Severe Storms

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0755 PM CDT Thu Aug 21 2025 Valid 220100Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN PLAINS... ...SUMMARY... Scattered severe thunderstorms remain possible across portions of the northern Plains and Upper Midwest tonight, with severe wind gusts and large hail the primary concerns. A few strong to severe storms may also occur across parts of southern Arizona this evening. ...01z Update... Upper ridge has flattened considerably across the northern Plains in response to SK short-wave trough. Mid-level flow will gradually veer across the Dakotas as a strong 500mb speed max translates through the base of the trough along the international border late tonight. As this occurs, surface front currently draped from northwest MN-central SD will gradually sag southeast. Thunderstorm coverage along the boundary remains isolated, and this may continue much of the evening until a secondary short wave approaches later tonight. While a meaningful LLJ is not expected ahead of this feature, latest model guidance continues to suggest a weak disturbance will eject across northeast WY/Black Hills region. Elevated convection could markedly increase after 06z across much of SD along/north of the front. Earlier thoughts regarding severe continue, but have lowered severe probabilities across northern MN to reflect less storm coverage along this portion of the boundary. AZ: Upper ridge is holding across the Four Corners region and favorable easterly flow is guiding terrain-induced convection toward the lower deserts. Scattered robust convection is expected to spread toward the more populated ares of the PHX metro over the next few hours. Gusty winds are the primary concern. ..Darrow.. 08/22/2025 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0755 PM CDT Thu Aug 21 2025 Valid 220100Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN PLAINS... ...SUMMARY... Scattered severe thunderstorms remain possible across portions of the northern Plains and Upper Midwest tonight, with severe wind gusts and large hail the primary concerns. A few strong to severe storms may also occur across parts of southern Arizona this evening. ...01z Update... Upper ridge has flattened considerably across the northern Plains in response to SK short-wave trough. Mid-level flow will gradually veer across the Dakotas as a strong 500mb speed max translates through the base of the trough along the international border late tonight. As this occurs, surface front currently draped from northwest MN-central SD will gradually sag southeast. Thunderstorm coverage along the boundary remains isolated, and this may continue much of the evening until a secondary short wave approaches later tonight. While a meaningful LLJ is not expected ahead of this feature, latest model guidance continues to suggest a weak disturbance will eject across northeast WY/Black Hills region. Elevated convection could markedly increase after 06z across much of SD along/north of the front. Earlier thoughts regarding severe continue, but have lowered severe probabilities across northern MN to reflect less storm coverage along this portion of the boundary. AZ: Upper ridge is holding across the Four Corners region and favorable easterly flow is guiding terrain-induced convection toward the lower deserts. Scattered robust convection is expected to spread toward the more populated ares of the PHX metro over the next few hours. Gusty winds are the primary concern. ..Darrow.. 08/22/2025 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0755 PM CDT Thu Aug 21 2025 Valid 220100Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN PLAINS... ...SUMMARY... Scattered severe thunderstorms remain possible across portions of the northern Plains and Upper Midwest tonight, with severe wind gusts and large hail the primary concerns. A few strong to severe storms may also occur across parts of southern Arizona this evening. ...01z Update... Upper ridge has flattened considerably across the northern Plains in response to SK short-wave trough. Mid-level flow will gradually veer across the Dakotas as a strong 500mb speed max translates through the base of the trough along the international border late tonight. As this occurs, surface front currently draped from northwest MN-central SD will gradually sag southeast. Thunderstorm coverage along the boundary remains isolated, and this may continue much of the evening until a secondary short wave approaches later tonight. While a meaningful LLJ is not expected ahead of this feature, latest model guidance continues to suggest a weak disturbance will eject across northeast WY/Black Hills region. Elevated convection could markedly increase after 06z across much of SD along/north of the front. Earlier thoughts regarding severe continue, but have lowered severe probabilities across northern MN to reflect less storm coverage along this portion of the boundary. AZ: Upper ridge is holding across the Four Corners region and favorable easterly flow is guiding terrain-induced convection toward the lower deserts. Scattered robust convection is expected to spread toward the more populated ares of the PHX metro over the next few hours. Gusty winds are the primary concern. ..Darrow.. 08/22/2025 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0755 PM CDT Thu Aug 21 2025 Valid 220100Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN PLAINS... ...SUMMARY... Scattered severe thunderstorms remain possible across portions of the northern Plains and Upper Midwest tonight, with severe wind gusts and large hail the primary concerns. A few strong to severe storms may also occur across parts of southern Arizona this evening. ...01z Update... Upper ridge has flattened considerably across the northern Plains in response to SK short-wave trough. Mid-level flow will gradually veer across the Dakotas as a strong 500mb speed max translates through the base of the trough along the international border late tonight. As this occurs, surface front currently draped from northwest MN-central SD will gradually sag southeast. Thunderstorm coverage along the boundary remains isolated, and this may continue much of the evening until a secondary short wave approaches later tonight. While a meaningful LLJ is not expected ahead of this feature, latest model guidance continues to suggest a weak disturbance will eject across northeast WY/Black Hills region. Elevated convection could markedly increase after 06z across much of SD along/north of the front. Earlier thoughts regarding severe continue, but have lowered severe probabilities across northern MN to reflect less storm coverage along this portion of the boundary. AZ: Upper ridge is holding across the Four Corners region and favorable easterly flow is guiding terrain-induced convection toward the lower deserts. Scattered robust convection is expected to spread toward the more populated ares of the PHX metro over the next few hours. Gusty winds are the primary concern. ..Darrow.. 08/22/2025 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0755 PM CDT Thu Aug 21 2025 Valid 220100Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN PLAINS... ...SUMMARY... Scattered severe thunderstorms remain possible across portions of the northern Plains and Upper Midwest tonight, with severe wind gusts and large hail the primary concerns. A few strong to severe storms may also occur across parts of southern Arizona this evening. ...01z Update... Upper ridge has flattened considerably across the northern Plains in response to SK short-wave trough. Mid-level flow will gradually veer across the Dakotas as a strong 500mb speed max translates through the base of the trough along the international border late tonight. As this occurs, surface front currently draped from northwest MN-central SD will gradually sag southeast. Thunderstorm coverage along the boundary remains isolated, and this may continue much of the evening until a secondary short wave approaches later tonight. While a meaningful LLJ is not expected ahead of this feature, latest model guidance continues to suggest a weak disturbance will eject across northeast WY/Black Hills region. Elevated convection could markedly increase after 06z across much of SD along/north of the front. Earlier thoughts regarding severe continue, but have lowered severe probabilities across northern MN to reflect less storm coverage along this portion of the boundary. AZ: Upper ridge is holding across the Four Corners region and favorable easterly flow is guiding terrain-induced convection toward the lower deserts. Scattered robust convection is expected to spread toward the more populated ares of the PHX metro over the next few hours. Gusty winds are the primary concern. ..Darrow.. 08/22/2025 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0755 PM CDT Thu Aug 21 2025 Valid 220100Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN PLAINS... ...SUMMARY... Scattered severe thunderstorms remain possible across portions of the northern Plains and Upper Midwest tonight, with severe wind gusts and large hail the primary concerns. A few strong to severe storms may also occur across parts of southern Arizona this evening. ...01z Update... Upper ridge has flattened considerably across the northern Plains in response to SK short-wave trough. Mid-level flow will gradually veer across the Dakotas as a strong 500mb speed max translates through the base of the trough along the international border late tonight. As this occurs, surface front currently draped from northwest MN-central SD will gradually sag southeast. Thunderstorm coverage along the boundary remains isolated, and this may continue much of the evening until a secondary short wave approaches later tonight. While a meaningful LLJ is not expected ahead of this feature, latest model guidance continues to suggest a weak disturbance will eject across northeast WY/Black Hills region. Elevated convection could markedly increase after 06z across much of SD along/north of the front. Earlier thoughts regarding severe continue, but have lowered severe probabilities across northern MN to reflect less storm coverage along this portion of the boundary. AZ: Upper ridge is holding across the Four Corners region and favorable easterly flow is guiding terrain-induced convection toward the lower deserts. Scattered robust convection is expected to spread toward the more populated ares of the PHX metro over the next few hours. Gusty winds are the primary concern. ..Darrow.. 08/22/2025 Read more

No watches are valid as of Thu Aug 21 23:46:02 UTC 2025.

MD 1998 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF CENTRAL INTO SOUTHERN ARIZONA
Mesoscale Discussion 1998 NWS Storm Prediction Center Norman OK 0451 PM CDT Thu Aug 21 2025 Areas affected...portions of central into southern Arizona Concerning...Severe potential...Watch unlikely Valid 212151Z - 220015Z Probability of Watch Issuance...20 percent SUMMARY...A few severe gusts are possible with the stronger storms today, especially if cold-pool mergers can occur. DISCUSSION...Thunderstorms are maturing atop and to the south of the Mogollon Rim given orographic lift and strong surface heating. These storms continue to propagate south-southwestward and are preceded by a hot surface airmass (e.g. 100-110 F temperatures). This is supporting a deep, mixed boundary layer, characterized by dry-adiabatic low-level lapse rates. 20+ kts of easterly mid-level flow and accompanying deep-layer speed shear pivoting around an upper anticyclone will encourage multicellular organization. Given ample expected evaporative cooling, the stronger downbursts may support isolated severe gusts, especially if cold pools from multicellular clusters manage to merge. Nonetheless, the severe gust threat should be isolated, so a WW issuance is not currently expected. ..Squitieri/Mosier.. 08/21/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...TWC...FGZ...PSR... LAT...LON 34051303 34071095 33700961 33120916 32320924 31910961 31671024 31581102 31701181 32061264 32761319 34051303 MOST PROBABLE PEAK WIND GUST...55-70 MPH Read more

MD 1999 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PARTS OF WEST-CENTRAL MN...FAR SOUTHEASTERN ND...AND EASTERN/CENTRAL SD
Mesoscale Discussion 1999 NWS Storm Prediction Center Norman OK 0521 PM CDT Thu Aug 21 2025 Areas affected...Parts of west-central MN...far southeastern ND...and eastern/central SD Concerning...Severe potential...Watch possible Valid 212221Z - 212345Z Probability of Watch Issuance...40 percent SUMMARY...Monitoring the area for some increase in severe-thunderstorm potential over the next few hours. Any sustained storms will be capable of producing large hail and severe gusts. It is unclear if a watch is needed. DISCUSSION...Latest surface observations show a pre-frontal wind shift extending from far southeastern ND into eastern/central SD. Isolated thunderstorms have developed along the wind shift in far southeastern ND, while a separate area of boundary-layer cumulus has attempted to deepen over east-central SD. Along/ahead of the surface boundary, strong diurnal heating amid middle 70s dewpoints and steep midlevel lapse rates has eroded antecedent convective inhibition and is contributing to a strongly unstable air mass. At the same time, the ABR VWP is sampling around 40 kt of 0-6 km shear, which is oriented oblique to the surface boundary. While generally weak large-scale forcing for ascent and some lingering inhibition cast uncertainty on storm coverage and longevity, any storms that do evolve could become discrete/semi-discrete supercells and pose a risk of large hail and locally severe wind gusts. Given the uncertainty in storm coverage/longevity, it is unclear if a watch will be needed, though convective trends are being monitored. ..Weinman/Mosier.. 08/21/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...MPX...FGF...FSD...ABR... LAT...LON 46899512 46409501 45769528 45139602 44659674 43919833 43759901 43919947 44189970 44709965 45099893 46139719 46909649 47179601 47179555 46899512 MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 95 MPH MOST PROBABLE PEAK WIND GUST...55-70 MPH MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN Read more

No Mesoscale Discussions are in effect as of Thu Aug 21 21:35:02 UTC 2025.

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0426 PM CDT Thu Aug 21 2025 Valid 231200Z - 291200Z Upper-level ridging will continue over much of the West this weekend but will begin to weaken Day 4/Sunday - Day 5/Monday. The upper high is likely to retreat towards Texas, with weak ridging maintaining over portions of the West early to mid-next week. Weak flow overall is likely over the West, while weak troughing may develop off the West Coast and possibly into the Northwest next week. Monsoonal moisture will stream north through the Great Basin and into the Northwest and northern Rockies, but a backdoor cold front and weakening ridging may limit monsoonal moisture in the northern Rockies. Isolated to scattered mixed wet/dry thunderstorms are likely in the northern Sierra into the southern Cascades and across the northwest Great Basin on Day 3/Saturday, with another round slightly farther north on Day 4/Sunday. A few concerns regarding dry thunderstorm potential are the expected cloud cover with the monsoonal moisture moving northward limiting instability, potential training of storms/deeper moisture leading to more wetting rain, and fuels still rebounding from recent rainfall. However, given the hot, dry, unstable, and locally breezy conditions ahead of and coincident with the initial monsoonal surge, fuels will cure rapidly and cloud bases and storm motions could be high and fast enough, respectively, to result in at least isolated dry thunderstorm coverage in portions of Oregon, northern California, and northern Nevada. Beyond Day 4/Sunday, there is too much uncertainty regarding dry thunderstorm potential to include probabilities at this time in the Northwest, northern California, northern Great Basin, and northern Rockies. Daily scattered to widespread mostly wet thunderstorms are expected across much of the southern/central Great Basin, Colorado Rockies, Southwest, and eastern California. This will significantly slow fire season for these areas and possibly provide season ending rain for some areas. Well above normal temperatures and prolonged low RH are expected across northern California, the Northwest, northern Great Basin, and northern Rockies Day 3/Saturday, with portions of northern California and the northern Great Basin seeing higher RH and slightly lower temperatures on Day 4/Sunday due to the monsoonal moisture. Above normal temperatures will continue much of the northwestern US into early next, with continued prolonged low RH from the Inland Northwest into the northern Rockies. ..Nauslar.. 08/21/2025 ...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 0426 PM CDT Thu Aug 21 2025 Valid 231200Z - 291200Z Upper-level ridging will continue over much of the West this weekend but will begin to weaken Day 4/Sunday - Day 5/Monday. The upper high is likely to retreat towards Texas, with weak ridging maintaining over portions of the West early to mid-next week. Weak flow overall is likely over the West, while weak troughing may develop off the West Coast and possibly into the Northwest next week. Monsoonal moisture will stream north through the Great Basin and into the Northwest and northern Rockies, but a backdoor cold front and weakening ridging may limit monsoonal moisture in the northern Rockies. Isolated to scattered mixed wet/dry thunderstorms are likely in the northern Sierra into the southern Cascades and across the northwest Great Basin on Day 3/Saturday, with another round slightly farther north on Day 4/Sunday. A few concerns regarding dry thunderstorm potential are the expected cloud cover with the monsoonal moisture moving northward limiting instability, potential training of storms/deeper moisture leading to more wetting rain, and fuels still rebounding from recent rainfall. However, given the hot, dry, unstable, and locally breezy conditions ahead of and coincident with the initial monsoonal surge, fuels will cure rapidly and cloud bases and storm motions could be high and fast enough, respectively, to result in at least isolated dry thunderstorm coverage in portions of Oregon, northern California, and northern Nevada. Beyond Day 4/Sunday, there is too much uncertainty regarding dry thunderstorm potential to include probabilities at this time in the Northwest, northern California, northern Great Basin, and northern Rockies. Daily scattered to widespread mostly wet thunderstorms are expected across much of the southern/central Great Basin, Colorado Rockies, Southwest, and eastern California. This will significantly slow fire season for these areas and possibly provide season ending rain for some areas. Well above normal temperatures and prolonged low RH are expected across northern California, the Northwest, northern Great Basin, and northern Rockies Day 3/Saturday, with portions of northern California and the northern Great Basin seeing higher RH and slightly lower temperatures on Day 4/Sunday due to the monsoonal moisture. Above normal temperatures will continue much of the northwestern US into early next, with continued prolonged low RH from the Inland Northwest into the northern Rockies. ..Nauslar.. 08/21/2025 ...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 0426 PM CDT Thu Aug 21 2025 Valid 231200Z - 291200Z Upper-level ridging will continue over much of the West this weekend but will begin to weaken Day 4/Sunday - Day 5/Monday. The upper high is likely to retreat towards Texas, with weak ridging maintaining over portions of the West early to mid-next week. Weak flow overall is likely over the West, while weak troughing may develop off the West Coast and possibly into the Northwest next week. Monsoonal moisture will stream north through the Great Basin and into the Northwest and northern Rockies, but a backdoor cold front and weakening ridging may limit monsoonal moisture in the northern Rockies. Isolated to scattered mixed wet/dry thunderstorms are likely in the northern Sierra into the southern Cascades and across the northwest Great Basin on Day 3/Saturday, with another round slightly farther north on Day 4/Sunday. A few concerns regarding dry thunderstorm potential are the expected cloud cover with the monsoonal moisture moving northward limiting instability, potential training of storms/deeper moisture leading to more wetting rain, and fuels still rebounding from recent rainfall. However, given the hot, dry, unstable, and locally breezy conditions ahead of and coincident with the initial monsoonal surge, fuels will cure rapidly and cloud bases and storm motions could be high and fast enough, respectively, to result in at least isolated dry thunderstorm coverage in portions of Oregon, northern California, and northern Nevada. Beyond Day 4/Sunday, there is too much uncertainty regarding dry thunderstorm potential to include probabilities at this time in the Northwest, northern California, northern Great Basin, and northern Rockies. Daily scattered to widespread mostly wet thunderstorms are expected across much of the southern/central Great Basin, Colorado Rockies, Southwest, and eastern California. This will significantly slow fire season for these areas and possibly provide season ending rain for some areas. Well above normal temperatures and prolonged low RH are expected across northern California, the Northwest, northern Great Basin, and northern Rockies Day 3/Saturday, with portions of northern California and the northern Great Basin seeing higher RH and slightly lower temperatures on Day 4/Sunday due to the monsoonal moisture. Above normal temperatures will continue much of the northwestern US into early next, with continued prolonged low RH from the Inland Northwest into the northern Rockies. ..Nauslar.. 08/21/2025 ...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 0426 PM CDT Thu Aug 21 2025 Valid 231200Z - 291200Z Upper-level ridging will continue over much of the West this weekend but will begin to weaken Day 4/Sunday - Day 5/Monday. The upper high is likely to retreat towards Texas, with weak ridging maintaining over portions of the West early to mid-next week. Weak flow overall is likely over the West, while weak troughing may develop off the West Coast and possibly into the Northwest next week. Monsoonal moisture will stream north through the Great Basin and into the Northwest and northern Rockies, but a backdoor cold front and weakening ridging may limit monsoonal moisture in the northern Rockies. Isolated to scattered mixed wet/dry thunderstorms are likely in the northern Sierra into the southern Cascades and across the northwest Great Basin on Day 3/Saturday, with another round slightly farther north on Day 4/Sunday. A few concerns regarding dry thunderstorm potential are the expected cloud cover with the monsoonal moisture moving northward limiting instability, potential training of storms/deeper moisture leading to more wetting rain, and fuels still rebounding from recent rainfall. However, given the hot, dry, unstable, and locally breezy conditions ahead of and coincident with the initial monsoonal surge, fuels will cure rapidly and cloud bases and storm motions could be high and fast enough, respectively, to result in at least isolated dry thunderstorm coverage in portions of Oregon, northern California, and northern Nevada. Beyond Day 4/Sunday, there is too much uncertainty regarding dry thunderstorm potential to include probabilities at this time in the Northwest, northern California, northern Great Basin, and northern Rockies. Daily scattered to widespread mostly wet thunderstorms are expected across much of the southern/central Great Basin, Colorado Rockies, Southwest, and eastern California. This will significantly slow fire season for these areas and possibly provide season ending rain for some areas. Well above normal temperatures and prolonged low RH are expected across northern California, the Northwest, northern Great Basin, and northern Rockies Day 3/Saturday, with portions of northern California and the northern Great Basin seeing higher RH and slightly lower temperatures on Day 4/Sunday due to the monsoonal moisture. Above normal temperatures will continue much of the northwestern US into early next, with continued prolonged low RH from the Inland Northwest into the northern Rockies. ..Nauslar.. 08/21/2025 ...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 0426 PM CDT Thu Aug 21 2025 Valid 231200Z - 291200Z Upper-level ridging will continue over much of the West this weekend but will begin to weaken Day 4/Sunday - Day 5/Monday. The upper high is likely to retreat towards Texas, with weak ridging maintaining over portions of the West early to mid-next week. Weak flow overall is likely over the West, while weak troughing may develop off the West Coast and possibly into the Northwest next week. Monsoonal moisture will stream north through the Great Basin and into the Northwest and northern Rockies, but a backdoor cold front and weakening ridging may limit monsoonal moisture in the northern Rockies. Isolated to scattered mixed wet/dry thunderstorms are likely in the northern Sierra into the southern Cascades and across the northwest Great Basin on Day 3/Saturday, with another round slightly farther north on Day 4/Sunday. A few concerns regarding dry thunderstorm potential are the expected cloud cover with the monsoonal moisture moving northward limiting instability, potential training of storms/deeper moisture leading to more wetting rain, and fuels still rebounding from recent rainfall. However, given the hot, dry, unstable, and locally breezy conditions ahead of and coincident with the initial monsoonal surge, fuels will cure rapidly and cloud bases and storm motions could be high and fast enough, respectively, to result in at least isolated dry thunderstorm coverage in portions of Oregon, northern California, and northern Nevada. Beyond Day 4/Sunday, there is too much uncertainty regarding dry thunderstorm potential to include probabilities at this time in the Northwest, northern California, northern Great Basin, and northern Rockies. Daily scattered to widespread mostly wet thunderstorms are expected across much of the southern/central Great Basin, Colorado Rockies, Southwest, and eastern California. This will significantly slow fire season for these areas and possibly provide season ending rain for some areas. Well above normal temperatures and prolonged low RH are expected across northern California, the Northwest, northern Great Basin, and northern Rockies Day 3/Saturday, with portions of northern California and the northern Great Basin seeing higher RH and slightly lower temperatures on Day 4/Sunday due to the monsoonal moisture. Above normal temperatures will continue much of the northwestern US into early next, with continued prolonged low RH from the Inland Northwest into the northern Rockies. ..Nauslar.. 08/21/2025 ...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 0426 PM CDT Thu Aug 21 2025 Valid 231200Z - 291200Z Upper-level ridging will continue over much of the West this weekend but will begin to weaken Day 4/Sunday - Day 5/Monday. The upper high is likely to retreat towards Texas, with weak ridging maintaining over portions of the West early to mid-next week. Weak flow overall is likely over the West, while weak troughing may develop off the West Coast and possibly into the Northwest next week. Monsoonal moisture will stream north through the Great Basin and into the Northwest and northern Rockies, but a backdoor cold front and weakening ridging may limit monsoonal moisture in the northern Rockies. Isolated to scattered mixed wet/dry thunderstorms are likely in the northern Sierra into the southern Cascades and across the northwest Great Basin on Day 3/Saturday, with another round slightly farther north on Day 4/Sunday. A few concerns regarding dry thunderstorm potential are the expected cloud cover with the monsoonal moisture moving northward limiting instability, potential training of storms/deeper moisture leading to more wetting rain, and fuels still rebounding from recent rainfall. However, given the hot, dry, unstable, and locally breezy conditions ahead of and coincident with the initial monsoonal surge, fuels will cure rapidly and cloud bases and storm motions could be high and fast enough, respectively, to result in at least isolated dry thunderstorm coverage in portions of Oregon, northern California, and northern Nevada. Beyond Day 4/Sunday, there is too much uncertainty regarding dry thunderstorm potential to include probabilities at this time in the Northwest, northern California, northern Great Basin, and northern Rockies. Daily scattered to widespread mostly wet thunderstorms are expected across much of the southern/central Great Basin, Colorado Rockies, Southwest, and eastern California. This will significantly slow fire season for these areas and possibly provide season ending rain for some areas. Well above normal temperatures and prolonged low RH are expected across northern California, the Northwest, northern Great Basin, and northern Rockies Day 3/Saturday, with portions of northern California and the northern Great Basin seeing higher RH and slightly lower temperatures on Day 4/Sunday due to the monsoonal moisture. Above normal temperatures will continue much of the northwestern US into early next, with continued prolonged low RH from the Inland Northwest into the northern Rockies. ..Nauslar.. 08/21/2025 ...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 0426 PM CDT Thu Aug 21 2025 Valid 231200Z - 291200Z Upper-level ridging will continue over much of the West this weekend but will begin to weaken Day 4/Sunday - Day 5/Monday. The upper high is likely to retreat towards Texas, with weak ridging maintaining over portions of the West early to mid-next week. Weak flow overall is likely over the West, while weak troughing may develop off the West Coast and possibly into the Northwest next week. Monsoonal moisture will stream north through the Great Basin and into the Northwest and northern Rockies, but a backdoor cold front and weakening ridging may limit monsoonal moisture in the northern Rockies. Isolated to scattered mixed wet/dry thunderstorms are likely in the northern Sierra into the southern Cascades and across the northwest Great Basin on Day 3/Saturday, with another round slightly farther north on Day 4/Sunday. A few concerns regarding dry thunderstorm potential are the expected cloud cover with the monsoonal moisture moving northward limiting instability, potential training of storms/deeper moisture leading to more wetting rain, and fuels still rebounding from recent rainfall. However, given the hot, dry, unstable, and locally breezy conditions ahead of and coincident with the initial monsoonal surge, fuels will cure rapidly and cloud bases and storm motions could be high and fast enough, respectively, to result in at least isolated dry thunderstorm coverage in portions of Oregon, northern California, and northern Nevada. Beyond Day 4/Sunday, there is too much uncertainty regarding dry thunderstorm potential to include probabilities at this time in the Northwest, northern California, northern Great Basin, and northern Rockies. Daily scattered to widespread mostly wet thunderstorms are expected across much of the southern/central Great Basin, Colorado Rockies, Southwest, and eastern California. This will significantly slow fire season for these areas and possibly provide season ending rain for some areas. Well above normal temperatures and prolonged low RH are expected across northern California, the Northwest, northern Great Basin, and northern Rockies Day 3/Saturday, with portions of northern California and the northern Great Basin seeing higher RH and slightly lower temperatures on Day 4/Sunday due to the monsoonal moisture. Above normal temperatures will continue much of the northwestern US into early next, with continued prolonged low RH from the Inland Northwest into the northern Rockies. ..Nauslar.. 08/21/2025 ...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 0426 PM CDT Thu Aug 21 2025 Valid 231200Z - 291200Z Upper-level ridging will continue over much of the West this weekend but will begin to weaken Day 4/Sunday - Day 5/Monday. The upper high is likely to retreat towards Texas, with weak ridging maintaining over portions of the West early to mid-next week. Weak flow overall is likely over the West, while weak troughing may develop off the West Coast and possibly into the Northwest next week. Monsoonal moisture will stream north through the Great Basin and into the Northwest and northern Rockies, but a backdoor cold front and weakening ridging may limit monsoonal moisture in the northern Rockies. Isolated to scattered mixed wet/dry thunderstorms are likely in the northern Sierra into the southern Cascades and across the northwest Great Basin on Day 3/Saturday, with another round slightly farther north on Day 4/Sunday. A few concerns regarding dry thunderstorm potential are the expected cloud cover with the monsoonal moisture moving northward limiting instability, potential training of storms/deeper moisture leading to more wetting rain, and fuels still rebounding from recent rainfall. However, given the hot, dry, unstable, and locally breezy conditions ahead of and coincident with the initial monsoonal surge, fuels will cure rapidly and cloud bases and storm motions could be high and fast enough, respectively, to result in at least isolated dry thunderstorm coverage in portions of Oregon, northern California, and northern Nevada. Beyond Day 4/Sunday, there is too much uncertainty regarding dry thunderstorm potential to include probabilities at this time in the Northwest, northern California, northern Great Basin, and northern Rockies. Daily scattered to widespread mostly wet thunderstorms are expected across much of the southern/central Great Basin, Colorado Rockies, Southwest, and eastern California. This will significantly slow fire season for these areas and possibly provide season ending rain for some areas. Well above normal temperatures and prolonged low RH are expected across northern California, the Northwest, northern Great Basin, and northern Rockies Day 3/Saturday, with portions of northern California and the northern Great Basin seeing higher RH and slightly lower temperatures on Day 4/Sunday due to the monsoonal moisture. Above normal temperatures will continue much of the northwestern US into early next, with continued prolonged low RH from the Inland Northwest into the northern Rockies. ..Nauslar.. 08/21/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0253 PM CDT Thu Aug 21 2025 Valid 212000Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF EASTERN SOUTH DAKOTA INTO NORTHWEST MINNESOTA... ...SUMMARY... Scattered severe thunderstorms are possible across portions of the northern Plains and Upper Midwest this afternoon into tonight, with severe wind gusts and large hail the primary concerns. A few strong to severe storms may also occur across parts of southern Arizona. ...20z Update... No changes are needed to the D1 Convective Outlook. See previous discussion for more information. ..Thornton.. 08/21/2025 .PREV DISCUSSION... /ISSUED 1130 AM CDT Thu Aug 21 2025/ ...Northern Plains into the Upper Midwest... Enhanced mid/upper-level westerly flow will persist today across the northern Plains/Upper Midwest, sandwiched between upper troughing over the Canadian Prairie provinces and a stout mid/upper-level anticyclone centered over the Four Corners/Southwest. Multiple low-amplitude perturbations, some associated with ongoing convection across eastern MT into ND and northern MN, will move eastward today and potentially aid in additional thunderstorm development this afternoon and evening. At the surface, the primary low associated with the upper trough will remain well north in Canada, with a trailing cold front expected to continue moving east-southeastward across the northern Plains and Upper Midwest through the period. There is still considerable uncertainty regarding potential robust convective development and subsequent evolution along/near the cold front later today. This is mainly due to the stronger large-scale ascent aloft forecast to remain in central Canada, and capping concerns with southward extent along the front in the northern Plains due to fairly warm low/mid-level temperatures. Multiple potential scenarios remain plausible, ranging from little to no convection developing this afternoon/evening, as some recent convection-allowing model guidance suggests, to multiple supercells/clusters forming in a narrow zone of favorable instability and shear. Given these considerations, confidence is lower than usual regarding severe potential across the northern Plains/Upper Midwest. Still, a narrow corridor of moderate to strong instability will likely exist late this afternoon and into the evening along/near the front from northwest MN into eastern SD, aided by steep mid-level lapse rates and diurnal heating. Modest low-level flow veering to westerly at mid/upper levels will foster sufficient deep-layer shear (around 30-40 kt) to support organized convection, including the potential for a few supercells and clusters. Scattered large hail and severe/damaging winds may occur with this activity if it develops and can be sustained. So, a Slight Risk has been included with this update to account for this potential. Farther west, a post-frontal regime will exist this afternoon/evening across the northern High Plains of northeast WY and vicinity. Low-level upslope flow against the higher terrain may promote a supercell or two to develop and spread east-southeastward through the late afternoon and evening, with mainly an isolated hail threat. Some potential for clustering is also apparent this evening/overnight across parts of SD along/near the surface front. If this occurs, then a continued threat for strong to locally severe gusts may persist. Have therefore connected the Marginal Risks across SD for this possibility. ...Arizona... Modest mid/upper-level easterly flow will persist today over southern AZ, to the south of an anticyclone aloft centered over the Four Corners. Convection that initially develops over the higher terrain of southeast/east-central AZ may gradually develop westward into lower elevations through the late afternoon and continuing into the evening. Ample daytime heating of a seasonably moist low-level airmass already in place (reference observed 12Z PHX sounding) will act to further steepen low/mid-level lapse rates. At least isolated strong to severe gusts may occur with these thunderstorms given the favorable thermodynamic/lapse rate environment. The Marginal Risk has been expanded some to account for latest short-term guidance trends. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0253 PM CDT Thu Aug 21 2025 Valid 212000Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF EASTERN SOUTH DAKOTA INTO NORTHWEST MINNESOTA... ...SUMMARY... Scattered severe thunderstorms are possible across portions of the northern Plains and Upper Midwest this afternoon into tonight, with severe wind gusts and large hail the primary concerns. A few strong to severe storms may also occur across parts of southern Arizona. ...20z Update... No changes are needed to the D1 Convective Outlook. See previous discussion for more information. ..Thornton.. 08/21/2025 .PREV DISCUSSION... /ISSUED 1130 AM CDT Thu Aug 21 2025/ ...Northern Plains into the Upper Midwest... Enhanced mid/upper-level westerly flow will persist today across the northern Plains/Upper Midwest, sandwiched between upper troughing over the Canadian Prairie provinces and a stout mid/upper-level anticyclone centered over the Four Corners/Southwest. Multiple low-amplitude perturbations, some associated with ongoing convection across eastern MT into ND and northern MN, will move eastward today and potentially aid in additional thunderstorm development this afternoon and evening. At the surface, the primary low associated with the upper trough will remain well north in Canada, with a trailing cold front expected to continue moving east-southeastward across the northern Plains and Upper Midwest through the period. There is still considerable uncertainty regarding potential robust convective development and subsequent evolution along/near the cold front later today. This is mainly due to the stronger large-scale ascent aloft forecast to remain in central Canada, and capping concerns with southward extent along the front in the northern Plains due to fairly warm low/mid-level temperatures. Multiple potential scenarios remain plausible, ranging from little to no convection developing this afternoon/evening, as some recent convection-allowing model guidance suggests, to multiple supercells/clusters forming in a narrow zone of favorable instability and shear. Given these considerations, confidence is lower than usual regarding severe potential across the northern Plains/Upper Midwest. Still, a narrow corridor of moderate to strong instability will likely exist late this afternoon and into the evening along/near the front from northwest MN into eastern SD, aided by steep mid-level lapse rates and diurnal heating. Modest low-level flow veering to westerly at mid/upper levels will foster sufficient deep-layer shear (around 30-40 kt) to support organized convection, including the potential for a few supercells and clusters. Scattered large hail and severe/damaging winds may occur with this activity if it develops and can be sustained. So, a Slight Risk has been included with this update to account for this potential. Farther west, a post-frontal regime will exist this afternoon/evening across the northern High Plains of northeast WY and vicinity. Low-level upslope flow against the higher terrain may promote a supercell or two to develop and spread east-southeastward through the late afternoon and evening, with mainly an isolated hail threat. Some potential for clustering is also apparent this evening/overnight across parts of SD along/near the surface front. If this occurs, then a continued threat for strong to locally severe gusts may persist. Have therefore connected the Marginal Risks across SD for this possibility. ...Arizona... Modest mid/upper-level easterly flow will persist today over southern AZ, to the south of an anticyclone aloft centered over the Four Corners. Convection that initially develops over the higher terrain of southeast/east-central AZ may gradually develop westward into lower elevations through the late afternoon and continuing into the evening. Ample daytime heating of a seasonably moist low-level airmass already in place (reference observed 12Z PHX sounding) will act to further steepen low/mid-level lapse rates. At least isolated strong to severe gusts may occur with these thunderstorms given the favorable thermodynamic/lapse rate environment. The Marginal Risk has been expanded some to account for latest short-term guidance trends. Read more