Severe Storms

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1255 AM CDT Fri Aug 23 2019 Valid 231200Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN HIGH PLAINS AND ACROSS PARTS OF SOUTHEAST VA INTO NORTHEAST NC... ...SUMMARY... Severe thunderstorms capable of large hail and damaging wind gusts are possible this afternoon and evening, mainly across eastern Wyoming/Colorado into western Nebraska/Kansas. Severe thunderstorms, mainly capable of damaging wind gusts, are also expected across portions of southeast Virginia into northeast North Carolina this afternoon and evening. ...Synopsis... An upper trough over the northeastern states will continue to lift east/northeast today. The associated surface cold front will extend from near the New England coast this morning, arcing southwest into northern VA and the lower OH/middle MS Valley vicinity. The western extent of the front will push southward and become a focus for strong to severe thunderstorm development across portions of southern VA into NC. Meanwhile, the upper shortwave trough over the western U.S. will slowly shift east across the Rockies to the High Plains. A lee trough and moist, upslope flow regime amidst upper level height falls will focus another round of strong to severe thunderstorms across portions of the High Plains. Elsewhere, a very moist and unstable boundary layer will support sporadic downbursts from Oklahoma into portions of the South. Organized severe threat will be limited by weak flow and a lack of upper forcing for ascent as the area remains under the influence of lower-amplitude southern-stream flow. ...High Plains... While the upper shortwave trough migrating across the region is not particularly strong, unseasonably moist conditions will spread north and west on southeasterly low-level flow. Surface dewpoints well into the 60s will envelop much of the Plains and extend as far west as eastern MT/WY/CO. At the same time, a surface trough will extend southward from eastern WY into the OK/TX Panhandles. Strong heating along the trough beneath very steep midlevel lapse rates (7.5-8.5 C/km) will result in MLCAPE from 1500-3500 J/kg. Scattered thunderstorms will develop near the higher terrain in CO/WY during the afternoon as weak ascent increases with the approach of the trough. Deep-layer flow will remain modest, but vertically veering profiles and stronger low level southeasterly flow will result in 25-40 kt effective shear. This will aid in maintaining organized convection with eastward extent over the High Plains into the evening. By 00z, a 25-35 kt southerly low level jet will develop, aiding in upscale growth of storm clusters. Various guidance is consistent in developing one or more bowing segments tracking east/southeast across parts of eastern WY/CO into western NE/KS. Initial convection could pose a large-hail threat as it remains semi-discrete moving off of the higher terrain. However, with time, cells and clusters are expected to organized into one or more bowing segments with an attendant increase in damaging wind potential during the evening hours. The northward extent of severe potential will be limited across eastern MT/western ND as remnant overnight convection and cloud cover limit heating, resulting in capping concerns. Any convection that redevelops overnight tonight likely will be elevated. ...Portions of Southern VA into the Carolinas... A very moist airmass (surface dewpoints in the 70s F) will reside across southeast VA into the Carolinas ahead of the southward-advancing cold front. Deep-layer flow is not particularly strong, similar to the previous few days. However, guidance suggests a shortwave impulse will eject across the central Appalachians during the afternoon as the southern extent of the upper trough pivots across the area. This will result in a band of around 25-30 kt midlevel flow and effective shear will increase modestly. As forcing increases both in relation to this shortwave impulse and the approaching front, strong destabilization will result in scattered thunderstorm development by midday. Somewhat stronger flow compared to previous days in the presence of the cold front should allow for better organized storm clusters and possibly one or more bowing segments tracking eastward across southeast VA into central/eastern NC and possibly parts of SC, though deep layer weakens quickly with southward extent. Steep low-level lapse rates and PW values greater than 2 inches will further support organized damaging-wind potential during the afternoon and evening. While midlevel lapse rates will be modest, some stronger cells could produce hail as well. ..Leitman/Wendt.. 08/23/2019 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1255 AM CDT Fri Aug 23 2019 Valid 231200Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN HIGH PLAINS AND ACROSS PARTS OF SOUTHEAST VA INTO NORTHEAST NC... ...SUMMARY... Severe thunderstorms capable of large hail and damaging wind gusts are possible this afternoon and evening, mainly across eastern Wyoming/Colorado into western Nebraska/Kansas. Severe thunderstorms, mainly capable of damaging wind gusts, are also expected across portions of southeast Virginia into northeast North Carolina this afternoon and evening. ...Synopsis... An upper trough over the northeastern states will continue to lift east/northeast today. The associated surface cold front will extend from near the New England coast this morning, arcing southwest into northern VA and the lower OH/middle MS Valley vicinity. The western extent of the front will push southward and become a focus for strong to severe thunderstorm development across portions of southern VA into NC. Meanwhile, the upper shortwave trough over the western U.S. will slowly shift east across the Rockies to the High Plains. A lee trough and moist, upslope flow regime amidst upper level height falls will focus another round of strong to severe thunderstorms across portions of the High Plains. Elsewhere, a very moist and unstable boundary layer will support sporadic downbursts from Oklahoma into portions of the South. Organized severe threat will be limited by weak flow and a lack of upper forcing for ascent as the area remains under the influence of lower-amplitude southern-stream flow. ...High Plains... While the upper shortwave trough migrating across the region is not particularly strong, unseasonably moist conditions will spread north and west on southeasterly low-level flow. Surface dewpoints well into the 60s will envelop much of the Plains and extend as far west as eastern MT/WY/CO. At the same time, a surface trough will extend southward from eastern WY into the OK/TX Panhandles. Strong heating along the trough beneath very steep midlevel lapse rates (7.5-8.5 C/km) will result in MLCAPE from 1500-3500 J/kg. Scattered thunderstorms will develop near the higher terrain in CO/WY during the afternoon as weak ascent increases with the approach of the trough. Deep-layer flow will remain modest, but vertically veering profiles and stronger low level southeasterly flow will result in 25-40 kt effective shear. This will aid in maintaining organized convection with eastward extent over the High Plains into the evening. By 00z, a 25-35 kt southerly low level jet will develop, aiding in upscale growth of storm clusters. Various guidance is consistent in developing one or more bowing segments tracking east/southeast across parts of eastern WY/CO into western NE/KS. Initial convection could pose a large-hail threat as it remains semi-discrete moving off of the higher terrain. However, with time, cells and clusters are expected to organized into one or more bowing segments with an attendant increase in damaging wind potential during the evening hours. The northward extent of severe potential will be limited across eastern MT/western ND as remnant overnight convection and cloud cover limit heating, resulting in capping concerns. Any convection that redevelops overnight tonight likely will be elevated. ...Portions of Southern VA into the Carolinas... A very moist airmass (surface dewpoints in the 70s F) will reside across southeast VA into the Carolinas ahead of the southward-advancing cold front. Deep-layer flow is not particularly strong, similar to the previous few days. However, guidance suggests a shortwave impulse will eject across the central Appalachians during the afternoon as the southern extent of the upper trough pivots across the area. This will result in a band of around 25-30 kt midlevel flow and effective shear will increase modestly. As forcing increases both in relation to this shortwave impulse and the approaching front, strong destabilization will result in scattered thunderstorm development by midday. Somewhat stronger flow compared to previous days in the presence of the cold front should allow for better organized storm clusters and possibly one or more bowing segments tracking eastward across southeast VA into central/eastern NC and possibly parts of SC, though deep layer weakens quickly with southward extent. Steep low-level lapse rates and PW values greater than 2 inches will further support organized damaging-wind potential during the afternoon and evening. While midlevel lapse rates will be modest, some stronger cells could produce hail as well. ..Leitman/Wendt.. 08/23/2019 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0744 PM CDT Thu Aug 22 2019 Valid 230100Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE HIGH PLAINS...OK/AR...AND PARTS OF THE MID-ATLANTIC... ...SUMMARY... Isolated damaging winds and hail remain possible across parts of the northern High Plains through tonight. Additional strong gusts are possible across parts of northeast Colorado and southwest Nebraska, as well as parts of Oklahoma and Arkansas and the Mid-Atlantic over the next couple of hours. ...01z Update... Changes to the Day 1 outlook have been made to reflect current strong to occasionally severe storms/clusters ongoing this evening. Some areas have been dropped from the Marginal risk, with a continued Marginal risk being highlighted across parts of the northern Rockies and adjacent High Plains of northeast WY into eastern MT and far western ND. Widely scattered storms have begun developing in the vicinity of a surface low and cold front from Johnson and Sheridan Counties in WY northward into Rosebud County MT. These storms will pose a threat of strong wind gusts and possibly some hail through the evening. Discrete cells are still expected to quickly transition into eastward progressing clusters or line segments, with a continued risk for sporadically severe wind gusts through the overnight hours. Elsewhere, a short-term threat will exist with ongoing storms across several areas of the country, before weakening over the next 1-3 hours. This includes: A cluster of storms across northeast CO into southwest NE continue to pose a threat for strong wind gusts in the short term. This cluster is expected to gradually weaken with time with the loss of daytime heating and a stabilizing boundary layer. Another cluster of storms has developed across central OK along an outflow boundary, with additional sub-severe clusters further east into northern AR. These storms could produce marginally severe wind gusts and hail over the next couple of hours, with the Oklahoma segment appearing somewhat more organized. However, the lack of a stronger developing low level jet should result in gradual weakening over the next couple of hours as the boundary layer stabilizes and remaining convection becomes more elevated. Across the Mid-Atlantic, clusters of storms were ongoing across eastern NC northward to the Washington D.C./Chesapeake Bay area, as well as a cluster moving over NYC and Long Island. These storms will continue to pose a threat for strong gusts, especially from the greater Washington D.C. area northward to Long Island. These clusters are maintaining organization/intensity aided by 25-35 kt effective shear. As storms move offshore, the threat will end. ..Leitman.. 08/23/2019 Read more

MD 1836 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF EASTERN MONTANA...FAR WESTERN NORTH DAKOTA
Mesoscale Discussion 1836 NWS Storm Prediction Center Norman OK 0628 PM CDT Thu Aug 22 2019 Areas affected...Portions of eastern Montana...far western North Dakota Concerning...Severe potential...Watch unlikely Valid 222328Z - 230130Z Probability of Watch Issuance...20 percent SUMMARY...Isolated to scattered thunderstorms are likely this evening with latest observational/model trends suggesting development by 7-8 PM MDT. Large hail and strong/severe wind gusts will be possible with these storms. Overall lack of storm organization will likely preclude WW issuance. DISCUSSION...Visible satellite imagery shows an increase in agitated cumulus from the northern Big Horn vicinity and points northward into eastern Montana. Convergence within the central/eastern Montana surface trough coupled with increasing mid-level ascent will lead to isolated to scattered storm development by early evening. Deep-layer shear is currently relatively weak across eastern Montana and is not expected to increase significantly this evening as the mid-level jet is expected to be displaced south/southwestward of the discussion area. Still, marginal effective shear (20-30 kts) and steep mid-level lapse rates of 7.5-8 C/km will support semi-organized storms capable of large hail. Strong/severe wind gusts will also be possible as low-level lapse rates have become very steep with strong heating/mixing this afternoon in eastern Montana. A WW is not anticipated given the overall lack of storm organization expected. ..Wendt/Grams.. 08/22/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BIS...UNR...BYZ...GGW... LAT...LON 45390645 47230734 48740738 48970636 48900432 48660401 46390362 45430382 45110469 45130575 45390645 Read more

No watches are valid as of Thu Aug 22 22:32:03 UTC 2019.

MD 1835 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF SOUTHERN/CENTRAL OKLAHOMA AND NORTHWESTERN ARKANSAS
Mesoscale Discussion 1835 NWS Storm Prediction Center Norman OK 0517 PM CDT Thu Aug 22 2019 Areas affected...Portions of southern/central Oklahoma and northwestern Arkansas Concerning...Severe potential...Watch unlikely Valid 222217Z - 230015Z Probability of Watch Issuance...5 percent SUMMARY...A few isolated strong to near severe wind gusts possible with storms along old outflow boundary. Threat should remain isolated and diminish after sunset. No WW is anticipated. DISCUSSION...An increase in convection along a residual outflow boundary across southwestern/central Oklahoma into northwestern Arkansas has been noted in last hour. With 1000-1200 J/kg DCAPE, a few isolated strong wind gusts are possible -- a 50 mph gust was recorded by the Frederick mesonet site roughly 90 minutes ago -- until convection decreases in intensity after sunset. Storms will remain relatively disorganized with only 20 to perhaps 30 kts of effective deep-layer shear along/near the boundary. Greatest threat for strong gusts will be with any clusters of storms that congeal and form a semi-organized cold pool. Isolated nature and short duration of the threat will likely preclude any watch issuance this evening. ..Wendt/Grams.. 08/22/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LZK...TSA...OUN... LAT...LON 34969887 35449726 36089460 36189385 35879347 35349392 34669646 34529802 34599874 34789887 34969887 Read more

No Mesoscale Discussions are in effect as of Thu Aug 22 21:54:01 UTC 2019.

MD 1834 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF NORTHEAST COLORADO...SOUTHEAST WYOMING AND THE NEBRASKA PANHANDLE
Mesoscale Discussion 1834 NWS Storm Prediction Center Norman OK 0311 PM CDT Thu Aug 22 2019 Areas affected...portions of northeast Colorado...southeast Wyoming and the Nebraska Panhandle Concerning...Severe potential...Watch unlikely Valid 222011Z - 222145Z Probability of Watch Issuance...20 percent SUMMARY...Isolated strong/severe thunderstorms are anticipated this afternoon, with a risk for large hail and strong wind gusts. A watch is not currently anticipated. DISCUSSION...Regional radar and satellite imagery reveals an increase in showers/thunderstorms from the Denver Metro north into southeast WY, aided by moist southeasterly low-level flow and strong diurnal heating. Although mid-level flow is generally at or below 25 kts, the strength of the low-level flow is contributing to 25-35 kts of effective shear, and this should prove sufficient for some updraft organization as storms move east of the higher terrain through this evening. In the presence of moderate MLCAPE and steep low- and mid-level lapse rates, isolated stronger storms will be capable of severe hail and strong wind gusts. As storms merge into a small cluster this evening, some risk for strong winds may continue to exist within a more localized area. Convective trends will continue to be monitored, however a watch is not currently anticipated. ..Bunting/Guyer.. 08/22/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...GLD...BOU...CYS... LAT...LON 39330315 39230457 39620509 40420542 40940543 41390521 41680502 41870467 41960394 41710326 40830262 39900247 39330315 Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0257 PM CDT Thu Aug 22 2019 Valid 222000Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN AND CENTRAL PLAINS...AND FROM PORTIONS OF THE NORTHEAST AND MID ATLANTIC/CAROLINAS WESTWARD TO OKLAHOMA/NORTH TEXAS... ...SUMMARY... Isolated damaging winds remain 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. ...Discussion... Little change appears necessary to the ongoing outlook areas and/or reasoning at this time, with convective weather largely evolving as anticipated. As such, aside from a few line tweaks, no changes are being implemented to the outlook in this update. ..Goss.. 08/22/2019 .PREV DISCUSSION... /ISSUED 1136 AM CDT Thu Aug 22 2019/ ...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. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0257 PM CDT Thu Aug 22 2019 Valid 222000Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN AND CENTRAL PLAINS...AND FROM PORTIONS OF THE NORTHEAST AND MID ATLANTIC/CAROLINAS WESTWARD TO OKLAHOMA/NORTH TEXAS... ...SUMMARY... Isolated damaging winds remain 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. ...Discussion... Little change appears necessary to the ongoing outlook areas and/or reasoning at this time, with convective weather largely evolving as anticipated. As such, aside from a few line tweaks, no changes are being implemented to the outlook in this update. ..Goss.. 08/22/2019 .PREV DISCUSSION... /ISSUED 1136 AM CDT Thu Aug 22 2019/ ...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. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0257 PM CDT Thu Aug 22 2019 Valid 222000Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN AND CENTRAL PLAINS...AND FROM PORTIONS OF THE NORTHEAST AND MID ATLANTIC/CAROLINAS WESTWARD TO OKLAHOMA/NORTH TEXAS... ...SUMMARY... Isolated damaging winds remain 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. ...Discussion... Little change appears necessary to the ongoing outlook areas and/or reasoning at this time, with convective weather largely evolving as anticipated. As such, aside from a few line tweaks, no changes are being implemented to the outlook in this update. ..Goss.. 08/22/2019 .PREV DISCUSSION... /ISSUED 1136 AM CDT Thu Aug 22 2019/ ...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. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0257 PM CDT Thu Aug 22 2019 Valid 222000Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN AND CENTRAL PLAINS...AND FROM PORTIONS OF THE NORTHEAST AND MID ATLANTIC/CAROLINAS WESTWARD TO OKLAHOMA/NORTH TEXAS... ...SUMMARY... Isolated damaging winds remain 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. ...Discussion... Little change appears necessary to the ongoing outlook areas and/or reasoning at this time, with convective weather largely evolving as anticipated. As such, aside from a few line tweaks, no changes are being implemented to the outlook in this update. ..Goss.. 08/22/2019 .PREV DISCUSSION... /ISSUED 1136 AM CDT Thu Aug 22 2019/ ...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. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0257 PM CDT Thu Aug 22 2019 Valid 222000Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHERN AND CENTRAL PLAINS...AND FROM PORTIONS OF THE NORTHEAST AND MID ATLANTIC/CAROLINAS WESTWARD TO OKLAHOMA/NORTH TEXAS... ...SUMMARY... Isolated damaging winds remain 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. ...Discussion... Little change appears necessary to the ongoing outlook areas and/or reasoning at this time, with convective weather largely evolving as anticipated. As such, aside from a few line tweaks, no changes are being implemented to the outlook in this update. ..Goss.. 08/22/2019 .PREV DISCUSSION... /ISSUED 1136 AM CDT Thu Aug 22 2019/ ...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. Read more

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