of the Ozarks and south-central Plains. While a strong storm or two will be possible in this area, relatively weak deep-layer flow/shear and generally modest instability may tend to limit organized severe potential. ...CO Front Range and adjacent parts of the High Plains... Scattered thunderstorms will again be possible across parts of the CO Front Range and adjacent High Plains Saturday. While wind profiles will remain favorable for organized convection, with modestly elongated hodographs within the post-frontal regime, guidance generally depicts weaker midlevel lapse rates compared to previous days, especially across the High Plains. There may be a tendency for storms to remain confined to the higher terrain for much of the period, with uncertain severe potential. However, a marginal supercell or two with hail potential cannot be ruled out, and severe probabilities may eventually be needed for some part of this region, if trends support sufficient destabilization. ..Dean.. 08/21/2025 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 AM CDT Thu Aug 21 2025 Valid 231200Z - 241200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorm potential currently appears low on Saturday. ...Parts of the Midwest/Lower Great Lakes into the south-central Plains... A mid/upper-level trough is forecast to gradually amplify across the north-central and eastern CONUS Saturday. A cold front will continue moving southeastward across parts of the Great Lakes/Midwest into the south-central Plains. Midlevel lapse rates along/ahead of the front will generally be weak, but low-level moisture will be sufficient for moderate buoyancy by afternoon. The strongest deep-layer flow/shear will located across parts of the central Great Lakes, but the convective signal in most guidance is rather sparse across this area, likely due to limited frontal convergence and very dry air aloft. The 00Z NAM is a notable outlier, depicting both a much slower front, and more substantial development along/ahead of the front during the afternoon and evening. Severe probabilities may eventually be needed if trends end up supporting more robust convection along/ahead of the front across the Midwest and Great Lakes. Farther southwest, isolated to widely scattered storms will be possible across parts of the Ozarks and south-central Plains. While a strong storm or two will be possible in this area, relatively weak deep-layer flow/shear and generally modest instability may tend to limit organized severe potential. ...CO Front Range and adjacent parts of the High Plains... Scattered thunderstorms will again be possible across parts of the CO Front Range and adjacent High Plains Saturday. While wind profiles will remain favorable for organized convection, with modestly elongated hodographs within the post-frontal regime, guidance generally depicts weaker midlevel lapse rates compared to previous days, especially across the High Plains. There may be a tendency for storms to remain confined to the higher terrain for much of the period, with uncertain severe potential. However, a marginal supercell or two with hail potential cannot be ruled out, and severe probabilities may eventually be needed for some part of this region, if trends support sufficient destabilization. ..Dean.. 08/21/2025 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 AM CDT Thu Aug 21 2025 Valid 231200Z - 241200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorm potential currently appears low on Saturday. ...Parts of the Midwest/Lower Great Lakes into the south-central Plains... A mid/upper-level trough is forecast to gradually amplify across the north-central and eastern CONUS Saturday. A cold front will continue moving southeastward across parts of the Great Lakes/Midwest into the south-central Plains. Midlevel lapse rates along/ahead of the front will generally be weak, but low-level moisture will be sufficient for moderate buoyancy by afternoon. The strongest deep-layer flow/shear will located across parts of the central Great Lakes, but the convective signal in most guidance is rather sparse across this area, likely due to limited frontal convergence and very dry air aloft. The 00Z NAM is a notable outlier, depicting both a much slower front, and more substantial development along/ahead of the front during the afternoon and evening. Severe probabilities may eventually be needed if trends end up supporting more robust convection along/ahead of the front across the Midwest and Great Lakes. Farther southwest, isolated to widely scattered storms will be possible across parts of the Ozarks and south-central Plains. While a strong storm or two will be possible in this area, relatively weak deep-layer flow/shear and generally modest instability may tend to limit organized severe potential. ...CO Front Range and adjacent parts of the High Plains... Scattered thunderstorms will again be possible across parts of the CO Front Range and adjacent High Plains Saturday. While wind profiles will remain favorable for organized convection, with modestly elongated hodographs within the post-frontal regime, guidance generally depicts weaker midlevel lapse rates compared to previous days, especially across the High Plains. There may be a tendency for storms to remain confined to the higher terrain for much of the period, with uncertain severe potential. However, a marginal supercell or two with hail potential cannot be ruled out, and severe probabilities may eventually be needed for some part of this region, if trends support sufficient destabilization. ..Dean.. 08/21/2025 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 AM CDT Thu Aug 21 2025 Valid 231200Z - 241200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorm potential currently appears low on Saturday. ...Parts of the Midwest/Lower Great Lakes into the south-central Plains... A mid/upper-level trough is forecast to gradually amplify across the north-central and eastern CONUS Saturday. A cold front will continue moving southeastward across parts of the Great Lakes/Midwest into the south-central Plains. Midlevel lapse rates along/ahead of the front will generally be weak, but low-level moisture will be sufficient for moderate buoyancy by afternoon. The strongest deep-layer flow/shear will located across parts of the central Great Lakes, but the convective signal in most guidance is rather sparse across this area, likely due to limited frontal convergence and very dry air aloft. The 00Z NAM is a notable outlier, depicting both a much slower front, and more substantial development along/ahead of the front during the afternoon and evening. Severe probabilities may eventually be needed if trends end up supporting more robust convection along/ahead of the front across the Midwest and Great Lakes. Farther southwest, isolated to widely scattered storms will be possible across parts of the Ozarks and south-central Plains. While a strong storm or two will be possible in this area, relatively weak deep-layer flow/shear and generally modest instability may tend to limit organized severe potential. ...CO Front Range and adjacent parts of the High Plains... Scattered thunderstorms will again be possible across parts of the CO Front Range and adjacent High Plains Saturday. While wind profiles will remain favorable for organized convection, with modestly elongated hodographs within the post-frontal regime, guidance generally depicts weaker midlevel lapse rates compared to previous days, especially across the High Plains. There may be a tendency for storms to remain confined to the higher terrain for much of the period, with uncertain severe potential. However, a marginal supercell or two with hail potential cannot be ruled out, and severe probabilities may eventually be needed for some part of this region, if trends support sufficient destabilization. ..Dean.. 08/21/2025 Read more

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 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 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 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 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