Severe Storms

MD 1833 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PENNSYLVANIA
Mesoscale Discussion 1833 NWS Storm Prediction Center Norman OK 0153 PM CDT Thu Aug 22 2019 Areas affected...Pennsylvania Concerning...Severe potential...Watch unlikely Valid 221853Z - 222100Z Probability of Watch Issuance...20 percent SUMMARY...Thunderstorm activity is expected to continue to develop and increase across the region through 4-6 PM, accompanied by at least some risk for potentially damaging wind gusts. This threat still appears isolated/marginal enough that a watch will not be needed, but trends will continue to be monitored. DISCUSSION...Deepening convection along the primary surface front, near the Interstate 70 corridor through the western slopes of the Allegheny mountains, may be aided by forcing for ascent associated with a remnant convectively generated or enhanced mid-level perturbation. This impulse is accompanied by a seasonably strong westerly mid-level speed maximum, including 30-50 kt in the 2-5 km (AGL) layer, and forecast to progress east of the Alleghenies, across much of central Pennsylvania through 20-22Z. Due to generally weak mid/upper lapse rates, CAPE for moist boundary layer air characterized by mid/upper 60s F surface dew points is generally weak across much of the region. However, it may still be sufficient to support increasing convection and embedded thunderstorm activity. Coinciding with peak daytime heating, and apparent relatively deep boundary layer mixing, the environment may still become conducive to locally strong downbursts near the most vigorous convection, which may be accompanied by potentially damaging surface gusts. ..Kerr/Guyer.. 08/22/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...PHI...BGM...CTP...PBZ... LAT...LON 41097889 41517644 40917557 40357630 40207691 40247838 40257945 41097889 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0135 PM CDT Thu Aug 22 2019 Valid 231200Z - 241200Z Added an elevated fire weather area for portions of the Great Basin into western Colorado and southwest Wyoming. Wind speeds of 15 to 20 mph should be widespread with relative humidity 10 to 20 percent. Therefore, an elevated fire weather area is warranted. ..Bentley.. 08/22/2019 .PREV DISCUSSION... /ISSUED 0133 AM CDT Thu Aug 22 2019/ ...Synopsis... The upper-level shortwave trough that tracked over the Pacific Northwest and northern Rockies during the past couple of days will begin to weaken while slowly lifting east-northeast across the northern Plains. A stronger upper-level trough will approach the Pacific Northwest tomorrow with a westerly mid-level jet (35-50 knots) preceding it and stretching across the Pacific Northwest and northern Rockies. The south/east progress of the surface cold front will slow with it likely becoming a stationary front across northern Utah and central Nevada. Elevated conditions may develop across portions of southwest Wyoming into northwest Colorado, but they should be confined to vegetation-sparse areas. Elevated conditions may also develop across portions southern Utah and northern Arizona. However, a weakening surface pressure gradient, lack of mid-level flow, and the possibility of high clouds moving northward preclude an elevated area 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 0135 PM CDT Thu Aug 22 2019 Valid 231200Z - 241200Z Added an elevated fire weather area for portions of the Great Basin into western Colorado and southwest Wyoming. Wind speeds of 15 to 20 mph should be widespread with relative humidity 10 to 20 percent. Therefore, an elevated fire weather area is warranted. ..Bentley.. 08/22/2019 .PREV DISCUSSION... /ISSUED 0133 AM CDT Thu Aug 22 2019/ ...Synopsis... The upper-level shortwave trough that tracked over the Pacific Northwest and northern Rockies during the past couple of days will begin to weaken while slowly lifting east-northeast across the northern Plains. A stronger upper-level trough will approach the Pacific Northwest tomorrow with a westerly mid-level jet (35-50 knots) preceding it and stretching across the Pacific Northwest and northern Rockies. The south/east progress of the surface cold front will slow with it likely becoming a stationary front across northern Utah and central Nevada. Elevated conditions may develop across portions of southwest Wyoming into northwest Colorado, but they should be confined to vegetation-sparse areas. Elevated conditions may also develop across portions southern Utah and northern Arizona. However, a weakening surface pressure gradient, lack of mid-level flow, and the possibility of high clouds moving northward preclude an elevated area 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 0135 PM CDT Thu Aug 22 2019 Valid 231200Z - 241200Z Added an elevated fire weather area for portions of the Great Basin into western Colorado and southwest Wyoming. Wind speeds of 15 to 20 mph should be widespread with relative humidity 10 to 20 percent. Therefore, an elevated fire weather area is warranted. ..Bentley.. 08/22/2019 .PREV DISCUSSION... /ISSUED 0133 AM CDT Thu Aug 22 2019/ ...Synopsis... The upper-level shortwave trough that tracked over the Pacific Northwest and northern Rockies during the past couple of days will begin to weaken while slowly lifting east-northeast across the northern Plains. A stronger upper-level trough will approach the Pacific Northwest tomorrow with a westerly mid-level jet (35-50 knots) preceding it and stretching across the Pacific Northwest and northern Rockies. The south/east progress of the surface cold front will slow with it likely becoming a stationary front across northern Utah and central Nevada. Elevated conditions may develop across portions of southwest Wyoming into northwest Colorado, but they should be confined to vegetation-sparse areas. Elevated conditions may also develop across portions southern Utah and northern Arizona. However, a weakening surface pressure gradient, lack of mid-level flow, and the possibility of high clouds moving northward preclude an elevated area 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 0135 PM CDT Thu Aug 22 2019 Valid 231200Z - 241200Z Added an elevated fire weather area for portions of the Great Basin into western Colorado and southwest Wyoming. Wind speeds of 15 to 20 mph should be widespread with relative humidity 10 to 20 percent. Therefore, an elevated fire weather area is warranted. ..Bentley.. 08/22/2019 .PREV DISCUSSION... /ISSUED 0133 AM CDT Thu Aug 22 2019/ ...Synopsis... The upper-level shortwave trough that tracked over the Pacific Northwest and northern Rockies during the past couple of days will begin to weaken while slowly lifting east-northeast across the northern Plains. A stronger upper-level trough will approach the Pacific Northwest tomorrow with a westerly mid-level jet (35-50 knots) preceding it and stretching across the Pacific Northwest and northern Rockies. The south/east progress of the surface cold front will slow with it likely becoming a stationary front across northern Utah and central Nevada. Elevated conditions may develop across portions of southwest Wyoming into northwest Colorado, but they should be confined to vegetation-sparse areas. Elevated conditions may also develop across portions southern Utah and northern Arizona. However, a weakening surface pressure gradient, lack of mid-level flow, and the possibility of high clouds moving northward preclude an elevated area 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 0135 PM CDT Thu Aug 22 2019 Valid 231200Z - 241200Z Added an elevated fire weather area for portions of the Great Basin into western Colorado and southwest Wyoming. Wind speeds of 15 to 20 mph should be widespread with relative humidity 10 to 20 percent. Therefore, an elevated fire weather area is warranted. ..Bentley.. 08/22/2019 .PREV DISCUSSION... /ISSUED 0133 AM CDT Thu Aug 22 2019/ ...Synopsis... The upper-level shortwave trough that tracked over the Pacific Northwest and northern Rockies during the past couple of days will begin to weaken while slowly lifting east-northeast across the northern Plains. A stronger upper-level trough will approach the Pacific Northwest tomorrow with a westerly mid-level jet (35-50 knots) preceding it and stretching across the Pacific Northwest and northern Rockies. The south/east progress of the surface cold front will slow with it likely becoming a stationary front across northern Utah and central Nevada. Elevated conditions may develop across portions of southwest Wyoming into northwest Colorado, but they should be confined to vegetation-sparse areas. Elevated conditions may also develop across portions southern Utah and northern Arizona. However, a weakening surface pressure gradient, lack of mid-level flow, and the possibility of high clouds moving northward preclude an elevated area at this time. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

MD 1832 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PARTS OF SOUTHWESTERN/SOUTH CENTRAL VIRGINIA AND NORTHERN NORTH CAROLINA
Mesoscale Discussion 1832 NWS Storm Prediction Center Norman OK 0102 PM CDT Thu Aug 22 2019 Areas affected...Parts of southwestern/south central Virginia and northern North Carolina Concerning...Severe potential...Watch unlikely Valid 221802Z - 222000Z Probability of Watch Issuance...20 percent SUMMARY...An evolving cluster of thunderstorms may persist, and could intensify further, while spreading eastward along the western into central Virginia and North Carolina border area through 4-6 PM EDT. This activity may be accompanied by a period of strong wind gusts, which, while probably remaining mostly less than 50 kt, could still be locally damaging. DISCUSSION...Weak inhibition associated with a relatively cool pocket of air aloft (in the 700-500 mb layer) has allowed for initiation of scattered thunderstorm activity along the Blue Ridge. Perhaps more prominently, a cluster of thunderstorms appears to be emerging from the upper Tennessee Valley, in the presence of light west-southwesterly deep layer mean flow on the order of 10-20 kt. Mid/upper support for the evolving storm cluster appears weak to negligible, or is at least unclear, but activity may have already supported the development of a substantive surface cold pool, with 2-3 mb 2 hourly surface pressure rises noted in the 17Z surface observation from Bristol/Tri-City TN. The leading/eastern edge of this cold pool appears to be advancing eastward at 25-30 kt, and is providing the focus for renewed vigorous thunderstorm activity. This appears likely to continue, with further intensification possible, as it advances east of the higher terrain into a warm, seasonably moist boundary layer characterized by CAPE up to 2000+ J/kg. As convection is maintained, the cold pool may continue to strengthen and pose increasing risk for potentially damaging winds along its gust front, roughly either side of the western/central Virginia/North Carolina border area through 21-22Z. ..Kerr/Guyer.. 08/22/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...AKQ...LWX...RAH...RNK...GSP... LAT...LON 36968100 37238039 37397981 37867913 37187817 35937883 35777917 35608007 35738108 35878147 36298119 36688111 36968100 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Thu Aug 22 2019 Valid 231200Z - 241200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF SOUTHERN VIRGINIA AND NORTH CAROLINA...AND OVER PARTS OF THE NORTHERN AND CENTRAL HIGH PLAINS... ...SUMMARY... Isolated/local wind gusts possibly reaching severe levels are possible Friday over parts of North Carolina and southern Virginia, while a limited risk for hail and localized strong gusts will also be possible over the northern and central High Plains. ...Synopsis... As an upper trough progresses across eastern Canada and the northeastern U.S. Friday, an associated/surface cold front is expected to have cleared the New England and mid Atlantic coasts by the start of the period. The trailing portion of this boundary, arcing from Virginia westward across the mid South, into the southern Plains, and then northwestward across the central and northern high Plains, will make gradual southward progress over the eastern half of the country. Meanwhile, a second/weaker trough is forecast to cross the Rockies, reaching the Plains states late. In conjunction with this trough, a cold front will continue crossing the northern Intermountain region and will eventually reach the high Plains, intersecting the prior/remnant front lingering in lee of the mountains. ...Southern Virginia/North Carolina... Afternoon thunderstorm development is expected from the Virginia/North Carolina region westward across the mid South/mid Mississippi Valley area, as diurnal destabilization occurs. Although a local/pulse-type severe risk may occur with a few more intense updrafts along the entire frontal zone, weak shear should hinder updraft organization in most areas. One area of slightly greater risk -- coincident with slightly greater flow aloft lingering onshore on the southern periphery of the departing upper system -- is apparent over portions of Virginia and North Carolina. Here, moderate mid-level westerlies may promote slightly more organized, eastward-moving storms/storm clusters, and thus slightly greater severe risk as compared to other areas within the remnant frontal zone. Risk should diminish during the evening, as the airmass stabilizes diurnally. ...Northern and central High Plains... Afternoon storm development is expected -- initially over the eastern Wyoming vicinity, near the intersection of a cold front crossing the northern Intermountain region and the remnant front/lee trough over the high Plains. With moderate CAPE expected to evolve (2000 to 3000 J/kg across the region), a few stronger storms -- and some upscale clustering -- is expected. However, somewhat limited westerly flow aloft suggests marginal shear in most areas. With low-level southeasterlies expected across the Plains however, shear may prove sufficient -- beneath a small, slightly enhanced belt of westerlies indicated over the Wyoming vicinity -- for development of a couple of supercells initially, then possibly growing into a cluster of storms that may shift off the higher terrain. As such, local hail/wind risk warrants continuation of MRGL risk, with some chance that a small SLGT risk could be added in future outlook updates. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 5% - Marginal Hail: 5% - Marginal ..Goss.. 08/22/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Thu Aug 22 2019 Valid 231200Z - 241200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF SOUTHERN VIRGINIA AND NORTH CAROLINA...AND OVER PARTS OF THE NORTHERN AND CENTRAL HIGH PLAINS... ...SUMMARY... Isolated/local wind gusts possibly reaching severe levels are possible Friday over parts of North Carolina and southern Virginia, while a limited risk for hail and localized strong gusts will also be possible over the northern and central High Plains. ...Synopsis... As an upper trough progresses across eastern Canada and the northeastern U.S. Friday, an associated/surface cold front is expected to have cleared the New England and mid Atlantic coasts by the start of the period. The trailing portion of this boundary, arcing from Virginia westward across the mid South, into the southern Plains, and then northwestward across the central and northern high Plains, will make gradual southward progress over the eastern half of the country. Meanwhile, a second/weaker trough is forecast to cross the Rockies, reaching the Plains states late. In conjunction with this trough, a cold front will continue crossing the northern Intermountain region and will eventually reach the high Plains, intersecting the prior/remnant front lingering in lee of the mountains. ...Southern Virginia/North Carolina... Afternoon thunderstorm development is expected from the Virginia/North Carolina region westward across the mid South/mid Mississippi Valley area, as diurnal destabilization occurs. Although a local/pulse-type severe risk may occur with a few more intense updrafts along the entire frontal zone, weak shear should hinder updraft organization in most areas. One area of slightly greater risk -- coincident with slightly greater flow aloft lingering onshore on the southern periphery of the departing upper system -- is apparent over portions of Virginia and North Carolina. Here, moderate mid-level westerlies may promote slightly more organized, eastward-moving storms/storm clusters, and thus slightly greater severe risk as compared to other areas within the remnant frontal zone. Risk should diminish during the evening, as the airmass stabilizes diurnally. ...Northern and central High Plains... Afternoon storm development is expected -- initially over the eastern Wyoming vicinity, near the intersection of a cold front crossing the northern Intermountain region and the remnant front/lee trough over the high Plains. With moderate CAPE expected to evolve (2000 to 3000 J/kg across the region), a few stronger storms -- and some upscale clustering -- is expected. However, somewhat limited westerly flow aloft suggests marginal shear in most areas. With low-level southeasterlies expected across the Plains however, shear may prove sufficient -- beneath a small, slightly enhanced belt of westerlies indicated over the Wyoming vicinity -- for development of a couple of supercells initially, then possibly growing into a cluster of storms that may shift off the higher terrain. As such, local hail/wind risk warrants continuation of MRGL risk, with some chance that a small SLGT risk could be added in future outlook updates. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 5% - Marginal Hail: 5% - Marginal ..Goss.. 08/22/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Thu Aug 22 2019 Valid 231200Z - 241200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF SOUTHERN VIRGINIA AND NORTH CAROLINA...AND OVER PARTS OF THE NORTHERN AND CENTRAL HIGH PLAINS... ...SUMMARY... Isolated/local wind gusts possibly reaching severe levels are possible Friday over parts of North Carolina and southern Virginia, while a limited risk for hail and localized strong gusts will also be possible over the northern and central High Plains. ...Synopsis... As an upper trough progresses across eastern Canada and the northeastern U.S. Friday, an associated/surface cold front is expected to have cleared the New England and mid Atlantic coasts by the start of the period. The trailing portion of this boundary, arcing from Virginia westward across the mid South, into the southern Plains, and then northwestward across the central and northern high Plains, will make gradual southward progress over the eastern half of the country. Meanwhile, a second/weaker trough is forecast to cross the Rockies, reaching the Plains states late. In conjunction with this trough, a cold front will continue crossing the northern Intermountain region and will eventually reach the high Plains, intersecting the prior/remnant front lingering in lee of the mountains. ...Southern Virginia/North Carolina... Afternoon thunderstorm development is expected from the Virginia/North Carolina region westward across the mid South/mid Mississippi Valley area, as diurnal destabilization occurs. Although a local/pulse-type severe risk may occur with a few more intense updrafts along the entire frontal zone, weak shear should hinder updraft organization in most areas. One area of slightly greater risk -- coincident with slightly greater flow aloft lingering onshore on the southern periphery of the departing upper system -- is apparent over portions of Virginia and North Carolina. Here, moderate mid-level westerlies may promote slightly more organized, eastward-moving storms/storm clusters, and thus slightly greater severe risk as compared to other areas within the remnant frontal zone. Risk should diminish during the evening, as the airmass stabilizes diurnally. ...Northern and central High Plains... Afternoon storm development is expected -- initially over the eastern Wyoming vicinity, near the intersection of a cold front crossing the northern Intermountain region and the remnant front/lee trough over the high Plains. With moderate CAPE expected to evolve (2000 to 3000 J/kg across the region), a few stronger storms -- and some upscale clustering -- is expected. However, somewhat limited westerly flow aloft suggests marginal shear in most areas. With low-level southeasterlies expected across the Plains however, shear may prove sufficient -- beneath a small, slightly enhanced belt of westerlies indicated over the Wyoming vicinity -- for development of a couple of supercells initially, then possibly growing into a cluster of storms that may shift off the higher terrain. As such, local hail/wind risk warrants continuation of MRGL risk, with some chance that a small SLGT risk could be added in future outlook updates. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 5% - Marginal Hail: 5% - Marginal ..Goss.. 08/22/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Thu Aug 22 2019 Valid 231200Z - 241200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF SOUTHERN VIRGINIA AND NORTH CAROLINA...AND OVER PARTS OF THE NORTHERN AND CENTRAL HIGH PLAINS... ...SUMMARY... Isolated/local wind gusts possibly reaching severe levels are possible Friday over parts of North Carolina and southern Virginia, while a limited risk for hail and localized strong gusts will also be possible over the northern and central High Plains. ...Synopsis... As an upper trough progresses across eastern Canada and the northeastern U.S. Friday, an associated/surface cold front is expected to have cleared the New England and mid Atlantic coasts by the start of the period. The trailing portion of this boundary, arcing from Virginia westward across the mid South, into the southern Plains, and then northwestward across the central and northern high Plains, will make gradual southward progress over the eastern half of the country. Meanwhile, a second/weaker trough is forecast to cross the Rockies, reaching the Plains states late. In conjunction with this trough, a cold front will continue crossing the northern Intermountain region and will eventually reach the high Plains, intersecting the prior/remnant front lingering in lee of the mountains. ...Southern Virginia/North Carolina... Afternoon thunderstorm development is expected from the Virginia/North Carolina region westward across the mid South/mid Mississippi Valley area, as diurnal destabilization occurs. Although a local/pulse-type severe risk may occur with a few more intense updrafts along the entire frontal zone, weak shear should hinder updraft organization in most areas. One area of slightly greater risk -- coincident with slightly greater flow aloft lingering onshore on the southern periphery of the departing upper system -- is apparent over portions of Virginia and North Carolina. Here, moderate mid-level westerlies may promote slightly more organized, eastward-moving storms/storm clusters, and thus slightly greater severe risk as compared to other areas within the remnant frontal zone. Risk should diminish during the evening, as the airmass stabilizes diurnally. ...Northern and central High Plains... Afternoon storm development is expected -- initially over the eastern Wyoming vicinity, near the intersection of a cold front crossing the northern Intermountain region and the remnant front/lee trough over the high Plains. With moderate CAPE expected to evolve (2000 to 3000 J/kg across the region), a few stronger storms -- and some upscale clustering -- is expected. However, somewhat limited westerly flow aloft suggests marginal shear in most areas. With low-level southeasterlies expected across the Plains however, shear may prove sufficient -- beneath a small, slightly enhanced belt of westerlies indicated over the Wyoming vicinity -- for development of a couple of supercells initially, then possibly growing into a cluster of storms that may shift off the higher terrain. As such, local hail/wind risk warrants continuation of MRGL risk, with some chance that a small SLGT risk could be added in future outlook updates. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 5% - Marginal Hail: 5% - Marginal ..Goss.. 08/22/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Thu Aug 22 2019 Valid 231200Z - 241200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF SOUTHERN VIRGINIA AND NORTH CAROLINA...AND OVER PARTS OF THE NORTHERN AND CENTRAL HIGH PLAINS... ...SUMMARY... Isolated/local wind gusts possibly reaching severe levels are possible Friday over parts of North Carolina and southern Virginia, while a limited risk for hail and localized strong gusts will also be possible over the northern and central High Plains. ...Synopsis... As an upper trough progresses across eastern Canada and the northeastern U.S. Friday, an associated/surface cold front is expected to have cleared the New England and mid Atlantic coasts by the start of the period. The trailing portion of this boundary, arcing from Virginia westward across the mid South, into the southern Plains, and then northwestward across the central and northern high Plains, will make gradual southward progress over the eastern half of the country. Meanwhile, a second/weaker trough is forecast to cross the Rockies, reaching the Plains states late. In conjunction with this trough, a cold front will continue crossing the northern Intermountain region and will eventually reach the high Plains, intersecting the prior/remnant front lingering in lee of the mountains. ...Southern Virginia/North Carolina... Afternoon thunderstorm development is expected from the Virginia/North Carolina region westward across the mid South/mid Mississippi Valley area, as diurnal destabilization occurs. Although a local/pulse-type severe risk may occur with a few more intense updrafts along the entire frontal zone, weak shear should hinder updraft organization in most areas. One area of slightly greater risk -- coincident with slightly greater flow aloft lingering onshore on the southern periphery of the departing upper system -- is apparent over portions of Virginia and North Carolina. Here, moderate mid-level westerlies may promote slightly more organized, eastward-moving storms/storm clusters, and thus slightly greater severe risk as compared to other areas within the remnant frontal zone. Risk should diminish during the evening, as the airmass stabilizes diurnally. ...Northern and central High Plains... Afternoon storm development is expected -- initially over the eastern Wyoming vicinity, near the intersection of a cold front crossing the northern Intermountain region and the remnant front/lee trough over the high Plains. With moderate CAPE expected to evolve (2000 to 3000 J/kg across the region), a few stronger storms -- and some upscale clustering -- is expected. However, somewhat limited westerly flow aloft suggests marginal shear in most areas. With low-level southeasterlies expected across the Plains however, shear may prove sufficient -- beneath a small, slightly enhanced belt of westerlies indicated over the Wyoming vicinity -- for development of a couple of supercells initially, then possibly growing into a cluster of storms that may shift off the higher terrain. As such, local hail/wind risk warrants continuation of MRGL risk, with some chance that a small SLGT risk could be added in future outlook updates. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 5% - Marginal Hail: 5% - Marginal ..Goss.. 08/22/2019 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1151 AM CDT Thu Aug 22 2019 Valid 221700Z - 231200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF UTAH...NORTHERN ARIZONA...SOUTHEAST NEVADA...SOUTHWEST WYOMING...AND NORTHWEST COLORADO... Only minor changes to ongoing elevated and critical areas based on the latest forecast guidance. See previous discussion below for additional details. ..Bentley.. 08/22/2019 .PREV DISCUSSION... /ISSUED 0157 AM CDT Thu Aug 22 2019/ ...Synopsis... An upper-level shortwave trough will continue moving eastward over the Pacific Northwest and northern Rockies today. An associated surface cold front will also continue pushing east and south through much of the northern Rockies and northern California and into the Great Basin. A pre-frontal surface pressure trough will run parallel to the cold front stretching southwest from north-central Montana into southern Nevada. A broad area of elevated conditions will develop stretching from northern Arizona/southern Nevada into central Wyoming, with critical conditions likely developing in far northwest Arizona/southeast Nevada through central Utah into southwest Wyoming. West-southwest sustained surface winds of 15-25 mph with RH values of 8-20% are likely to develop ahead of the cold front during the afternoon and into the evening. ERCs are mostly above the 80th percentile within the elevated/critical areas including some locations above the 95th percentile. Elevated conditions are likely across portions of the Snake River Plain and vicinity this afternoon. The cold front will likely push through the area this morning. However, daytime heating will help mix/deepen the boundary layer and increase surface temperatures with west-southwest surface winds of 15-20 mph and RH values of 15-20% developing during the afternoon. ...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 1151 AM CDT Thu Aug 22 2019 Valid 221700Z - 231200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF UTAH...NORTHERN ARIZONA...SOUTHEAST NEVADA...SOUTHWEST WYOMING...AND NORTHWEST COLORADO... Only minor changes to ongoing elevated and critical areas based on the latest forecast guidance. See previous discussion below for additional details. ..Bentley.. 08/22/2019 .PREV DISCUSSION... /ISSUED 0157 AM CDT Thu Aug 22 2019/ ...Synopsis... An upper-level shortwave trough will continue moving eastward over the Pacific Northwest and northern Rockies today. An associated surface cold front will also continue pushing east and south through much of the northern Rockies and northern California and into the Great Basin. A pre-frontal surface pressure trough will run parallel to the cold front stretching southwest from north-central Montana into southern Nevada. A broad area of elevated conditions will develop stretching from northern Arizona/southern Nevada into central Wyoming, with critical conditions likely developing in far northwest Arizona/southeast Nevada through central Utah into southwest Wyoming. West-southwest sustained surface winds of 15-25 mph with RH values of 8-20% are likely to develop ahead of the cold front during the afternoon and into the evening. ERCs are mostly above the 80th percentile within the elevated/critical areas including some locations above the 95th percentile. Elevated conditions are likely across portions of the Snake River Plain and vicinity this afternoon. The cold front will likely push through the area this morning. However, daytime heating will help mix/deepen the boundary layer and increase surface temperatures with west-southwest surface winds of 15-20 mph and RH values of 15-20% developing during the afternoon. ...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 1151 AM CDT Thu Aug 22 2019 Valid 221700Z - 231200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF UTAH...NORTHERN ARIZONA...SOUTHEAST NEVADA...SOUTHWEST WYOMING...AND NORTHWEST COLORADO... Only minor changes to ongoing elevated and critical areas based on the latest forecast guidance. See previous discussion below for additional details. ..Bentley.. 08/22/2019 .PREV DISCUSSION... /ISSUED 0157 AM CDT Thu Aug 22 2019/ ...Synopsis... An upper-level shortwave trough will continue moving eastward over the Pacific Northwest and northern Rockies today. An associated surface cold front will also continue pushing east and south through much of the northern Rockies and northern California and into the Great Basin. A pre-frontal surface pressure trough will run parallel to the cold front stretching southwest from north-central Montana into southern Nevada. A broad area of elevated conditions will develop stretching from northern Arizona/southern Nevada into central Wyoming, with critical conditions likely developing in far northwest Arizona/southeast Nevada through central Utah into southwest Wyoming. West-southwest sustained surface winds of 15-25 mph with RH values of 8-20% are likely to develop ahead of the cold front during the afternoon and into the evening. ERCs are mostly above the 80th percentile within the elevated/critical areas including some locations above the 95th percentile. Elevated conditions are likely across portions of the Snake River Plain and vicinity this afternoon. The cold front will likely push through the area this morning. However, daytime heating will help mix/deepen the boundary layer and increase surface temperatures with west-southwest surface winds of 15-20 mph and RH values of 15-20% developing during the afternoon. ...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 1151 AM CDT Thu Aug 22 2019 Valid 221700Z - 231200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF UTAH...NORTHERN ARIZONA...SOUTHEAST NEVADA...SOUTHWEST WYOMING...AND NORTHWEST COLORADO... Only minor changes to ongoing elevated and critical areas based on the latest forecast guidance. See previous discussion below for additional details. ..Bentley.. 08/22/2019 .PREV DISCUSSION... /ISSUED 0157 AM CDT Thu Aug 22 2019/ ...Synopsis... An upper-level shortwave trough will continue moving eastward over the Pacific Northwest and northern Rockies today. An associated surface cold front will also continue pushing east and south through much of the northern Rockies and northern California and into the Great Basin. A pre-frontal surface pressure trough will run parallel to the cold front stretching southwest from north-central Montana into southern Nevada. A broad area of elevated conditions will develop stretching from northern Arizona/southern Nevada into central Wyoming, with critical conditions likely developing in far northwest Arizona/southeast Nevada through central Utah into southwest Wyoming. West-southwest sustained surface winds of 15-25 mph with RH values of 8-20% are likely to develop ahead of the cold front during the afternoon and into the evening. ERCs are mostly above the 80th percentile within the elevated/critical areas including some locations above the 95th percentile. Elevated conditions are likely across portions of the Snake River Plain and vicinity this afternoon. The cold front will likely push through the area this morning. However, daytime heating will help mix/deepen the boundary layer and increase surface temperatures with west-southwest surface winds of 15-20 mph and RH values of 15-20% developing during the afternoon. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1136 AM CDT Thu Aug 22 2019 Valid 221630Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE SOUTHERN PLAINS TO THE MID-ATLANTIC STATES AND THE NORTHERN/CENTRAL HIGH PLAINS... ...SUMMARY... Isolated damaging winds are possible this afternoon and evening from the southern Plains and Mid-South to the Mid-Atlantic States. Isolated severe hail and wind are also possible over the northern and central High Plains. ...Mid-Atlantic States/Carolinas... A belt of cyclonically curved/moderately strong westerlies aloft will persist over the Upper Ohio Valley and Mid-Atlantic region, with a cold front gradually progressing southeastward across these regions through tonight. Thunderstorms are expected to develop/increase over the mountains and/or in association with ongoing persistent clusters. As low-level lapse rates steepen, damaging winds will be the primary risk. A few sustained/semi-organized clusters of storms may materialize this afternoon, particularly from south-central Pennsylvania southward to near/east of the Blue Ridge in Virginia/Northern Carolina. However, current thinking is that the overall severe storm coverage/risk magnitude will be a bit lower as compared to prior days across the region. ...Southeast Wyoming/Central High Plains... To the north of an eastern Colorado-centered surface low, low-level upslope flow and differential heating in vicinity of the higher terrain is likely to contribute to isolated thunderstorm development this afternoon. Storms should intensify as they move east-southeastward within a moist/increasingly unstable environment. A few instances of isolated severe hail will initially be possible. Storms may gradually cluster with localized severe-caliber wind gust potential this evening across the southern Nebraska Panhandle/northeast Colorado vicinity, and possibly southwest Nebraska/northwest Kansas. ...Southern/eastern Montana to northern High Plains... Isolated to scattered thunderstorms are expected to develop across this area during the afternoon, and into evening with eastward extent. Isolated severe gusts/hail are the main concerns. A relative concentration of convection is possible during about 00Z-06Z across portions of eastern Montana and perhaps northeastern Wyoming. During that time frame, some of the stronger low-level mass response and convergence (related to the approaching shortwave trough), and perhaps the leading fringe of mid/upper synoptic forcing, will impinge upon a narrow plume of relatively maximized buoyancy and boundary-layer moisture. Pre-convective MLCAPE of 1000-2000 J/kg is possible this evening near an axis from RAP-GGW, amidst well-mixed subcloud layers supporting strong-severe gust potential. However, weak mid/upper-level winds suggest that severe potential should remain fairly disorganized and/or short-lived. ...Southern Plains to Mid-South/Tennessee Valley... Within a moist/unstable environment, surface-based thunderstorm development later this afternoon will be focused along zones of residual outflow/differential heating. While weak westerlies will generally prevail, ample heating/buoyancy could support localized severe-caliber downdrafts late this afternoon/early evening. ..Guyer/Bunting.. 08/22/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1136 AM CDT Thu Aug 22 2019 Valid 221630Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE SOUTHERN PLAINS TO THE MID-ATLANTIC STATES AND THE NORTHERN/CENTRAL HIGH PLAINS... ...SUMMARY... Isolated damaging winds are possible this afternoon and evening from the southern Plains and Mid-South to the Mid-Atlantic States. Isolated severe hail and wind are also possible over the northern and central High Plains. ...Mid-Atlantic States/Carolinas... A belt of cyclonically curved/moderately strong westerlies aloft will persist over the Upper Ohio Valley and Mid-Atlantic region, with a cold front gradually progressing southeastward across these regions through tonight. Thunderstorms are expected to develop/increase over the mountains and/or in association with ongoing persistent clusters. As low-level lapse rates steepen, damaging winds will be the primary risk. A few sustained/semi-organized clusters of storms may materialize this afternoon, particularly from south-central Pennsylvania southward to near/east of the Blue Ridge in Virginia/Northern Carolina. However, current thinking is that the overall severe storm coverage/risk magnitude will be a bit lower as compared to prior days across the region. ...Southeast Wyoming/Central High Plains... To the north of an eastern Colorado-centered surface low, low-level upslope flow and differential heating in vicinity of the higher terrain is likely to contribute to isolated thunderstorm development this afternoon. Storms should intensify as they move east-southeastward within a moist/increasingly unstable environment. A few instances of isolated severe hail will initially be possible. Storms may gradually cluster with localized severe-caliber wind gust potential this evening across the southern Nebraska Panhandle/northeast Colorado vicinity, and possibly southwest Nebraska/northwest Kansas. ...Southern/eastern Montana to northern High Plains... Isolated to scattered thunderstorms are expected to develop across this area during the afternoon, and into evening with eastward extent. Isolated severe gusts/hail are the main concerns. A relative concentration of convection is possible during about 00Z-06Z across portions of eastern Montana and perhaps northeastern Wyoming. During that time frame, some of the stronger low-level mass response and convergence (related to the approaching shortwave trough), and perhaps the leading fringe of mid/upper synoptic forcing, will impinge upon a narrow plume of relatively maximized buoyancy and boundary-layer moisture. Pre-convective MLCAPE of 1000-2000 J/kg is possible this evening near an axis from RAP-GGW, amidst well-mixed subcloud layers supporting strong-severe gust potential. However, weak mid/upper-level winds suggest that severe potential should remain fairly disorganized and/or short-lived. ...Southern Plains to Mid-South/Tennessee Valley... Within a moist/unstable environment, surface-based thunderstorm development later this afternoon will be focused along zones of residual outflow/differential heating. While weak westerlies will generally prevail, ample heating/buoyancy could support localized severe-caliber downdrafts late this afternoon/early evening. ..Guyer/Bunting.. 08/22/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1136 AM CDT Thu Aug 22 2019 Valid 221630Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE SOUTHERN PLAINS TO THE MID-ATLANTIC STATES AND THE NORTHERN/CENTRAL HIGH PLAINS... ...SUMMARY... Isolated damaging winds are possible this afternoon and evening from the southern Plains and Mid-South to the Mid-Atlantic States. Isolated severe hail and wind are also possible over the northern and central High Plains. ...Mid-Atlantic States/Carolinas... A belt of cyclonically curved/moderately strong westerlies aloft will persist over the Upper Ohio Valley and Mid-Atlantic region, with a cold front gradually progressing southeastward across these regions through tonight. Thunderstorms are expected to develop/increase over the mountains and/or in association with ongoing persistent clusters. As low-level lapse rates steepen, damaging winds will be the primary risk. A few sustained/semi-organized clusters of storms may materialize this afternoon, particularly from south-central Pennsylvania southward to near/east of the Blue Ridge in Virginia/Northern Carolina. However, current thinking is that the overall severe storm coverage/risk magnitude will be a bit lower as compared to prior days across the region. ...Southeast Wyoming/Central High Plains... To the north of an eastern Colorado-centered surface low, low-level upslope flow and differential heating in vicinity of the higher terrain is likely to contribute to isolated thunderstorm development this afternoon. Storms should intensify as they move east-southeastward within a moist/increasingly unstable environment. A few instances of isolated severe hail will initially be possible. Storms may gradually cluster with localized severe-caliber wind gust potential this evening across the southern Nebraska Panhandle/northeast Colorado vicinity, and possibly southwest Nebraska/northwest Kansas. ...Southern/eastern Montana to northern High Plains... Isolated to scattered thunderstorms are expected to develop across this area during the afternoon, and into evening with eastward extent. Isolated severe gusts/hail are the main concerns. A relative concentration of convection is possible during about 00Z-06Z across portions of eastern Montana and perhaps northeastern Wyoming. During that time frame, some of the stronger low-level mass response and convergence (related to the approaching shortwave trough), and perhaps the leading fringe of mid/upper synoptic forcing, will impinge upon a narrow plume of relatively maximized buoyancy and boundary-layer moisture. Pre-convective MLCAPE of 1000-2000 J/kg is possible this evening near an axis from RAP-GGW, amidst well-mixed subcloud layers supporting strong-severe gust potential. However, weak mid/upper-level winds suggest that severe potential should remain fairly disorganized and/or short-lived. ...Southern Plains to Mid-South/Tennessee Valley... Within a moist/unstable environment, surface-based thunderstorm development later this afternoon will be focused along zones of residual outflow/differential heating. While weak westerlies will generally prevail, ample heating/buoyancy could support localized severe-caliber downdrafts late this afternoon/early evening. ..Guyer/Bunting.. 08/22/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1136 AM CDT Thu Aug 22 2019 Valid 221630Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE SOUTHERN PLAINS TO THE MID-ATLANTIC STATES AND THE NORTHERN/CENTRAL HIGH PLAINS... ...SUMMARY... Isolated damaging winds are possible this afternoon and evening from the southern Plains and Mid-South to the Mid-Atlantic States. Isolated severe hail and wind are also possible over the northern and central High Plains. ...Mid-Atlantic States/Carolinas... A belt of cyclonically curved/moderately strong westerlies aloft will persist over the Upper Ohio Valley and Mid-Atlantic region, with a cold front gradually progressing southeastward across these regions through tonight. Thunderstorms are expected to develop/increase over the mountains and/or in association with ongoing persistent clusters. As low-level lapse rates steepen, damaging winds will be the primary risk. A few sustained/semi-organized clusters of storms may materialize this afternoon, particularly from south-central Pennsylvania southward to near/east of the Blue Ridge in Virginia/Northern Carolina. However, current thinking is that the overall severe storm coverage/risk magnitude will be a bit lower as compared to prior days across the region. ...Southeast Wyoming/Central High Plains... To the north of an eastern Colorado-centered surface low, low-level upslope flow and differential heating in vicinity of the higher terrain is likely to contribute to isolated thunderstorm development this afternoon. Storms should intensify as they move east-southeastward within a moist/increasingly unstable environment. A few instances of isolated severe hail will initially be possible. Storms may gradually cluster with localized severe-caliber wind gust potential this evening across the southern Nebraska Panhandle/northeast Colorado vicinity, and possibly southwest Nebraska/northwest Kansas. ...Southern/eastern Montana to northern High Plains... Isolated to scattered thunderstorms are expected to develop across this area during the afternoon, and into evening with eastward extent. Isolated severe gusts/hail are the main concerns. A relative concentration of convection is possible during about 00Z-06Z across portions of eastern Montana and perhaps northeastern Wyoming. During that time frame, some of the stronger low-level mass response and convergence (related to the approaching shortwave trough), and perhaps the leading fringe of mid/upper synoptic forcing, will impinge upon a narrow plume of relatively maximized buoyancy and boundary-layer moisture. Pre-convective MLCAPE of 1000-2000 J/kg is possible this evening near an axis from RAP-GGW, amidst well-mixed subcloud layers supporting strong-severe gust potential. However, weak mid/upper-level winds suggest that severe potential should remain fairly disorganized and/or short-lived. ...Southern Plains to Mid-South/Tennessee Valley... Within a moist/unstable environment, surface-based thunderstorm development later this afternoon will be focused along zones of residual outflow/differential heating. While weak westerlies will generally prevail, ample heating/buoyancy could support localized severe-caliber downdrafts late this afternoon/early evening. ..Guyer/Bunting.. 08/22/2019 Read more