Aggregator

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1153 AM CDT Sat Aug 16 2025 Valid 161700Z - 171200Z Current satellite imagery shows a broad cloud shield associated with an influx of Pacific moisture along a cold front draped from northwestern CA into the ID Panhandle. PWAT values of around 1.00 inch along with higher surface dewpoints and relative humidity near and behind the frontal boundary will promote more wetting rainfall within heavier shower and thunderstorm cores. This has shifted the dry thunderstorm threat slightly southeastward where diurnal heating is more accessible in conjunction with a drier sub-cloud layer, supporting more limited rainfall within northeastward thunderstorm motions of up to 30 knots expected this afternoon and evening. A mid-level wind maxima of 30-40 knots and associated increased shear stretching from eastern OR into western MT could aid in sustained convection through tonight across eastern OR, central ID mountains and western MT. ..Williams.. 08/16/2025 .PREV DISCUSSION... /ISSUED 0202 AM CDT Sat Aug 16 2025/ ...Synopsis... A broad mid-level trough over the Northwestern US is forecast to consolidate and intensify today/tonight as it impinges on the northwestern edge of a ridge of high pressure over the central US. The tightening height gradient will bolster flow aloft, while at the same time, a surface cold front will move in from the Northwest. Monsoon moisture will support showers and thunderstorms along/ahead of the front, while localized dry and breezy conditions are possible over the Southwestern US. ...Northwest and Rockies Dry Thunder... Across the Northwest and central Rockies, persistent monsoon moisture will be in palace ahead of the upper trough and attendant cold front. Increasing PWATs (0.8-1 inch) will favor a mix of wet and dry storms across far northern CA into eastern OR and ID/MT from the afternoon into the evening hours. While the air mass in the low-levels will not be as dry as recent days, with increasing RH ahead of the front, 30-40 kt of mid-level flow should support faster northeastward storm motions of 25-30 kt. This will allow for less wetting rainfall as storms track eastward over areas of very receptive fuels supportive of lightning ignitions. Additionally, gusty outflow winds are expected, potentially impacting existing active fires across the area. The risk for lightning may continue overnight as the upper trough and front shift eastward towards ID and MT. IsoDryT highlights will remain, and have been expanded over areas of the expected driest fuels and storms. ...Southern Great Basin... As the mid-level trough continues eastward across the Northwest, southwesterly flow aloft should continue to promote locally breezy and dry conditions across portions of southern NV and western UT. South-southwest winds of up to 15 mph, along with daytime relative humidity as low as 15%, are expected in some valleys in the southern Great Basin. Amidst dry fuels, some locally elevated fire-weather conditions are possible. The lack of stronger winds for now precludes elevated highlights. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1153 AM CDT Sat Aug 16 2025 Valid 161700Z - 171200Z Current satellite imagery shows a broad cloud shield associated with an influx of Pacific moisture along a cold front draped from northwestern CA into the ID Panhandle. PWAT values of around 1.00 inch along with higher surface dewpoints and relative humidity near and behind the frontal boundary will promote more wetting rainfall within heavier shower and thunderstorm cores. This has shifted the dry thunderstorm threat slightly southeastward where diurnal heating is more accessible in conjunction with a drier sub-cloud layer, supporting more limited rainfall within northeastward thunderstorm motions of up to 30 knots expected this afternoon and evening. A mid-level wind maxima of 30-40 knots and associated increased shear stretching from eastern OR into western MT could aid in sustained convection through tonight across eastern OR, central ID mountains and western MT. ..Williams.. 08/16/2025 .PREV DISCUSSION... /ISSUED 0202 AM CDT Sat Aug 16 2025/ ...Synopsis... A broad mid-level trough over the Northwestern US is forecast to consolidate and intensify today/tonight as it impinges on the northwestern edge of a ridge of high pressure over the central US. The tightening height gradient will bolster flow aloft, while at the same time, a surface cold front will move in from the Northwest. Monsoon moisture will support showers and thunderstorms along/ahead of the front, while localized dry and breezy conditions are possible over the Southwestern US. ...Northwest and Rockies Dry Thunder... Across the Northwest and central Rockies, persistent monsoon moisture will be in palace ahead of the upper trough and attendant cold front. Increasing PWATs (0.8-1 inch) will favor a mix of wet and dry storms across far northern CA into eastern OR and ID/MT from the afternoon into the evening hours. While the air mass in the low-levels will not be as dry as recent days, with increasing RH ahead of the front, 30-40 kt of mid-level flow should support faster northeastward storm motions of 25-30 kt. This will allow for less wetting rainfall as storms track eastward over areas of very receptive fuels supportive of lightning ignitions. Additionally, gusty outflow winds are expected, potentially impacting existing active fires across the area. The risk for lightning may continue overnight as the upper trough and front shift eastward towards ID and MT. IsoDryT highlights will remain, and have been expanded over areas of the expected driest fuels and storms. ...Southern Great Basin... As the mid-level trough continues eastward across the Northwest, southwesterly flow aloft should continue to promote locally breezy and dry conditions across portions of southern NV and western UT. South-southwest winds of up to 15 mph, along with daytime relative humidity as low as 15%, are expected in some valleys in the southern Great Basin. Amidst dry fuels, some locally elevated fire-weather conditions are possible. The lack of stronger winds for now precludes elevated highlights. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1153 AM CDT Sat Aug 16 2025 Valid 161700Z - 171200Z Current satellite imagery shows a broad cloud shield associated with an influx of Pacific moisture along a cold front draped from northwestern CA into the ID Panhandle. PWAT values of around 1.00 inch along with higher surface dewpoints and relative humidity near and behind the frontal boundary will promote more wetting rainfall within heavier shower and thunderstorm cores. This has shifted the dry thunderstorm threat slightly southeastward where diurnal heating is more accessible in conjunction with a drier sub-cloud layer, supporting more limited rainfall within northeastward thunderstorm motions of up to 30 knots expected this afternoon and evening. A mid-level wind maxima of 30-40 knots and associated increased shear stretching from eastern OR into western MT could aid in sustained convection through tonight across eastern OR, central ID mountains and western MT. ..Williams.. 08/16/2025 .PREV DISCUSSION... /ISSUED 0202 AM CDT Sat Aug 16 2025/ ...Synopsis... A broad mid-level trough over the Northwestern US is forecast to consolidate and intensify today/tonight as it impinges on the northwestern edge of a ridge of high pressure over the central US. The tightening height gradient will bolster flow aloft, while at the same time, a surface cold front will move in from the Northwest. Monsoon moisture will support showers and thunderstorms along/ahead of the front, while localized dry and breezy conditions are possible over the Southwestern US. ...Northwest and Rockies Dry Thunder... Across the Northwest and central Rockies, persistent monsoon moisture will be in palace ahead of the upper trough and attendant cold front. Increasing PWATs (0.8-1 inch) will favor a mix of wet and dry storms across far northern CA into eastern OR and ID/MT from the afternoon into the evening hours. While the air mass in the low-levels will not be as dry as recent days, with increasing RH ahead of the front, 30-40 kt of mid-level flow should support faster northeastward storm motions of 25-30 kt. This will allow for less wetting rainfall as storms track eastward over areas of very receptive fuels supportive of lightning ignitions. Additionally, gusty outflow winds are expected, potentially impacting existing active fires across the area. The risk for lightning may continue overnight as the upper trough and front shift eastward towards ID and MT. IsoDryT highlights will remain, and have been expanded over areas of the expected driest fuels and storms. ...Southern Great Basin... As the mid-level trough continues eastward across the Northwest, southwesterly flow aloft should continue to promote locally breezy and dry conditions across portions of southern NV and western UT. South-southwest winds of up to 15 mph, along with daytime relative humidity as low as 15%, are expected in some valleys in the southern Great Basin. Amidst dry fuels, some locally elevated fire-weather conditions are possible. The lack of stronger winds for now precludes elevated highlights. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1153 AM CDT Sat Aug 16 2025 Valid 161700Z - 171200Z Current satellite imagery shows a broad cloud shield associated with an influx of Pacific moisture along a cold front draped from northwestern CA into the ID Panhandle. PWAT values of around 1.00 inch along with higher surface dewpoints and relative humidity near and behind the frontal boundary will promote more wetting rainfall within heavier shower and thunderstorm cores. This has shifted the dry thunderstorm threat slightly southeastward where diurnal heating is more accessible in conjunction with a drier sub-cloud layer, supporting more limited rainfall within northeastward thunderstorm motions of up to 30 knots expected this afternoon and evening. A mid-level wind maxima of 30-40 knots and associated increased shear stretching from eastern OR into western MT could aid in sustained convection through tonight across eastern OR, central ID mountains and western MT. ..Williams.. 08/16/2025 .PREV DISCUSSION... /ISSUED 0202 AM CDT Sat Aug 16 2025/ ...Synopsis... A broad mid-level trough over the Northwestern US is forecast to consolidate and intensify today/tonight as it impinges on the northwestern edge of a ridge of high pressure over the central US. The tightening height gradient will bolster flow aloft, while at the same time, a surface cold front will move in from the Northwest. Monsoon moisture will support showers and thunderstorms along/ahead of the front, while localized dry and breezy conditions are possible over the Southwestern US. ...Northwest and Rockies Dry Thunder... Across the Northwest and central Rockies, persistent monsoon moisture will be in palace ahead of the upper trough and attendant cold front. Increasing PWATs (0.8-1 inch) will favor a mix of wet and dry storms across far northern CA into eastern OR and ID/MT from the afternoon into the evening hours. While the air mass in the low-levels will not be as dry as recent days, with increasing RH ahead of the front, 30-40 kt of mid-level flow should support faster northeastward storm motions of 25-30 kt. This will allow for less wetting rainfall as storms track eastward over areas of very receptive fuels supportive of lightning ignitions. Additionally, gusty outflow winds are expected, potentially impacting existing active fires across the area. The risk for lightning may continue overnight as the upper trough and front shift eastward towards ID and MT. IsoDryT highlights will remain, and have been expanded over areas of the expected driest fuels and storms. ...Southern Great Basin... As the mid-level trough continues eastward across the Northwest, southwesterly flow aloft should continue to promote locally breezy and dry conditions across portions of southern NV and western UT. South-southwest winds of up to 15 mph, along with daytime relative humidity as low as 15%, are expected in some valleys in the southern Great Basin. Amidst dry fuels, some locally elevated fire-weather conditions are possible. The lack of stronger winds for now precludes elevated highlights. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1153 AM CDT Sat Aug 16 2025 Valid 161700Z - 171200Z Current satellite imagery shows a broad cloud shield associated with an influx of Pacific moisture along a cold front draped from northwestern CA into the ID Panhandle. PWAT values of around 1.00 inch along with higher surface dewpoints and relative humidity near and behind the frontal boundary will promote more wetting rainfall within heavier shower and thunderstorm cores. This has shifted the dry thunderstorm threat slightly southeastward where diurnal heating is more accessible in conjunction with a drier sub-cloud layer, supporting more limited rainfall within northeastward thunderstorm motions of up to 30 knots expected this afternoon and evening. A mid-level wind maxima of 30-40 knots and associated increased shear stretching from eastern OR into western MT could aid in sustained convection through tonight across eastern OR, central ID mountains and western MT. ..Williams.. 08/16/2025 .PREV DISCUSSION... /ISSUED 0202 AM CDT Sat Aug 16 2025/ ...Synopsis... A broad mid-level trough over the Northwestern US is forecast to consolidate and intensify today/tonight as it impinges on the northwestern edge of a ridge of high pressure over the central US. The tightening height gradient will bolster flow aloft, while at the same time, a surface cold front will move in from the Northwest. Monsoon moisture will support showers and thunderstorms along/ahead of the front, while localized dry and breezy conditions are possible over the Southwestern US. ...Northwest and Rockies Dry Thunder... Across the Northwest and central Rockies, persistent monsoon moisture will be in palace ahead of the upper trough and attendant cold front. Increasing PWATs (0.8-1 inch) will favor a mix of wet and dry storms across far northern CA into eastern OR and ID/MT from the afternoon into the evening hours. While the air mass in the low-levels will not be as dry as recent days, with increasing RH ahead of the front, 30-40 kt of mid-level flow should support faster northeastward storm motions of 25-30 kt. This will allow for less wetting rainfall as storms track eastward over areas of very receptive fuels supportive of lightning ignitions. Additionally, gusty outflow winds are expected, potentially impacting existing active fires across the area. The risk for lightning may continue overnight as the upper trough and front shift eastward towards ID and MT. IsoDryT highlights will remain, and have been expanded over areas of the expected driest fuels and storms. ...Southern Great Basin... As the mid-level trough continues eastward across the Northwest, southwesterly flow aloft should continue to promote locally breezy and dry conditions across portions of southern NV and western UT. South-southwest winds of up to 15 mph, along with daytime relative humidity as low as 15%, are expected in some valleys in the southern Great Basin. Amidst dry fuels, some locally elevated fire-weather conditions are possible. The lack of stronger winds for now precludes elevated highlights. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1153 AM CDT Sat Aug 16 2025 Valid 161700Z - 171200Z Current satellite imagery shows a broad cloud shield associated with an influx of Pacific moisture along a cold front draped from northwestern CA into the ID Panhandle. PWAT values of around 1.00 inch along with higher surface dewpoints and relative humidity near and behind the frontal boundary will promote more wetting rainfall within heavier shower and thunderstorm cores. This has shifted the dry thunderstorm threat slightly southeastward where diurnal heating is more accessible in conjunction with a drier sub-cloud layer, supporting more limited rainfall within northeastward thunderstorm motions of up to 30 knots expected this afternoon and evening. A mid-level wind maxima of 30-40 knots and associated increased shear stretching from eastern OR into western MT could aid in sustained convection through tonight across eastern OR, central ID mountains and western MT. ..Williams.. 08/16/2025 .PREV DISCUSSION... /ISSUED 0202 AM CDT Sat Aug 16 2025/ ...Synopsis... A broad mid-level trough over the Northwestern US is forecast to consolidate and intensify today/tonight as it impinges on the northwestern edge of a ridge of high pressure over the central US. The tightening height gradient will bolster flow aloft, while at the same time, a surface cold front will move in from the Northwest. Monsoon moisture will support showers and thunderstorms along/ahead of the front, while localized dry and breezy conditions are possible over the Southwestern US. ...Northwest and Rockies Dry Thunder... Across the Northwest and central Rockies, persistent monsoon moisture will be in palace ahead of the upper trough and attendant cold front. Increasing PWATs (0.8-1 inch) will favor a mix of wet and dry storms across far northern CA into eastern OR and ID/MT from the afternoon into the evening hours. While the air mass in the low-levels will not be as dry as recent days, with increasing RH ahead of the front, 30-40 kt of mid-level flow should support faster northeastward storm motions of 25-30 kt. This will allow for less wetting rainfall as storms track eastward over areas of very receptive fuels supportive of lightning ignitions. Additionally, gusty outflow winds are expected, potentially impacting existing active fires across the area. The risk for lightning may continue overnight as the upper trough and front shift eastward towards ID and MT. IsoDryT highlights will remain, and have been expanded over areas of the expected driest fuels and storms. ...Southern Great Basin... As the mid-level trough continues eastward across the Northwest, southwesterly flow aloft should continue to promote locally breezy and dry conditions across portions of southern NV and western UT. South-southwest winds of up to 15 mph, along with daytime relative humidity as low as 15%, are expected in some valleys in the southern Great Basin. Amidst dry fuels, some locally elevated fire-weather conditions are possible. The lack of stronger winds for now precludes elevated highlights. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1153 AM CDT Sat Aug 16 2025 Valid 161700Z - 171200Z Current satellite imagery shows a broad cloud shield associated with an influx of Pacific moisture along a cold front draped from northwestern CA into the ID Panhandle. PWAT values of around 1.00 inch along with higher surface dewpoints and relative humidity near and behind the frontal boundary will promote more wetting rainfall within heavier shower and thunderstorm cores. This has shifted the dry thunderstorm threat slightly southeastward where diurnal heating is more accessible in conjunction with a drier sub-cloud layer, supporting more limited rainfall within northeastward thunderstorm motions of up to 30 knots expected this afternoon and evening. A mid-level wind maxima of 30-40 knots and associated increased shear stretching from eastern OR into western MT could aid in sustained convection through tonight across eastern OR, central ID mountains and western MT. ..Williams.. 08/16/2025 .PREV DISCUSSION... /ISSUED 0202 AM CDT Sat Aug 16 2025/ ...Synopsis... A broad mid-level trough over the Northwestern US is forecast to consolidate and intensify today/tonight as it impinges on the northwestern edge of a ridge of high pressure over the central US. The tightening height gradient will bolster flow aloft, while at the same time, a surface cold front will move in from the Northwest. Monsoon moisture will support showers and thunderstorms along/ahead of the front, while localized dry and breezy conditions are possible over the Southwestern US. ...Northwest and Rockies Dry Thunder... Across the Northwest and central Rockies, persistent monsoon moisture will be in palace ahead of the upper trough and attendant cold front. Increasing PWATs (0.8-1 inch) will favor a mix of wet and dry storms across far northern CA into eastern OR and ID/MT from the afternoon into the evening hours. While the air mass in the low-levels will not be as dry as recent days, with increasing RH ahead of the front, 30-40 kt of mid-level flow should support faster northeastward storm motions of 25-30 kt. This will allow for less wetting rainfall as storms track eastward over areas of very receptive fuels supportive of lightning ignitions. Additionally, gusty outflow winds are expected, potentially impacting existing active fires across the area. The risk for lightning may continue overnight as the upper trough and front shift eastward towards ID and MT. IsoDryT highlights will remain, and have been expanded over areas of the expected driest fuels and storms. ...Southern Great Basin... As the mid-level trough continues eastward across the Northwest, southwesterly flow aloft should continue to promote locally breezy and dry conditions across portions of southern NV and western UT. South-southwest winds of up to 15 mph, along with daytime relative humidity as low as 15%, are expected in some valleys in the southern Great Basin. Amidst dry fuels, some locally elevated fire-weather conditions are possible. The lack of stronger winds for now precludes elevated highlights. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1153 AM CDT Sat Aug 16 2025 Valid 161700Z - 171200Z Current satellite imagery shows a broad cloud shield associated with an influx of Pacific moisture along a cold front draped from northwestern CA into the ID Panhandle. PWAT values of around 1.00 inch along with higher surface dewpoints and relative humidity near and behind the frontal boundary will promote more wetting rainfall within heavier shower and thunderstorm cores. This has shifted the dry thunderstorm threat slightly southeastward where diurnal heating is more accessible in conjunction with a drier sub-cloud layer, supporting more limited rainfall within northeastward thunderstorm motions of up to 30 knots expected this afternoon and evening. A mid-level wind maxima of 30-40 knots and associated increased shear stretching from eastern OR into western MT could aid in sustained convection through tonight across eastern OR, central ID mountains and western MT. ..Williams.. 08/16/2025 .PREV DISCUSSION... /ISSUED 0202 AM CDT Sat Aug 16 2025/ ...Synopsis... A broad mid-level trough over the Northwestern US is forecast to consolidate and intensify today/tonight as it impinges on the northwestern edge of a ridge of high pressure over the central US. The tightening height gradient will bolster flow aloft, while at the same time, a surface cold front will move in from the Northwest. Monsoon moisture will support showers and thunderstorms along/ahead of the front, while localized dry and breezy conditions are possible over the Southwestern US. ...Northwest and Rockies Dry Thunder... Across the Northwest and central Rockies, persistent monsoon moisture will be in palace ahead of the upper trough and attendant cold front. Increasing PWATs (0.8-1 inch) will favor a mix of wet and dry storms across far northern CA into eastern OR and ID/MT from the afternoon into the evening hours. While the air mass in the low-levels will not be as dry as recent days, with increasing RH ahead of the front, 30-40 kt of mid-level flow should support faster northeastward storm motions of 25-30 kt. This will allow for less wetting rainfall as storms track eastward over areas of very receptive fuels supportive of lightning ignitions. Additionally, gusty outflow winds are expected, potentially impacting existing active fires across the area. The risk for lightning may continue overnight as the upper trough and front shift eastward towards ID and MT. IsoDryT highlights will remain, and have been expanded over areas of the expected driest fuels and storms. ...Southern Great Basin... As the mid-level trough continues eastward across the Northwest, southwesterly flow aloft should continue to promote locally breezy and dry conditions across portions of southern NV and western UT. South-southwest winds of up to 15 mph, along with daytime relative humidity as low as 15%, are expected in some valleys in the southern Great Basin. Amidst dry fuels, some locally elevated fire-weather conditions are possible. The lack of stronger winds for now precludes elevated highlights. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1153 AM CDT Sat Aug 16 2025 Valid 161700Z - 171200Z Current satellite imagery shows a broad cloud shield associated with an influx of Pacific moisture along a cold front draped from northwestern CA into the ID Panhandle. PWAT values of around 1.00 inch along with higher surface dewpoints and relative humidity near and behind the frontal boundary will promote more wetting rainfall within heavier shower and thunderstorm cores. This has shifted the dry thunderstorm threat slightly southeastward where diurnal heating is more accessible in conjunction with a drier sub-cloud layer, supporting more limited rainfall within northeastward thunderstorm motions of up to 30 knots expected this afternoon and evening. A mid-level wind maxima of 30-40 knots and associated increased shear stretching from eastern OR into western MT could aid in sustained convection through tonight across eastern OR, central ID mountains and western MT. ..Williams.. 08/16/2025 .PREV DISCUSSION... /ISSUED 0202 AM CDT Sat Aug 16 2025/ ...Synopsis... A broad mid-level trough over the Northwestern US is forecast to consolidate and intensify today/tonight as it impinges on the northwestern edge of a ridge of high pressure over the central US. The tightening height gradient will bolster flow aloft, while at the same time, a surface cold front will move in from the Northwest. Monsoon moisture will support showers and thunderstorms along/ahead of the front, while localized dry and breezy conditions are possible over the Southwestern US. ...Northwest and Rockies Dry Thunder... Across the Northwest and central Rockies, persistent monsoon moisture will be in palace ahead of the upper trough and attendant cold front. Increasing PWATs (0.8-1 inch) will favor a mix of wet and dry storms across far northern CA into eastern OR and ID/MT from the afternoon into the evening hours. While the air mass in the low-levels will not be as dry as recent days, with increasing RH ahead of the front, 30-40 kt of mid-level flow should support faster northeastward storm motions of 25-30 kt. This will allow for less wetting rainfall as storms track eastward over areas of very receptive fuels supportive of lightning ignitions. Additionally, gusty outflow winds are expected, potentially impacting existing active fires across the area. The risk for lightning may continue overnight as the upper trough and front shift eastward towards ID and MT. IsoDryT highlights will remain, and have been expanded over areas of the expected driest fuels and storms. ...Southern Great Basin... As the mid-level trough continues eastward across the Northwest, southwesterly flow aloft should continue to promote locally breezy and dry conditions across portions of southern NV and western UT. South-southwest winds of up to 15 mph, along with daytime relative humidity as low as 15%, are expected in some valleys in the southern Great Basin. Amidst dry fuels, some locally elevated fire-weather conditions are possible. The lack of stronger winds for now precludes elevated highlights. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1153 AM CDT Sat Aug 16 2025 Valid 161700Z - 171200Z Current satellite imagery shows a broad cloud shield associated with an influx of Pacific moisture along a cold front draped from northwestern CA into the ID Panhandle. PWAT values of around 1.00 inch along with higher surface dewpoints and relative humidity near and behind the frontal boundary will promote more wetting rainfall within heavier shower and thunderstorm cores. This has shifted the dry thunderstorm threat slightly southeastward where diurnal heating is more accessible in conjunction with a drier sub-cloud layer, supporting more limited rainfall within northeastward thunderstorm motions of up to 30 knots expected this afternoon and evening. A mid-level wind maxima of 30-40 knots and associated increased shear stretching from eastern OR into western MT could aid in sustained convection through tonight across eastern OR, central ID mountains and western MT. ..Williams.. 08/16/2025 .PREV DISCUSSION... /ISSUED 0202 AM CDT Sat Aug 16 2025/ ...Synopsis... A broad mid-level trough over the Northwestern US is forecast to consolidate and intensify today/tonight as it impinges on the northwestern edge of a ridge of high pressure over the central US. The tightening height gradient will bolster flow aloft, while at the same time, a surface cold front will move in from the Northwest. Monsoon moisture will support showers and thunderstorms along/ahead of the front, while localized dry and breezy conditions are possible over the Southwestern US. ...Northwest and Rockies Dry Thunder... Across the Northwest and central Rockies, persistent monsoon moisture will be in palace ahead of the upper trough and attendant cold front. Increasing PWATs (0.8-1 inch) will favor a mix of wet and dry storms across far northern CA into eastern OR and ID/MT from the afternoon into the evening hours. While the air mass in the low-levels will not be as dry as recent days, with increasing RH ahead of the front, 30-40 kt of mid-level flow should support faster northeastward storm motions of 25-30 kt. This will allow for less wetting rainfall as storms track eastward over areas of very receptive fuels supportive of lightning ignitions. Additionally, gusty outflow winds are expected, potentially impacting existing active fires across the area. The risk for lightning may continue overnight as the upper trough and front shift eastward towards ID and MT. IsoDryT highlights will remain, and have been expanded over areas of the expected driest fuels and storms. ...Southern Great Basin... As the mid-level trough continues eastward across the Northwest, southwesterly flow aloft should continue to promote locally breezy and dry conditions across portions of southern NV and western UT. South-southwest winds of up to 15 mph, along with daytime relative humidity as low as 15%, are expected in some valleys in the southern Great Basin. Amidst dry fuels, some locally elevated fire-weather conditions are possible. The lack of stronger winds for now precludes elevated highlights. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Aug 16 2025 Valid 161630Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING AND TONIGHT OVER PART OF SD...AND THIS AFTERNOON THROUGH TONIGHT OVER SOUTHEAST MN...SOUTHERN WI...AND NORTHERN IL... ...SUMMARY... Scattered strong/severe thunderstorms are possible today into tonight across parts of the northern Great Plains into Midwest and Great Lakes region. ...Upper Midwest into the Mid MS Valley and Upper Great Lakes Region... An expansive MCS continues to move eastward across the Upper Midwest, with a well-defined MCV evident in radar imagery over the central WI/MN border vicinity. This MCS has continued to gradually weaken throughout the morning, but a few strong updrafts persist along its southeastern periphery over central WI. This portion of the MCS is on the far northeastern periphery of the plume of steeper mid-level lapse rates that extends from the northern/central High Plains across the central Plains and into the Mid MS Valley. This plume is observable in the 12Z sounding from DVN and ILX, which sampled 700-500 mb lapse rates of 7.8 and 7.2 deg C per km, respectively. Dewpoints downstream across southern WI, northern IL, and northern IN are in the low 70s, with upper 60s dewpoints also covering much of southern Lower MI. The combination of ample low-level moisture and steep mid-level lapse rates will result in strong to very strong buoyancy to the south of the MCS from the MN/IA border into northern/central IL. Given the lack of a well-defined surface boundary and negligible large-scale ascent, additional thunderstorm development will be associated with outflow from with the MCS, which results in greater-than-average uncertainty for the Day 1 period. Ample moisture and buoyancy downstream of the leading edge of the MCS suggests the greater severe potential this afternoon/evening will likely be associated with redevelopment/reintensification of the MCS. Additionally, even if reintensification does not occur along the leading edge of the MCS this afternoon, most guidance suggests redevelopment does eventually occur this evening along the southern periphery of the MCV circulation as it moves into northern/central WI. Increased severe-wind probabilities (i.e. 15%) were introduced with this outlook to cover both of these potential scenarios. A small 15% hail probability was introduce to cover potential for later evening storms atop the outflow as well. Storms are possible into northern IN and the Lower MI this afternoon and evening as well, but the lower buoyancy should temper the overall coverage and magnitude in these areas. ...SD and Vicinity... A well-defined but rather weak shortwave trough is currently moving through western CO/western WY, and will continue northeastward into eastern WY/western Dakotas by this evening. Similar to yesterday, high-based storms will develop ahead of the approaching shortwave and intensify as they move eastward into a progressively more moist/unstable air mass over west-central SD. Upscale growth into another nocturnal MCS is forecast by most guidance, with the MCS tracking northeastward across western/central SD tonight. Strong to severe gusts are possible with this potential MCS across much of western/central SD. ..Mosier/Wendt.. 08/16/2025 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Aug 16 2025 Valid 161630Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING AND TONIGHT OVER PART OF SD...AND THIS AFTERNOON THROUGH TONIGHT OVER SOUTHEAST MN...SOUTHERN WI...AND NORTHERN IL... ...SUMMARY... Scattered strong/severe thunderstorms are possible today into tonight across parts of the northern Great Plains into Midwest and Great Lakes region. ...Upper Midwest into the Mid MS Valley and Upper Great Lakes Region... An expansive MCS continues to move eastward across the Upper Midwest, with a well-defined MCV evident in radar imagery over the central WI/MN border vicinity. This MCS has continued to gradually weaken throughout the morning, but a few strong updrafts persist along its southeastern periphery over central WI. This portion of the MCS is on the far northeastern periphery of the plume of steeper mid-level lapse rates that extends from the northern/central High Plains across the central Plains and into the Mid MS Valley. This plume is observable in the 12Z sounding from DVN and ILX, which sampled 700-500 mb lapse rates of 7.8 and 7.2 deg C per km, respectively. Dewpoints downstream across southern WI, northern IL, and northern IN are in the low 70s, with upper 60s dewpoints also covering much of southern Lower MI. The combination of ample low-level moisture and steep mid-level lapse rates will result in strong to very strong buoyancy to the south of the MCS from the MN/IA border into northern/central IL. Given the lack of a well-defined surface boundary and negligible large-scale ascent, additional thunderstorm development will be associated with outflow from with the MCS, which results in greater-than-average uncertainty for the Day 1 period. Ample moisture and buoyancy downstream of the leading edge of the MCS suggests the greater severe potential this afternoon/evening will likely be associated with redevelopment/reintensification of the MCS. Additionally, even if reintensification does not occur along the leading edge of the MCS this afternoon, most guidance suggests redevelopment does eventually occur this evening along the southern periphery of the MCV circulation as it moves into northern/central WI. Increased severe-wind probabilities (i.e. 15%) were introduced with this outlook to cover both of these potential scenarios. A small 15% hail probability was introduce to cover potential for later evening storms atop the outflow as well. Storms are possible into northern IN and the Lower MI this afternoon and evening as well, but the lower buoyancy should temper the overall coverage and magnitude in these areas. ...SD and Vicinity... A well-defined but rather weak shortwave trough is currently moving through western CO/western WY, and will continue northeastward into eastern WY/western Dakotas by this evening. Similar to yesterday, high-based storms will develop ahead of the approaching shortwave and intensify as they move eastward into a progressively more moist/unstable air mass over west-central SD. Upscale growth into another nocturnal MCS is forecast by most guidance, with the MCS tracking northeastward across western/central SD tonight. Strong to severe gusts are possible with this potential MCS across much of western/central SD. ..Mosier/Wendt.. 08/16/2025 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Aug 16 2025 Valid 161630Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING AND TONIGHT OVER PART OF SD...AND THIS AFTERNOON THROUGH TONIGHT OVER SOUTHEAST MN...SOUTHERN WI...AND NORTHERN IL... ...SUMMARY... Scattered strong/severe thunderstorms are possible today into tonight across parts of the northern Great Plains into Midwest and Great Lakes region. ...Upper Midwest into the Mid MS Valley and Upper Great Lakes Region... An expansive MCS continues to move eastward across the Upper Midwest, with a well-defined MCV evident in radar imagery over the central WI/MN border vicinity. This MCS has continued to gradually weaken throughout the morning, but a few strong updrafts persist along its southeastern periphery over central WI. This portion of the MCS is on the far northeastern periphery of the plume of steeper mid-level lapse rates that extends from the northern/central High Plains across the central Plains and into the Mid MS Valley. This plume is observable in the 12Z sounding from DVN and ILX, which sampled 700-500 mb lapse rates of 7.8 and 7.2 deg C per km, respectively. Dewpoints downstream across southern WI, northern IL, and northern IN are in the low 70s, with upper 60s dewpoints also covering much of southern Lower MI. The combination of ample low-level moisture and steep mid-level lapse rates will result in strong to very strong buoyancy to the south of the MCS from the MN/IA border into northern/central IL. Given the lack of a well-defined surface boundary and negligible large-scale ascent, additional thunderstorm development will be associated with outflow from with the MCS, which results in greater-than-average uncertainty for the Day 1 period. Ample moisture and buoyancy downstream of the leading edge of the MCS suggests the greater severe potential this afternoon/evening will likely be associated with redevelopment/reintensification of the MCS. Additionally, even if reintensification does not occur along the leading edge of the MCS this afternoon, most guidance suggests redevelopment does eventually occur this evening along the southern periphery of the MCV circulation as it moves into northern/central WI. Increased severe-wind probabilities (i.e. 15%) were introduced with this outlook to cover both of these potential scenarios. A small 15% hail probability was introduce to cover potential for later evening storms atop the outflow as well. Storms are possible into northern IN and the Lower MI this afternoon and evening as well, but the lower buoyancy should temper the overall coverage and magnitude in these areas. ...SD and Vicinity... A well-defined but rather weak shortwave trough is currently moving through western CO/western WY, and will continue northeastward into eastern WY/western Dakotas by this evening. Similar to yesterday, high-based storms will develop ahead of the approaching shortwave and intensify as they move eastward into a progressively more moist/unstable air mass over west-central SD. Upscale growth into another nocturnal MCS is forecast by most guidance, with the MCS tracking northeastward across western/central SD tonight. Strong to severe gusts are possible with this potential MCS across much of western/central SD. ..Mosier/Wendt.. 08/16/2025 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Aug 16 2025 Valid 161630Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING AND TONIGHT OVER PART OF SD...AND THIS AFTERNOON THROUGH TONIGHT OVER SOUTHEAST MN...SOUTHERN WI...AND NORTHERN IL... ...SUMMARY... Scattered strong/severe thunderstorms are possible today into tonight across parts of the northern Great Plains into Midwest and Great Lakes region. ...Upper Midwest into the Mid MS Valley and Upper Great Lakes Region... An expansive MCS continues to move eastward across the Upper Midwest, with a well-defined MCV evident in radar imagery over the central WI/MN border vicinity. This MCS has continued to gradually weaken throughout the morning, but a few strong updrafts persist along its southeastern periphery over central WI. This portion of the MCS is on the far northeastern periphery of the plume of steeper mid-level lapse rates that extends from the northern/central High Plains across the central Plains and into the Mid MS Valley. This plume is observable in the 12Z sounding from DVN and ILX, which sampled 700-500 mb lapse rates of 7.8 and 7.2 deg C per km, respectively. Dewpoints downstream across southern WI, northern IL, and northern IN are in the low 70s, with upper 60s dewpoints also covering much of southern Lower MI. The combination of ample low-level moisture and steep mid-level lapse rates will result in strong to very strong buoyancy to the south of the MCS from the MN/IA border into northern/central IL. Given the lack of a well-defined surface boundary and negligible large-scale ascent, additional thunderstorm development will be associated with outflow from with the MCS, which results in greater-than-average uncertainty for the Day 1 period. Ample moisture and buoyancy downstream of the leading edge of the MCS suggests the greater severe potential this afternoon/evening will likely be associated with redevelopment/reintensification of the MCS. Additionally, even if reintensification does not occur along the leading edge of the MCS this afternoon, most guidance suggests redevelopment does eventually occur this evening along the southern periphery of the MCV circulation as it moves into northern/central WI. Increased severe-wind probabilities (i.e. 15%) were introduced with this outlook to cover both of these potential scenarios. A small 15% hail probability was introduce to cover potential for later evening storms atop the outflow as well. Storms are possible into northern IN and the Lower MI this afternoon and evening as well, but the lower buoyancy should temper the overall coverage and magnitude in these areas. ...SD and Vicinity... A well-defined but rather weak shortwave trough is currently moving through western CO/western WY, and will continue northeastward into eastern WY/western Dakotas by this evening. Similar to yesterday, high-based storms will develop ahead of the approaching shortwave and intensify as they move eastward into a progressively more moist/unstable air mass over west-central SD. Upscale growth into another nocturnal MCS is forecast by most guidance, with the MCS tracking northeastward across western/central SD tonight. Strong to severe gusts are possible with this potential MCS across much of western/central SD. ..Mosier/Wendt.. 08/16/2025 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Aug 16 2025 Valid 161630Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING AND TONIGHT OVER PART OF SD...AND THIS AFTERNOON THROUGH TONIGHT OVER SOUTHEAST MN...SOUTHERN WI...AND NORTHERN IL... ...SUMMARY... Scattered strong/severe thunderstorms are possible today into tonight across parts of the northern Great Plains into Midwest and Great Lakes region. ...Upper Midwest into the Mid MS Valley and Upper Great Lakes Region... An expansive MCS continues to move eastward across the Upper Midwest, with a well-defined MCV evident in radar imagery over the central WI/MN border vicinity. This MCS has continued to gradually weaken throughout the morning, but a few strong updrafts persist along its southeastern periphery over central WI. This portion of the MCS is on the far northeastern periphery of the plume of steeper mid-level lapse rates that extends from the northern/central High Plains across the central Plains and into the Mid MS Valley. This plume is observable in the 12Z sounding from DVN and ILX, which sampled 700-500 mb lapse rates of 7.8 and 7.2 deg C per km, respectively. Dewpoints downstream across southern WI, northern IL, and northern IN are in the low 70s, with upper 60s dewpoints also covering much of southern Lower MI. The combination of ample low-level moisture and steep mid-level lapse rates will result in strong to very strong buoyancy to the south of the MCS from the MN/IA border into northern/central IL. Given the lack of a well-defined surface boundary and negligible large-scale ascent, additional thunderstorm development will be associated with outflow from with the MCS, which results in greater-than-average uncertainty for the Day 1 period. Ample moisture and buoyancy downstream of the leading edge of the MCS suggests the greater severe potential this afternoon/evening will likely be associated with redevelopment/reintensification of the MCS. Additionally, even if reintensification does not occur along the leading edge of the MCS this afternoon, most guidance suggests redevelopment does eventually occur this evening along the southern periphery of the MCV circulation as it moves into northern/central WI. Increased severe-wind probabilities (i.e. 15%) were introduced with this outlook to cover both of these potential scenarios. A small 15% hail probability was introduce to cover potential for later evening storms atop the outflow as well. Storms are possible into northern IN and the Lower MI this afternoon and evening as well, but the lower buoyancy should temper the overall coverage and magnitude in these areas. ...SD and Vicinity... A well-defined but rather weak shortwave trough is currently moving through western CO/western WY, and will continue northeastward into eastern WY/western Dakotas by this evening. Similar to yesterday, high-based storms will develop ahead of the approaching shortwave and intensify as they move eastward into a progressively more moist/unstable air mass over west-central SD. Upscale growth into another nocturnal MCS is forecast by most guidance, with the MCS tracking northeastward across western/central SD tonight. Strong to severe gusts are possible with this potential MCS across much of western/central SD. ..Mosier/Wendt.. 08/16/2025 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Aug 16 2025 Valid 161630Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING AND TONIGHT OVER PART OF SD...AND THIS AFTERNOON THROUGH TONIGHT OVER SOUTHEAST MN...SOUTHERN WI...AND NORTHERN IL... ...SUMMARY... Scattered strong/severe thunderstorms are possible today into tonight across parts of the northern Great Plains into Midwest and Great Lakes region. ...Upper Midwest into the Mid MS Valley and Upper Great Lakes Region... An expansive MCS continues to move eastward across the Upper Midwest, with a well-defined MCV evident in radar imagery over the central WI/MN border vicinity. This MCS has continued to gradually weaken throughout the morning, but a few strong updrafts persist along its southeastern periphery over central WI. This portion of the MCS is on the far northeastern periphery of the plume of steeper mid-level lapse rates that extends from the northern/central High Plains across the central Plains and into the Mid MS Valley. This plume is observable in the 12Z sounding from DVN and ILX, which sampled 700-500 mb lapse rates of 7.8 and 7.2 deg C per km, respectively. Dewpoints downstream across southern WI, northern IL, and northern IN are in the low 70s, with upper 60s dewpoints also covering much of southern Lower MI. The combination of ample low-level moisture and steep mid-level lapse rates will result in strong to very strong buoyancy to the south of the MCS from the MN/IA border into northern/central IL. Given the lack of a well-defined surface boundary and negligible large-scale ascent, additional thunderstorm development will be associated with outflow from with the MCS, which results in greater-than-average uncertainty for the Day 1 period. Ample moisture and buoyancy downstream of the leading edge of the MCS suggests the greater severe potential this afternoon/evening will likely be associated with redevelopment/reintensification of the MCS. Additionally, even if reintensification does not occur along the leading edge of the MCS this afternoon, most guidance suggests redevelopment does eventually occur this evening along the southern periphery of the MCV circulation as it moves into northern/central WI. Increased severe-wind probabilities (i.e. 15%) were introduced with this outlook to cover both of these potential scenarios. A small 15% hail probability was introduce to cover potential for later evening storms atop the outflow as well. Storms are possible into northern IN and the Lower MI this afternoon and evening as well, but the lower buoyancy should temper the overall coverage and magnitude in these areas. ...SD and Vicinity... A well-defined but rather weak shortwave trough is currently moving through western CO/western WY, and will continue northeastward into eastern WY/western Dakotas by this evening. Similar to yesterday, high-based storms will develop ahead of the approaching shortwave and intensify as they move eastward into a progressively more moist/unstable air mass over west-central SD. Upscale growth into another nocturnal MCS is forecast by most guidance, with the MCS tracking northeastward across western/central SD tonight. Strong to severe gusts are possible with this potential MCS across much of western/central SD. ..Mosier/Wendt.. 08/16/2025 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Aug 16 2025 Valid 161630Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING AND TONIGHT OVER PART OF SD...AND THIS AFTERNOON THROUGH TONIGHT OVER SOUTHEAST MN...SOUTHERN WI...AND NORTHERN IL... ...SUMMARY... Scattered strong/severe thunderstorms are possible today into tonight across parts of the northern Great Plains into Midwest and Great Lakes region. ...Upper Midwest into the Mid MS Valley and Upper Great Lakes Region... An expansive MCS continues to move eastward across the Upper Midwest, with a well-defined MCV evident in radar imagery over the central WI/MN border vicinity. This MCS has continued to gradually weaken throughout the morning, but a few strong updrafts persist along its southeastern periphery over central WI. This portion of the MCS is on the far northeastern periphery of the plume of steeper mid-level lapse rates that extends from the northern/central High Plains across the central Plains and into the Mid MS Valley. This plume is observable in the 12Z sounding from DVN and ILX, which sampled 700-500 mb lapse rates of 7.8 and 7.2 deg C per km, respectively. Dewpoints downstream across southern WI, northern IL, and northern IN are in the low 70s, with upper 60s dewpoints also covering much of southern Lower MI. The combination of ample low-level moisture and steep mid-level lapse rates will result in strong to very strong buoyancy to the south of the MCS from the MN/IA border into northern/central IL. Given the lack of a well-defined surface boundary and negligible large-scale ascent, additional thunderstorm development will be associated with outflow from with the MCS, which results in greater-than-average uncertainty for the Day 1 period. Ample moisture and buoyancy downstream of the leading edge of the MCS suggests the greater severe potential this afternoon/evening will likely be associated with redevelopment/reintensification of the MCS. Additionally, even if reintensification does not occur along the leading edge of the MCS this afternoon, most guidance suggests redevelopment does eventually occur this evening along the southern periphery of the MCV circulation as it moves into northern/central WI. Increased severe-wind probabilities (i.e. 15%) were introduced with this outlook to cover both of these potential scenarios. A small 15% hail probability was introduce to cover potential for later evening storms atop the outflow as well. Storms are possible into northern IN and the Lower MI this afternoon and evening as well, but the lower buoyancy should temper the overall coverage and magnitude in these areas. ...SD and Vicinity... A well-defined but rather weak shortwave trough is currently moving through western CO/western WY, and will continue northeastward into eastern WY/western Dakotas by this evening. Similar to yesterday, high-based storms will develop ahead of the approaching shortwave and intensify as they move eastward into a progressively more moist/unstable air mass over west-central SD. Upscale growth into another nocturnal MCS is forecast by most guidance, with the MCS tracking northeastward across western/central SD tonight. Strong to severe gusts are possible with this potential MCS across much of western/central SD. ..Mosier/Wendt.. 08/16/2025 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Aug 16 2025 Valid 161630Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING AND TONIGHT OVER PART OF SD...AND THIS AFTERNOON THROUGH TONIGHT OVER SOUTHEAST MN...SOUTHERN WI...AND NORTHERN IL... ...SUMMARY... Scattered strong/severe thunderstorms are possible today into tonight across parts of the northern Great Plains into Midwest and Great Lakes region. ...Upper Midwest into the Mid MS Valley and Upper Great Lakes Region... An expansive MCS continues to move eastward across the Upper Midwest, with a well-defined MCV evident in radar imagery over the central WI/MN border vicinity. This MCS has continued to gradually weaken throughout the morning, but a few strong updrafts persist along its southeastern periphery over central WI. This portion of the MCS is on the far northeastern periphery of the plume of steeper mid-level lapse rates that extends from the northern/central High Plains across the central Plains and into the Mid MS Valley. This plume is observable in the 12Z sounding from DVN and ILX, which sampled 700-500 mb lapse rates of 7.8 and 7.2 deg C per km, respectively. Dewpoints downstream across southern WI, northern IL, and northern IN are in the low 70s, with upper 60s dewpoints also covering much of southern Lower MI. The combination of ample low-level moisture and steep mid-level lapse rates will result in strong to very strong buoyancy to the south of the MCS from the MN/IA border into northern/central IL. Given the lack of a well-defined surface boundary and negligible large-scale ascent, additional thunderstorm development will be associated with outflow from with the MCS, which results in greater-than-average uncertainty for the Day 1 period. Ample moisture and buoyancy downstream of the leading edge of the MCS suggests the greater severe potential this afternoon/evening will likely be associated with redevelopment/reintensification of the MCS. Additionally, even if reintensification does not occur along the leading edge of the MCS this afternoon, most guidance suggests redevelopment does eventually occur this evening along the southern periphery of the MCV circulation as it moves into northern/central WI. Increased severe-wind probabilities (i.e. 15%) were introduced with this outlook to cover both of these potential scenarios. A small 15% hail probability was introduce to cover potential for later evening storms atop the outflow as well. Storms are possible into northern IN and the Lower MI this afternoon and evening as well, but the lower buoyancy should temper the overall coverage and magnitude in these areas. ...SD and Vicinity... A well-defined but rather weak shortwave trough is currently moving through western CO/western WY, and will continue northeastward into eastern WY/western Dakotas by this evening. Similar to yesterday, high-based storms will develop ahead of the approaching shortwave and intensify as they move eastward into a progressively more moist/unstable air mass over west-central SD. Upscale growth into another nocturnal MCS is forecast by most guidance, with the MCS tracking northeastward across western/central SD tonight. Strong to severe gusts are possible with this potential MCS across much of western/central SD. ..Mosier/Wendt.. 08/16/2025 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Aug 16 2025 Valid 161630Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING AND TONIGHT OVER PART OF SD...AND THIS AFTERNOON THROUGH TONIGHT OVER SOUTHEAST MN...SOUTHERN WI...AND NORTHERN IL... ...SUMMARY... Scattered strong/severe thunderstorms are possible today into tonight across parts of the northern Great Plains into Midwest and Great Lakes region. ...Upper Midwest into the Mid MS Valley and Upper Great Lakes Region... An expansive MCS continues to move eastward across the Upper Midwest, with a well-defined MCV evident in radar imagery over the central WI/MN border vicinity. This MCS has continued to gradually weaken throughout the morning, but a few strong updrafts persist along its southeastern periphery over central WI. This portion of the MCS is on the far northeastern periphery of the plume of steeper mid-level lapse rates that extends from the northern/central High Plains across the central Plains and into the Mid MS Valley. This plume is observable in the 12Z sounding from DVN and ILX, which sampled 700-500 mb lapse rates of 7.8 and 7.2 deg C per km, respectively. Dewpoints downstream across southern WI, northern IL, and northern IN are in the low 70s, with upper 60s dewpoints also covering much of southern Lower MI. The combination of ample low-level moisture and steep mid-level lapse rates will result in strong to very strong buoyancy to the south of the MCS from the MN/IA border into northern/central IL. Given the lack of a well-defined surface boundary and negligible large-scale ascent, additional thunderstorm development will be associated with outflow from with the MCS, which results in greater-than-average uncertainty for the Day 1 period. Ample moisture and buoyancy downstream of the leading edge of the MCS suggests the greater severe potential this afternoon/evening will likely be associated with redevelopment/reintensification of the MCS. Additionally, even if reintensification does not occur along the leading edge of the MCS this afternoon, most guidance suggests redevelopment does eventually occur this evening along the southern periphery of the MCV circulation as it moves into northern/central WI. Increased severe-wind probabilities (i.e. 15%) were introduced with this outlook to cover both of these potential scenarios. A small 15% hail probability was introduce to cover potential for later evening storms atop the outflow as well. Storms are possible into northern IN and the Lower MI this afternoon and evening as well, but the lower buoyancy should temper the overall coverage and magnitude in these areas. ...SD and Vicinity... A well-defined but rather weak shortwave trough is currently moving through western CO/western WY, and will continue northeastward into eastern WY/western Dakotas by this evening. Similar to yesterday, high-based storms will develop ahead of the approaching shortwave and intensify as they move eastward into a progressively more moist/unstable air mass over west-central SD. Upscale growth into another nocturnal MCS is forecast by most guidance, with the MCS tracking northeastward across western/central SD tonight. Strong to severe gusts are possible with this potential MCS across much of western/central SD. ..Mosier/Wendt.. 08/16/2025 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Aug 16 2025 Valid 161630Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING AND TONIGHT OVER PART OF SD...AND THIS AFTERNOON THROUGH TONIGHT OVER SOUTHEAST MN...SOUTHERN WI...AND NORTHERN IL... ...SUMMARY... Scattered strong/severe thunderstorms are possible today into tonight across parts of the northern Great Plains into Midwest and Great Lakes region. ...Upper Midwest into the Mid MS Valley and Upper Great Lakes Region... An expansive MCS continues to move eastward across the Upper Midwest, with a well-defined MCV evident in radar imagery over the central WI/MN border vicinity. This MCS has continued to gradually weaken throughout the morning, but a few strong updrafts persist along its southeastern periphery over central WI. This portion of the MCS is on the far northeastern periphery of the plume of steeper mid-level lapse rates that extends from the northern/central High Plains across the central Plains and into the Mid MS Valley. This plume is observable in the 12Z sounding from DVN and ILX, which sampled 700-500 mb lapse rates of 7.8 and 7.2 deg C per km, respectively. Dewpoints downstream across southern WI, northern IL, and northern IN are in the low 70s, with upper 60s dewpoints also covering much of southern Lower MI. The combination of ample low-level moisture and steep mid-level lapse rates will result in strong to very strong buoyancy to the south of the MCS from the MN/IA border into northern/central IL. Given the lack of a well-defined surface boundary and negligible large-scale ascent, additional thunderstorm development will be associated with outflow from with the MCS, which results in greater-than-average uncertainty for the Day 1 period. Ample moisture and buoyancy downstream of the leading edge of the MCS suggests the greater severe potential this afternoon/evening will likely be associated with redevelopment/reintensification of the MCS. Additionally, even if reintensification does not occur along the leading edge of the MCS this afternoon, most guidance suggests redevelopment does eventually occur this evening along the southern periphery of the MCV circulation as it moves into northern/central WI. Increased severe-wind probabilities (i.e. 15%) were introduced with this outlook to cover both of these potential scenarios. A small 15% hail probability was introduce to cover potential for later evening storms atop the outflow as well. Storms are possible into northern IN and the Lower MI this afternoon and evening as well, but the lower buoyancy should temper the overall coverage and magnitude in these areas. ...SD and Vicinity... A well-defined but rather weak shortwave trough is currently moving through western CO/western WY, and will continue northeastward into eastern WY/western Dakotas by this evening. Similar to yesterday, high-based storms will develop ahead of the approaching shortwave and intensify as they move eastward into a progressively more moist/unstable air mass over west-central SD. Upscale growth into another nocturnal MCS is forecast by most guidance, with the MCS tracking northeastward across western/central SD tonight. Strong to severe gusts are possible with this potential MCS across much of western/central SD. ..Mosier/Wendt.. 08/16/2025 Read more