Severe Storms

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0244 PM CDT Sat Aug 31 2019 Valid 312000Z - 011200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM NORTHERN KENTUCKY INTO FAR WEST-CENTRAL VIRGINIA... ...SUMMARY... A few strong storms are possible across parts of the Ohio Valley to central Appalachians this afternoon. No significant changes were made to the previous outlook. Only isolated storms are expected along the east-west instability axis from northern KY into far western VA, aided by strong heating. 18Z soundings indicate a subsidence inversion aloft, and weak shear, with only short lived, marginal wind or hail expected. ..Jewell.. 08/31/2019 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sat Aug 31 2019/ ...Ohio Valley to central Appalachians... Robust boundary-layer heating near a weakly convergent quasi-stationary front, ahead of a decaying mid-level impulse, should aid in isolated thunderstorms forming by mid afternoon. A confined corridor of modest buoyancy should develop, characterized by MLCAPE of 1000-1500 J/kg. While low-level winds will be weak, a belt of 25-30 kt 500-mb southwesterlies should support transient updraft rotation in a few cells. This may yield locally strong wind gusts along with marginally severe hail. ...Northern Nebraska to southern/eastern South Dakota... While overall forcing for ascent will be limited, sufficient moist/convergence could influence isolated thunderstorm development near a weak surface/boundary across northern Nebraska/southern South Dakota. If storms develop, a severe storm or two cannot be entirely ruled out given adequate buoyancy and moderately strong northwesterly flow aloft. Storms are a bit more likely to develop later tonight across eastern South Dakota with increasing warm advection, although hail potential will tend to be limited by modest mid-level lapse rates. Overall scenario across the region currently appears too marginal/uncertain to warrant severe probabilities. ...Southern Arizona... An isolated storm or two could develop over/near the mountains of southeast Arizona this afternoon and drift generally westward. However, storm organization should be limited by weaker mid-level winds, while the strongest updrafts should be relegated to south of the international border. As such, severe wind probabilities do not appear warranted. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0244 PM CDT Sat Aug 31 2019 Valid 312000Z - 011200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM NORTHERN KENTUCKY INTO FAR WEST-CENTRAL VIRGINIA... ...SUMMARY... A few strong storms are possible across parts of the Ohio Valley to central Appalachians this afternoon. No significant changes were made to the previous outlook. Only isolated storms are expected along the east-west instability axis from northern KY into far western VA, aided by strong heating. 18Z soundings indicate a subsidence inversion aloft, and weak shear, with only short lived, marginal wind or hail expected. ..Jewell.. 08/31/2019 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sat Aug 31 2019/ ...Ohio Valley to central Appalachians... Robust boundary-layer heating near a weakly convergent quasi-stationary front, ahead of a decaying mid-level impulse, should aid in isolated thunderstorms forming by mid afternoon. A confined corridor of modest buoyancy should develop, characterized by MLCAPE of 1000-1500 J/kg. While low-level winds will be weak, a belt of 25-30 kt 500-mb southwesterlies should support transient updraft rotation in a few cells. This may yield locally strong wind gusts along with marginally severe hail. ...Northern Nebraska to southern/eastern South Dakota... While overall forcing for ascent will be limited, sufficient moist/convergence could influence isolated thunderstorm development near a weak surface/boundary across northern Nebraska/southern South Dakota. If storms develop, a severe storm or two cannot be entirely ruled out given adequate buoyancy and moderately strong northwesterly flow aloft. Storms are a bit more likely to develop later tonight across eastern South Dakota with increasing warm advection, although hail potential will tend to be limited by modest mid-level lapse rates. Overall scenario across the region currently appears too marginal/uncertain to warrant severe probabilities. ...Southern Arizona... An isolated storm or two could develop over/near the mountains of southeast Arizona this afternoon and drift generally westward. However, storm organization should be limited by weaker mid-level winds, while the strongest updrafts should be relegated to south of the international border. As such, severe wind probabilities do not appear warranted. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0244 PM CDT Sat Aug 31 2019 Valid 312000Z - 011200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM NORTHERN KENTUCKY INTO FAR WEST-CENTRAL VIRGINIA... ...SUMMARY... A few strong storms are possible across parts of the Ohio Valley to central Appalachians this afternoon. No significant changes were made to the previous outlook. Only isolated storms are expected along the east-west instability axis from northern KY into far western VA, aided by strong heating. 18Z soundings indicate a subsidence inversion aloft, and weak shear, with only short lived, marginal wind or hail expected. ..Jewell.. 08/31/2019 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sat Aug 31 2019/ ...Ohio Valley to central Appalachians... Robust boundary-layer heating near a weakly convergent quasi-stationary front, ahead of a decaying mid-level impulse, should aid in isolated thunderstorms forming by mid afternoon. A confined corridor of modest buoyancy should develop, characterized by MLCAPE of 1000-1500 J/kg. While low-level winds will be weak, a belt of 25-30 kt 500-mb southwesterlies should support transient updraft rotation in a few cells. This may yield locally strong wind gusts along with marginally severe hail. ...Northern Nebraska to southern/eastern South Dakota... While overall forcing for ascent will be limited, sufficient moist/convergence could influence isolated thunderstorm development near a weak surface/boundary across northern Nebraska/southern South Dakota. If storms develop, a severe storm or two cannot be entirely ruled out given adequate buoyancy and moderately strong northwesterly flow aloft. Storms are a bit more likely to develop later tonight across eastern South Dakota with increasing warm advection, although hail potential will tend to be limited by modest mid-level lapse rates. Overall scenario across the region currently appears too marginal/uncertain to warrant severe probabilities. ...Southern Arizona... An isolated storm or two could develop over/near the mountains of southeast Arizona this afternoon and drift generally westward. However, storm organization should be limited by weaker mid-level winds, while the strongest updrafts should be relegated to south of the international border. As such, severe wind probabilities do not appear warranted. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0244 PM CDT Sat Aug 31 2019 Valid 312000Z - 011200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM NORTHERN KENTUCKY INTO FAR WEST-CENTRAL VIRGINIA... ...SUMMARY... A few strong storms are possible across parts of the Ohio Valley to central Appalachians this afternoon. No significant changes were made to the previous outlook. Only isolated storms are expected along the east-west instability axis from northern KY into far western VA, aided by strong heating. 18Z soundings indicate a subsidence inversion aloft, and weak shear, with only short lived, marginal wind or hail expected. ..Jewell.. 08/31/2019 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sat Aug 31 2019/ ...Ohio Valley to central Appalachians... Robust boundary-layer heating near a weakly convergent quasi-stationary front, ahead of a decaying mid-level impulse, should aid in isolated thunderstorms forming by mid afternoon. A confined corridor of modest buoyancy should develop, characterized by MLCAPE of 1000-1500 J/kg. While low-level winds will be weak, a belt of 25-30 kt 500-mb southwesterlies should support transient updraft rotation in a few cells. This may yield locally strong wind gusts along with marginally severe hail. ...Northern Nebraska to southern/eastern South Dakota... While overall forcing for ascent will be limited, sufficient moist/convergence could influence isolated thunderstorm development near a weak surface/boundary across northern Nebraska/southern South Dakota. If storms develop, a severe storm or two cannot be entirely ruled out given adequate buoyancy and moderately strong northwesterly flow aloft. Storms are a bit more likely to develop later tonight across eastern South Dakota with increasing warm advection, although hail potential will tend to be limited by modest mid-level lapse rates. Overall scenario across the region currently appears too marginal/uncertain to warrant severe probabilities. ...Southern Arizona... An isolated storm or two could develop over/near the mountains of southeast Arizona this afternoon and drift generally westward. However, storm organization should be limited by weaker mid-level winds, while the strongest updrafts should be relegated to south of the international border. As such, severe wind probabilities do not appear warranted. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0141 PM CDT Sat Aug 31 2019 Valid 011200Z - 021200Z The primary change with this forecast update was to expand the elevated fire weather area farther east across southern portions of Wyoming. While this area will be on the extreme southern periphery of the stronger mid-level flow, breezy westerly/northwesterly downslope winds amidst critically-lowered RH values and receptive fuels should foster several hours of Elevated fire weather conditions during the afternoon. While locally critically conditions are possible -- especially over the Sawtooth Mountains and Snake River plain in Idaho, the northern Wasatch Mountains in Utah, and across portions of southeast Wyoming -- the coverage of sustained wind speeds at or above 20 mph appears too limited/brief to introduce a critical fire weather area at this time. An elevated fire weather area was also considered over portions of northwest Nevada, where afternoon breeziness will overlap a large area of critical RH values (i.e., < 15%). While Vaisala National Lightning Detection Network cloud-to-ground lightning data over the past 72-hours does indicate a few flashes (and potential holdovers) occurred nearby, most of these were west of where the breezy winds are expected. Additionally, the brief/spotty nature of the threat precludes the introduction of an elevated fire weather area at this time. ..Elliott.. 08/31/2019 .PREV DISCUSSION... /ISSUED 0146 AM CDT Sat Aug 31 2019/ ...Synopsis... A vigorous mid-level shortwave trough will translate across the upper-level ridge axis over the Pacific Northwest, northern Rockies, and northern Great Basin areas on Day 2/Sunday. As a result, dry and breezy surface conditions due to the mass response associated with the passing shortwave will encourage at least a few hours of wildfire-spread potential across parts of the northwest CONUS. In addition, afternoon heating atop the higher terrain of the Rockies in central Colorado may encourage the development of a few high based storms capable of very sparse, dry lightning strikes. ...Central Rockies into the Great Basin... Widespread west-southwesterly sustained surface winds exceeding 15 mph are expected by peak afternoon heating, that in tandem with 10-20% RH, will foster conditions favorable for fire-spread through at least sunset. Fuels are quite dry across much of the Great Basin into the central Rockies. Currently, an elevated delineation is in place across parts of the Snake River Plain and surrounding locations, where aforementioned stronger flow aloft/synoptic forcing will overlap most favorably with the aforementioned elevated conditions. Widespread elevated conditions may also occur across much of the central Great Basin, but given that the strongest upper-level support will likely remain north of the area, and lack of run-to-run consistency among model guidance members, an elevated delineation will be withheld at this time. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0141 PM CDT Sat Aug 31 2019 Valid 011200Z - 021200Z The primary change with this forecast update was to expand the elevated fire weather area farther east across southern portions of Wyoming. While this area will be on the extreme southern periphery of the stronger mid-level flow, breezy westerly/northwesterly downslope winds amidst critically-lowered RH values and receptive fuels should foster several hours of Elevated fire weather conditions during the afternoon. While locally critically conditions are possible -- especially over the Sawtooth Mountains and Snake River plain in Idaho, the northern Wasatch Mountains in Utah, and across portions of southeast Wyoming -- the coverage of sustained wind speeds at or above 20 mph appears too limited/brief to introduce a critical fire weather area at this time. An elevated fire weather area was also considered over portions of northwest Nevada, where afternoon breeziness will overlap a large area of critical RH values (i.e., < 15%). While Vaisala National Lightning Detection Network cloud-to-ground lightning data over the past 72-hours does indicate a few flashes (and potential holdovers) occurred nearby, most of these were west of where the breezy winds are expected. Additionally, the brief/spotty nature of the threat precludes the introduction of an elevated fire weather area at this time. ..Elliott.. 08/31/2019 .PREV DISCUSSION... /ISSUED 0146 AM CDT Sat Aug 31 2019/ ...Synopsis... A vigorous mid-level shortwave trough will translate across the upper-level ridge axis over the Pacific Northwest, northern Rockies, and northern Great Basin areas on Day 2/Sunday. As a result, dry and breezy surface conditions due to the mass response associated with the passing shortwave will encourage at least a few hours of wildfire-spread potential across parts of the northwest CONUS. In addition, afternoon heating atop the higher terrain of the Rockies in central Colorado may encourage the development of a few high based storms capable of very sparse, dry lightning strikes. ...Central Rockies into the Great Basin... Widespread west-southwesterly sustained surface winds exceeding 15 mph are expected by peak afternoon heating, that in tandem with 10-20% RH, will foster conditions favorable for fire-spread through at least sunset. Fuels are quite dry across much of the Great Basin into the central Rockies. Currently, an elevated delineation is in place across parts of the Snake River Plain and surrounding locations, where aforementioned stronger flow aloft/synoptic forcing will overlap most favorably with the aforementioned elevated conditions. Widespread elevated conditions may also occur across much of the central Great Basin, but given that the strongest upper-level support will likely remain north of the area, and lack of run-to-run consistency among model guidance members, an elevated delineation will be withheld at this time. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0141 PM CDT Sat Aug 31 2019 Valid 011200Z - 021200Z The primary change with this forecast update was to expand the elevated fire weather area farther east across southern portions of Wyoming. While this area will be on the extreme southern periphery of the stronger mid-level flow, breezy westerly/northwesterly downslope winds amidst critically-lowered RH values and receptive fuels should foster several hours of Elevated fire weather conditions during the afternoon. While locally critically conditions are possible -- especially over the Sawtooth Mountains and Snake River plain in Idaho, the northern Wasatch Mountains in Utah, and across portions of southeast Wyoming -- the coverage of sustained wind speeds at or above 20 mph appears too limited/brief to introduce a critical fire weather area at this time. An elevated fire weather area was also considered over portions of northwest Nevada, where afternoon breeziness will overlap a large area of critical RH values (i.e., < 15%). While Vaisala National Lightning Detection Network cloud-to-ground lightning data over the past 72-hours does indicate a few flashes (and potential holdovers) occurred nearby, most of these were west of where the breezy winds are expected. Additionally, the brief/spotty nature of the threat precludes the introduction of an elevated fire weather area at this time. ..Elliott.. 08/31/2019 .PREV DISCUSSION... /ISSUED 0146 AM CDT Sat Aug 31 2019/ ...Synopsis... A vigorous mid-level shortwave trough will translate across the upper-level ridge axis over the Pacific Northwest, northern Rockies, and northern Great Basin areas on Day 2/Sunday. As a result, dry and breezy surface conditions due to the mass response associated with the passing shortwave will encourage at least a few hours of wildfire-spread potential across parts of the northwest CONUS. In addition, afternoon heating atop the higher terrain of the Rockies in central Colorado may encourage the development of a few high based storms capable of very sparse, dry lightning strikes. ...Central Rockies into the Great Basin... Widespread west-southwesterly sustained surface winds exceeding 15 mph are expected by peak afternoon heating, that in tandem with 10-20% RH, will foster conditions favorable for fire-spread through at least sunset. Fuels are quite dry across much of the Great Basin into the central Rockies. Currently, an elevated delineation is in place across parts of the Snake River Plain and surrounding locations, where aforementioned stronger flow aloft/synoptic forcing will overlap most favorably with the aforementioned elevated conditions. Widespread elevated conditions may also occur across much of the central Great Basin, but given that the strongest upper-level support will likely remain north of the area, and lack of run-to-run consistency among model guidance members, an elevated delineation will be withheld at this time. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0141 PM CDT Sat Aug 31 2019 Valid 011200Z - 021200Z The primary change with this forecast update was to expand the elevated fire weather area farther east across southern portions of Wyoming. While this area will be on the extreme southern periphery of the stronger mid-level flow, breezy westerly/northwesterly downslope winds amidst critically-lowered RH values and receptive fuels should foster several hours of Elevated fire weather conditions during the afternoon. While locally critically conditions are possible -- especially over the Sawtooth Mountains and Snake River plain in Idaho, the northern Wasatch Mountains in Utah, and across portions of southeast Wyoming -- the coverage of sustained wind speeds at or above 20 mph appears too limited/brief to introduce a critical fire weather area at this time. An elevated fire weather area was also considered over portions of northwest Nevada, where afternoon breeziness will overlap a large area of critical RH values (i.e., < 15%). While Vaisala National Lightning Detection Network cloud-to-ground lightning data over the past 72-hours does indicate a few flashes (and potential holdovers) occurred nearby, most of these were west of where the breezy winds are expected. Additionally, the brief/spotty nature of the threat precludes the introduction of an elevated fire weather area at this time. ..Elliott.. 08/31/2019 .PREV DISCUSSION... /ISSUED 0146 AM CDT Sat Aug 31 2019/ ...Synopsis... A vigorous mid-level shortwave trough will translate across the upper-level ridge axis over the Pacific Northwest, northern Rockies, and northern Great Basin areas on Day 2/Sunday. As a result, dry and breezy surface conditions due to the mass response associated with the passing shortwave will encourage at least a few hours of wildfire-spread potential across parts of the northwest CONUS. In addition, afternoon heating atop the higher terrain of the Rockies in central Colorado may encourage the development of a few high based storms capable of very sparse, dry lightning strikes. ...Central Rockies into the Great Basin... Widespread west-southwesterly sustained surface winds exceeding 15 mph are expected by peak afternoon heating, that in tandem with 10-20% RH, will foster conditions favorable for fire-spread through at least sunset. Fuels are quite dry across much of the Great Basin into the central Rockies. Currently, an elevated delineation is in place across parts of the Snake River Plain and surrounding locations, where aforementioned stronger flow aloft/synoptic forcing will overlap most favorably with the aforementioned elevated conditions. Widespread elevated conditions may also occur across much of the central Great Basin, but given that the strongest upper-level support will likely remain north of the area, and lack of run-to-run consistency among model guidance members, an elevated delineation will be withheld at this time. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Sat Aug 31 2019 Valid 011200Z - 021200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for severe thunderstorms on Sunday is low across the Lower 48, but a few strong storms are possible over parts of the northern High Plains, and the Ohio Valley. ...Synopsis... An upper high will remain over the Four Corners region, with ridge axis extending north across the Rockies. This ridge will break down late Sunday into Monday as a positive-tilt upper trough drops south out of British Columbia and Alberta. To the east, moderate to strong northwest flow aloft will remain over the northern Plains and toward the upper Great Lakes, with the primary upper cyclone moving from Hudson Bay into northern Quebec. Well south of the Canadian trough, cool temperatures aloft and weak height falls will sweep eastward across the OH Valley and northeastern states. At the surface, low pressure will develop from MT into the northern High Plains, with increasing southeast low-level winds resulting in warming and moistening over the region with increasing thunderstorms chances overnight from northeast MT into ND. To the east, high pressure depart New England, with gradually lowering pressure westward across the OH Valley. Here, sufficient moisture combined with cool temperatures aloft will remain to support thunderstorms, developing eastward throughout the period. Elsewhere, wind shear and the bulk of the outer convective bands associated with Hurricane Dorian is forecast to remain offshore/east of the FL coast. ...Northeast MT into ND Sunday evening and overnight... Shortwave ridging will occur over MT during the day, though strong deep-layer shear will be in place along with marginal instability. An isolated storm cannot be ruled out over northwest and north-central MT during the heat of the afternoon. Long hodographs would favor small cells, conditionally with marginal hail. The greater chance of thunderstorms will be from evening into the overnight, from northeast MT into ND, where an increasing low-level jet will aid lift. Currently, it is unclear whether elevated instability will be sufficient to support hail, but low severe probabilities cannot be ruled out in future updates. ...OH into western PA... Aside from possible ongoing rain and outflow boundaries, the surface pattern will offer little to focus storms over the OH Valley during the day. However, the presence of 60s F dewpoints beneath cool temperatures aloft along with heating will lead to scattered storms over IN and OH, then into PA and NY during the evening. A few strong wind gusts or small hail cannot be ruled out as weakly veering winds with height may support cellular activity, but in general sub-severe storms are expected. A Marginal Risk cannot be ruled out in future outlooks if instability looks to be stronger than currently expected. ...MAXIMUM RISK BY HAZARD... Tornado: <2% - None Wind: <5% - None Hail: <5% - None ..Jewell.. 08/31/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Sat Aug 31 2019 Valid 011200Z - 021200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for severe thunderstorms on Sunday is low across the Lower 48, but a few strong storms are possible over parts of the northern High Plains, and the Ohio Valley. ...Synopsis... An upper high will remain over the Four Corners region, with ridge axis extending north across the Rockies. This ridge will break down late Sunday into Monday as a positive-tilt upper trough drops south out of British Columbia and Alberta. To the east, moderate to strong northwest flow aloft will remain over the northern Plains and toward the upper Great Lakes, with the primary upper cyclone moving from Hudson Bay into northern Quebec. Well south of the Canadian trough, cool temperatures aloft and weak height falls will sweep eastward across the OH Valley and northeastern states. At the surface, low pressure will develop from MT into the northern High Plains, with increasing southeast low-level winds resulting in warming and moistening over the region with increasing thunderstorms chances overnight from northeast MT into ND. To the east, high pressure depart New England, with gradually lowering pressure westward across the OH Valley. Here, sufficient moisture combined with cool temperatures aloft will remain to support thunderstorms, developing eastward throughout the period. Elsewhere, wind shear and the bulk of the outer convective bands associated with Hurricane Dorian is forecast to remain offshore/east of the FL coast. ...Northeast MT into ND Sunday evening and overnight... Shortwave ridging will occur over MT during the day, though strong deep-layer shear will be in place along with marginal instability. An isolated storm cannot be ruled out over northwest and north-central MT during the heat of the afternoon. Long hodographs would favor small cells, conditionally with marginal hail. The greater chance of thunderstorms will be from evening into the overnight, from northeast MT into ND, where an increasing low-level jet will aid lift. Currently, it is unclear whether elevated instability will be sufficient to support hail, but low severe probabilities cannot be ruled out in future updates. ...OH into western PA... Aside from possible ongoing rain and outflow boundaries, the surface pattern will offer little to focus storms over the OH Valley during the day. However, the presence of 60s F dewpoints beneath cool temperatures aloft along with heating will lead to scattered storms over IN and OH, then into PA and NY during the evening. A few strong wind gusts or small hail cannot be ruled out as weakly veering winds with height may support cellular activity, but in general sub-severe storms are expected. A Marginal Risk cannot be ruled out in future outlooks if instability looks to be stronger than currently expected. ...MAXIMUM RISK BY HAZARD... Tornado: <2% - None Wind: <5% - None Hail: <5% - None ..Jewell.. 08/31/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Sat Aug 31 2019 Valid 011200Z - 021200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for severe thunderstorms on Sunday is low across the Lower 48, but a few strong storms are possible over parts of the northern High Plains, and the Ohio Valley. ...Synopsis... An upper high will remain over the Four Corners region, with ridge axis extending north across the Rockies. This ridge will break down late Sunday into Monday as a positive-tilt upper trough drops south out of British Columbia and Alberta. To the east, moderate to strong northwest flow aloft will remain over the northern Plains and toward the upper Great Lakes, with the primary upper cyclone moving from Hudson Bay into northern Quebec. Well south of the Canadian trough, cool temperatures aloft and weak height falls will sweep eastward across the OH Valley and northeastern states. At the surface, low pressure will develop from MT into the northern High Plains, with increasing southeast low-level winds resulting in warming and moistening over the region with increasing thunderstorms chances overnight from northeast MT into ND. To the east, high pressure depart New England, with gradually lowering pressure westward across the OH Valley. Here, sufficient moisture combined with cool temperatures aloft will remain to support thunderstorms, developing eastward throughout the period. Elsewhere, wind shear and the bulk of the outer convective bands associated with Hurricane Dorian is forecast to remain offshore/east of the FL coast. ...Northeast MT into ND Sunday evening and overnight... Shortwave ridging will occur over MT during the day, though strong deep-layer shear will be in place along with marginal instability. An isolated storm cannot be ruled out over northwest and north-central MT during the heat of the afternoon. Long hodographs would favor small cells, conditionally with marginal hail. The greater chance of thunderstorms will be from evening into the overnight, from northeast MT into ND, where an increasing low-level jet will aid lift. Currently, it is unclear whether elevated instability will be sufficient to support hail, but low severe probabilities cannot be ruled out in future updates. ...OH into western PA... Aside from possible ongoing rain and outflow boundaries, the surface pattern will offer little to focus storms over the OH Valley during the day. However, the presence of 60s F dewpoints beneath cool temperatures aloft along with heating will lead to scattered storms over IN and OH, then into PA and NY during the evening. A few strong wind gusts or small hail cannot be ruled out as weakly veering winds with height may support cellular activity, but in general sub-severe storms are expected. A Marginal Risk cannot be ruled out in future outlooks if instability looks to be stronger than currently expected. ...MAXIMUM RISK BY HAZARD... Tornado: <2% - None Wind: <5% - None Hail: <5% - None ..Jewell.. 08/31/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Sat Aug 31 2019 Valid 011200Z - 021200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for severe thunderstorms on Sunday is low across the Lower 48, but a few strong storms are possible over parts of the northern High Plains, and the Ohio Valley. ...Synopsis... An upper high will remain over the Four Corners region, with ridge axis extending north across the Rockies. This ridge will break down late Sunday into Monday as a positive-tilt upper trough drops south out of British Columbia and Alberta. To the east, moderate to strong northwest flow aloft will remain over the northern Plains and toward the upper Great Lakes, with the primary upper cyclone moving from Hudson Bay into northern Quebec. Well south of the Canadian trough, cool temperatures aloft and weak height falls will sweep eastward across the OH Valley and northeastern states. At the surface, low pressure will develop from MT into the northern High Plains, with increasing southeast low-level winds resulting in warming and moistening over the region with increasing thunderstorms chances overnight from northeast MT into ND. To the east, high pressure depart New England, with gradually lowering pressure westward across the OH Valley. Here, sufficient moisture combined with cool temperatures aloft will remain to support thunderstorms, developing eastward throughout the period. Elsewhere, wind shear and the bulk of the outer convective bands associated with Hurricane Dorian is forecast to remain offshore/east of the FL coast. ...Northeast MT into ND Sunday evening and overnight... Shortwave ridging will occur over MT during the day, though strong deep-layer shear will be in place along with marginal instability. An isolated storm cannot be ruled out over northwest and north-central MT during the heat of the afternoon. Long hodographs would favor small cells, conditionally with marginal hail. The greater chance of thunderstorms will be from evening into the overnight, from northeast MT into ND, where an increasing low-level jet will aid lift. Currently, it is unclear whether elevated instability will be sufficient to support hail, but low severe probabilities cannot be ruled out in future updates. ...OH into western PA... Aside from possible ongoing rain and outflow boundaries, the surface pattern will offer little to focus storms over the OH Valley during the day. However, the presence of 60s F dewpoints beneath cool temperatures aloft along with heating will lead to scattered storms over IN and OH, then into PA and NY during the evening. A few strong wind gusts or small hail cannot be ruled out as weakly veering winds with height may support cellular activity, but in general sub-severe storms are expected. A Marginal Risk cannot be ruled out in future outlooks if instability looks to be stronger than currently expected. ...MAXIMUM RISK BY HAZARD... Tornado: <2% - None Wind: <5% - None Hail: <5% - None ..Jewell.. 08/31/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Aug 31 2019 Valid 311630Z - 011200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS NORTHERN/EASTERN KY TO CENTRAL/SOUTHERN WV... ...SUMMARY... Isolated, marginally severe thunderstorms are possible across parts of the Ohio Valley to central Applachians between 2 to 8 PM EDT. ...Ohio Valley to central Appalachians... Robust boundary-layer heating near a weakly convergent quasi-stationary front, ahead of a decaying mid-level impulse, should aid in isolated thunderstorms forming by mid afternoon. A confined corridor of modest buoyancy should develop, characterized by MLCAPE of 1000-1500 J/kg. While low-level winds will be weak, a belt of 25-30 kt 500-mb southwesterlies should support transient updraft rotation in a few cells. This may yield locally strong wind gusts along with marginally severe hail. ...Northern Nebraska to southern/eastern South Dakota... While overall forcing for ascent will be limited, sufficient moist/convergence could influence isolated thunderstorm development near a weak surface/boundary across northern Nebraska/southern South Dakota. If storms develop, a severe storm or two cannot be entirely ruled out given adequate buoyancy and moderately strong northwesterly flow aloft. Storms are a bit more likely to develop later tonight across eastern South Dakota with increasing warm advection, although hail potential will tend to be limited by modest mid-level lapse rates. Overall scenario across the region currently appears too marginal/uncertain to warrant severe probabilities. ...Southern Arizona... An isolated storm or two could develop over/near the mountains of southeast Arizona this afternoon and drift generally westward. However, storm organization should be limited by weaker mid-level winds, while the strongest updrafts should be relegated to south of the international border. As such, severe wind probabilities do not appear warranted. ..Guyer/Nauslar.. 08/31/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Aug 31 2019 Valid 311630Z - 011200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS NORTHERN/EASTERN KY TO CENTRAL/SOUTHERN WV... ...SUMMARY... Isolated, marginally severe thunderstorms are possible across parts of the Ohio Valley to central Applachians between 2 to 8 PM EDT. ...Ohio Valley to central Appalachians... Robust boundary-layer heating near a weakly convergent quasi-stationary front, ahead of a decaying mid-level impulse, should aid in isolated thunderstorms forming by mid afternoon. A confined corridor of modest buoyancy should develop, characterized by MLCAPE of 1000-1500 J/kg. While low-level winds will be weak, a belt of 25-30 kt 500-mb southwesterlies should support transient updraft rotation in a few cells. This may yield locally strong wind gusts along with marginally severe hail. ...Northern Nebraska to southern/eastern South Dakota... While overall forcing for ascent will be limited, sufficient moist/convergence could influence isolated thunderstorm development near a weak surface/boundary across northern Nebraska/southern South Dakota. If storms develop, a severe storm or two cannot be entirely ruled out given adequate buoyancy and moderately strong northwesterly flow aloft. Storms are a bit more likely to develop later tonight across eastern South Dakota with increasing warm advection, although hail potential will tend to be limited by modest mid-level lapse rates. Overall scenario across the region currently appears too marginal/uncertain to warrant severe probabilities. ...Southern Arizona... An isolated storm or two could develop over/near the mountains of southeast Arizona this afternoon and drift generally westward. However, storm organization should be limited by weaker mid-level winds, while the strongest updrafts should be relegated to south of the international border. As such, severe wind probabilities do not appear warranted. ..Guyer/Nauslar.. 08/31/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Aug 31 2019 Valid 311630Z - 011200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS NORTHERN/EASTERN KY TO CENTRAL/SOUTHERN WV... ...SUMMARY... Isolated, marginally severe thunderstorms are possible across parts of the Ohio Valley to central Applachians between 2 to 8 PM EDT. ...Ohio Valley to central Appalachians... Robust boundary-layer heating near a weakly convergent quasi-stationary front, ahead of a decaying mid-level impulse, should aid in isolated thunderstorms forming by mid afternoon. A confined corridor of modest buoyancy should develop, characterized by MLCAPE of 1000-1500 J/kg. While low-level winds will be weak, a belt of 25-30 kt 500-mb southwesterlies should support transient updraft rotation in a few cells. This may yield locally strong wind gusts along with marginally severe hail. ...Northern Nebraska to southern/eastern South Dakota... While overall forcing for ascent will be limited, sufficient moist/convergence could influence isolated thunderstorm development near a weak surface/boundary across northern Nebraska/southern South Dakota. If storms develop, a severe storm or two cannot be entirely ruled out given adequate buoyancy and moderately strong northwesterly flow aloft. Storms are a bit more likely to develop later tonight across eastern South Dakota with increasing warm advection, although hail potential will tend to be limited by modest mid-level lapse rates. Overall scenario across the region currently appears too marginal/uncertain to warrant severe probabilities. ...Southern Arizona... An isolated storm or two could develop over/near the mountains of southeast Arizona this afternoon and drift generally westward. However, storm organization should be limited by weaker mid-level winds, while the strongest updrafts should be relegated to south of the international border. As such, severe wind probabilities do not appear warranted. ..Guyer/Nauslar.. 08/31/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Aug 31 2019 Valid 311630Z - 011200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS NORTHERN/EASTERN KY TO CENTRAL/SOUTHERN WV... ...SUMMARY... Isolated, marginally severe thunderstorms are possible across parts of the Ohio Valley to central Applachians between 2 to 8 PM EDT. ...Ohio Valley to central Appalachians... Robust boundary-layer heating near a weakly convergent quasi-stationary front, ahead of a decaying mid-level impulse, should aid in isolated thunderstorms forming by mid afternoon. A confined corridor of modest buoyancy should develop, characterized by MLCAPE of 1000-1500 J/kg. While low-level winds will be weak, a belt of 25-30 kt 500-mb southwesterlies should support transient updraft rotation in a few cells. This may yield locally strong wind gusts along with marginally severe hail. ...Northern Nebraska to southern/eastern South Dakota... While overall forcing for ascent will be limited, sufficient moist/convergence could influence isolated thunderstorm development near a weak surface/boundary across northern Nebraska/southern South Dakota. If storms develop, a severe storm or two cannot be entirely ruled out given adequate buoyancy and moderately strong northwesterly flow aloft. Storms are a bit more likely to develop later tonight across eastern South Dakota with increasing warm advection, although hail potential will tend to be limited by modest mid-level lapse rates. Overall scenario across the region currently appears too marginal/uncertain to warrant severe probabilities. ...Southern Arizona... An isolated storm or two could develop over/near the mountains of southeast Arizona this afternoon and drift generally westward. However, storm organization should be limited by weaker mid-level winds, while the strongest updrafts should be relegated to south of the international border. As such, severe wind probabilities do not appear warranted. ..Guyer/Nauslar.. 08/31/2019 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1054 AM CDT Sat Aug 31 2019 Valid 311700Z - 011200Z ...NO CRITICAL AREAS... No changes have been made to the ongoing forecast. See the previous discussion below for more information. ..Elliott.. 08/31/2019 .PREV DISCUSSION... /ISSUED 0100 AM CDT Sat Aug 31 2019/ ...Synopsis... A mid-level ridge will become established across the western CONUS, promoting weak flow aloft and associated weak synoptic forcing. As such, weak surface flow is expected to prevail across much of the western CONUS, resulting in relatively quiescent fire weather conditions for much of the period. A few localized areas in/near the Great Divide Basin may briefly experience elevated conditions (surface RH less than 20% and westerly winds greater than 15 mph) in terrain favoring locations, but the localized nature of these conditions precludes an elevated delineation. A few dry lightning strikes may also occur across portions of central Colorado, in the higher terrain of the Rockies, though sparse storm coverage suggests that an isolated dry thunderstorm area is not warranted. ...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 1054 AM CDT Sat Aug 31 2019 Valid 311700Z - 011200Z ...NO CRITICAL AREAS... No changes have been made to the ongoing forecast. See the previous discussion below for more information. ..Elliott.. 08/31/2019 .PREV DISCUSSION... /ISSUED 0100 AM CDT Sat Aug 31 2019/ ...Synopsis... A mid-level ridge will become established across the western CONUS, promoting weak flow aloft and associated weak synoptic forcing. As such, weak surface flow is expected to prevail across much of the western CONUS, resulting in relatively quiescent fire weather conditions for much of the period. A few localized areas in/near the Great Divide Basin may briefly experience elevated conditions (surface RH less than 20% and westerly winds greater than 15 mph) in terrain favoring locations, but the localized nature of these conditions precludes an elevated delineation. A few dry lightning strikes may also occur across portions of central Colorado, in the higher terrain of the Rockies, though sparse storm coverage suggests that an isolated dry thunderstorm area is not warranted. ...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 1054 AM CDT Sat Aug 31 2019 Valid 311700Z - 011200Z ...NO CRITICAL AREAS... No changes have been made to the ongoing forecast. See the previous discussion below for more information. ..Elliott.. 08/31/2019 .PREV DISCUSSION... /ISSUED 0100 AM CDT Sat Aug 31 2019/ ...Synopsis... A mid-level ridge will become established across the western CONUS, promoting weak flow aloft and associated weak synoptic forcing. As such, weak surface flow is expected to prevail across much of the western CONUS, resulting in relatively quiescent fire weather conditions for much of the period. A few localized areas in/near the Great Divide Basin may briefly experience elevated conditions (surface RH less than 20% and westerly winds greater than 15 mph) in terrain favoring locations, but the localized nature of these conditions precludes an elevated delineation. A few dry lightning strikes may also occur across portions of central Colorado, in the higher terrain of the Rockies, though sparse storm coverage suggests that an isolated dry thunderstorm area is not warranted. ...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 1054 AM CDT Sat Aug 31 2019 Valid 311700Z - 011200Z ...NO CRITICAL AREAS... No changes have been made to the ongoing forecast. See the previous discussion below for more information. ..Elliott.. 08/31/2019 .PREV DISCUSSION... /ISSUED 0100 AM CDT Sat Aug 31 2019/ ...Synopsis... A mid-level ridge will become established across the western CONUS, promoting weak flow aloft and associated weak synoptic forcing. As such, weak surface flow is expected to prevail across much of the western CONUS, resulting in relatively quiescent fire weather conditions for much of the period. A few localized areas in/near the Great Divide Basin may briefly experience elevated conditions (surface RH less than 20% and westerly winds greater than 15 mph) in terrain favoring locations, but the localized nature of these conditions precludes an elevated delineation. A few dry lightning strikes may also occur across portions of central Colorado, in the higher terrain of the Rockies, though sparse storm coverage suggests that an isolated dry thunderstorm area is not warranted. ...Please see www.spc.noaa.gov/fire for graphic product... Read more