Severe Storms

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

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0738 AM CDT Sat Aug 31 2019 Valid 311300Z - 011200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS 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. ...OH 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. ..Grams/Leitman.. 08/31/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0738 AM CDT Sat Aug 31 2019 Valid 311300Z - 011200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS 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. ...OH 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. ..Grams/Leitman.. 08/31/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0738 AM CDT Sat Aug 31 2019 Valid 311300Z - 011200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS 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. ...OH 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. ..Grams/Leitman.. 08/31/2019 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0326 AM CDT Sat Aug 31 2019 Valid 031200Z - 081200Z ...DISCUSSION... Severe potential across the Southeastern U.S. (particularly coastal areas) will depend heavily on the eventual track of Hurricane Dorian. Some recent guidance has slowed its progress and gradually shifted the storm east of the coastline, and if this trend continues, any tropical-cyclone tornado threat in coastal areas should be minimal. Elsewhere, a vigorous mid-level trough should migrate from the western Great Lakes early D4/Tue into Ontario while phasing/becoming absorbed with a longer wave trough near Hudson Bay. Meanwhile, a surface low and trailing cold front will traverse Wisconsin/Michigan and a narrow axis of at least weak instability will exist ahead of that front. It appears that at least an isolated severe risk will exist as fast, but veered, wind fields will exist within the instability axis. This risk should be spatially limited and dependent on evolution of early-morning convection. The front will reach the Northeast on D5/Wed, although with even lesser instability due to weaker lapse rates aloft. Elsewhere, mid/upper ridging over the West will spread eastward and encompass the central Plains. A dearth of major synoptic systems should keep any appreciable severe threat to a minimum through the extended forecast period. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0326 AM CDT Sat Aug 31 2019 Valid 031200Z - 081200Z ...DISCUSSION... Severe potential across the Southeastern U.S. (particularly coastal areas) will depend heavily on the eventual track of Hurricane Dorian. Some recent guidance has slowed its progress and gradually shifted the storm east of the coastline, and if this trend continues, any tropical-cyclone tornado threat in coastal areas should be minimal. Elsewhere, a vigorous mid-level trough should migrate from the western Great Lakes early D4/Tue into Ontario while phasing/becoming absorbed with a longer wave trough near Hudson Bay. Meanwhile, a surface low and trailing cold front will traverse Wisconsin/Michigan and a narrow axis of at least weak instability will exist ahead of that front. It appears that at least an isolated severe risk will exist as fast, but veered, wind fields will exist within the instability axis. This risk should be spatially limited and dependent on evolution of early-morning convection. The front will reach the Northeast on D5/Wed, although with even lesser instability due to weaker lapse rates aloft. Elsewhere, mid/upper ridging over the West will spread eastward and encompass the central Plains. A dearth of major synoptic systems should keep any appreciable severe threat to a minimum through the extended forecast period. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0326 AM CDT Sat Aug 31 2019 Valid 031200Z - 081200Z ...DISCUSSION... Severe potential across the Southeastern U.S. (particularly coastal areas) will depend heavily on the eventual track of Hurricane Dorian. Some recent guidance has slowed its progress and gradually shifted the storm east of the coastline, and if this trend continues, any tropical-cyclone tornado threat in coastal areas should be minimal. Elsewhere, a vigorous mid-level trough should migrate from the western Great Lakes early D4/Tue into Ontario while phasing/becoming absorbed with a longer wave trough near Hudson Bay. Meanwhile, a surface low and trailing cold front will traverse Wisconsin/Michigan and a narrow axis of at least weak instability will exist ahead of that front. It appears that at least an isolated severe risk will exist as fast, but veered, wind fields will exist within the instability axis. This risk should be spatially limited and dependent on evolution of early-morning convection. The front will reach the Northeast on D5/Wed, although with even lesser instability due to weaker lapse rates aloft. Elsewhere, mid/upper ridging over the West will spread eastward and encompass the central Plains. A dearth of major synoptic systems should keep any appreciable severe threat to a minimum through the extended forecast period. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0219 AM CDT Sat Aug 31 2019 Valid 021200Z - 031200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF NORTH DAKOTA...NORTHEASTERN SOUTH DAKOTA...MUCH OF MINNESOTA...AND WESTERN WISCONSIN... ...SUMMARY... Severe thunderstorms are expected across portions of the Northern Plains and Upper Midwest Monday and Monday night. ...Synopsis... Mid/upper ridging will remain centered over the Four Corners while an amplifying shortwave trough treks from Montana eastward into the Dakotas by the latter half of the day on Monday. Downstream, a broader, lower amplitude trough will migrate through the Northeast. In the low-levels, a sharpening trough will extend from the Dakotas southwestward into eastern Colorado. As the mid-level wave approaches, cyclogenesis will occur across the Dakotas and a strong (45-55kt) nocturnal boundary layer jet will become established along an axis from eastern Nebraska to Minnesota overnight. Hurricane Dorian should remain in the general vicinity of the northern Bahamas/eastern Florida - see latest National Hurricane Center forecast products for information on its track and intensity. ...Dakotas eastward to Wisconsin... General consensus is that elevated storms will be ongoing across western North Dakota and vicinity during the first half of the day. As the mid-level wave approaches and low-level cyclogenesis commences, surface boundaries will begin to sharpen, with 1) a cold front expected to surge southward across western South Dakota, 2) a surface trough/dryline from central South Dakota through central Nebraska, and 3) a warm front from northern North Dakota east-southeastward to northern Wisconsin. Over the warm sector south and east of these boundaries, a warm, moist airmass (characterized by 60s to 70s F dewpoints) will reside. Models are fairly consistent in developing scattered to widespread convection after 00Z along an axis from northeastern North Dakota east-southeastward through western/central Wisconsin along the eastern edge of a stout EML. These storms are expected to be elevated, though steep lapse rates aloft will likely result in a risk of hail. A surface-based storm or two evolving within this activity may attain a greater risk of tornadoes and damaging wind gusts especially given supercellular shear profiles and moderate to strong instability, though this scenario is not particularly clear. Another uncertainty regarding the severe-weather scenario is the strength/warmth of the EML and associated mid-level inhibition across the open warm sector. The EC/GFS solutions are more aggressive in developing convection across south-central/southeastern North Dakota and vicinity during/just after peak heating in a strongly sheared, strongly unstable environment supporting supercellular development, very large hail, and perhaps significant tornadoes. Other models (Nam, UKMET) were much warmer/stronger with mid-level capping and limited convective initiation even with a southeastward-surging cold front. Thus, the southern extents of the MRGL/SLGT risk areas are highly conditional upon warm-sector development and refinements to the current risk areas and probabilities are a near certainty in subsequent outlooks. ...Pennsylvania/New York... Models are inconsistent with the extent of morning precipitation in portions of these areas, with casts some doubt on subsequent surface heating/destabilization during the afternoon hours. Nevertheless, the presence of modest mid-level flow/shear, lift associated with a well-timed mid-level trough, and warm/moist low-levels suggests some risk of loosely organized clusters of storms with a damaging-wind risk during the afternoon. This activity should be mostly diurnally driven. Subsequent outlooks may introduce low probabilities to address this scenario pending clearer mesoscale details. ...Florida... Westward progress of Hurricane Dorian remains uncertain at this time. If Dorian approaches the eastern Florida coast as depicted by the Nam, it is likely that a brief tornado threat will exist across coastal areas. The EC/GFS are much farther east with the center of Dorian, however. Given the uncertainties, severe probabilities are withheld for this outlook, but may be updated at a later time. ..Cook.. 08/31/2019 Read more