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SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0347 PM CDT Sat Sep 21 2024 Valid 231200Z - 291200Z A complicated/chaotic upper-air pattern will evolve across the United States this week. Early in the week, the upper-low across the Southwest this weekend will continue to open up and lift in/through the Plains. In its wake, an expansive ridge will take hold across the West, driving a short-wave trough southward through the Plains, by midweek. By late week, a series of short-wave troughs will move across the Pacific Northwest coincident with a closed low developing across the southern Plains. The result will be cooler/wetter pattern across southern Plains and eastern United States. Across the west, although a ridge will develop by early week, generally weak flow and unreceptive fuels will limit fire-weather concerns. Thus, large-scale critical fire-weather concerns appear to be minimal this week. ..Marsh.. 09/21/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0347 PM CDT Sat Sep 21 2024 Valid 231200Z - 291200Z A complicated/chaotic upper-air pattern will evolve across the United States this week. Early in the week, the upper-low across the Southwest this weekend will continue to open up and lift in/through the Plains. In its wake, an expansive ridge will take hold across the West, driving a short-wave trough southward through the Plains, by midweek. By late week, a series of short-wave troughs will move across the Pacific Northwest coincident with a closed low developing across the southern Plains. The result will be cooler/wetter pattern across southern Plains and eastern United States. Across the west, although a ridge will develop by early week, generally weak flow and unreceptive fuels will limit fire-weather concerns. Thus, large-scale critical fire-weather concerns appear to be minimal this week. ..Marsh.. 09/21/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0347 PM CDT Sat Sep 21 2024 Valid 231200Z - 291200Z A complicated/chaotic upper-air pattern will evolve across the United States this week. Early in the week, the upper-low across the Southwest this weekend will continue to open up and lift in/through the Plains. In its wake, an expansive ridge will take hold across the West, driving a short-wave trough southward through the Plains, by midweek. By late week, a series of short-wave troughs will move across the Pacific Northwest coincident with a closed low developing across the southern Plains. The result will be cooler/wetter pattern across southern Plains and eastern United States. Across the west, although a ridge will develop by early week, generally weak flow and unreceptive fuels will limit fire-weather concerns. Thus, large-scale critical fire-weather concerns appear to be minimal this week. ..Marsh.. 09/21/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0347 PM CDT Sat Sep 21 2024 Valid 231200Z - 291200Z A complicated/chaotic upper-air pattern will evolve across the United States this week. Early in the week, the upper-low across the Southwest this weekend will continue to open up and lift in/through the Plains. In its wake, an expansive ridge will take hold across the West, driving a short-wave trough southward through the Plains, by midweek. By late week, a series of short-wave troughs will move across the Pacific Northwest coincident with a closed low developing across the southern Plains. The result will be cooler/wetter pattern across southern Plains and eastern United States. Across the west, although a ridge will develop by early week, generally weak flow and unreceptive fuels will limit fire-weather concerns. Thus, large-scale critical fire-weather concerns appear to be minimal this week. ..Marsh.. 09/21/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0347 PM CDT Sat Sep 21 2024 Valid 231200Z - 291200Z A complicated/chaotic upper-air pattern will evolve across the United States this week. Early in the week, the upper-low across the Southwest this weekend will continue to open up and lift in/through the Plains. In its wake, an expansive ridge will take hold across the West, driving a short-wave trough southward through the Plains, by midweek. By late week, a series of short-wave troughs will move across the Pacific Northwest coincident with a closed low developing across the southern Plains. The result will be cooler/wetter pattern across southern Plains and eastern United States. Across the west, although a ridge will develop by early week, generally weak flow and unreceptive fuels will limit fire-weather concerns. Thus, large-scale critical fire-weather concerns appear to be minimal this week. ..Marsh.. 09/21/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0347 PM CDT Sat Sep 21 2024 Valid 231200Z - 291200Z A complicated/chaotic upper-air pattern will evolve across the United States this week. Early in the week, the upper-low across the Southwest this weekend will continue to open up and lift in/through the Plains. In its wake, an expansive ridge will take hold across the West, driving a short-wave trough southward through the Plains, by midweek. By late week, a series of short-wave troughs will move across the Pacific Northwest coincident with a closed low developing across the southern Plains. The result will be cooler/wetter pattern across southern Plains and eastern United States. Across the west, although a ridge will develop by early week, generally weak flow and unreceptive fuels will limit fire-weather concerns. Thus, large-scale critical fire-weather concerns appear to be minimal this week. ..Marsh.. 09/21/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0347 PM CDT Sat Sep 21 2024 Valid 231200Z - 291200Z A complicated/chaotic upper-air pattern will evolve across the United States this week. Early in the week, the upper-low across the Southwest this weekend will continue to open up and lift in/through the Plains. In its wake, an expansive ridge will take hold across the West, driving a short-wave trough southward through the Plains, by midweek. By late week, a series of short-wave troughs will move across the Pacific Northwest coincident with a closed low developing across the southern Plains. The result will be cooler/wetter pattern across southern Plains and eastern United States. Across the west, although a ridge will develop by early week, generally weak flow and unreceptive fuels will limit fire-weather concerns. Thus, large-scale critical fire-weather concerns appear to be minimal this week. ..Marsh.. 09/21/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0347 PM CDT Sat Sep 21 2024 Valid 231200Z - 291200Z A complicated/chaotic upper-air pattern will evolve across the United States this week. Early in the week, the upper-low across the Southwest this weekend will continue to open up and lift in/through the Plains. In its wake, an expansive ridge will take hold across the West, driving a short-wave trough southward through the Plains, by midweek. By late week, a series of short-wave troughs will move across the Pacific Northwest coincident with a closed low developing across the southern Plains. The result will be cooler/wetter pattern across southern Plains and eastern United States. Across the west, although a ridge will develop by early week, generally weak flow and unreceptive fuels will limit fire-weather concerns. Thus, large-scale critical fire-weather concerns appear to be minimal this week. ..Marsh.. 09/21/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0347 PM CDT Sat Sep 21 2024 Valid 231200Z - 291200Z A complicated/chaotic upper-air pattern will evolve across the United States this week. Early in the week, the upper-low across the Southwest this weekend will continue to open up and lift in/through the Plains. In its wake, an expansive ridge will take hold across the West, driving a short-wave trough southward through the Plains, by midweek. By late week, a series of short-wave troughs will move across the Pacific Northwest coincident with a closed low developing across the southern Plains. The result will be cooler/wetter pattern across southern Plains and eastern United States. Across the west, although a ridge will develop by early week, generally weak flow and unreceptive fuels will limit fire-weather concerns. Thus, large-scale critical fire-weather concerns appear to be minimal this week. ..Marsh.. 09/21/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0347 PM CDT Sat Sep 21 2024 Valid 231200Z - 291200Z A complicated/chaotic upper-air pattern will evolve across the United States this week. Early in the week, the upper-low across the Southwest this weekend will continue to open up and lift in/through the Plains. In its wake, an expansive ridge will take hold across the West, driving a short-wave trough southward through the Plains, by midweek. By late week, a series of short-wave troughs will move across the Pacific Northwest coincident with a closed low developing across the southern Plains. The result will be cooler/wetter pattern across southern Plains and eastern United States. Across the west, although a ridge will develop by early week, generally weak flow and unreceptive fuels will limit fire-weather concerns. Thus, large-scale critical fire-weather concerns appear to be minimal this week. ..Marsh.. 09/21/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

MD 2095 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR WESTERN NEW YORK...WESTERN PENNSYLVANIA...SOUTHEASTERN OHIO...MUCH OF WEST VIRGINIA...WESTERN VIRGINIA...AND THE WESTERN MARYLAND PANHANDLE
Mesoscale Discussion 2095 NWS Storm Prediction Center Norman OK 0137 PM CDT Sat Sep 21 2024 Areas affected...western New York...western Pennsylvania...southeastern Ohio...much of West Virginia...western Virginia...and the western Maryland Panhandle Concerning...Severe potential...Watch unlikely Valid 211837Z - 212100Z Probability of Watch Issuance...20 percent SUMMARY...A few strong thunderstorms briefly reaching marginal severe levels can be expected through this afternoon. Marginal hail and tree damage can be expected locally. However, the very isolated/marginal nature of the risk currently expected should preclude the need for WW consideration. DISCUSSION...A weak cool front will continue moving southeastward across the Mid and Upper Ohio Valley area and into the central Appalachians today, as a vort max near Lake Huron shifts across the Lower Great Lakes toward the Chesapeake Bay area this afternoon and tonight. Ahead of the front, a modestly moist boundary layer (low 60s dewpoints) combined with warm-sector heating is resulting in around 1000 J/kg mixed-layer CAPE across much of the area, though into the 1500 to 2000 J/kg range over the middle Ohio Valley portion of the region. This destabilization is fueling a gradual increase in convective coverage and intensity near and ahead of the front -- from southeastern Ohio to southwestern New York. Though low-level flow remains weak, moderate mid-level northwesterlies are contributing to an environment amply sheared to support organized updrafts. As such, locally strong/briefly vigorous updrafts will likely be associated with marginal severe potential into early evening -- with risk spreading gradually eastward/southeastward with time. ..Goss/Guyer.. 09/21/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BGM...BUF...CTP...LWX...RNK...PBZ...RLX... LAT...LON 39598204 39888105 40368027 40797954 41487892 42507897 42717843 42207672 41327693 38777771 37647890 37308026 38618177 39598204 Read more

WW 0680 Status Updates
STATUS FOR WATCH 0680 HAS NOT BEEN ISSUED YET Read more

WW 0680 Status Updates
STATUS FOR WATCH 0680 HAS NOT BEEN ISSUED YET Read more

WW 0680 Status Updates
STATUS FOR WATCH 0680 HAS NOT BEEN ISSUED YET Read more

WW 680 SEVERE TSTM NM TX 212030Z - 220400Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 680 NWS Storm Prediction Center Norman OK 230 PM MDT Sat Sep 21 2024 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Eastern New Mexico West Texas South Plains and Panhandle * Effective this Saturday afternoon and evening from 230 PM until 1000 PM MDT. * Primary threats include... Scattered large hail and isolated very large hail events to 2.5 inches in diameter possible Isolated damaging wind gusts to 65 mph possible A tornado or two possible SUMMARY...Severe storms are expected to develop initially across a broad north/south part of eastern New Mexico this afternoon, as well as near the New Mexico/Texas border vicinity. This includes the potential for some supercell storms. The severe thunderstorm watch area is approximately along and 105 statute miles north and south of a line from 50 miles west northwest of Roswell NM to 55 miles southeast of Amarillo TX. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU0). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && AVIATION...A few severe thunderstorms with hail surface and aloft to 2.5 inches. Extreme turbulence and surface wind gusts to 55 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 25030. ...Guyer Read more

No watches are valid as of Sat Sep 21 20:16:01 UTC 2024.

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0306 PM CDT Sat Sep 21 2024 Valid 212000Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE SOUTHERN HIGH PLAINS... ...SUMMARY... Scattered severe storms capable of all hazards are possible this afternoon and evening across portions of the southern High Plains. ...20Z Update... Severe probabilities have been trimmed behind convection in parts of western Pennsylvania as it appears potential for severe storms will be diminished through the remainder of the afternoon. In north-central/northeast Iowa, temperatures have risen into the low 90s ahead of the cold front and near an outflow boundary in the southeast Minnesota/west-central Wisconsin. This area could see a locally higher potential for large hail/damaging winds. Still, linear forcing along the front and very modest mid-level ascent reduces confidence in a discrete storm mode and sufficient storm coverage, precluding any increase in severe probabilities. ..Wendt.. 09/21/2024 .PREV DISCUSSION... /ISSUED 1127 AM CDT Sat Sep 21 2024/ ...Southern High Plains... A potent upper low and associated 65-75 kt mid-level jet max centered over AZ are expected to quickly move eastward, overspreading the southern Rockies/High Plains this afternoon and evening. At the surface, sustained southerly flow ahead of a deepening surface low and trailing cold front over western NM will support moderate destabilization (MLCAPE 1500-2000 J/kg) with afternoon heating and continued low-level upslope. As the mid-level system approaches, mid-level height falls and flow aloft will intensify, elongating low and mid-level hodographs, allowing for convective development/organization in the form of supercells. One source of continued uncertainty is the ongoing elevated convection and cloud debris centered north of a diffuse surface boundary stretching from central NM to the western TX Panhandle. So far, this boundary has been slowly lifting north with pronounced low-level theta-e advection taking place to the south. As deep-layer ascent intensifies through the late morning, continued convective development to the north may support reinforcement and stalling of the boundary. The northward extent of destabilization remains unclear, though this boundary could serve as a focus for renewed development of more robust convection expected later this afternoon. Most CAM guidance shows scattered thunderstorms initiating off the higher terrain of eastern NM, or ahead of the cold front farther west by early this afternoon. These storms should quickly mature with supportive thermodynamics and kinematics, eventually spreading eastward into the TX Panhandle. The risk for large to very large hail/severe gusts will likely accompany the stronger supercells, and a threat for a couple tornadoes may be realized later this afternoon/early evening from eastern NM into parts of adjacent west TX, especially near the boundary where low-level shear may be locally enhanced. ...Upper Midwest and MO Valley... A second upper low near the international border is forecast to quickly move eastward reaching the western Great Lakes by early this evening. Weak ascent is expected ahead of a surging cold front and diffuse wave cyclone across the northern MO valley and southern MN. Surface moistening with a warm front lifting north near the IA/MN border may act as a focus for more robust convective development along the cold front late this afternoon. Increasingly orthogonal deep-layer flow and steeping low/mid-level lapse rates could support a mix of supercells and multi-cell clusters. A few of the stronger storms may pose some hail/wind threat, which should peak in intensity during the early evening. However, somewhat limited heating and the lack of broader forcing for ascent suggests storm coverage should remain isolated. ...Western PA into the Mid Atlantic... Short-wave troughing across the upper OH Valley within mid-level northwesterly flow is expected to support isolated to widely scattered thunderstorms across western PA/VA later this afternoon. Model forecast soundings with moderate buoyancy and modest deep-layer shear would imply some of the stronger storms being capable of an isolated risk for wind damage (50-60 mph) and perhaps some hail. This activity will likely diminish by early evening coincident with nocturnal cooling. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0306 PM CDT Sat Sep 21 2024 Valid 212000Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE SOUTHERN HIGH PLAINS... ...SUMMARY... Scattered severe storms capable of all hazards are possible this afternoon and evening across portions of the southern High Plains. ...20Z Update... Severe probabilities have been trimmed behind convection in parts of western Pennsylvania as it appears potential for severe storms will be diminished through the remainder of the afternoon. In north-central/northeast Iowa, temperatures have risen into the low 90s ahead of the cold front and near an outflow boundary in the southeast Minnesota/west-central Wisconsin. This area could see a locally higher potential for large hail/damaging winds. Still, linear forcing along the front and very modest mid-level ascent reduces confidence in a discrete storm mode and sufficient storm coverage, precluding any increase in severe probabilities. ..Wendt.. 09/21/2024 .PREV DISCUSSION... /ISSUED 1127 AM CDT Sat Sep 21 2024/ ...Southern High Plains... A potent upper low and associated 65-75 kt mid-level jet max centered over AZ are expected to quickly move eastward, overspreading the southern Rockies/High Plains this afternoon and evening. At the surface, sustained southerly flow ahead of a deepening surface low and trailing cold front over western NM will support moderate destabilization (MLCAPE 1500-2000 J/kg) with afternoon heating and continued low-level upslope. As the mid-level system approaches, mid-level height falls and flow aloft will intensify, elongating low and mid-level hodographs, allowing for convective development/organization in the form of supercells. One source of continued uncertainty is the ongoing elevated convection and cloud debris centered north of a diffuse surface boundary stretching from central NM to the western TX Panhandle. So far, this boundary has been slowly lifting north with pronounced low-level theta-e advection taking place to the south. As deep-layer ascent intensifies through the late morning, continued convective development to the north may support reinforcement and stalling of the boundary. The northward extent of destabilization remains unclear, though this boundary could serve as a focus for renewed development of more robust convection expected later this afternoon. Most CAM guidance shows scattered thunderstorms initiating off the higher terrain of eastern NM, or ahead of the cold front farther west by early this afternoon. These storms should quickly mature with supportive thermodynamics and kinematics, eventually spreading eastward into the TX Panhandle. The risk for large to very large hail/severe gusts will likely accompany the stronger supercells, and a threat for a couple tornadoes may be realized later this afternoon/early evening from eastern NM into parts of adjacent west TX, especially near the boundary where low-level shear may be locally enhanced. ...Upper Midwest and MO Valley... A second upper low near the international border is forecast to quickly move eastward reaching the western Great Lakes by early this evening. Weak ascent is expected ahead of a surging cold front and diffuse wave cyclone across the northern MO valley and southern MN. Surface moistening with a warm front lifting north near the IA/MN border may act as a focus for more robust convective development along the cold front late this afternoon. Increasingly orthogonal deep-layer flow and steeping low/mid-level lapse rates could support a mix of supercells and multi-cell clusters. A few of the stronger storms may pose some hail/wind threat, which should peak in intensity during the early evening. However, somewhat limited heating and the lack of broader forcing for ascent suggests storm coverage should remain isolated. ...Western PA into the Mid Atlantic... Short-wave troughing across the upper OH Valley within mid-level northwesterly flow is expected to support isolated to widely scattered thunderstorms across western PA/VA later this afternoon. Model forecast soundings with moderate buoyancy and modest deep-layer shear would imply some of the stronger storms being capable of an isolated risk for wind damage (50-60 mph) and perhaps some hail. This activity will likely diminish by early evening coincident with nocturnal cooling. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0306 PM CDT Sat Sep 21 2024 Valid 212000Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE SOUTHERN HIGH PLAINS... ...SUMMARY... Scattered severe storms capable of all hazards are possible this afternoon and evening across portions of the southern High Plains. ...20Z Update... Severe probabilities have been trimmed behind convection in parts of western Pennsylvania as it appears potential for severe storms will be diminished through the remainder of the afternoon. In north-central/northeast Iowa, temperatures have risen into the low 90s ahead of the cold front and near an outflow boundary in the southeast Minnesota/west-central Wisconsin. This area could see a locally higher potential for large hail/damaging winds. Still, linear forcing along the front and very modest mid-level ascent reduces confidence in a discrete storm mode and sufficient storm coverage, precluding any increase in severe probabilities. ..Wendt.. 09/21/2024 .PREV DISCUSSION... /ISSUED 1127 AM CDT Sat Sep 21 2024/ ...Southern High Plains... A potent upper low and associated 65-75 kt mid-level jet max centered over AZ are expected to quickly move eastward, overspreading the southern Rockies/High Plains this afternoon and evening. At the surface, sustained southerly flow ahead of a deepening surface low and trailing cold front over western NM will support moderate destabilization (MLCAPE 1500-2000 J/kg) with afternoon heating and continued low-level upslope. As the mid-level system approaches, mid-level height falls and flow aloft will intensify, elongating low and mid-level hodographs, allowing for convective development/organization in the form of supercells. One source of continued uncertainty is the ongoing elevated convection and cloud debris centered north of a diffuse surface boundary stretching from central NM to the western TX Panhandle. So far, this boundary has been slowly lifting north with pronounced low-level theta-e advection taking place to the south. As deep-layer ascent intensifies through the late morning, continued convective development to the north may support reinforcement and stalling of the boundary. The northward extent of destabilization remains unclear, though this boundary could serve as a focus for renewed development of more robust convection expected later this afternoon. Most CAM guidance shows scattered thunderstorms initiating off the higher terrain of eastern NM, or ahead of the cold front farther west by early this afternoon. These storms should quickly mature with supportive thermodynamics and kinematics, eventually spreading eastward into the TX Panhandle. The risk for large to very large hail/severe gusts will likely accompany the stronger supercells, and a threat for a couple tornadoes may be realized later this afternoon/early evening from eastern NM into parts of adjacent west TX, especially near the boundary where low-level shear may be locally enhanced. ...Upper Midwest and MO Valley... A second upper low near the international border is forecast to quickly move eastward reaching the western Great Lakes by early this evening. Weak ascent is expected ahead of a surging cold front and diffuse wave cyclone across the northern MO valley and southern MN. Surface moistening with a warm front lifting north near the IA/MN border may act as a focus for more robust convective development along the cold front late this afternoon. Increasingly orthogonal deep-layer flow and steeping low/mid-level lapse rates could support a mix of supercells and multi-cell clusters. A few of the stronger storms may pose some hail/wind threat, which should peak in intensity during the early evening. However, somewhat limited heating and the lack of broader forcing for ascent suggests storm coverage should remain isolated. ...Western PA into the Mid Atlantic... Short-wave troughing across the upper OH Valley within mid-level northwesterly flow is expected to support isolated to widely scattered thunderstorms across western PA/VA later this afternoon. Model forecast soundings with moderate buoyancy and modest deep-layer shear would imply some of the stronger storms being capable of an isolated risk for wind damage (50-60 mph) and perhaps some hail. This activity will likely diminish by early evening coincident with nocturnal cooling. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0306 PM CDT Sat Sep 21 2024 Valid 212000Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE SOUTHERN HIGH PLAINS... ...SUMMARY... Scattered severe storms capable of all hazards are possible this afternoon and evening across portions of the southern High Plains. ...20Z Update... Severe probabilities have been trimmed behind convection in parts of western Pennsylvania as it appears potential for severe storms will be diminished through the remainder of the afternoon. In north-central/northeast Iowa, temperatures have risen into the low 90s ahead of the cold front and near an outflow boundary in the southeast Minnesota/west-central Wisconsin. This area could see a locally higher potential for large hail/damaging winds. Still, linear forcing along the front and very modest mid-level ascent reduces confidence in a discrete storm mode and sufficient storm coverage, precluding any increase in severe probabilities. ..Wendt.. 09/21/2024 .PREV DISCUSSION... /ISSUED 1127 AM CDT Sat Sep 21 2024/ ...Southern High Plains... A potent upper low and associated 65-75 kt mid-level jet max centered over AZ are expected to quickly move eastward, overspreading the southern Rockies/High Plains this afternoon and evening. At the surface, sustained southerly flow ahead of a deepening surface low and trailing cold front over western NM will support moderate destabilization (MLCAPE 1500-2000 J/kg) with afternoon heating and continued low-level upslope. As the mid-level system approaches, mid-level height falls and flow aloft will intensify, elongating low and mid-level hodographs, allowing for convective development/organization in the form of supercells. One source of continued uncertainty is the ongoing elevated convection and cloud debris centered north of a diffuse surface boundary stretching from central NM to the western TX Panhandle. So far, this boundary has been slowly lifting north with pronounced low-level theta-e advection taking place to the south. As deep-layer ascent intensifies through the late morning, continued convective development to the north may support reinforcement and stalling of the boundary. The northward extent of destabilization remains unclear, though this boundary could serve as a focus for renewed development of more robust convection expected later this afternoon. Most CAM guidance shows scattered thunderstorms initiating off the higher terrain of eastern NM, or ahead of the cold front farther west by early this afternoon. These storms should quickly mature with supportive thermodynamics and kinematics, eventually spreading eastward into the TX Panhandle. The risk for large to very large hail/severe gusts will likely accompany the stronger supercells, and a threat for a couple tornadoes may be realized later this afternoon/early evening from eastern NM into parts of adjacent west TX, especially near the boundary where low-level shear may be locally enhanced. ...Upper Midwest and MO Valley... A second upper low near the international border is forecast to quickly move eastward reaching the western Great Lakes by early this evening. Weak ascent is expected ahead of a surging cold front and diffuse wave cyclone across the northern MO valley and southern MN. Surface moistening with a warm front lifting north near the IA/MN border may act as a focus for more robust convective development along the cold front late this afternoon. Increasingly orthogonal deep-layer flow and steeping low/mid-level lapse rates could support a mix of supercells and multi-cell clusters. A few of the stronger storms may pose some hail/wind threat, which should peak in intensity during the early evening. However, somewhat limited heating and the lack of broader forcing for ascent suggests storm coverage should remain isolated. ...Western PA into the Mid Atlantic... Short-wave troughing across the upper OH Valley within mid-level northwesterly flow is expected to support isolated to widely scattered thunderstorms across western PA/VA later this afternoon. Model forecast soundings with moderate buoyancy and modest deep-layer shear would imply some of the stronger storms being capable of an isolated risk for wind damage (50-60 mph) and perhaps some hail. This activity will likely diminish by early evening coincident with nocturnal cooling. Read more