Severe Storms

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0156 AM CDT Wed Aug 20 2025 Valid 201200Z - 211200Z ...Synopsis... A strong ridge of high pressure building over the central US is forecast to gradually move west while a weak trough on the western edge, suppresses the northern extent. The increasingly strong height gradient along the western periphery of the ridge will bolster mid-level winds aloft over the Northwest and northern Great Basin. At the surface, a cold front will move into the western Great Basin before stalling this afternoon. The front, and increased flow aloft will support gusty surface winds and isolated storms, increasing fire danger today and tonight. ...Great Basin... Several hours of dry/breezy conditions are expected this afternoon with the breakdown of the upper-level ridge. Very warm temperatures are expected, supporting deep vertical mixing and low boundary-layer RH. West/southwesterly winds of 15-20 mph with gusts of 20-30 mph near the front, and RH below 15% on a widespread basis will support elevated to locally critical fire-weather conditions from southern ID into the Great Basin. Increased southwesterly flow aloft on the western edge of the ridge will help monsoon moisture (PWATs 0.6-0.8 inches) advect northward over NV and western UT. The surface cold front associated with the upper trough will stall over the western Great Basin, serving as a focus for isolated thunderstorm development through the afternoon. Uncertainty remains high regarding coverage of thunderstorms, especially with southern extent. While moisture and instability will be more limited, enough instability and forcing are expected to produce isolated high-based showers and thunderstorms capable of dry lightning. Should these storms develop they may track eastward, persisting overnight into eastern ID and western MT with a continued threat for dry strikes. Additionally, any active large wildfires may have increased chances of deep pyroconvection/localized extreme fire behavior given the steep lapse rates and unstable troposphere. ..Lyons.. 08/20/2025 ...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 1256 AM CDT Wed Aug 20 2025 Valid 211200Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR THE CENTRAL/EASTERN DAKOTAS INTO PARTS OF MINNESOTA... ...SUMMARY... An isolated severe threat is expected to develop Thursday into Thursday night over parts of the Dakotas into Minnesota, with severe gusts and hail possible. ...Northern Plains into parts of MN... A mid/upper-level shortwave trough is forecast to evolve into a deep-layer cyclone as it moves eastward across parts of the Canadian Prairies on Thursday. A trailing cold front will move through the Dakotas and northwest MN, with a weak frontal wave potentially developing across SD. Diurnal heating of a relatively moist airmass will result in moderate to locally strong destabilization by late afternoon. An embedded mid/upper-level shortwave trough and associated remnant convection is expected to move across MB/ND and northern MN early in the day. In the wake of this shortwave, large-scale ascent is expected to be generally weak until later Thursday night, resulting in uncertainty regarding afternoon/evening storm development. Isolated storm development cannot be ruled out near the front, and potentially near the weak surface low across SD. An increase in storm coverage is expected late Thursday night, as somewhat stronger midlevel height falls and upper-level difluence overspread the region. The strongest mid/upper-level flow will tend to lag behind the front, but deep-layer shear will still be sufficient for some storm organization, including conditional supercell potential. The Marginal Risk has been maintained with this outlook, but greater severe probabilities may eventually be needed, depending on trends regarding storm coverage and timing from parts of the Dakotas into northwest MN. Other strong storms may develop Thursday night across parts of the northern High Plains, within a favorably sheared post-frontal regime. Severe probabilities may eventually need to be expanded westward, if confidence increases in a favored post-frontal corridor. ...Coastal NC... The center of Hurricane Erin is forecast by NHC to remain well offshore of coastal NC on Thursday as it begins moving northeastward. However, the western periphery of Erin's large wind field will result in rather strong deep-layer northerly flow across the Outer Banks and vicinity. If modest diurnal heating can occur, then showers and possibly a few weak storms may develop during the afternoon, though it is uncertain if any such development would be sufficiently vigorous to support convectively augmented gusts. ...Parts of the Southeast/southern Appalachians... Scattered thunderstorms are forecast to develop across parts of the Southeast and southern Appalachians vicinity Thursday afternoon. Deep-layer shear will remain quite weak, but northerly low-midlevel flow may support one or more southward-moving clusters. Poor midlevel lapse rates will tend to limit updraft intensity, and the organized severe threat appears low, but localized tree damage could accompany these storms during the afternoon and early evening. ...Arizona... Thunderstorms are expected to develop Thursday afternoon and evening across parts of AZ, initially near the higher terrain. Isolated strong gusts could accompany these storms. With an amplified upper-level ridge anchored near the Four Corners, midlevel flow will generally be easterly across central/southern AZ. The easterly steering flow and a very hot and well-mixed environment could support a threat of strong outflow gusts into the lower elevations, though it is uncertain if storm coverage will be sufficient for larger-scale outflow development and more than very isolated damaging-wind potential. ..Dean.. 08/20/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1256 AM CDT Wed Aug 20 2025 Valid 211200Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR THE CENTRAL/EASTERN DAKOTAS INTO PARTS OF MINNESOTA... ...SUMMARY... An isolated severe threat is expected to develop Thursday into Thursday night over parts of the Dakotas into Minnesota, with severe gusts and hail possible. ...Northern Plains into parts of MN... A mid/upper-level shortwave trough is forecast to evolve into a deep-layer cyclone as it moves eastward across parts of the Canadian Prairies on Thursday. A trailing cold front will move through the Dakotas and northwest MN, with a weak frontal wave potentially developing across SD. Diurnal heating of a relatively moist airmass will result in moderate to locally strong destabilization by late afternoon. An embedded mid/upper-level shortwave trough and associated remnant convection is expected to move across MB/ND and northern MN early in the day. In the wake of this shortwave, large-scale ascent is expected to be generally weak until later Thursday night, resulting in uncertainty regarding afternoon/evening storm development. Isolated storm development cannot be ruled out near the front, and potentially near the weak surface low across SD. An increase in storm coverage is expected late Thursday night, as somewhat stronger midlevel height falls and upper-level difluence overspread the region. The strongest mid/upper-level flow will tend to lag behind the front, but deep-layer shear will still be sufficient for some storm organization, including conditional supercell potential. The Marginal Risk has been maintained with this outlook, but greater severe probabilities may eventually be needed, depending on trends regarding storm coverage and timing from parts of the Dakotas into northwest MN. Other strong storms may develop Thursday night across parts of the northern High Plains, within a favorably sheared post-frontal regime. Severe probabilities may eventually need to be expanded westward, if confidence increases in a favored post-frontal corridor. ...Coastal NC... The center of Hurricane Erin is forecast by NHC to remain well offshore of coastal NC on Thursday as it begins moving northeastward. However, the western periphery of Erin's large wind field will result in rather strong deep-layer northerly flow across the Outer Banks and vicinity. If modest diurnal heating can occur, then showers and possibly a few weak storms may develop during the afternoon, though it is uncertain if any such development would be sufficiently vigorous to support convectively augmented gusts. ...Parts of the Southeast/southern Appalachians... Scattered thunderstorms are forecast to develop across parts of the Southeast and southern Appalachians vicinity Thursday afternoon. Deep-layer shear will remain quite weak, but northerly low-midlevel flow may support one or more southward-moving clusters. Poor midlevel lapse rates will tend to limit updraft intensity, and the organized severe threat appears low, but localized tree damage could accompany these storms during the afternoon and early evening. ...Arizona... Thunderstorms are expected to develop Thursday afternoon and evening across parts of AZ, initially near the higher terrain. Isolated strong gusts could accompany these storms. With an amplified upper-level ridge anchored near the Four Corners, midlevel flow will generally be easterly across central/southern AZ. The easterly steering flow and a very hot and well-mixed environment could support a threat of strong outflow gusts into the lower elevations, though it is uncertain if storm coverage will be sufficient for larger-scale outflow development and more than very isolated damaging-wind potential. ..Dean.. 08/20/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1256 AM CDT Wed Aug 20 2025 Valid 211200Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR THE CENTRAL/EASTERN DAKOTAS INTO PARTS OF MINNESOTA... ...SUMMARY... An isolated severe threat is expected to develop Thursday into Thursday night over parts of the Dakotas into Minnesota, with severe gusts and hail possible. ...Northern Plains into parts of MN... A mid/upper-level shortwave trough is forecast to evolve into a deep-layer cyclone as it moves eastward across parts of the Canadian Prairies on Thursday. A trailing cold front will move through the Dakotas and northwest MN, with a weak frontal wave potentially developing across SD. Diurnal heating of a relatively moist airmass will result in moderate to locally strong destabilization by late afternoon. An embedded mid/upper-level shortwave trough and associated remnant convection is expected to move across MB/ND and northern MN early in the day. In the wake of this shortwave, large-scale ascent is expected to be generally weak until later Thursday night, resulting in uncertainty regarding afternoon/evening storm development. Isolated storm development cannot be ruled out near the front, and potentially near the weak surface low across SD. An increase in storm coverage is expected late Thursday night, as somewhat stronger midlevel height falls and upper-level difluence overspread the region. The strongest mid/upper-level flow will tend to lag behind the front, but deep-layer shear will still be sufficient for some storm organization, including conditional supercell potential. The Marginal Risk has been maintained with this outlook, but greater severe probabilities may eventually be needed, depending on trends regarding storm coverage and timing from parts of the Dakotas into northwest MN. Other strong storms may develop Thursday night across parts of the northern High Plains, within a favorably sheared post-frontal regime. Severe probabilities may eventually need to be expanded westward, if confidence increases in a favored post-frontal corridor. ...Coastal NC... The center of Hurricane Erin is forecast by NHC to remain well offshore of coastal NC on Thursday as it begins moving northeastward. However, the western periphery of Erin's large wind field will result in rather strong deep-layer northerly flow across the Outer Banks and vicinity. If modest diurnal heating can occur, then showers and possibly a few weak storms may develop during the afternoon, though it is uncertain if any such development would be sufficiently vigorous to support convectively augmented gusts. ...Parts of the Southeast/southern Appalachians... Scattered thunderstorms are forecast to develop across parts of the Southeast and southern Appalachians vicinity Thursday afternoon. Deep-layer shear will remain quite weak, but northerly low-midlevel flow may support one or more southward-moving clusters. Poor midlevel lapse rates will tend to limit updraft intensity, and the organized severe threat appears low, but localized tree damage could accompany these storms during the afternoon and early evening. ...Arizona... Thunderstorms are expected to develop Thursday afternoon and evening across parts of AZ, initially near the higher terrain. Isolated strong gusts could accompany these storms. With an amplified upper-level ridge anchored near the Four Corners, midlevel flow will generally be easterly across central/southern AZ. The easterly steering flow and a very hot and well-mixed environment could support a threat of strong outflow gusts into the lower elevations, though it is uncertain if storm coverage will be sufficient for larger-scale outflow development and more than very isolated damaging-wind potential. ..Dean.. 08/20/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1256 AM CDT Wed Aug 20 2025 Valid 211200Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR THE CENTRAL/EASTERN DAKOTAS INTO PARTS OF MINNESOTA... ...SUMMARY... An isolated severe threat is expected to develop Thursday into Thursday night over parts of the Dakotas into Minnesota, with severe gusts and hail possible. ...Northern Plains into parts of MN... A mid/upper-level shortwave trough is forecast to evolve into a deep-layer cyclone as it moves eastward across parts of the Canadian Prairies on Thursday. A trailing cold front will move through the Dakotas and northwest MN, with a weak frontal wave potentially developing across SD. Diurnal heating of a relatively moist airmass will result in moderate to locally strong destabilization by late afternoon. An embedded mid/upper-level shortwave trough and associated remnant convection is expected to move across MB/ND and northern MN early in the day. In the wake of this shortwave, large-scale ascent is expected to be generally weak until later Thursday night, resulting in uncertainty regarding afternoon/evening storm development. Isolated storm development cannot be ruled out near the front, and potentially near the weak surface low across SD. An increase in storm coverage is expected late Thursday night, as somewhat stronger midlevel height falls and upper-level difluence overspread the region. The strongest mid/upper-level flow will tend to lag behind the front, but deep-layer shear will still be sufficient for some storm organization, including conditional supercell potential. The Marginal Risk has been maintained with this outlook, but greater severe probabilities may eventually be needed, depending on trends regarding storm coverage and timing from parts of the Dakotas into northwest MN. Other strong storms may develop Thursday night across parts of the northern High Plains, within a favorably sheared post-frontal regime. Severe probabilities may eventually need to be expanded westward, if confidence increases in a favored post-frontal corridor. ...Coastal NC... The center of Hurricane Erin is forecast by NHC to remain well offshore of coastal NC on Thursday as it begins moving northeastward. However, the western periphery of Erin's large wind field will result in rather strong deep-layer northerly flow across the Outer Banks and vicinity. If modest diurnal heating can occur, then showers and possibly a few weak storms may develop during the afternoon, though it is uncertain if any such development would be sufficiently vigorous to support convectively augmented gusts. ...Parts of the Southeast/southern Appalachians... Scattered thunderstorms are forecast to develop across parts of the Southeast and southern Appalachians vicinity Thursday afternoon. Deep-layer shear will remain quite weak, but northerly low-midlevel flow may support one or more southward-moving clusters. Poor midlevel lapse rates will tend to limit updraft intensity, and the organized severe threat appears low, but localized tree damage could accompany these storms during the afternoon and early evening. ...Arizona... Thunderstorms are expected to develop Thursday afternoon and evening across parts of AZ, initially near the higher terrain. Isolated strong gusts could accompany these storms. With an amplified upper-level ridge anchored near the Four Corners, midlevel flow will generally be easterly across central/southern AZ. The easterly steering flow and a very hot and well-mixed environment could support a threat of strong outflow gusts into the lower elevations, though it is uncertain if storm coverage will be sufficient for larger-scale outflow development and more than very isolated damaging-wind potential. ..Dean.. 08/20/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1256 AM CDT Wed Aug 20 2025 Valid 211200Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR THE CENTRAL/EASTERN DAKOTAS INTO PARTS OF MINNESOTA... ...SUMMARY... An isolated severe threat is expected to develop Thursday into Thursday night over parts of the Dakotas into Minnesota, with severe gusts and hail possible. ...Northern Plains into parts of MN... A mid/upper-level shortwave trough is forecast to evolve into a deep-layer cyclone as it moves eastward across parts of the Canadian Prairies on Thursday. A trailing cold front will move through the Dakotas and northwest MN, with a weak frontal wave potentially developing across SD. Diurnal heating of a relatively moist airmass will result in moderate to locally strong destabilization by late afternoon. An embedded mid/upper-level shortwave trough and associated remnant convection is expected to move across MB/ND and northern MN early in the day. In the wake of this shortwave, large-scale ascent is expected to be generally weak until later Thursday night, resulting in uncertainty regarding afternoon/evening storm development. Isolated storm development cannot be ruled out near the front, and potentially near the weak surface low across SD. An increase in storm coverage is expected late Thursday night, as somewhat stronger midlevel height falls and upper-level difluence overspread the region. The strongest mid/upper-level flow will tend to lag behind the front, but deep-layer shear will still be sufficient for some storm organization, including conditional supercell potential. The Marginal Risk has been maintained with this outlook, but greater severe probabilities may eventually be needed, depending on trends regarding storm coverage and timing from parts of the Dakotas into northwest MN. Other strong storms may develop Thursday night across parts of the northern High Plains, within a favorably sheared post-frontal regime. Severe probabilities may eventually need to be expanded westward, if confidence increases in a favored post-frontal corridor. ...Coastal NC... The center of Hurricane Erin is forecast by NHC to remain well offshore of coastal NC on Thursday as it begins moving northeastward. However, the western periphery of Erin's large wind field will result in rather strong deep-layer northerly flow across the Outer Banks and vicinity. If modest diurnal heating can occur, then showers and possibly a few weak storms may develop during the afternoon, though it is uncertain if any such development would be sufficiently vigorous to support convectively augmented gusts. ...Parts of the Southeast/southern Appalachians... Scattered thunderstorms are forecast to develop across parts of the Southeast and southern Appalachians vicinity Thursday afternoon. Deep-layer shear will remain quite weak, but northerly low-midlevel flow may support one or more southward-moving clusters. Poor midlevel lapse rates will tend to limit updraft intensity, and the organized severe threat appears low, but localized tree damage could accompany these storms during the afternoon and early evening. ...Arizona... Thunderstorms are expected to develop Thursday afternoon and evening across parts of AZ, initially near the higher terrain. Isolated strong gusts could accompany these storms. With an amplified upper-level ridge anchored near the Four Corners, midlevel flow will generally be easterly across central/southern AZ. The easterly steering flow and a very hot and well-mixed environment could support a threat of strong outflow gusts into the lower elevations, though it is uncertain if storm coverage will be sufficient for larger-scale outflow development and more than very isolated damaging-wind potential. ..Dean.. 08/20/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1234 AM CDT Wed Aug 20 2025 Valid 201200Z - 211200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TODAY ACROSS THE WESTERN AND CENTRAL GULF COAST STATES AND THE INTERNATIONAL BORDER VICINITY OF NORTH DAKOTA... ...SUMMARY... Scattered thunderstorms developing this afternoon and evening across the western and central Gulf Coast states may pose a risk for localized potentially damaging wind gusts. Otherwise, there appears some risk for an isolated severe thunderstorm or two across parts of northern North Dakota. ...Discussion... Models indicate that a prominent mid/upper high will be maintained over the Four Corners vicinity through this period. However, initially amplified ridging extending to its north, as far as the Canadian Prairies, appears likely to become suppressed southeastward toward the central international border vicinity, as a significant short wave perturbation progresses east of the Canadian Rockies into Prairies by late tonight. It appears that this may be accompanied by weak cyclogenesis across southern Saskatchewan toward the central Saskatchewan/Manitoba border vicinity, with a trailing cold front advancing across the Montana international border by late tonight. At the same time, an increasingly sheared perturbation will continue progressing through weak larger-scale mid-level troughing digging across the Northeast, and southeastward around the periphery of the high, across the Ohio/Tennessee Valleys and southern Great Plains. To the southeast of this feature, Hurricane Erin is forecast to turn slowly north-northeastward, offshore of the southern through middle Atlantic Seaboard. ...Gulf Coast States... A diffuse surface frontal zone, reinforced in segments by convective outflow, will continue slowly southward ahead of the mid-level shear axis, likely reaching portions of central Texas through Louisiana and central/northern Mississippi and Alabama by mid to late afternoon. Along and ahead of this front, a corridor of stronger heating of a seasonably moist boundary layer, perhaps still coincident with a residual plume of relatively steep lower/mid-tropospheric lapse rates, may continue to contribute to thermodynamic profiles supportive of localized downbursts and gusty winds on convectively generated surface cold pools. It is not clear that the severe threat will be any more widespread than the sparse coverage of preceding days, but it may perhaps be marginally sufficient to justify 5 percent severe wind probabilities. ...North Dakota... Models indicate that a narrow corridor of moderate to large potential instability may develop along/ahead of the surface cold front, a pre-frontal surface trough and developing warm frontal zone across parts of the Dakotas into eastern Saskatchewan by late this afternoon. However, beneath the nose of a plume of warm and capping elevated mixed-layer air, mid/upper support for the initiation of boundary-layer based thunderstorm development is forecast to generally remain to the north of the international border. While the risk for severe thunderstorms appears largely conditional, guidance does indicate that a weak surface low may develop within the pre-frontal troughing and provide a potential focus for convective development across northwestern North Dakota late this afternoon and evening. If this forcing, coupled with the approach of convective temperatures, is sufficient to overcome the mid-level inhibition, forecast soundings indicate the environment will be conducive to supercell development. ..Kerr/Lyons.. 08/20/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1234 AM CDT Wed Aug 20 2025 Valid 201200Z - 211200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TODAY ACROSS THE WESTERN AND CENTRAL GULF COAST STATES AND THE INTERNATIONAL BORDER VICINITY OF NORTH DAKOTA... ...SUMMARY... Scattered thunderstorms developing this afternoon and evening across the western and central Gulf Coast states may pose a risk for localized potentially damaging wind gusts. Otherwise, there appears some risk for an isolated severe thunderstorm or two across parts of northern North Dakota. ...Discussion... Models indicate that a prominent mid/upper high will be maintained over the Four Corners vicinity through this period. However, initially amplified ridging extending to its north, as far as the Canadian Prairies, appears likely to become suppressed southeastward toward the central international border vicinity, as a significant short wave perturbation progresses east of the Canadian Rockies into Prairies by late tonight. It appears that this may be accompanied by weak cyclogenesis across southern Saskatchewan toward the central Saskatchewan/Manitoba border vicinity, with a trailing cold front advancing across the Montana international border by late tonight. At the same time, an increasingly sheared perturbation will continue progressing through weak larger-scale mid-level troughing digging across the Northeast, and southeastward around the periphery of the high, across the Ohio/Tennessee Valleys and southern Great Plains. To the southeast of this feature, Hurricane Erin is forecast to turn slowly north-northeastward, offshore of the southern through middle Atlantic Seaboard. ...Gulf Coast States... A diffuse surface frontal zone, reinforced in segments by convective outflow, will continue slowly southward ahead of the mid-level shear axis, likely reaching portions of central Texas through Louisiana and central/northern Mississippi and Alabama by mid to late afternoon. Along and ahead of this front, a corridor of stronger heating of a seasonably moist boundary layer, perhaps still coincident with a residual plume of relatively steep lower/mid-tropospheric lapse rates, may continue to contribute to thermodynamic profiles supportive of localized downbursts and gusty winds on convectively generated surface cold pools. It is not clear that the severe threat will be any more widespread than the sparse coverage of preceding days, but it may perhaps be marginally sufficient to justify 5 percent severe wind probabilities. ...North Dakota... Models indicate that a narrow corridor of moderate to large potential instability may develop along/ahead of the surface cold front, a pre-frontal surface trough and developing warm frontal zone across parts of the Dakotas into eastern Saskatchewan by late this afternoon. However, beneath the nose of a plume of warm and capping elevated mixed-layer air, mid/upper support for the initiation of boundary-layer based thunderstorm development is forecast to generally remain to the north of the international border. While the risk for severe thunderstorms appears largely conditional, guidance does indicate that a weak surface low may develop within the pre-frontal troughing and provide a potential focus for convective development across northwestern North Dakota late this afternoon and evening. If this forcing, coupled with the approach of convective temperatures, is sufficient to overcome the mid-level inhibition, forecast soundings indicate the environment will be conducive to supercell development. ..Kerr/Lyons.. 08/20/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1234 AM CDT Wed Aug 20 2025 Valid 201200Z - 211200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TODAY ACROSS THE WESTERN AND CENTRAL GULF COAST STATES AND THE INTERNATIONAL BORDER VICINITY OF NORTH DAKOTA... ...SUMMARY... Scattered thunderstorms developing this afternoon and evening across the western and central Gulf Coast states may pose a risk for localized potentially damaging wind gusts. Otherwise, there appears some risk for an isolated severe thunderstorm or two across parts of northern North Dakota. ...Discussion... Models indicate that a prominent mid/upper high will be maintained over the Four Corners vicinity through this period. However, initially amplified ridging extending to its north, as far as the Canadian Prairies, appears likely to become suppressed southeastward toward the central international border vicinity, as a significant short wave perturbation progresses east of the Canadian Rockies into Prairies by late tonight. It appears that this may be accompanied by weak cyclogenesis across southern Saskatchewan toward the central Saskatchewan/Manitoba border vicinity, with a trailing cold front advancing across the Montana international border by late tonight. At the same time, an increasingly sheared perturbation will continue progressing through weak larger-scale mid-level troughing digging across the Northeast, and southeastward around the periphery of the high, across the Ohio/Tennessee Valleys and southern Great Plains. To the southeast of this feature, Hurricane Erin is forecast to turn slowly north-northeastward, offshore of the southern through middle Atlantic Seaboard. ...Gulf Coast States... A diffuse surface frontal zone, reinforced in segments by convective outflow, will continue slowly southward ahead of the mid-level shear axis, likely reaching portions of central Texas through Louisiana and central/northern Mississippi and Alabama by mid to late afternoon. Along and ahead of this front, a corridor of stronger heating of a seasonably moist boundary layer, perhaps still coincident with a residual plume of relatively steep lower/mid-tropospheric lapse rates, may continue to contribute to thermodynamic profiles supportive of localized downbursts and gusty winds on convectively generated surface cold pools. It is not clear that the severe threat will be any more widespread than the sparse coverage of preceding days, but it may perhaps be marginally sufficient to justify 5 percent severe wind probabilities. ...North Dakota... Models indicate that a narrow corridor of moderate to large potential instability may develop along/ahead of the surface cold front, a pre-frontal surface trough and developing warm frontal zone across parts of the Dakotas into eastern Saskatchewan by late this afternoon. However, beneath the nose of a plume of warm and capping elevated mixed-layer air, mid/upper support for the initiation of boundary-layer based thunderstorm development is forecast to generally remain to the north of the international border. While the risk for severe thunderstorms appears largely conditional, guidance does indicate that a weak surface low may develop within the pre-frontal troughing and provide a potential focus for convective development across northwestern North Dakota late this afternoon and evening. If this forcing, coupled with the approach of convective temperatures, is sufficient to overcome the mid-level inhibition, forecast soundings indicate the environment will be conducive to supercell development. ..Kerr/Lyons.. 08/20/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1234 AM CDT Wed Aug 20 2025 Valid 201200Z - 211200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TODAY ACROSS THE WESTERN AND CENTRAL GULF COAST STATES AND THE INTERNATIONAL BORDER VICINITY OF NORTH DAKOTA... ...SUMMARY... Scattered thunderstorms developing this afternoon and evening across the western and central Gulf Coast states may pose a risk for localized potentially damaging wind gusts. Otherwise, there appears some risk for an isolated severe thunderstorm or two across parts of northern North Dakota. ...Discussion... Models indicate that a prominent mid/upper high will be maintained over the Four Corners vicinity through this period. However, initially amplified ridging extending to its north, as far as the Canadian Prairies, appears likely to become suppressed southeastward toward the central international border vicinity, as a significant short wave perturbation progresses east of the Canadian Rockies into Prairies by late tonight. It appears that this may be accompanied by weak cyclogenesis across southern Saskatchewan toward the central Saskatchewan/Manitoba border vicinity, with a trailing cold front advancing across the Montana international border by late tonight. At the same time, an increasingly sheared perturbation will continue progressing through weak larger-scale mid-level troughing digging across the Northeast, and southeastward around the periphery of the high, across the Ohio/Tennessee Valleys and southern Great Plains. To the southeast of this feature, Hurricane Erin is forecast to turn slowly north-northeastward, offshore of the southern through middle Atlantic Seaboard. ...Gulf Coast States... A diffuse surface frontal zone, reinforced in segments by convective outflow, will continue slowly southward ahead of the mid-level shear axis, likely reaching portions of central Texas through Louisiana and central/northern Mississippi and Alabama by mid to late afternoon. Along and ahead of this front, a corridor of stronger heating of a seasonably moist boundary layer, perhaps still coincident with a residual plume of relatively steep lower/mid-tropospheric lapse rates, may continue to contribute to thermodynamic profiles supportive of localized downbursts and gusty winds on convectively generated surface cold pools. It is not clear that the severe threat will be any more widespread than the sparse coverage of preceding days, but it may perhaps be marginally sufficient to justify 5 percent severe wind probabilities. ...North Dakota... Models indicate that a narrow corridor of moderate to large potential instability may develop along/ahead of the surface cold front, a pre-frontal surface trough and developing warm frontal zone across parts of the Dakotas into eastern Saskatchewan by late this afternoon. However, beneath the nose of a plume of warm and capping elevated mixed-layer air, mid/upper support for the initiation of boundary-layer based thunderstorm development is forecast to generally remain to the north of the international border. While the risk for severe thunderstorms appears largely conditional, guidance does indicate that a weak surface low may develop within the pre-frontal troughing and provide a potential focus for convective development across northwestern North Dakota late this afternoon and evening. If this forcing, coupled with the approach of convective temperatures, is sufficient to overcome the mid-level inhibition, forecast soundings indicate the environment will be conducive to supercell development. ..Kerr/Lyons.. 08/20/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1234 AM CDT Wed Aug 20 2025 Valid 201200Z - 211200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TODAY ACROSS THE WESTERN AND CENTRAL GULF COAST STATES AND THE INTERNATIONAL BORDER VICINITY OF NORTH DAKOTA... ...SUMMARY... Scattered thunderstorms developing this afternoon and evening across the western and central Gulf Coast states may pose a risk for localized potentially damaging wind gusts. Otherwise, there appears some risk for an isolated severe thunderstorm or two across parts of northern North Dakota. ...Discussion... Models indicate that a prominent mid/upper high will be maintained over the Four Corners vicinity through this period. However, initially amplified ridging extending to its north, as far as the Canadian Prairies, appears likely to become suppressed southeastward toward the central international border vicinity, as a significant short wave perturbation progresses east of the Canadian Rockies into Prairies by late tonight. It appears that this may be accompanied by weak cyclogenesis across southern Saskatchewan toward the central Saskatchewan/Manitoba border vicinity, with a trailing cold front advancing across the Montana international border by late tonight. At the same time, an increasingly sheared perturbation will continue progressing through weak larger-scale mid-level troughing digging across the Northeast, and southeastward around the periphery of the high, across the Ohio/Tennessee Valleys and southern Great Plains. To the southeast of this feature, Hurricane Erin is forecast to turn slowly north-northeastward, offshore of the southern through middle Atlantic Seaboard. ...Gulf Coast States... A diffuse surface frontal zone, reinforced in segments by convective outflow, will continue slowly southward ahead of the mid-level shear axis, likely reaching portions of central Texas through Louisiana and central/northern Mississippi and Alabama by mid to late afternoon. Along and ahead of this front, a corridor of stronger heating of a seasonably moist boundary layer, perhaps still coincident with a residual plume of relatively steep lower/mid-tropospheric lapse rates, may continue to contribute to thermodynamic profiles supportive of localized downbursts and gusty winds on convectively generated surface cold pools. It is not clear that the severe threat will be any more widespread than the sparse coverage of preceding days, but it may perhaps be marginally sufficient to justify 5 percent severe wind probabilities. ...North Dakota... Models indicate that a narrow corridor of moderate to large potential instability may develop along/ahead of the surface cold front, a pre-frontal surface trough and developing warm frontal zone across parts of the Dakotas into eastern Saskatchewan by late this afternoon. However, beneath the nose of a plume of warm and capping elevated mixed-layer air, mid/upper support for the initiation of boundary-layer based thunderstorm development is forecast to generally remain to the north of the international border. While the risk for severe thunderstorms appears largely conditional, guidance does indicate that a weak surface low may develop within the pre-frontal troughing and provide a potential focus for convective development across northwestern North Dakota late this afternoon and evening. If this forcing, coupled with the approach of convective temperatures, is sufficient to overcome the mid-level inhibition, forecast soundings indicate the environment will be conducive to supercell development. ..Kerr/Lyons.. 08/20/2025 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0731 PM CDT Tue Aug 19 2025 Valid 200100Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS EVENING INTO THE OVERNIGHT HOURS ACROSS PARTS OF WESTERN INTO NORTH CENTRAL MONTANA... ...SUMMARY... Strong to severe wind gusts may develop with a consolidating cluster of thunderstorms across western through north central Montana this evening into the overnight hours. ...01Z Update... ...Northern Rockies... Thunderstorms have begun to initiate across the Bitterroots vicinity, with deepening convection also evident to the lee of the mountains of western Montana, between Great Falls and Cut Bank. Although the hot and deeply mixed boundary layer which has evolved across the region appears only characterized by weak CAPE, models suggest that mid-level forcing for ascent overspreading the region will probably become supportive of a consolidating cluster, in the presence of cloud-bearing layer mean flow strengthening to 30-40+ kt. Even with onset of boundary-layer cooling within the next couple of hours, sub-cloud thermodynamic profiles will remain conducive to strengthening downward momentum transfer accompanied by surface gusts approaching or exceeding severe limits. As convection approaches better boundary-layer moisture across the Havre vicinity by late evening, more unstable updraft inflow might support further intensification of thunderstorms before spreading across the international border. ..Kerr.. 08/20/2025 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0731 PM CDT Tue Aug 19 2025 Valid 200100Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS EVENING INTO THE OVERNIGHT HOURS ACROSS PARTS OF WESTERN INTO NORTH CENTRAL MONTANA... ...SUMMARY... Strong to severe wind gusts may develop with a consolidating cluster of thunderstorms across western through north central Montana this evening into the overnight hours. ...01Z Update... ...Northern Rockies... Thunderstorms have begun to initiate across the Bitterroots vicinity, with deepening convection also evident to the lee of the mountains of western Montana, between Great Falls and Cut Bank. Although the hot and deeply mixed boundary layer which has evolved across the region appears only characterized by weak CAPE, models suggest that mid-level forcing for ascent overspreading the region will probably become supportive of a consolidating cluster, in the presence of cloud-bearing layer mean flow strengthening to 30-40+ kt. Even with onset of boundary-layer cooling within the next couple of hours, sub-cloud thermodynamic profiles will remain conducive to strengthening downward momentum transfer accompanied by surface gusts approaching or exceeding severe limits. As convection approaches better boundary-layer moisture across the Havre vicinity by late evening, more unstable updraft inflow might support further intensification of thunderstorms before spreading across the international border. ..Kerr.. 08/20/2025 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0731 PM CDT Tue Aug 19 2025 Valid 200100Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS EVENING INTO THE OVERNIGHT HOURS ACROSS PARTS OF WESTERN INTO NORTH CENTRAL MONTANA... ...SUMMARY... Strong to severe wind gusts may develop with a consolidating cluster of thunderstorms across western through north central Montana this evening into the overnight hours. ...01Z Update... ...Northern Rockies... Thunderstorms have begun to initiate across the Bitterroots vicinity, with deepening convection also evident to the lee of the mountains of western Montana, between Great Falls and Cut Bank. Although the hot and deeply mixed boundary layer which has evolved across the region appears only characterized by weak CAPE, models suggest that mid-level forcing for ascent overspreading the region will probably become supportive of a consolidating cluster, in the presence of cloud-bearing layer mean flow strengthening to 30-40+ kt. Even with onset of boundary-layer cooling within the next couple of hours, sub-cloud thermodynamic profiles will remain conducive to strengthening downward momentum transfer accompanied by surface gusts approaching or exceeding severe limits. As convection approaches better boundary-layer moisture across the Havre vicinity by late evening, more unstable updraft inflow might support further intensification of thunderstorms before spreading across the international border. ..Kerr.. 08/20/2025 Read more

No Mesoscale Discussions are in effect as of Tue Aug 19 23:14:02 UTC 2025.

No watches are valid as of Tue Aug 19 23:14:02 UTC 2025.

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0325 PM CDT Tue Aug 19 2025 Valid 211200Z - 271200Z The breakdown of the upper-level ridge over the northern Rockies will be complete on Day 3/Thursday. Monsoonal moisture will continue to push west and north into California, the Great Basin, and the Rockies of Colorado and Wyoming into the weekend as the upper-level ridge rebuilds over the West. Thunderstorm coverage will increase across these areas with wetter storms anticipated. Hot, dry, and unstable conditions will precede and follow along the leading edge of the monsoonal moisture as it traverses west/north. A 10% area for dry thunderstorms was introduced on Day 3/Thursday in the higher terrain of Utah, western Wyoming, and eastern Nevada. PWAT values are likely to be between 0.5-0.8" with a dry sub-cloud layer, although storm motions will be slower over Utah and parts of Nevada under the upper high. Areas of dry thunderstorms are likely near the leading edge of the monsoonal moisture in portions of California and the Great Basin possibly into the weekend. However, enough uncertainty regarding the magnitude, timing, and location of the monsoonal moisture exists to preclude additional probabilities later in the outlook period. Some areas in the southern/central Intermountain West are likely to have only one day of dry or mixed wet/dry thunderstorms before deeper moisture moves in and mitigates fire weather concerns. Hot, dry, and unstable conditions will increase across the West ahead of the monsoonal moisture from California and the Great Basin eventually into the Northwest and northern Rockies by the weekend. A strong West Coast thermal trough is likely to develop and will be monitored for potential offshore winds and focus for hot, dry, unstable, and breezy conditions. The duration of these hotter and drier conditions remains uncertain as forecast guidance of the upper-level pattern early next week over the West is a mix of persisting ridging and some sort of weakening or break down of the ridge. ..Nauslar.. 08/19/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0325 PM CDT Tue Aug 19 2025 Valid 211200Z - 271200Z The breakdown of the upper-level ridge over the northern Rockies will be complete on Day 3/Thursday. Monsoonal moisture will continue to push west and north into California, the Great Basin, and the Rockies of Colorado and Wyoming into the weekend as the upper-level ridge rebuilds over the West. Thunderstorm coverage will increase across these areas with wetter storms anticipated. Hot, dry, and unstable conditions will precede and follow along the leading edge of the monsoonal moisture as it traverses west/north. A 10% area for dry thunderstorms was introduced on Day 3/Thursday in the higher terrain of Utah, western Wyoming, and eastern Nevada. PWAT values are likely to be between 0.5-0.8" with a dry sub-cloud layer, although storm motions will be slower over Utah and parts of Nevada under the upper high. Areas of dry thunderstorms are likely near the leading edge of the monsoonal moisture in portions of California and the Great Basin possibly into the weekend. However, enough uncertainty regarding the magnitude, timing, and location of the monsoonal moisture exists to preclude additional probabilities later in the outlook period. Some areas in the southern/central Intermountain West are likely to have only one day of dry or mixed wet/dry thunderstorms before deeper moisture moves in and mitigates fire weather concerns. Hot, dry, and unstable conditions will increase across the West ahead of the monsoonal moisture from California and the Great Basin eventually into the Northwest and northern Rockies by the weekend. A strong West Coast thermal trough is likely to develop and will be monitored for potential offshore winds and focus for hot, dry, unstable, and breezy conditions. The duration of these hotter and drier conditions remains uncertain as forecast guidance of the upper-level pattern early next week over the West is a mix of persisting ridging and some sort of weakening or break down of the ridge. ..Nauslar.. 08/19/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0325 PM CDT Tue Aug 19 2025 Valid 211200Z - 271200Z The breakdown of the upper-level ridge over the northern Rockies will be complete on Day 3/Thursday. Monsoonal moisture will continue to push west and north into California, the Great Basin, and the Rockies of Colorado and Wyoming into the weekend as the upper-level ridge rebuilds over the West. Thunderstorm coverage will increase across these areas with wetter storms anticipated. Hot, dry, and unstable conditions will precede and follow along the leading edge of the monsoonal moisture as it traverses west/north. A 10% area for dry thunderstorms was introduced on Day 3/Thursday in the higher terrain of Utah, western Wyoming, and eastern Nevada. PWAT values are likely to be between 0.5-0.8" with a dry sub-cloud layer, although storm motions will be slower over Utah and parts of Nevada under the upper high. Areas of dry thunderstorms are likely near the leading edge of the monsoonal moisture in portions of California and the Great Basin possibly into the weekend. However, enough uncertainty regarding the magnitude, timing, and location of the monsoonal moisture exists to preclude additional probabilities later in the outlook period. Some areas in the southern/central Intermountain West are likely to have only one day of dry or mixed wet/dry thunderstorms before deeper moisture moves in and mitigates fire weather concerns. Hot, dry, and unstable conditions will increase across the West ahead of the monsoonal moisture from California and the Great Basin eventually into the Northwest and northern Rockies by the weekend. A strong West Coast thermal trough is likely to develop and will be monitored for potential offshore winds and focus for hot, dry, unstable, and breezy conditions. The duration of these hotter and drier conditions remains uncertain as forecast guidance of the upper-level pattern early next week over the West is a mix of persisting ridging and some sort of weakening or break down of the ridge. ..Nauslar.. 08/19/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0325 PM CDT Tue Aug 19 2025 Valid 211200Z - 271200Z The breakdown of the upper-level ridge over the northern Rockies will be complete on Day 3/Thursday. Monsoonal moisture will continue to push west and north into California, the Great Basin, and the Rockies of Colorado and Wyoming into the weekend as the upper-level ridge rebuilds over the West. Thunderstorm coverage will increase across these areas with wetter storms anticipated. Hot, dry, and unstable conditions will precede and follow along the leading edge of the monsoonal moisture as it traverses west/north. A 10% area for dry thunderstorms was introduced on Day 3/Thursday in the higher terrain of Utah, western Wyoming, and eastern Nevada. PWAT values are likely to be between 0.5-0.8" with a dry sub-cloud layer, although storm motions will be slower over Utah and parts of Nevada under the upper high. Areas of dry thunderstorms are likely near the leading edge of the monsoonal moisture in portions of California and the Great Basin possibly into the weekend. However, enough uncertainty regarding the magnitude, timing, and location of the monsoonal moisture exists to preclude additional probabilities later in the outlook period. Some areas in the southern/central Intermountain West are likely to have only one day of dry or mixed wet/dry thunderstorms before deeper moisture moves in and mitigates fire weather concerns. Hot, dry, and unstable conditions will increase across the West ahead of the monsoonal moisture from California and the Great Basin eventually into the Northwest and northern Rockies by the weekend. A strong West Coast thermal trough is likely to develop and will be monitored for potential offshore winds and focus for hot, dry, unstable, and breezy conditions. The duration of these hotter and drier conditions remains uncertain as forecast guidance of the upper-level pattern early next week over the West is a mix of persisting ridging and some sort of weakening or break down of the ridge. ..Nauslar.. 08/19/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more