Severe Storms

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0751 AM CDT Thu Aug 21 2025 Valid 211300Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN PLAINS/UPPER MIDWEST AND SOUTHERN ARIZONA... ...SUMMARY... Isolated severe thunderstorms are possible across portions of the northern Plains and Upper Midwest this afternoon and evening, with severe wind gusts and hail the primary concerns. A few strong to severe storms could also occur across southern Arizona. ...Northern Plains/Minnesota... Late-day height falls are expected regionally in relation to an amplifying shortwave trough over the Canadian prairies. While the primary large-scale forcing will be north of the international border, high-level diffluent flow is expected across the eastern Dakotas/Minnesota, coincident with the front that will be draped across the region at peak heating. Short-term models (HRRR/RRFS) are tending to limit late-afternoon/evening convective development, while most global models and most HREF constituents are a bit more aggressive, which is plausible and lends credence to the potential for at isolated severe storms within a moderately to strongly unstable environment near the front. Deep-layer should be sufficient to potentially yield a few supercells. Increasing storm coverage later into the evening/overnight will be supported by an increasing low-level jet. ...North-central High Plains including eastern Wyoming... Northeasterly low-level upslope flow evolving within the post-frontal environment, and differential heating in vicinity of higher terrain, are expected to influence widely scattered thunderstorm development by late afternoon, particularly across eastern Wyoming. 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, including the possibility that a couple of eastward-moving clusters could evolve by early evening. ...Southern Arizona... The upper ridge should shift slightly northward regionally, with a modest enhancement to mid-level easterly flow late today particularly across southeast Arizona. With isolated storm development expected initially over the rim/mountains this afternoon, storms should drift west-southwestward into a moist/very hot boundary layer, with the potential for outflows/blowing dust to reach the desert floor. ..Guyer/Marsh.. 08/21/2025 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0751 AM CDT Thu Aug 21 2025 Valid 211300Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN PLAINS/UPPER MIDWEST AND SOUTHERN ARIZONA... ...SUMMARY... Isolated severe thunderstorms are possible across portions of the northern Plains and Upper Midwest this afternoon and evening, with severe wind gusts and hail the primary concerns. A few strong to severe storms could also occur across southern Arizona. ...Northern Plains/Minnesota... Late-day height falls are expected regionally in relation to an amplifying shortwave trough over the Canadian prairies. While the primary large-scale forcing will be north of the international border, high-level diffluent flow is expected across the eastern Dakotas/Minnesota, coincident with the front that will be draped across the region at peak heating. Short-term models (HRRR/RRFS) are tending to limit late-afternoon/evening convective development, while most global models and most HREF constituents are a bit more aggressive, which is plausible and lends credence to the potential for at isolated severe storms within a moderately to strongly unstable environment near the front. Deep-layer should be sufficient to potentially yield a few supercells. Increasing storm coverage later into the evening/overnight will be supported by an increasing low-level jet. ...North-central High Plains including eastern Wyoming... Northeasterly low-level upslope flow evolving within the post-frontal environment, and differential heating in vicinity of higher terrain, are expected to influence widely scattered thunderstorm development by late afternoon, particularly across eastern Wyoming. 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, including the possibility that a couple of eastward-moving clusters could evolve by early evening. ...Southern Arizona... The upper ridge should shift slightly northward regionally, with a modest enhancement to mid-level easterly flow late today particularly across southeast Arizona. With isolated storm development expected initially over the rim/mountains this afternoon, storms should drift west-southwestward into a moist/very hot boundary layer, with the potential for outflows/blowing dust to reach the desert floor. ..Guyer/Marsh.. 08/21/2025 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0751 AM CDT Thu Aug 21 2025 Valid 211300Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN PLAINS/UPPER MIDWEST AND SOUTHERN ARIZONA... ...SUMMARY... Isolated severe thunderstorms are possible across portions of the northern Plains and Upper Midwest this afternoon and evening, with severe wind gusts and hail the primary concerns. A few strong to severe storms could also occur across southern Arizona. ...Northern Plains/Minnesota... Late-day height falls are expected regionally in relation to an amplifying shortwave trough over the Canadian prairies. While the primary large-scale forcing will be north of the international border, high-level diffluent flow is expected across the eastern Dakotas/Minnesota, coincident with the front that will be draped across the region at peak heating. Short-term models (HRRR/RRFS) are tending to limit late-afternoon/evening convective development, while most global models and most HREF constituents are a bit more aggressive, which is plausible and lends credence to the potential for at isolated severe storms within a moderately to strongly unstable environment near the front. Deep-layer should be sufficient to potentially yield a few supercells. Increasing storm coverage later into the evening/overnight will be supported by an increasing low-level jet. ...North-central High Plains including eastern Wyoming... Northeasterly low-level upslope flow evolving within the post-frontal environment, and differential heating in vicinity of higher terrain, are expected to influence widely scattered thunderstorm development by late afternoon, particularly across eastern Wyoming. 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, including the possibility that a couple of eastward-moving clusters could evolve by early evening. ...Southern Arizona... The upper ridge should shift slightly northward regionally, with a modest enhancement to mid-level easterly flow late today particularly across southeast Arizona. With isolated storm development expected initially over the rim/mountains this afternoon, storms should drift west-southwestward into a moist/very hot boundary layer, with the potential for outflows/blowing dust to reach the desert floor. ..Guyer/Marsh.. 08/21/2025 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0751 AM CDT Thu Aug 21 2025 Valid 211300Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN PLAINS/UPPER MIDWEST AND SOUTHERN ARIZONA... ...SUMMARY... Isolated severe thunderstorms are possible across portions of the northern Plains and Upper Midwest this afternoon and evening, with severe wind gusts and hail the primary concerns. A few strong to severe storms could also occur across southern Arizona. ...Northern Plains/Minnesota... Late-day height falls are expected regionally in relation to an amplifying shortwave trough over the Canadian prairies. While the primary large-scale forcing will be north of the international border, high-level diffluent flow is expected across the eastern Dakotas/Minnesota, coincident with the front that will be draped across the region at peak heating. Short-term models (HRRR/RRFS) are tending to limit late-afternoon/evening convective development, while most global models and most HREF constituents are a bit more aggressive, which is plausible and lends credence to the potential for at isolated severe storms within a moderately to strongly unstable environment near the front. Deep-layer should be sufficient to potentially yield a few supercells. Increasing storm coverage later into the evening/overnight will be supported by an increasing low-level jet. ...North-central High Plains including eastern Wyoming... Northeasterly low-level upslope flow evolving within the post-frontal environment, and differential heating in vicinity of higher terrain, are expected to influence widely scattered thunderstorm development by late afternoon, particularly across eastern Wyoming. 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, including the possibility that a couple of eastward-moving clusters could evolve by early evening. ...Southern Arizona... The upper ridge should shift slightly northward regionally, with a modest enhancement to mid-level easterly flow late today particularly across southeast Arizona. With isolated storm development expected initially over the rim/mountains this afternoon, storms should drift west-southwestward into a moist/very hot boundary layer, with the potential for outflows/blowing dust to reach the desert floor. ..Guyer/Marsh.. 08/21/2025 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0751 AM CDT Thu Aug 21 2025 Valid 211300Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN PLAINS/UPPER MIDWEST AND SOUTHERN ARIZONA... ...SUMMARY... Isolated severe thunderstorms are possible across portions of the northern Plains and Upper Midwest this afternoon and evening, with severe wind gusts and hail the primary concerns. A few strong to severe storms could also occur across southern Arizona. ...Northern Plains/Minnesota... Late-day height falls are expected regionally in relation to an amplifying shortwave trough over the Canadian prairies. While the primary large-scale forcing will be north of the international border, high-level diffluent flow is expected across the eastern Dakotas/Minnesota, coincident with the front that will be draped across the region at peak heating. Short-term models (HRRR/RRFS) are tending to limit late-afternoon/evening convective development, while most global models and most HREF constituents are a bit more aggressive, which is plausible and lends credence to the potential for at isolated severe storms within a moderately to strongly unstable environment near the front. Deep-layer should be sufficient to potentially yield a few supercells. Increasing storm coverage later into the evening/overnight will be supported by an increasing low-level jet. ...North-central High Plains including eastern Wyoming... Northeasterly low-level upslope flow evolving within the post-frontal environment, and differential heating in vicinity of higher terrain, are expected to influence widely scattered thunderstorm development by late afternoon, particularly across eastern Wyoming. 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, including the possibility that a couple of eastward-moving clusters could evolve by early evening. ...Southern Arizona... The upper ridge should shift slightly northward regionally, with a modest enhancement to mid-level easterly flow late today particularly across southeast Arizona. With isolated storm development expected initially over the rim/mountains this afternoon, storms should drift west-southwestward into a moist/very hot boundary layer, with the potential for outflows/blowing dust to reach the desert floor. ..Guyer/Marsh.. 08/21/2025 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0309 AM CDT Thu Aug 21 2025 Valid 241200Z - 291200Z ...DISCUSSION... ...D4/Sunday - D5/Monday... A cold front that moves into the eastern CONUS on Sunday may tend to slow down, as a reinforcing shortwave moves through the base of a deep mid/upper-level trough covering the region. Scattered storms will be possible from the Northeast into the central/southern Appalachians on D4/Sunday, though with only modest instability and deep-layer shear forecast to be in place, any severe potential may remain isolated. Stronger deep-layer flow/shear is generally forecast to overspread parts of the Northeast/New England on D5/Monday, though with generally weak instability expected, severe potential is uncertain. Scattered storms will also be possible on Sunday and Monday across the CO Front Range vicinity into the central High Plains, within a persistent post-frontal regime. While details are uncertain, strong to isolated severe storms cannot be ruled out, especially if any organized clustering can develop and emerge into parts of the High Plains. ...D6/Tuesday - D8/Thursday... While typical model spread is noted by Days 6-8, guidance generally depicts relatively limited severe potential into the middle of next week, as an expansive surface ridge suppresses richer low-level moisture to parts of the Gulf Coast and Texas. Some guidance shows potential for recovery by D8/Thursday across parts of the southern/central Plains, but deep-layer flow is generally forecast to remain weak to modest across the region. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0309 AM CDT Thu Aug 21 2025 Valid 241200Z - 291200Z ...DISCUSSION... ...D4/Sunday - D5/Monday... A cold front that moves into the eastern CONUS on Sunday may tend to slow down, as a reinforcing shortwave moves through the base of a deep mid/upper-level trough covering the region. Scattered storms will be possible from the Northeast into the central/southern Appalachians on D4/Sunday, though with only modest instability and deep-layer shear forecast to be in place, any severe potential may remain isolated. Stronger deep-layer flow/shear is generally forecast to overspread parts of the Northeast/New England on D5/Monday, though with generally weak instability expected, severe potential is uncertain. Scattered storms will also be possible on Sunday and Monday across the CO Front Range vicinity into the central High Plains, within a persistent post-frontal regime. While details are uncertain, strong to isolated severe storms cannot be ruled out, especially if any organized clustering can develop and emerge into parts of the High Plains. ...D6/Tuesday - D8/Thursday... While typical model spread is noted by Days 6-8, guidance generally depicts relatively limited severe potential into the middle of next week, as an expansive surface ridge suppresses richer low-level moisture to parts of the Gulf Coast and Texas. Some guidance shows potential for recovery by D8/Thursday across parts of the southern/central Plains, but deep-layer flow is generally forecast to remain weak to modest across the region. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0309 AM CDT Thu Aug 21 2025 Valid 241200Z - 291200Z ...DISCUSSION... ...D4/Sunday - D5/Monday... A cold front that moves into the eastern CONUS on Sunday may tend to slow down, as a reinforcing shortwave moves through the base of a deep mid/upper-level trough covering the region. Scattered storms will be possible from the Northeast into the central/southern Appalachians on D4/Sunday, though with only modest instability and deep-layer shear forecast to be in place, any severe potential may remain isolated. Stronger deep-layer flow/shear is generally forecast to overspread parts of the Northeast/New England on D5/Monday, though with generally weak instability expected, severe potential is uncertain. Scattered storms will also be possible on Sunday and Monday across the CO Front Range vicinity into the central High Plains, within a persistent post-frontal regime. While details are uncertain, strong to isolated severe storms cannot be ruled out, especially if any organized clustering can develop and emerge into parts of the High Plains. ...D6/Tuesday - D8/Thursday... While typical model spread is noted by Days 6-8, guidance generally depicts relatively limited severe potential into the middle of next week, as an expansive surface ridge suppresses richer low-level moisture to parts of the Gulf Coast and Texas. Some guidance shows potential for recovery by D8/Thursday across parts of the southern/central Plains, but deep-layer flow is generally forecast to remain weak to modest across the region. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0309 AM CDT Thu Aug 21 2025 Valid 241200Z - 291200Z ...DISCUSSION... ...D4/Sunday - D5/Monday... A cold front that moves into the eastern CONUS on Sunday may tend to slow down, as a reinforcing shortwave moves through the base of a deep mid/upper-level trough covering the region. Scattered storms will be possible from the Northeast into the central/southern Appalachians on D4/Sunday, though with only modest instability and deep-layer shear forecast to be in place, any severe potential may remain isolated. Stronger deep-layer flow/shear is generally forecast to overspread parts of the Northeast/New England on D5/Monday, though with generally weak instability expected, severe potential is uncertain. Scattered storms will also be possible on Sunday and Monday across the CO Front Range vicinity into the central High Plains, within a persistent post-frontal regime. While details are uncertain, strong to isolated severe storms cannot be ruled out, especially if any organized clustering can develop and emerge into parts of the High Plains. ...D6/Tuesday - D8/Thursday... While typical model spread is noted by Days 6-8, guidance generally depicts relatively limited severe potential into the middle of next week, as an expansive surface ridge suppresses richer low-level moisture to parts of the Gulf Coast and Texas. Some guidance shows potential for recovery by D8/Thursday across parts of the southern/central Plains, but deep-layer flow is generally forecast to remain weak to modest across the region. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0309 AM CDT Thu Aug 21 2025 Valid 241200Z - 291200Z ...DISCUSSION... ...D4/Sunday - D5/Monday... A cold front that moves into the eastern CONUS on Sunday may tend to slow down, as a reinforcing shortwave moves through the base of a deep mid/upper-level trough covering the region. Scattered storms will be possible from the Northeast into the central/southern Appalachians on D4/Sunday, though with only modest instability and deep-layer shear forecast to be in place, any severe potential may remain isolated. Stronger deep-layer flow/shear is generally forecast to overspread parts of the Northeast/New England on D5/Monday, though with generally weak instability expected, severe potential is uncertain. Scattered storms will also be possible on Sunday and Monday across the CO Front Range vicinity into the central High Plains, within a persistent post-frontal regime. While details are uncertain, strong to isolated severe storms cannot be ruled out, especially if any organized clustering can develop and emerge into parts of the High Plains. ...D6/Tuesday - D8/Thursday... While typical model spread is noted by Days 6-8, guidance generally depicts relatively limited severe potential into the middle of next week, as an expansive surface ridge suppresses richer low-level moisture to parts of the Gulf Coast and Texas. Some guidance shows potential for recovery by D8/Thursday across parts of the southern/central Plains, but deep-layer flow is generally forecast to remain weak to modest across the region. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0309 AM CDT Thu Aug 21 2025 Valid 241200Z - 291200Z ...DISCUSSION... ...D4/Sunday - D5/Monday... A cold front that moves into the eastern CONUS on Sunday may tend to slow down, as a reinforcing shortwave moves through the base of a deep mid/upper-level trough covering the region. Scattered storms will be possible from the Northeast into the central/southern Appalachians on D4/Sunday, though with only modest instability and deep-layer shear forecast to be in place, any severe potential may remain isolated. Stronger deep-layer flow/shear is generally forecast to overspread parts of the Northeast/New England on D5/Monday, though with generally weak instability expected, severe potential is uncertain. Scattered storms will also be possible on Sunday and Monday across the CO Front Range vicinity into the central High Plains, within a persistent post-frontal regime. While details are uncertain, strong to isolated severe storms cannot be ruled out, especially if any organized clustering can develop and emerge into parts of the High Plains. ...D6/Tuesday - D8/Thursday... While typical model spread is noted by Days 6-8, guidance generally depicts relatively limited severe potential into the middle of next week, as an expansive surface ridge suppresses richer low-level moisture to parts of the Gulf Coast and Texas. Some guidance shows potential for recovery by D8/Thursday across parts of the southern/central Plains, but deep-layer flow is generally forecast to remain weak to modest across the region. 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 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