Severe Storms

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

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

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

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0146 AM CDT Sat Aug 31 2019 Valid 011200Z - 021200Z ...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. ..Squitieri.. 08/31/2019 ...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 0146 AM CDT Sat Aug 31 2019 Valid 011200Z - 021200Z ...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. ..Squitieri.. 08/31/2019 ...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 0146 AM CDT Sat Aug 31 2019 Valid 011200Z - 021200Z ...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. ..Squitieri.. 08/31/2019 ...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 0100 AM CDT Sat Aug 31 2019 Valid 311200Z - 011200Z ...NO CRITICAL AREAS... ...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. ..Squitieri.. 08/31/2019 ...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 0100 AM CDT Sat Aug 31 2019 Valid 311200Z - 011200Z ...NO CRITICAL AREAS... ...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. ..Squitieri.. 08/31/2019 ...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 0100 AM CDT Sat Aug 31 2019 Valid 311200Z - 011200Z ...NO CRITICAL AREAS... ...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. ..Squitieri.. 08/31/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1222 AM 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. ...Synopsis... A stout upper ridge will remain nearly stationary across the West on Sunday, with anticyclonically curved mid-level flow extending from California northeastward to Montana and on to the Upper Mississippi Valley. Across the East, a broad mid/upper trough will extend from the eastern Great Lakes southward to the Carolinas. At the surface, a lee trough will extend from southeastern Montana through northeastern Colorado. East of this trough, a modified maritime tropical airmass (characterized mostly by 60s and 70s F dewpoints) will persist across much of the eastern two thirds of the CONUS. A surface ridge will extend from far southeastern Canada to the southern Appalachians. Meanwhile, Hurricane Dorian will meander slowly westward toward Florida (see the latest National Hurricane Center forecast products for more information on Dorian). ...Northern High Plains... Though mid/upper ridging and subsidence will likely limit the extent of convective coverage across the region, convergence along the lee trough and southeasterly/upslope flow across the eastern Montana/western South Dakota may combine with abundant insolation and steepening low-level lapse rates to result in a few isolated thunderstorms in the evening. These storms should form in a moderately unstable environment, with strong shear promoting some organization and vertically veering profiles suggestive of some updraft rotation should storms materialize. This may result in an isolated hail/wind threat, though convective coverage is a bit too uncertain to introduce probabilities. Overnight, models depict isolated to scattered elevated convection across northeastern Montana and northern North Dakota on the northern end of a steep EML/lapse rate plume. This could result in a few areas of hail, although convective coverage remains a limiting factor for a more robust severe threat that would necessitate probabilities. ...Hurricane Dorian... Lingering uncertainty exists regarding the speed and track of Dorian at this time. Pending the forward speed of the system, increased low-level buoyancy/shear may result in an isolated tornado risk as outer bands approach the eastern coast of Florida, though the bulk of this threat may hold off until after the D2 forecast period. ...MAXIMUM RISK BY HAZARD... Tornado: <2% - None Wind: <5% - None Hail: <5% - None ..Cook.. 08/31/2019 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1222 AM 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. ...Synopsis... A stout upper ridge will remain nearly stationary across the West on Sunday, with anticyclonically curved mid-level flow extending from California northeastward to Montana and on to the Upper Mississippi Valley. Across the East, a broad mid/upper trough will extend from the eastern Great Lakes southward to the Carolinas. At the surface, a lee trough will extend from southeastern Montana through northeastern Colorado. East of this trough, a modified maritime tropical airmass (characterized mostly by 60s and 70s F dewpoints) will persist across much of the eastern two thirds of the CONUS. A surface ridge will extend from far southeastern Canada to the southern Appalachians. Meanwhile, Hurricane Dorian will meander slowly westward toward Florida (see the latest National Hurricane Center forecast products for more information on Dorian). ...Northern High Plains... Though mid/upper ridging and subsidence will likely limit the extent of convective coverage across the region, convergence along the lee trough and southeasterly/upslope flow across the eastern Montana/western South Dakota may combine with abundant insolation and steepening low-level lapse rates to result in a few isolated thunderstorms in the evening. These storms should form in a moderately unstable environment, with strong shear promoting some organization and vertically veering profiles suggestive of some updraft rotation should storms materialize. This may result in an isolated hail/wind threat, though convective coverage is a bit too uncertain to introduce probabilities. Overnight, models depict isolated to scattered elevated convection across northeastern Montana and northern North Dakota on the northern end of a steep EML/lapse rate plume. This could result in a few areas of hail, although convective coverage remains a limiting factor for a more robust severe threat that would necessitate probabilities. ...Hurricane Dorian... Lingering uncertainty exists regarding the speed and track of Dorian at this time. Pending the forward speed of the system, increased low-level buoyancy/shear may result in an isolated tornado risk as outer bands approach the eastern coast of Florida, though the bulk of this threat may hold off until after the D2 forecast period. ...MAXIMUM RISK BY HAZARD... Tornado: <2% - None Wind: <5% - None Hail: <5% - None ..Cook.. 08/31/2019 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1222 AM 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. ...Synopsis... A stout upper ridge will remain nearly stationary across the West on Sunday, with anticyclonically curved mid-level flow extending from California northeastward to Montana and on to the Upper Mississippi Valley. Across the East, a broad mid/upper trough will extend from the eastern Great Lakes southward to the Carolinas. At the surface, a lee trough will extend from southeastern Montana through northeastern Colorado. East of this trough, a modified maritime tropical airmass (characterized mostly by 60s and 70s F dewpoints) will persist across much of the eastern two thirds of the CONUS. A surface ridge will extend from far southeastern Canada to the southern Appalachians. Meanwhile, Hurricane Dorian will meander slowly westward toward Florida (see the latest National Hurricane Center forecast products for more information on Dorian). ...Northern High Plains... Though mid/upper ridging and subsidence will likely limit the extent of convective coverage across the region, convergence along the lee trough and southeasterly/upslope flow across the eastern Montana/western South Dakota may combine with abundant insolation and steepening low-level lapse rates to result in a few isolated thunderstorms in the evening. These storms should form in a moderately unstable environment, with strong shear promoting some organization and vertically veering profiles suggestive of some updraft rotation should storms materialize. This may result in an isolated hail/wind threat, though convective coverage is a bit too uncertain to introduce probabilities. Overnight, models depict isolated to scattered elevated convection across northeastern Montana and northern North Dakota on the northern end of a steep EML/lapse rate plume. This could result in a few areas of hail, although convective coverage remains a limiting factor for a more robust severe threat that would necessitate probabilities. ...Hurricane Dorian... Lingering uncertainty exists regarding the speed and track of Dorian at this time. Pending the forward speed of the system, increased low-level buoyancy/shear may result in an isolated tornado risk as outer bands approach the eastern coast of Florida, though the bulk of this threat may hold off until after the D2 forecast period. ...MAXIMUM RISK BY HAZARD... Tornado: <2% - None Wind: <5% - None Hail: <5% - None ..Cook.. 08/31/2019 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1235 AM CDT Sat Aug 31 2019 Valid 311200Z - 011200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected across the continental U.S. today. ...DISCUSSION... An upper-level trough will move across the Mississippi Valley today as an upper-level ridge moves slowly eastward across the northern Rockies and Four Corners region. At the surface, a post-frontal airmass will be in place across much of the central and eastern U.S. Thunderstorm development may take place across parts of the mid Mississippi and Ohio Valleys southwestward into parts of the southern Plains. Instability and deep-layer shear are forecast to be too weak for a severe threat across these areas today through tonight. ..Broyles/Squitieri.. 08/31/2019 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1235 AM CDT Sat Aug 31 2019 Valid 311200Z - 011200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected across the continental U.S. today. ...DISCUSSION... An upper-level trough will move across the Mississippi Valley today as an upper-level ridge moves slowly eastward across the northern Rockies and Four Corners region. At the surface, a post-frontal airmass will be in place across much of the central and eastern U.S. Thunderstorm development may take place across parts of the mid Mississippi and Ohio Valleys southwestward into parts of the southern Plains. Instability and deep-layer shear are forecast to be too weak for a severe threat across these areas today through tonight. ..Broyles/Squitieri.. 08/31/2019 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1235 AM CDT Sat Aug 31 2019 Valid 311200Z - 011200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected across the continental U.S. today. ...DISCUSSION... An upper-level trough will move across the Mississippi Valley today as an upper-level ridge moves slowly eastward across the northern Rockies and Four Corners region. At the surface, a post-frontal airmass will be in place across much of the central and eastern U.S. Thunderstorm development may take place across parts of the mid Mississippi and Ohio Valleys southwestward into parts of the southern Plains. Instability and deep-layer shear are forecast to be too weak for a severe threat across these areas today through tonight. ..Broyles/Squitieri.. 08/31/2019 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0743 PM CDT Fri Aug 30 2019 Valid 310100Z - 311200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE HIGH PLAINS AND MID MISSISSIPPI VALLEY... ...SUMMARY... Marginally severe thunderstorms with hail and strong wind gusts will be possible this evening across parts of the High Plains. A few storms with strong wind gusts will also be possible in the mid Mississippi Valley. ...High Plains... The latest water vapor imagery shows a west to northwest mid-level flow pattern over the central U.S. with a subtle shortwave trough moving through the central High Plains. Thunderstorms have developed just ahead of the trough along a corridor of moderate instability from the western Texas Panhandle into eastern Colorado and western Nebraska. MLCAPE values across this area estimated by the RAP to be in the 1000 to 2000 J/kg range. This combined with 0-6 km shear of 40 to 50 kt, evident on regional WSR-88D VWPs and steep low to mid-level lapse rates should be enough for a marginal severe threat this evening. The stronger storms could produce hail and isolated wind gusts approaching severe limits. ...Mid Mississippi Valley... The latest water vapor imagery shows an upper-level trough over the Ozarks. Ahead of the trough, a cold front is located from southern Missouri into southern Illinois. Thunderstorms have developed along the front on the northwestern edge of a moist airmass with surface dewpoints from the mid 60s to lower 70s F. This is contributing to a corridor of moderate instability across southern Illinois into southern Indiana. As the MCV associated with the convective complex moves eastward, a marginal severe threat will likely continue along this corridor of instability. A few strong wind gusts are expected to be the primary hazard. ..Broyles.. 08/31/2019 Read more