SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0423 PM CDT Thu Aug 22 2024 Valid 241200Z - 301200Z An unseasonably deep upper low over the West Coast is forecast to move onshore over the Northwest through the weekend. Stronger southwesterly flow east of the low will overspread a modestly dry air mass across parts of the Great Basin and Northwest through the weekend. This should support elevated to critical fire-weather potential and some risk for isolated dry thunderstorms. ...Great Basin and Rockies... Strong west/southwesterly flow will continue to overspread the Great Basin and Rockies ahead of the upper low over the West. A cold front over the West coast will move inland shunting the warmer and drier air farther east. Widespread RH below 20% and wind of 20-25 mph are likely. A corridor of elevated to critical fire-weather conditions is expected over parts of eastern NV and across WY D3/Saturday. Elevated to critical fire-weather conditions may continue into D4/Sunday before the upper low moves east and temporarily limits the fire-weather threat. While confidence is lower, owing to varied model solutions, at least some risk for dry and breezy conditions continues over central WY and the Rockies into early next week. ...Dry Thunder... As the upper low progresses eastward this weekend and early next week, at least some risk for occasional dry storms will continue over the northern Rockies and eastern Great Basin. Storms will gradually transition to a wetter mode as the increase in moisture should gradually limit fuels and chances for wetting rains increase. ..Lyons.. 08/22/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

MD 1973 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF UTAH AND NORTHERN ARIZONA
Mesoscale Discussion 1973 NWS Storm Prediction Center Norman OK 0328 PM CDT Thu Aug 22 2024 Areas affected...Portions of Utah and Northern Arizona Concerning...Severe potential...Watch unlikely Valid 222028Z - 222230Z Probability of Watch Issuance...5 percent SUMMARY...Marginal risk of large hail and damaging wind. DISCUSSION...Thunderstorm activity is expected to continue and expand in coverage across portions of northern Arizona into Utah this afternoon/evening. Mid-level west to southwesterly flow around 30-40 kts through the base of a trough across the Pacific Northwest atop southeasterly flow near the surface is supporting modest shear around 30-35 kts across northwestern Arizona into central/northern Utah. Daytime heating has resulted in MLCAPE around 500-1500 J/kg across northwestern Arizona. In this region a few more organized transient supercells have been observed on radar, exhibiting broad weak rotation at times. Generally weak low-level flow and southwesterly mean flow led to back building cells along the terrain. Some instances of strong to severe gusts and severe hail will be possible given deep layer shear for organization and steep low to mid-level lapse rates. Overall, this threat is expected to remain localized and watch issuance is not anticipated. ..Thornton/Hart.. 08/22/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...RIW...FGZ...SLC...VEF...LKN... LAT...LON 36951454 37681438 39071408 40441358 41621307 41891287 41951198 41891135 41671104 40321121 39671137 38431188 37011162 36431158 36081156 35621191 35471255 35671333 36171407 36951454 Read more

No watches are valid as of Thu Aug 22 20:31:02 UTC 2024.

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0235 PM CDT Thu Aug 22 2024 Valid 222000Z - 231200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL HIGH PLAINS... ...SUMMARY... The greatest threat for severe gusts and hail appears to be over parts of the central High Plains this afternoon and evening. ...20z Update... The previous forecast remains on track with no changes needed based on recent observations and trends in guidance. See the previous discussion below for additional details. ..Moore.. 08/22/2024 .PREV DISCUSSION... /ISSUED 1125 AM CDT Thu Aug 22 2024/ ...CO/KS/NE... Pockets of strong heating are present today over the High Plains of eastern CO and western KS/NE. Dewpoints in the 60s and steep mid-level lapse rates will yield afternoon MLCAPE values of 2000+ J/kg in this area. Scattered high-based thunderstorms will form over the mountains and foothills later today and spread eastward, while isolated high-based storms form along the DCVZ/Palmer Ridge. As the storms move into the progressively more unstable air, a few severe storms are expected with a risk of damaging wind gusts and large hail. ...AZ/UT... A large upper low is centered off the Pacific Northwest coast today, with moderately strong southwesterly mid-level winds stretching from CO across the Great Basin. Strong heating beneath this flow regime, coupled with sufficient low/mid level moisture, will promote the development of widely scattered afternoon thunderstorms from northwest AZ across western UT. A few of the cells may produce gusty/damaging winds and/or hail. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0235 PM CDT Thu Aug 22 2024 Valid 222000Z - 231200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL HIGH PLAINS... ...SUMMARY... The greatest threat for severe gusts and hail appears to be over parts of the central High Plains this afternoon and evening. ...20z Update... The previous forecast remains on track with no changes needed based on recent observations and trends in guidance. See the previous discussion below for additional details. ..Moore.. 08/22/2024 .PREV DISCUSSION... /ISSUED 1125 AM CDT Thu Aug 22 2024/ ...CO/KS/NE... Pockets of strong heating are present today over the High Plains of eastern CO and western KS/NE. Dewpoints in the 60s and steep mid-level lapse rates will yield afternoon MLCAPE values of 2000+ J/kg in this area. Scattered high-based thunderstorms will form over the mountains and foothills later today and spread eastward, while isolated high-based storms form along the DCVZ/Palmer Ridge. As the storms move into the progressively more unstable air, a few severe storms are expected with a risk of damaging wind gusts and large hail. ...AZ/UT... A large upper low is centered off the Pacific Northwest coast today, with moderately strong southwesterly mid-level winds stretching from CO across the Great Basin. Strong heating beneath this flow regime, coupled with sufficient low/mid level moisture, will promote the development of widely scattered afternoon thunderstorms from northwest AZ across western UT. A few of the cells may produce gusty/damaging winds and/or hail. Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 PM CDT Thu Aug 22 2024 Valid 241200Z - 251200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE FOUR CORNERS AREA INTO PARTS OF THE CENTRAL AND NORTHERN PLAINS... ...SUMMARY... Marginally severe storms will be possible on Saturday across parts of the central and northern High Plains, and across the Four Corners region. ...Four Corners Region... The primary upper trough will move across the Great Basin on Saturday, with upper low moving from northern CA into MT. Midlevel moisture along with heating will lead to a marginally unstable air mass from eastern AZ into southwest CO, near the fringe of the stronger midlevel southwesterlies. As such, storms that develop here during the afternoon may be long-lived enough to produce swaths of strong to locally severe gusts. Stronger effective shear of 35-40 kt may also support cellular storm mode with marginal hail at times. ...Central/Northern High Plains... An upper high will remain over the southern Plains, but the ridge will be shunted east across the northern Plains as the western trough slowly progresses. Surface convergence will be maximized near the cold front/surface trough over eastern MT into the western Dakotas, where gradually increasing deep-layer shear may overlap stronger MLCAPE to the east. As such, any storms that develop in this region during the afternoon and evening may produce locally severe wind or hail. However, overall upper support will remain weak. Farther south into the central Plains, scattered storms over CO and southeast WY may move off the higher terrain, but shear will be weak. However, favorable time of day with steep low-level lapse rates may aid brief hail or strong outflows. ..Jewell.. 08/22/2024 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 PM CDT Thu Aug 22 2024 Valid 241200Z - 251200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE FOUR CORNERS AREA INTO PARTS OF THE CENTRAL AND NORTHERN PLAINS... ...SUMMARY... Marginally severe storms will be possible on Saturday across parts of the central and northern High Plains, and across the Four Corners region. ...Four Corners Region... The primary upper trough will move across the Great Basin on Saturday, with upper low moving from northern CA into MT. Midlevel moisture along with heating will lead to a marginally unstable air mass from eastern AZ into southwest CO, near the fringe of the stronger midlevel southwesterlies. As such, storms that develop here during the afternoon may be long-lived enough to produce swaths of strong to locally severe gusts. Stronger effective shear of 35-40 kt may also support cellular storm mode with marginal hail at times. ...Central/Northern High Plains... An upper high will remain over the southern Plains, but the ridge will be shunted east across the northern Plains as the western trough slowly progresses. Surface convergence will be maximized near the cold front/surface trough over eastern MT into the western Dakotas, where gradually increasing deep-layer shear may overlap stronger MLCAPE to the east. As such, any storms that develop in this region during the afternoon and evening may produce locally severe wind or hail. However, overall upper support will remain weak. Farther south into the central Plains, scattered storms over CO and southeast WY may move off the higher terrain, but shear will be weak. However, favorable time of day with steep low-level lapse rates may aid brief hail or strong outflows. ..Jewell.. 08/22/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0159 PM CDT Thu Aug 22 2024 Valid 231200Z - 241200Z ...CRITICAL FIRE WEATHER AREA FOR PARTS OF THE EASTERN GREAT BASIN... ...Dry Thunder... Model guidance continues to suggest isolated to widely scattered thunderstorms are likely east of the upper low across parts of OR, ID and MT Friday afternoon and evening. A mix of wet and dry storms is expected with PWATs of 0.7 to 1 inches expected. While the low-levels are not overly dry, relatively high cloud bases (~2 km) and fast storm speeds around 40 mph will tend to limit wetting rainfall. These drier storms will favor an increased risk for lightning atop very receptive fuels over eastern OR and western ID. Have adjusted the IsoDryT area to better match the expected coverage of storms over eastern OR and western ID. Otherwise, the previous forecast remains valid. Elevated to critical fire-weather conditions are likely over the Great Basin. Brief elevated fire-weather conditions are also possible over the southern Plains. See the previous discussion. ..Lyons.. 08/22/2024 .PREV DISCUSSION... /ISSUED 1156 PM CDT Wed Aug 21 2024/ ...Synopsis... A deepening mid-level trough will progress across the Interior West as upper ridging continues across the Plains to the Eastern Seaboard tomorrow (Friday). Strong mid-level flow aloft and associated upper support, amid a deep, dry boundary layer, will foster Elevated to Critical conditions across the Great Basin, with sustained southwesterly surface winds approaching 25 mph in spots, and RH dipping into the 15-20 percent range. Furthermore, upper support amid adequate buoyancy will promote the development of both wet and dry thunderstorms across portions of the Pacific Northwest (mainly central into eastern Oregon). Given receptive fuels in the area, isolated dry thunderstorm highlights have been added. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1228 PM CDT Thu Aug 22 2024 Valid 231200Z - 241200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM UTAH AND WESTERN COLORADO NORTHWARD INTO EASTERN IDAHO AND SOUTHWEST MONTANA...AND OVER PARTS OF THE CENTRAL AND NORTHERN HIGH PLAINS... ...SUMMARY... Isolated to perhaps scattered severe storms with strong to severe gusts will be possible on Friday across parts of the parts of the Intermountain West and central Rockies, and over a narrow portion of the central and northern High Plains. ...Synopsis... On Friday, an upper high will remain centered over the southern Plains, while a large trough develops across the West. The primary midlevel wave will eject northeastward across the Great Basin and into ID and MT through 00Z, providing substantial cooling aloft. Lift with this feature will be focused from northern NV and UT into MT. Overnight, a secondary lobe of vorticity will swing east across much of northern CA and OR. At the surface, low pressure will deepen throughout the day ahead of a cold front which will extend from the Bitterroots southwestward into central NV by 21Z. Farther east, another trough will extend from the low in western MT southeastward into the northern and central High Plains. Midlevel moisture already in place across the Four Corners states will spread north across UT and into MT, which will combine with daytime heating and cooling aloft to result in marginal instability. Farther east, backed/southeasterly surface winds will maintain a plume of lower 60s F dewpoints as far west as far eastern MT to northeast CO. ...Great Basin into eastern ID/western WY... A large area of moderate southwest flow aloft will spread east across the region as the negative-tilt wave passes through NV/UT relatively early in the day. While this wave is timed more favorable farther north, instability may be less favorable than points south. Given the moisture in place, storms will form over a large area beginning mid/late morning over UT and expending into eastern ID/western WY by midday. This is not timed particularly well in terms of diurnal heating, but strengthening wind fields may aid gust potential. Additional diurnally driven cells are then expected along and east of the Wasatch, with marginal hail or wind threat as this activity spreads northeast. The western fringe of the Marginal Risk may be a bit generous over ID given uncertainties with how quickly drying will occur from the west. ...Northern and central High Plains... Daytime heating will lead to an unstable and uncapped air mass over the High Plains, with storms expected to form roughly near a Billings to Cheyenne line by late afternoon. Further development is possible into eastern/northeastern CO as well. Given that these areas are well east of the cyclonic flow regime aloft, any severe is expected to be relatively isolated or in sparse clusters. However, both localized damaging gusts or hail will be possible, though wind profiles will generally favor disorganized storms. ..Jewell.. 08/22/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1125 AM CDT Thu Aug 22 2024 Valid 221630Z - 231200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE CENTRAL HIGH PLAINS... ...SUMMARY... The greatest threat for severe gusts and hail appears to be over parts of the central High Plains this afternoon and evening. ...CO/KS/NE... Pockets of strong heating are present today over the High Plains of eastern CO and western KS/NE. Dewpoints in the 60s and steep mid-level lapse rates will yield afternoon MLCAPE values of 2000+ J/kg in this area. Scattered high-based thunderstorms will form over the mountains and foothills later today and spread eastward, while isolated high-based storms form along the DCVZ/Palmer Ridge. As the storms move into the progressively more unstable air, a few severe storms are expected with a risk of damaging wind gusts and large hail. ...AZ/UT... A large upper low is centered off the Pacific Northwest coast today, with moderately strong southwesterly mid-level winds stretching from CO across the Great Basin. Strong heating beneath this flow regime, coupled with sufficient low/mid level moisture, will promote the development of widely scattered afternoon thunderstorms from northwest AZ across western UT. A few of the cells may produce gusty/damaging winds and/or hail. ..Hart/Thornton.. 08/22/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1125 AM CDT Thu Aug 22 2024 Valid 221630Z - 231200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE CENTRAL HIGH PLAINS... ...SUMMARY... The greatest threat for severe gusts and hail appears to be over parts of the central High Plains this afternoon and evening. ...CO/KS/NE... Pockets of strong heating are present today over the High Plains of eastern CO and western KS/NE. Dewpoints in the 60s and steep mid-level lapse rates will yield afternoon MLCAPE values of 2000+ J/kg in this area. Scattered high-based thunderstorms will form over the mountains and foothills later today and spread eastward, while isolated high-based storms form along the DCVZ/Palmer Ridge. As the storms move into the progressively more unstable air, a few severe storms are expected with a risk of damaging wind gusts and large hail. ...AZ/UT... A large upper low is centered off the Pacific Northwest coast today, with moderately strong southwesterly mid-level winds stretching from CO across the Great Basin. Strong heating beneath this flow regime, coupled with sufficient low/mid level moisture, will promote the development of widely scattered afternoon thunderstorms from northwest AZ across western UT. A few of the cells may produce gusty/damaging winds and/or hail. ..Hart/Thornton.. 08/22/2024 Read more

No Mesoscale Discussions are in effect as of Thu Aug 22 16:30:02 UTC 2024.

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1126 AM CDT Thu Aug 22 2024 Valid 221700Z - 231200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF CENTRAL AND EASTERN NEVADA... ...17z Update... No changes were made to the currently valid outlook. Elevated to critical fire-weather conditions are likely over much of the Great Basin. A few thunderstorms are also possible over parts of eastern ID late this evening and overnight. ...Southern Pains... Gusty southerly flow is expected east of a lee trough over parts of the southern Plains this afternoon. 10-15 mph winds and RH below 25% over parts of west TX and eastern NM will overlap with areas of very dry fuels, supporting a locally elevated fire-weather risk. Confidence in areal coverage and duration remains too low to introduce an area. See previous discussion. ..Lyons.. 08/22/2024 .PREV DISCUSSION... /ISSUED 1148 PM CDT Wed Aug 21 2024/ ...Synopsis... A mid-level trough will amplify across the Interior West as an upper ridge persists across the central U.S. today. Strong mid-level flow from the upper trough, overspreading a deepening boundary layer over the Great Basin, will support dry and windy conditions through the afternoon. 15-20 mph sustained southwesterly surface winds, overlapping with 15-20 percent RH and fuels receptive to fire spread, will result in widespread Elevated conditions for several hours. However, portions of central Nevada may also experience higher sustained southerly surface winds (i.e. over 25 mph), warranting Critical highlights. ...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 1126 AM CDT Thu Aug 22 2024 Valid 221700Z - 231200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF CENTRAL AND EASTERN NEVADA... ...17z Update... No changes were made to the currently valid outlook. Elevated to critical fire-weather conditions are likely over much of the Great Basin. A few thunderstorms are also possible over parts of eastern ID late this evening and overnight. ...Southern Pains... Gusty southerly flow is expected east of a lee trough over parts of the southern Plains this afternoon. 10-15 mph winds and RH below 25% over parts of west TX and eastern NM will overlap with areas of very dry fuels, supporting a locally elevated fire-weather risk. Confidence in areal coverage and duration remains too low to introduce an area. See previous discussion. ..Lyons.. 08/22/2024 .PREV DISCUSSION... /ISSUED 1148 PM CDT Wed Aug 21 2024/ ...Synopsis... A mid-level trough will amplify across the Interior West as an upper ridge persists across the central U.S. today. Strong mid-level flow from the upper trough, overspreading a deepening boundary layer over the Great Basin, will support dry and windy conditions through the afternoon. 15-20 mph sustained southwesterly surface winds, overlapping with 15-20 percent RH and fuels receptive to fire spread, will result in widespread Elevated conditions for several hours. However, portions of central Nevada may also experience higher sustained southerly surface winds (i.e. over 25 mph), warranting Critical highlights. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0754 AM CDT Thu Aug 22 2024 Valid 221300Z - 231200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE CENTRAL HIGH PLAINS... ...SUMMARY... The greatest threat for severe gusts and hail appears to be over parts of the central High Plains this afternoon and evening. ...Synopsis... A highly amplified pattern in mid/upper levels will persist through the period, but with some weakening noted for both mean troughing near the East Coast, and a central CONUS ridge extending northward from a high over west TX. Southwest flow over the Intermountain West will strengthen and back somewhat in response to slow southeastward movement of an intense cyclone -- now centered west of the northern OR Coast --- while a strong shortwave trough pivots through its southern semicircle and onshore the northern CA coast by the end of the period. Farther east, on the periphery of that southwest flow, a shortwave trough (with some incorporation of a Sonoran MCV from 24 hours earlier) was apparent in moisture-channel imagery over northern AZ and southern UT. This perturbation should eject northeastward over western CO by 00Z, then into the central Plains overnight, perhaps with some further convective-vorticity reinforcement then. To the north, closely spaced shortwave troughs now over south-central SK and parts of ND/southeastern SK should pivot eastward across the rest of ND, northern MN and southern/central MB through the period. At the surface, a quasistationary frontal zone from northern FL across the northern Gulf Coast, east/north TX and the TX Panhandle should remain near that position through the period, with the richest low-level moisture remaining to its south. However, gradual moisture return of more incompletely modified (yet still convectively sufficient) character is apparent up the High Plains from the Panhandles across western NE to the central Dakotas. This is east of a lee trough over eastern parts of WY/CO, and a weak cold front analyzed from north-central ND to western SD. The latter front should proceed eastward across the Dakotas and into northwestern MN through this evening. ...Central High Plains... Highly variable thunderstorm coverage is expected over this region, with the greatest density in the 15%/"slight" area, where upscale evolution of increasingly outflow-driven thunderstorm clusters should support severe-gust potential this afternoon into evening. The primary foci for formation of eventually severe activity should be the northern Raton Mesa region, Front Range/Sangre de Cristo, and/or Palmer Divide, with some contribution from the lee trough as well. Though far south and east of the stronger flow aloft, sufficient veering of wind with height is expected to result in effective-shear magnitude in the 30-40-kt range, indicating potential for some organized convection. The boundary layer will remain well-heated/ mixed and deep, with very steep lapse rates, even as moisture/ buoyancy increase eastward. With surface dewpoints in the mid 50s to mid 60s F, peak/preconvective MLCAPE should reach 1500-2000 J/kg (locally higher) in a corridor near and just east of the longitude of the CO/KS line. This will foster pulses of strong to isolated severe gusts in initially discrete to semi-discrete activity atop a drier boundary layer, becoming better-organized with potential cold-pool aggregation eastward toward east-central/northeastern CO and adjoining portions of KS/NE into the higher CAPE. While specific shape, size, and track(s) of this clustering still depend on mesoscale details, enough consensus/confidence is now apparent in the general area of greatest severe-wind potential to ratchet up unconditional probabilities a level. With MLCINH increasing eastward from about the KS/CO border longitude and nocturnal near-surface cooling, the severe threat should weaken eastward from northwestern KS and southwestern NE tonight. ...Eastern Great Basin and vicinity... Widely scattered to scattered thunderstorms are possible this afternoon into early evening, offering strong to isolated severe gusts and marginally severe hail. After the shortwave trough and related precip now over parts of this region shifts northeastward, most of the day should remain for diabatic heating/destabilization of the higher terrain across the region, with airmass recovery furthered by warm/theta-e advection from the south. In concert with available monsoonal moisture, a roughly meridional plume of essentially uninhibited MLCAPE in the 500-1500 J/kg range should develop. This will be superimposed under the southeastern rim of stronger upper flow related to the West Coast troughing/cyclone. The result should be strengthening cloud-layer shear and some potential for storm organization, as activity moves generally northeastward over well-mixed boundary layers. ...Upper Midwest... A large area of clouds and precip -- with widely scattered embedded thunderstorms -- should proceed eastward today across the remainder of eastern ND and parts of northern MN near the international border. Though the associated lead perturbation now over ND should be past the area before this afternoon, cyclonic flow aloft should continue in response to the stronger perturbation farther north, moving into MB. As such, little if any hindrance to convective potential is expected from large-scale subsidence, while the low-level airmass destabilizes diabatically from surface heating behind the morning activity. Isolated to widely scattered thunderstorms may develop along/ahead of the cold front, within a narrow plume of 1000-2000 J/kg MLCAPE supported by 60s F surface dewpoints. Modest low/middle-level flow is expected, through enough veering with height should develop to support effective-shear magnitudes locally near 35 kt. The strongest cells may produce marginally severe hail or gusts, before convection weakens this evening. ..Edwards/Mosier.. 08/22/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0754 AM CDT Thu Aug 22 2024 Valid 221300Z - 231200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE CENTRAL HIGH PLAINS... ...SUMMARY... The greatest threat for severe gusts and hail appears to be over parts of the central High Plains this afternoon and evening. ...Synopsis... A highly amplified pattern in mid/upper levels will persist through the period, but with some weakening noted for both mean troughing near the East Coast, and a central CONUS ridge extending northward from a high over west TX. Southwest flow over the Intermountain West will strengthen and back somewhat in response to slow southeastward movement of an intense cyclone -- now centered west of the northern OR Coast --- while a strong shortwave trough pivots through its southern semicircle and onshore the northern CA coast by the end of the period. Farther east, on the periphery of that southwest flow, a shortwave trough (with some incorporation of a Sonoran MCV from 24 hours earlier) was apparent in moisture-channel imagery over northern AZ and southern UT. This perturbation should eject northeastward over western CO by 00Z, then into the central Plains overnight, perhaps with some further convective-vorticity reinforcement then. To the north, closely spaced shortwave troughs now over south-central SK and parts of ND/southeastern SK should pivot eastward across the rest of ND, northern MN and southern/central MB through the period. At the surface, a quasistationary frontal zone from northern FL across the northern Gulf Coast, east/north TX and the TX Panhandle should remain near that position through the period, with the richest low-level moisture remaining to its south. However, gradual moisture return of more incompletely modified (yet still convectively sufficient) character is apparent up the High Plains from the Panhandles across western NE to the central Dakotas. This is east of a lee trough over eastern parts of WY/CO, and a weak cold front analyzed from north-central ND to western SD. The latter front should proceed eastward across the Dakotas and into northwestern MN through this evening. ...Central High Plains... Highly variable thunderstorm coverage is expected over this region, with the greatest density in the 15%/"slight" area, where upscale evolution of increasingly outflow-driven thunderstorm clusters should support severe-gust potential this afternoon into evening. The primary foci for formation of eventually severe activity should be the northern Raton Mesa region, Front Range/Sangre de Cristo, and/or Palmer Divide, with some contribution from the lee trough as well. Though far south and east of the stronger flow aloft, sufficient veering of wind with height is expected to result in effective-shear magnitude in the 30-40-kt range, indicating potential for some organized convection. The boundary layer will remain well-heated/ mixed and deep, with very steep lapse rates, even as moisture/ buoyancy increase eastward. With surface dewpoints in the mid 50s to mid 60s F, peak/preconvective MLCAPE should reach 1500-2000 J/kg (locally higher) in a corridor near and just east of the longitude of the CO/KS line. This will foster pulses of strong to isolated severe gusts in initially discrete to semi-discrete activity atop a drier boundary layer, becoming better-organized with potential cold-pool aggregation eastward toward east-central/northeastern CO and adjoining portions of KS/NE into the higher CAPE. While specific shape, size, and track(s) of this clustering still depend on mesoscale details, enough consensus/confidence is now apparent in the general area of greatest severe-wind potential to ratchet up unconditional probabilities a level. With MLCINH increasing eastward from about the KS/CO border longitude and nocturnal near-surface cooling, the severe threat should weaken eastward from northwestern KS and southwestern NE tonight. ...Eastern Great Basin and vicinity... Widely scattered to scattered thunderstorms are possible this afternoon into early evening, offering strong to isolated severe gusts and marginally severe hail. After the shortwave trough and related precip now over parts of this region shifts northeastward, most of the day should remain for diabatic heating/destabilization of the higher terrain across the region, with airmass recovery furthered by warm/theta-e advection from the south. In concert with available monsoonal moisture, a roughly meridional plume of essentially uninhibited MLCAPE in the 500-1500 J/kg range should develop. This will be superimposed under the southeastern rim of stronger upper flow related to the West Coast troughing/cyclone. The result should be strengthening cloud-layer shear and some potential for storm organization, as activity moves generally northeastward over well-mixed boundary layers. ...Upper Midwest... A large area of clouds and precip -- with widely scattered embedded thunderstorms -- should proceed eastward today across the remainder of eastern ND and parts of northern MN near the international border. Though the associated lead perturbation now over ND should be past the area before this afternoon, cyclonic flow aloft should continue in response to the stronger perturbation farther north, moving into MB. As such, little if any hindrance to convective potential is expected from large-scale subsidence, while the low-level airmass destabilizes diabatically from surface heating behind the morning activity. Isolated to widely scattered thunderstorms may develop along/ahead of the cold front, within a narrow plume of 1000-2000 J/kg MLCAPE supported by 60s F surface dewpoints. Modest low/middle-level flow is expected, through enough veering with height should develop to support effective-shear magnitudes locally near 35 kt. The strongest cells may produce marginally severe hail or gusts, before convection weakens this evening. ..Edwards/Mosier.. 08/22/2024 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Thu Aug 22 2024 Valid 251200Z - 301200Z ...DISCUSSION... ...Sunday/Day 4 to Tuesday/Day 6... Heights within an upper-level ridge over the Mississippi Valley will continue to rise on Sunday, as an upper-level trough moves through the western U.S. The ridge is forecast to move into the western Great Lakes from Monday into Tuesday, as the upper-level trough moves across the north-central U.S. Ahead of the approaching trough, thunderstorm development will be possible each day, from the northern Plains into the upper Mississippi Valley. For the three days, the greatest chance of severe storms appears to be in the Dakotas on Sunday and in the upper Mississippi Valley on Monday. Strong instability and moderate deep-layer shear, combined with increasing large-scale ascent, should result in a severe threat each afternoon and evening. Large hail and severe gusts will likely be the primary threats. ...Wednesday/Day 7 and Thursday/Day 8... On Wednesday and Thursday, the upper-level trough is forecast to move across the upper Mississippi Valley and into southern Canada, as a second trough moves through the northern Plains. At the surface, a moist airmass is forecast to remain in place over the Great Lakes region and Upper Midwest. Scattered to widely scattered thunderstorms will be possible across much of this moist airmass on both days. Although an isolated severe threat will be possible each afternoon and evening, the threat is expected to remain marginal due to a large area of mid-level high pressure that is forecast to be in place over much of the eastern half of the nation. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0213 AM CDT Thu Aug 22 2024 Valid 241200Z - 251200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL AND NORTHERN PLAINS...AND IN THE FOUR CORNERS REGION... ...SUMMARY... Marginally severe storms will be possible on Saturday across parts of the central and northern High Plains, and near the Four Corners. ...Central and Northern High Plains... Heights associated with a Great Plains upper-level ridge will rise on Saturday, as the ridge moves slowly eastward. A north-to-south corridor of maximized low-level moisture is forecast to the west of the ridge across the central and northern Plains. Moderate instability will likely develop across much of this airmass by afternoon, with isolated thunderstorms forming along the western edge of the instability corridor from west-central Nebraska into the western Dakotas. With the moist airmass, 0-6 km shear is forecast to be in the 20 to 30 knot range in most areas. This, combined with steep lapse rates, will likely be sufficient for an isolated threat for severe gusts and hail. Due to the presence of the ridge, any severe threat is expected to be marginal. ...Four Corners... An upper-level trough is forecast to move across the Intermountain West on Saturday, as southwest mid-level flow remains over the Four Corners and Rocky Mountains. At the surface, an axis of maximized low-level moisture is forecast over the Four Corners, where destabilization will take place during the day. Scattered thunderstorms will likely develop throughout the Four Corners region Saturday afternoon. Forecast soundings at 21Z in the Four Corners vicinity have MLCAPE peaking between 500 and 1000 J/kg, with 0-6 km shear in most areas between 30 and 40 knots. Lapse rates are also forecast to become steep from the surface to 700 mb. This environment should support an isolated severe threat with marginally severe gusts and hail possible. ..Broyles.. 08/22/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0213 AM CDT Thu Aug 22 2024 Valid 241200Z - 251200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL AND NORTHERN PLAINS...AND IN THE FOUR CORNERS REGION... ...SUMMARY... Marginally severe storms will be possible on Saturday across parts of the central and northern High Plains, and near the Four Corners. ...Central and Northern High Plains... Heights associated with a Great Plains upper-level ridge will rise on Saturday, as the ridge moves slowly eastward. A north-to-south corridor of maximized low-level moisture is forecast to the west of the ridge across the central and northern Plains. Moderate instability will likely develop across much of this airmass by afternoon, with isolated thunderstorms forming along the western edge of the instability corridor from west-central Nebraska into the western Dakotas. With the moist airmass, 0-6 km shear is forecast to be in the 20 to 30 knot range in most areas. This, combined with steep lapse rates, will likely be sufficient for an isolated threat for severe gusts and hail. Due to the presence of the ridge, any severe threat is expected to be marginal. ...Four Corners... An upper-level trough is forecast to move across the Intermountain West on Saturday, as southwest mid-level flow remains over the Four Corners and Rocky Mountains. At the surface, an axis of maximized low-level moisture is forecast over the Four Corners, where destabilization will take place during the day. Scattered thunderstorms will likely develop throughout the Four Corners region Saturday afternoon. Forecast soundings at 21Z in the Four Corners vicinity have MLCAPE peaking between 500 and 1000 J/kg, with 0-6 km shear in most areas between 30 and 40 knots. Lapse rates are also forecast to become steep from the surface to 700 mb. This environment should support an isolated severe threat with marginally severe gusts and hail possible. ..Broyles.. 08/22/2024 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1259 AM CDT Thu Aug 22 2024 Valid 231200Z - 241200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL AND NORTHERN PLAINS...AND IN PARTS OF THE INTERMOUNTAIN WEST AND CENTRAL ROCKIES... ...SUMMARY... Marginally severe storms with hail and isolated severe gusts will be possible on Friday across parts of the central and northern High Plains, and in parts of the Intermountain West and central Rockies. ...Central and Northern High Plains... An upper-level ridge will remain over the Great Plains on Friday. At the surface, a north-to-south corridor of maximized low-level moisture will be located across the central and northern Plains, where surface dewpoints will be mostly in the lower to mid 60s F. As temperatures warm during the day, moderate instability is expected to develop throughout much of this moist airmass. Isolated thunderstorms are expected to form during the afternoon over the western edge of the stronger instability, with storm coverage remaining relatively sparse due to subsidence associated with the upper-level ridge. Forecast soundings have directional shear in the low-levels and speed shear aloft over much of the moist airmass. The moderate deep-layer shear combined with steep mid-level lapse rates should support a threat for hail and severe wind gusts. However, the threat should be marginal. ...Intermountain West/Central Rockies... An upper-level low will move to near the coast of Oregon on Friday, as southwest mid-level flow remains over much of the western U.S. A subtle shortwave trough is forecast to move through the Four Corners region, where an axis of moisture and instability will likely be in place. As surface temperatures warm during the day, scattered thunderstorms are expected to develop from parts of eastern Utah into western and central Colorado, and northward into western Wyoming. MLCAPE is forecast to peak in the 500 to 1000 J/kg range, with 0-6 km shear around 35 knots. Low-level lapse rates will also be steep in the afternoon. This environment should support a marginal potential for hail and severe wind gusts during the mid to late afternoon. ..Broyles.. 08/22/2024 Read more