SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1256 AM CDT Sun Aug 25 2024 Valid 251200Z - 261200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR THE EASTERN DAKOTAS INTO WESTERN/NORTHERN MN... ...SUMMARY... Scattered severe storms may develop across the northern Plains this afternoon and evening, with more isolated severe potential from the High Plains into the Four Corners vicinity. A couple of strong/marginally severe storms may also occur across parts of Ohio and lower Michigan. ...Synopsis... The southern portion of a persistent upper-level trough over the West will move slowly eastward today, as an embedded mid/upper cyclone moves slowly northeastward over the Great Basin. An upper-level trough will persist over the northeast CONUS, to the south of a weak mid/upper cyclone over Quebec. At the surface, the southern extension of a cold front across the Canadian Prairies will move into the Northern Plains, with a weak surface cyclone potentially developing near the NE/SD border. ...Central/eastern Dakotas into Minnesota Strong instability is forecast by afternoon along/ahead of the cold front from the central/eastern Dakotas into Minnesota, with sufficient effective shear (generally 30-40 kt) for some storm organization. However, with some capping and generally modest large-scale ascent, details regarding storm development during the afternoon/evening remain somewhat uncertain. In general, at least isolated development will be possible near the front across the eastern Dakotas into northwest MN. There will be some supercell potential with initial development, with an attendant threat of hail, damaging wind, and possibly a tornado. Depending on the extent of storm coverage, some upscale growth into clusters with an increasing damaging-wind threat will be possible by evening. There is also some signal for elevated convection across parts of the region later tonight, which could pose a severe threat in the presence of large MUCAPE. ...Four Corners region into Wyoming and the adjacent High Plains... Some organized severe potential is evident from the Four Corners region into eastern UT/western CO this afternoon, as the mid/upper cyclone and related shortwave trough over the Great Basin begin to impinge on the western periphery of the midlevel moist plume. With scattered to numerous storms expected for much of the day, the magnitude of destabilization remains uncertain. However, sufficient deep-layer shear will support potential for marginal supercells and a few stronger clusters capable of strong to severe gusts and isolated hail. Farther east into parts of the High Plains, isolated storms will be possible during the afternoon/evening, though coverage and organization may tend to be limited by weak large-scale ascent and only weak to marginal deep-layer shear. Isolated strong to severe gusts will be possible within the well-mixed environment across the region. ...Parts of OH/lower MI... Showers and isolated thunderstorms may develop this afternoon across parts of OH and lower MI, in conjunction with diurnal heating. Guidance continues to vary considerably regarding instability and the coverage/intensity of convection across the region. However. steepening low-level lapse rates and modest northwesterly flow aloft could support gusty-wind and small-hail potential with any stronger storms. ..Dean/Elliott.. 08/25/2024 Read more

MD 1986 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR NORTHEAST MONTANA AND EXTREME NORTHWEST NORTH DAKOTA
Mesoscale Discussion 1986 NWS Storm Prediction Center Norman OK 1130 PM CDT Sat Aug 24 2024 Areas affected...Northeast Montana and extreme northwest North Dakota Concerning...Severe potential...Watch unlikely Valid 250430Z - 250630Z Probability of Watch Issuance...20 percent SUMMARY...Gusty winds and marginally severe hail threat are expected with convection into the early morning hours across northeast Montana. DISCUSSION...Right-entrance region of a mid-level jet over southern SK may be partly responsible for recent uptick in elevated convection that is spreading into northeast MT. Latest surface data suggests a weak low is tracking across southeast MT toward western ND. Primary pacific frontal surge is associated with a gradually expanding cluster of thunderstorms from southern Phillips to northern Rosebud County. Severe wind gust has recently been reported at JDN along the leading edge of this activity. Latest HREF guidance has a reasonable handle on this scenario and subsequent movement should spread across the remainder of northeast MT early this morning. Unless multiple supercells develop within this expanding cluster, hail production should be limited and generally less than one inch. Even so, an isolated severe report or two can not be ruled out, and most likely will be a gust approaching 50kt. Given the marginality of this convection, current thinking is a severe thunderstorm watch is not currently needed. ..Darrow/Gleason.. 08/25/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BIS...GGW... LAT...LON 48100763 49440522 48780356 47030593 48100763 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0800 PM CDT Sat Aug 24 2024 Valid 250100Z - 251200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR A SMALL PART OF NORTHEAST MT... ...SUMMARY... Isolated severe storms remain possible this evening into tonight across parts of northeast Montana, and for a few hours this evening from the central High Plains into the Four Corners region. ...Northeast MT vicinity... An isolated supercell or two remains possible through mid evening across extreme northeast MT into far northwest ND, within an environment characterized by moderate to strong buoyancy and favorable deep-layer shear (as noted in the 00Z GGW sounding). Later tonight, some guidance (most notably recent HRRR runs) suggests potential for an elevated storm cluster to develop and move across northeast MT and potentially extreme northwest ND. High-based convection currently developing across east-central MT lends some credence to this scenario, though uncertainty remains. Should this occur, MUCAPE and deep-layer shear will remain favorable for organized storms with hail and severe-gust potential, before the cluster moves into SK. A Slight Risk has been added for the conditional potential for hail and strong to severe gusts later tonight. ...Four Corners into the central High Plains... Multiple clusters of generally disorganized convection are ongoing early this evening from northern NM into parts of CO. Localized strong to severe gusts will be possible within the well-mixed environment across the region for a few hours this evening, before convection generally weakens. Some intensification cannot be ruled out where stronger instability is in place from northeast CO into western NE, though MLCINH should become increasingly prohibitive with time. ...Southern KS into western OK...northwest TX...OK/TX Panhandles... Isolated high-based storms may continue to pose a short-term threat of localized downbursts from northwest TX/western OK into the TX/OK Panhandles and southern KS. However, storms should continue to be disorganized, and tend to diminish quickly with time this evening. ..Dean.. 08/25/2024 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0800 PM CDT Sat Aug 24 2024 Valid 250100Z - 251200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR A SMALL PART OF NORTHEAST MT... ...SUMMARY... Isolated severe storms remain possible this evening into tonight across parts of northeast Montana, and for a few hours this evening from the central High Plains into the Four Corners region. ...Northeast MT vicinity... An isolated supercell or two remains possible through mid evening across extreme northeast MT into far northwest ND, within an environment characterized by moderate to strong buoyancy and favorable deep-layer shear (as noted in the 00Z GGW sounding). Later tonight, some guidance (most notably recent HRRR runs) suggests potential for an elevated storm cluster to develop and move across northeast MT and potentially extreme northwest ND. High-based convection currently developing across east-central MT lends some credence to this scenario, though uncertainty remains. Should this occur, MUCAPE and deep-layer shear will remain favorable for organized storms with hail and severe-gust potential, before the cluster moves into SK. A Slight Risk has been added for the conditional potential for hail and strong to severe gusts later tonight. ...Four Corners into the central High Plains... Multiple clusters of generally disorganized convection are ongoing early this evening from northern NM into parts of CO. Localized strong to severe gusts will be possible within the well-mixed environment across the region for a few hours this evening, before convection generally weakens. Some intensification cannot be ruled out where stronger instability is in place from northeast CO into western NE, though MLCINH should become increasingly prohibitive with time. ...Southern KS into western OK...northwest TX...OK/TX Panhandles... Isolated high-based storms may continue to pose a short-term threat of localized downbursts from northwest TX/western OK into the TX/OK Panhandles and southern KS. However, storms should continue to be disorganized, and tend to diminish quickly with time this evening. ..Dean.. 08/25/2024 Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0459 PM CDT Sat Aug 24 2024 Valid 261200Z - 011200Z On Day 3/Monday, enhanced deep-layer southwesterly flow -- preceding a midlevel shortwave trough crossing the northern Rockies -- will overspread the northern/central Rockies. Over southern/central Wyoming, boundary-layer mixing into the enhanced flow aloft will contribute to dry/breezy conditions during the afternoon. While elevated conditions are possible, confidence in the development of critical conditions is too low for probabilities. Thereafter, a deep mid/upper-level low will track east-southeastward from British Columbia into portions of the Northwest on Day 4/Tuesday. A related belt of strong midlevel west-southwesterly flow will cross the Cascades, promoting dry/windy downslope conditions in the Columbia Basin. Elevated to locally critical conditions will be possible, given some antecedent drying of fuels across the area. As the trough continues east on Day 5/Wednesday, dry/breezy conditions will spread eastward into the northern Rockies, potentially yielding elevated fire-weather conditions. However, preceding rainfall over much of the region limits confidence in the overall fire-weather risk -- precluding probabilities at this time. ..Weinman.. 08/24/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Sat Aug 24 21:54:02 UTC 2024.

MD 1984 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR NORTHWEST NEW MEXICO INTO SOUTH-CENTRAL COLORADO
Mesoscale Discussion 1984 NWS Storm Prediction Center Norman OK 0349 PM CDT Sat Aug 24 2024 Areas affected...Northwest New Mexico into south-central Colorado Concerning...Severe potential...Watch unlikely Valid 242049Z - 242245Z Probability of Watch Issuance...5 percent SUMMARY...Strong to severe winds and small to marginally severe hail are possible in the strongest storms. A watch is not likely this afternoon. DISCUSSION...A plume of mid-level moisture is lifting northward into the Four Corners vicinity on water vapor imagery. Widely-scattered to scattered storms have developed in the higher terrain this afternoon. Most storms have remained rather shallow, but a cluster of stronger storms has formed in northwest New Mexico where greater heating has occurred. With a belt of stronger mid-level winds between the Northwestern upper trough and the central U.S. upper ridge, effective shear of 35-40 kts will allow a few stronger multicells to develop. These storms could produce strong severe wind gusts as well as small to marginally severe hail. Overall forcing for ascent will remain weak as will buoyancy. The severe threat should remain isolated and marginal. ..Wendt/Guyer.. 08/24/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...PUB...BOU...ABQ...GJT...FGZ... LAT...LON 34330840 35370993 37220833 38350699 38780582 38240447 35760545 34500661 34330840 Read more

MD 1985 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PARTS OF NORTHEASTERN MONTANA
Mesoscale Discussion 1985 NWS Storm Prediction Center Norman OK 0400 PM CDT Sat Aug 24 2024 Areas affected...parts of northeastern Montana Concerning...Severe potential...Watch unlikely Valid 242100Z - 242330Z Probability of Watch Issuance...20 percent SUMMARY...Thunderstorm activity may begin to initiate, with the evolution of an isolated supercell possible, by 4-5 PM MDT. This may pose a risk for large hail, locally damaging wind gusts, and perhaps some potential for a brief tornado. DISCUSSION...Low-level convergence appears to be locally strengthening within weak surface troughing near the Wolf Point vicinity, where surface dew points remain in the lower/mid 60s F, as temperatures warm into the 90s F. Inhibition is gradually eroding with continuing insolation, and this may be aided by weak mid-level cooling through late afternoon, downstream of a mid-level perturbation progressing across and northeast of the Canadian Rockies. Initial attempts at deepening convective development appear slowly underway, in the presence of thermodynamic profiles already characterized by steep lower/mid-tropospheric lapse rates and CAPE in excess of 2000 J/kg. Beneath 35-60+ kt south-southwesterly flow in the 500-300 mb layer, deep-layer shear is already strong and conditionally supportive of supercells. Although the strength of mid/upper forcing for ascent remains a bit unclear, the High Resolution Rapid Refresh and Rapid Refresh, in particular, suggest that at least isolated thunderstorms may initiate as early as 22-23Z. Once this occurs, intensification may be fairly rapid, with storms becoming capable of producing large hail, locally damaging gusts gusts, and perhaps some risk for a brief tornado, despite generally small/linear low-level hodographs. ..Kerr/Guyer.. 08/24/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...GGW... LAT...LON 49550459 48250422 47870592 48790686 49660673 49550459 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0300 PM CDT Sat Aug 24 2024 Valid 251200Z - 261200Z The Elevated area in Wyoming was removed with this update, as the latest guidance consensus suggests increasing cloud coverage and precipitation/thunderstorms overspreading the area through the afternoon. While strong to severe outflow winds may accompany storms and pose some risk of fire-spread, the overlap of dry/windy conditions appears limited. For details on the severe-thunderstorm risk, see the SPC Day 2 Convective Outlook. Additionally, the Isolated Dry Thunderstorm highlights were trimmed over northeast Nevada -- where RH/moisture should be too high for an appreciable risk of dry thunderstorms. ..Weinman.. 08/24/2024 .PREV DISCUSSION... /ISSUED 0130 AM CDT Sat Aug 24 2024/ ...Synopsis... A mid-level trough positioned over the West will lift northeast into the Northern Rockies while undergoing gradual weakening. Still, enough residual enhanced mid-level flow will overspread adjacent regions of the Northern Rockies, to result in afternoon sustained surface winds of 15-20 mph and RH values into the low 20s F. These dry/breezy conditions will promote Elevated fire-weather conditions across portions of Wyoming where fuels remain at least marginally receptive to large-fire spread. In addition, an area delineating the potential for isolated dry thunderstorms has been added for portions of the northern Great Basin into the Northern Rockies. Isolated storms should develop during the afternoon in association with forcing/ascent with the mid-level trough. This highlight has been confined to areas where fuels appear receptive to large-fire spread. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0238 PM CDT Sat Aug 24 2024 Valid 242000Z - 251200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE FOUR CORNERS INTO THE CENTRAL HIGH PLAINS...ACROSS NORTHEAST MONTANA AND FAR NORTHWEST NORTH DAKOTA...AND WESTERN OKLAHOMA... ...SUMMARY... Strong to locally severe storms are possible today from the Four Corners region northeastward into the central High Plains, over northeast Montana/northwest North Dakota and also across western Oklahoma. ...20z Update... The primary change for this update was the removal of the Marginal risk area across southern Missouri/northern Arkansas. The ongoing MCS along the MO/AR border has shown a steady weakening trend over the past few hours in early all convective metrics (IR cloud top temperatures, lightning counts, maximum reflectivity, etc...). A sporadic strong updraft pulse or two will remain possible across northern AR given MLCAPE values between 1000-22000 J/kg, but the overall weakening trend is expected to continue as the MCS migrates closer to the center of an upper anti-cyclone where deep-layer wind shear is negligible. Elsewhere, the forecast remains on track with no changes required. See the previous discussion (below) for additional details. ..Moore.. 08/24/2024 .PREV DISCUSSION... /ISSUED 1128 AM CDT Sat Aug 24 2024/ ...Northeast Montana/northwest North Dakota... Have introduced severe hail/wind probabilities for the potential of isolated severe thunderstorm development beginning potentially as early as late afternoon across northeast Montana, but more likely this evening across the region. This development is possible along/behind a surface wave and eastward-moving front, where moderate buoyancy will coincide with strong shear through the cloud-bearing layer. ...Four Corners to Central High Plains... Widely scattered to scattered thunderstorms are expected by mid/late afternoon. Activity should move northward to northeastward over this corridor, with isolated severe gusts being the main concern, and hail near severe limits also possible over the High Plains. Effective shear will be modest (generally 30 kt or less), but enough cloud-layer shear for a few organized multicell storms, with a well-mixed sub-cloud layer supportive of strong/locally severe wind gusts. ...Southern Missouri/northern Arkansas... A linear convective cluster will continue to progress southward today. Deep-layer/low-level shear will remain weak, with the cluster tending to remain elevated to the east of the main reservoir of surface-based buoyancy and mid-level lapse rates. While some strong gusts and/or sub-severe hail could occur, the overall severe potential should remain isolated and relatively marginal in nature. ...Western/northern Oklahoma.... Isolated to widely scattered thunderstorms are possible by late afternoon through around sunset, with locally strong-severe microbursts possible. A surface moist/buoyancy axis will persist under and near the mid/upper high, with an effective dryline to its west across northwest Texas to northwest Oklahoma. Enough moisture should be present to support a minimally capped, deep, hot, well-mixed boundary layer with around 250-1000 J/kg MLCAPE and DCAPE values of 1000-2000 J/kg. Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0226 PM CDT Sat Aug 24 2024 Valid 261200Z - 271200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EASTERN SOUTH DAKOTA AND FAR NORTHERN NEBRASKA INTO PARTS OF MINNESOTA AND WISCONSIN... ...SUMMARY... Severe storms are expected to evolve within a zone extending from the northern High Plains eastward to the Wisconsin vicinity during the afternoon and evening Monday. A few severe storms are also expected across the Northeast and Mid-Atlantic region. ...Northern Plains/Upper Midwest... An upper trough will develop east across the northern Plains on Tuesday. Enhanced southwesterly mid/upper flow (50-60 kt at 500 mb) will overspread a very moist boundary layer (dewpoints in the 70s). A surface cold front will be oriented from northern MN southwest into western SD during the morning, and develop southeast through the period. Convection will develop along the boundary during the day and move across a strongly unstable airmass. Clusters may develop into a fast-moving MCS impacting portions of eastern SD into central/southern MN and parts of WI. Damaging wind swaths and isolated large hail will be possible. The south and east extent of the severe risk is uncertain, and adjustments may be needed in subsequent outlooks as mesoscale details become better resolved. Additional more isolated strong to severe storm may develop in the post-frontal upslope flow regime across NE and parts of the northern High Plains. Strong gusts and hail could accompany this activity. ...Northeast/Mid-Atlantic vicinity... Moderate northwesterly deep-layer flow will persist over the region as an upper trough shifts east over the Atlantic. A seasonally moist airmass will result in pockets of weak instability, supporting isolated to scattered corridors of thunderstorm activity. Steep low-level lapse rates and sufficient vertical shear amid weak instability will support isolated strong gusts and perhaps small hail. ...Central/Southern High Plains vicinity... Severe probabilities have been removed from this area with this update cycle. Forecast guidance varies considerable regarding the degree of destabilization across the region, with ECMWF members showing very little instability, while the more aggressive NAM solutions indicated MUCAPE to near 500 J/kg. Given potential for a large area with little risk, opted to remove this area until confidence increases in which particular areas may see greater thunderstorm coverage. ..Leitman.. 08/24/2024 Read more

No Mesoscale Discussions are in effect as of Sat Aug 24 17:54:02 UTC 2024.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1214 PM CDT Sat Aug 24 2024 Valid 251200Z - 261200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE EASTERN DAKOTAS INTO NORTHWEST MINNESOTA... ...SUMMARY... Scattered severe storms may develop across the northern Plains area on Sunday, with more isolated severe potential southwestward into the southern Rockies and adjacent High Plains. A couple of strong/marginally severe storms may also occur across the Lower Great Lakes/Upper Ohio Valley vicinity. ...Northern Plains/Upper Midwest... An upper anticyclone will be centered over KS/OK and the Ozark Plateau, with the upper ridge axis oriented northward over the Upper MS Valley on Sunday. Meanwhile, a shortwave upper trough will migrate east across the Canadian Prairies. This will focus an area of modestly enhanced mid/upper southwesterly flow over the Dakotas into the Upper Midwest. At the surface, south/southeasterly flow will maintain a very moist airmass, with dewpoints in the 70s F expected from the eastern Dakotas into IA/MN and vicinity. A plume of steeper midlevel lapse rates will advect northeast, aiding in strong destabilization. However, warm midlevel temps will likely maintain at least weak MLCIN across the region through the afternoon and into the evening as stronger forcing for ascent largely remains north of the international border. As a result, convective coverage during the afternoon is a bit uncertain/conditional. By late afternoon/evening, a surface front is forecast to progress eastward across the Dakotas and into MN through the nighttime hours. This may provide sufficient forcing for isolated thunderstorm development. Given strong instability and sufficient vertical shear for organized updrafts, large hail (especially with initial cellular development) and damaging gusts will be possible. ...Four Corners into WY and adjacent High Plains... An upper trough will lift northeast across the Great Basin on Sunday. Modestly enhanced southwesterly mid/upper flow will overspread the region between the eastern periphery of the trough and the western periphery of the upper ridge to the east. Boundary-layer moisture will remain modest for most of the region, but steep midlevel lapse rates and strong heating will support 500-1000 J/kg MLCAPE. Sporadic downbursts may produce locally severe gusts with this activity. ...Upper Ohio Valley Vicinity... Modest northwesterly mid/upper flow will overspread the region on Sunday on the western periphery of a Northeast upper trough. Latest forecast guidance shows warming midlevel temps/minor height rises during the day. However, a moist airmass will be in place and weak to moderate destabilization is expected. Convective coverage may be fairly low given latest forecast guidance trends. However, any stronger cells that develop may produce locally strong gusts or small hail given favorable shear and elongated/straight forecast hodographs. ..Leitman.. 08/24/2024 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1214 PM CDT Sat Aug 24 2024 Valid 251200Z - 261200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE EASTERN DAKOTAS INTO NORTHWEST MINNESOTA... ...SUMMARY... Scattered severe storms may develop across the northern Plains area on Sunday, with more isolated severe potential southwestward into the southern Rockies and adjacent High Plains. A couple of strong/marginally severe storms may also occur across the Lower Great Lakes/Upper Ohio Valley vicinity. ...Northern Plains/Upper Midwest... An upper anticyclone will be centered over KS/OK and the Ozark Plateau, with the upper ridge axis oriented northward over the Upper MS Valley on Sunday. Meanwhile, a shortwave upper trough will migrate east across the Canadian Prairies. This will focus an area of modestly enhanced mid/upper southwesterly flow over the Dakotas into the Upper Midwest. At the surface, south/southeasterly flow will maintain a very moist airmass, with dewpoints in the 70s F expected from the eastern Dakotas into IA/MN and vicinity. A plume of steeper midlevel lapse rates will advect northeast, aiding in strong destabilization. However, warm midlevel temps will likely maintain at least weak MLCIN across the region through the afternoon and into the evening as stronger forcing for ascent largely remains north of the international border. As a result, convective coverage during the afternoon is a bit uncertain/conditional. By late afternoon/evening, a surface front is forecast to progress eastward across the Dakotas and into MN through the nighttime hours. This may provide sufficient forcing for isolated thunderstorm development. Given strong instability and sufficient vertical shear for organized updrafts, large hail (especially with initial cellular development) and damaging gusts will be possible. ...Four Corners into WY and adjacent High Plains... An upper trough will lift northeast across the Great Basin on Sunday. Modestly enhanced southwesterly mid/upper flow will overspread the region between the eastern periphery of the trough and the western periphery of the upper ridge to the east. Boundary-layer moisture will remain modest for most of the region, but steep midlevel lapse rates and strong heating will support 500-1000 J/kg MLCAPE. Sporadic downbursts may produce locally severe gusts with this activity. ...Upper Ohio Valley Vicinity... Modest northwesterly mid/upper flow will overspread the region on Sunday on the western periphery of a Northeast upper trough. Latest forecast guidance shows warming midlevel temps/minor height rises during the day. However, a moist airmass will be in place and weak to moderate destabilization is expected. Convective coverage may be fairly low given latest forecast guidance trends. However, any stronger cells that develop may produce locally strong gusts or small hail given favorable shear and elongated/straight forecast hodographs. ..Leitman.. 08/24/2024 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1151 AM CDT Sat Aug 24 2024 Valid 241700Z - 251200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF NORTHERN/CENTRAL WYOMING... ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF WESTERN UTAH INTO SOUTHEAST NEVADA... The previous forecast (see below) remains on track, and only minor adjustments were made based on the latest observations and high-resolution guidance. ..Weinman.. 08/24/2024 .PREV DISCUSSION... /ISSUED 0129 AM CDT Sat Aug 24 2024/ ...Synopsis... A highly amplified mid-level trough will progress through portions of the interior West throughout the day. A mid-level jet streak will accompany this trough along its southern/eastern periphery. Daytime heating/mixing will allow these winds to mix toward the surface. This process will result in southwesterly sustained surface winds of 25-35 mph and RH values into the teens/single digits F across portions of western Utah into southeast Nevada, amid marginally receptive fuels, supporting Critical fire-weather conditions. Similar wind/RH conditions supporting Critical fire-weather conditions will occur across portions of northern/central Wyoming, albeit with sustained winds of 20-25 mph and RH values into the teens and low 20s F, amid receptive fuels. Farther west, upper forcing for ascent associated with the mid-level trough will foster isolated dry thunderstorms over portions of northern Nevada and vicinity. Fuels in this region remain receptive to large-fire spread with PWAT values ranging from 0.5-0.75 inches. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1128 AM CDT Sat Aug 24 2024 Valid 241630Z - 251200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN HIGH PLAINS...SOUTHERN PLAINS...OZARKS...AND FOUR CORNERS TO CENTRAL HIGH PLAINS... ...SUMMARY... Strong to locally severe storms are possible today from the Four Corners region northeastward into the central High Plains, over northeast Montana/northwest North Dakota, parts of the Ozarks, and also across western Oklahoma. ...Northeast Montana/northwest North Dakota... Have introduced severe hail/wind probabilities for the potential of isolated severe thunderstorm development beginning potentially as early as late afternoon across northeast Montana, but more likely this evening across the region. This development is possible along/behind a surface wave and eastward-moving front, where moderate buoyancy will coincide with strong shear through the cloud-bearing layer. ...Four Corners to Central High Plains... Widely scattered to scattered thunderstorms are expected by mid/late afternoon. Activity should move northward to northeastward over this corridor, with isolated severe gusts being the main concern, and hail near severe limits also possible over the High Plains. Effective shear will be modest (generally 30 kt or less), but enough cloud-layer shear for a few organized multicell storms, with a well-mixed sub-cloud layer supportive of strong/locally severe wind gusts. ...Southern Missouri/northern Arkansas... A linear convective cluster will continue to progress southward today. Deep-layer/low-level shear will remain weak, with the cluster tending to remain elevated to the east of the main reservoir of surface-based buoyancy and mid-level lapse rates. While some strong gusts and/or sub-severe hail could occur, the overall severe potential should remain isolated and relatively marginal in nature. ...Western/northern Oklahoma.... Isolated to widely scattered thunderstorms are possible by late afternoon through around sunset, with locally strong-severe microbursts possible. A surface moist/buoyancy axis will persist under and near the mid/upper high, with an effective dryline to its west across northwest Texas to northwest Oklahoma. Enough moisture should be present to support a minimally capped, deep, hot, well-mixed boundary layer with around 250-1000 J/kg MLCAPE and DCAPE values of 1000-2000 J/kg. ..Guyer/Wendt.. 08/24/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0749 AM CDT Sat Aug 24 2024 Valid 241300Z - 251200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE FOUR CORNERS REGION NORTHEASTWARD INTO THE CENTRAL HIGH PLAINS...OVER PARTS OF MISSOURI TO NORTHERN ARKANSAS...AND ALSO OVER AND NEAR WESTERN OKLAHOMA... ...SUMMARY... Strong to locally severe storms are possible today from the Four Corners region northeastward into the central High Plains, over parts of Missouri to northern Arkansas, and also over and near western Oklahoma. ...Synopsis... Positively tilted mid/upper-level troughing should shift slowly eastward through the period, from the West Coast States to the northern Rockies, Great Basin and southern CA. Several shortwaves will pivot through the associated tightly cyclonic regime astride the trough, then eject into the downstream southwest flow. Additional perturbations will move northeastward in continuing southwest flow over the southern Rockies and central Plains, closer to a pronounced anticyclone whose 500-mb high should move slowly northeastward over OK. Ridging accompanying that high should build northeastward to southern Hudson Bay by the end of the period. A broad fetch of deep-layer moisture was apparent in moisture-channel imagery and surface analysis from northwestern MX across the Four Corners to the central Rockies and adjacent High Plains. Otherwise, the 11Z surface chart showed a long-lived, quasistationary frontal zone from Atlantic waters off the Carolinas, southwestward over northern FL, to coastal LA, then northwestward as a warm front across southern/western OK to a low near DDC. Rich moisture has spread through the front over central eastern OK and into southern/central KS, with upper 60s and greater surface dewpoints. The low is expected to move/redevelop into the north-central KS/south-central NE vicinity by 00Z, with warm frontogenesis to its east across the southern IA/northern NE area. A separate cold front -- analyzed from eastern MT southwestward over northwestern UT and southern NV -- should move slowly eastward through the period, reaching the western Dakotas, central WY and southwestern UT by 12Z tomorrow. ...Four Corners to Central High Plains... Again today, the persistent monsoonal moisture plume (somewhat eastward-displaced from previous days) should host widely scattered to scattered thunderstorms by mid/late afternoon. Activity should move northward to northeastward over this corridor, with isolated severe gusts being the main concern, and hail near severe limits possible over the High Plains portion of the outlook area. Diurnal heating of higher terrain from just south of I-40 across the Four Corners, San Juans, and assorted ranges from there to the Laramies and Front Range, should remove MLCINH quickly into early afternoon, fostering deep convective growth. Effective shear will be modest (generally 30 kt or less) due to a lack of both 1. Stronger/backed near-surface flow and 2. Greater CAPE density and buoyant depth (related to modest lapse rates aloft in the monsoonal plume). Still, the southeastern fringe of the mass response in upper levels to the Western CONUS troughing should yield enough cloud-layer shear for a few organized multicell storms, with translational vector augmentation of outflow winds possibly contributing to marginal severe potential. The main supporting factor for downdraft intensity will be a well-mixed subcloud layer beneath around 200-800 J/kg ambient MLCAPE. ...MO/AR... An MCV was apparent in composited radar imagery over southeastern NE between LNK-FNB, and should pivot slowly southeastward through the day. Associated regionally enhanced low-level moist/warm advection, and isentropic lift to LFC, have been supporting swath of elevated convection now over portions of northwestern MO. Lightning coverage and cooling IR cloud tops have been noted the past hour in a roughly north/south-oriented band of embedded thunderstorms, though radar-reflectivity structures remain messy and disorganized. Further organization/intensification with a southward translational thrust is possible through the day, as a combination of surface heating and boundary-later warm/moist advection combine to destabilize the foregoing airmass. This will lead to at least isolated potential for damaging gusts and marginally severe hail. Guidance still varies considerably on the potential for this activity to merge upscale enough for a single, well-developed cold pool, which would create a greater conditional wind threat over parts of west-central/southwestern MO and perhaps into northern AR before encountering decreasing instability. Southern parts of the outlook area have been extended somewhat, and the area widened somewhat, to account for these mesobeta- to convective-scale uncertainties. ...Western OK and vicinity... Isolated to widely scattered thunderstorms are possible from mid- late afternoon, with a few perhaps straying into early evening, offering locally strong-severe microbursts. A surface moist/buoyancy axis will persist under and near the mid/upper high, across southern to northeastern OK and into eastern KS. West of the associated moisture plume, an effective dryline will set up by midafternoon from northwest TX to northwestern OK, representing a differential between more intense heating/mixing to the west and the more strongly capped, moist boundary-layer environment under and nearer the high aloft. That boundary also should conform closely to a wind-shift line and confluence/ convergence axis, west of which winds at the surface will have a substantial westerly component. With further westward extent into the Panhandles, the boundary layer will be too dry to support substantial convection. Within the transition zone, represented by the outlook area, just enough moisture should be present to support a minimally capped, deep, hot, well-mixed boundary layer with around 250-1000 J/kg MLCAPE and DCAPE values commonly 1000-2000 J/kg. the dryline should retreat northwestward through the area this evening, but under unfavorably strong (and intensifying) MLCINH, and without appreciable large-scale support, later development is not expected. ..Edwards/Bentley.. 08/24/2024 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0354 AM CDT Sat Aug 24 2024 Valid 271200Z - 011200Z ...DISCUSSION... Within the faster belt of upper flow across the northern U.S., substantial differences in timing of the disturbances in the flow are manifest from the very start of the medium-range period. On Tuesday/Day 4, an energetic short-wave trough should be crossing the north-central U.S., headed toward the Upper Mississippi Valley/southern Ontario, while an upstream trough crosses western Canada and the Pacific Northwest, and a downstream one crosses northern Quebec. However, noted differences in both timing and orientation of these features is immediately apparent. The north-central U.S. feature -- the one associated with Day-4 severe risk over the Great Lakes region -- is roughly 12 hours slower, and evolves to a more negatively tilted configuration in the ECMWF, as compared to the GFS. This results in fairly substantial differences in the surface pattern as well, prohibiting any forecast of the specifics regarding the severe-weather potential on Tuesday. Still, severe-weather risk is apparent despite east-west geographical uncertainties. Thus, will introduce an elongated 15% area across the Upper Midwest and Great Lakes region, given likelihood for existence of a favorably unstable/amply sheared environment in the vicinity of a surface front likely to stretch east-northeastward to west-southwestward across this region. Damaging winds and hail would likely be the primary risks. By Day 5, differences continue to amplify. Risk for severe weather may evolve across portions of the Northeast (favored by the GFS), and/or parts of the Midwest/Ohio Valley (favored by the ECMWF). However, the differences are substantial enough amongst the models to preclude an areal highlight at this time. Meanwhile farther west, an upper low/trough is forecast to be moving across the northwestern U.S. and Canadian Prairie early in the day, but location/timing, and intensity differences with this feature are pronounced. While some severe risk may evolve across parts of the north-central U.S. ahead of this feature and an associated cold front, the differences preclude any areal outlines at this time. Predictability issues persist through the remainder of the period, with model solutions diverging steadily through the upcoming Labor Day weekend. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0241 AM CDT Sat Aug 24 2024 Valid 261200Z - 271200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF SOUTH DAKOTA EASTWARD TO THE WISCONSIN VICINITY... ...SUMMARY... Severe storms are expected to evolve within a zone extending from the northern High Plains eastward to the Wisconsin vicinity, and southward to the southern High Plains during the afternoon and evening Monday. A few severe storms are also expected across the Northeast and Mid-Atlantic region. ...Synopsis... An upper trough over the Intermountain West at the start of the period is forecast to eject northeastward across the High Plains into the north-central U.S. by the second half of the period. This will result in weakening of the persistent upper ridge over the central CONUS. Meanwhile, a weak upper low is forecast to shift south-southeastward across the Northeast/New England through the period. At the surface, a baroclinic zone lying across the north-central U.S. will sharpen and shift southeastward through the second half of the period, as the upper system shifts into/across the northern Plains. This front will likely focus severe storm development during the afternoon and evening hours. ...South Dakota vicinity to the Upper Great Lakes... While timing of the ejection of the upper system into/across the north-central U.S. remains a bit uncertain due to differences in the output from various models, a general consensus that afternoon storm initiation will occur across this region exists, as a very unstable airmass evolves diurnally. With flow forecast to veer/increase with height to southwesterly at 40 to 50 kt, shear will support organized/supercell storms. Coverage through the daylight hours may remain isolated across much of the region however, due to low-level capping. Still, any storms which do develop would be capable of producing large hail and damaging winds. Storm coverage may increase overnight as the trough advances and a southwesterly low-level jet develops, with convection -- and ongoing severe risk, spreading eastward across the Upper Midwest into the Upper Mississippi Valley into early Tuesday morning ...The High Plains... Modest afternoon destabilization forecast across the High Plains from southeastern Montana southward to northeastern New Mexico and the Texas/Oklahoma Panhandles should support isolated storm development. This development will be aided by increasing large-scale ascent associated with the ejection of the upper trough across the High Plains region during the afternoon. While flow aloft will be stronger with northward extent, supporting a few strong/severe storms with damaging wind potential, the very deep afternoon mixed layer farther south (mixed to/above 700 mb) will likely compensate somewhat for the lack of shear. As such, isolated severe gust potential may extend southward into the southern High Plains. ...The Northeast and Mid-Atlantic region... As a weak upper low shifts southeastward across the Northeast, modest afternoon destabilization is expected across portions of the region. While uncertainty regarding ample CAPE development exists, a belt of enhanced northwesterly flow aloft on the southern and western flank of the low will provide sufficient shear for southeastward-moving storms and potentially linear segments/clusters. Presuming at least minimally sufficient afternoon destabilization, stronger storms would pose a risk for damaging gusts locally, into the early evening hours. ..Goss.. 08/24/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0241 AM CDT Sat Aug 24 2024 Valid 261200Z - 271200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF SOUTH DAKOTA EASTWARD TO THE WISCONSIN VICINITY... ...SUMMARY... Severe storms are expected to evolve within a zone extending from the northern High Plains eastward to the Wisconsin vicinity, and southward to the southern High Plains during the afternoon and evening Monday. A few severe storms are also expected across the Northeast and Mid-Atlantic region. ...Synopsis... An upper trough over the Intermountain West at the start of the period is forecast to eject northeastward across the High Plains into the north-central U.S. by the second half of the period. This will result in weakening of the persistent upper ridge over the central CONUS. Meanwhile, a weak upper low is forecast to shift south-southeastward across the Northeast/New England through the period. At the surface, a baroclinic zone lying across the north-central U.S. will sharpen and shift southeastward through the second half of the period, as the upper system shifts into/across the northern Plains. This front will likely focus severe storm development during the afternoon and evening hours. ...South Dakota vicinity to the Upper Great Lakes... While timing of the ejection of the upper system into/across the north-central U.S. remains a bit uncertain due to differences in the output from various models, a general consensus that afternoon storm initiation will occur across this region exists, as a very unstable airmass evolves diurnally. With flow forecast to veer/increase with height to southwesterly at 40 to 50 kt, shear will support organized/supercell storms. Coverage through the daylight hours may remain isolated across much of the region however, due to low-level capping. Still, any storms which do develop would be capable of producing large hail and damaging winds. Storm coverage may increase overnight as the trough advances and a southwesterly low-level jet develops, with convection -- and ongoing severe risk, spreading eastward across the Upper Midwest into the Upper Mississippi Valley into early Tuesday morning ...The High Plains... Modest afternoon destabilization forecast across the High Plains from southeastern Montana southward to northeastern New Mexico and the Texas/Oklahoma Panhandles should support isolated storm development. This development will be aided by increasing large-scale ascent associated with the ejection of the upper trough across the High Plains region during the afternoon. While flow aloft will be stronger with northward extent, supporting a few strong/severe storms with damaging wind potential, the very deep afternoon mixed layer farther south (mixed to/above 700 mb) will likely compensate somewhat for the lack of shear. As such, isolated severe gust potential may extend southward into the southern High Plains. ...The Northeast and Mid-Atlantic region... As a weak upper low shifts southeastward across the Northeast, modest afternoon destabilization is expected across portions of the region. While uncertainty regarding ample CAPE development exists, a belt of enhanced northwesterly flow aloft on the southern and western flank of the low will provide sufficient shear for southeastward-moving storms and potentially linear segments/clusters. Presuming at least minimally sufficient afternoon destabilization, stronger storms would pose a risk for damaging gusts locally, into the early evening hours. ..Goss.. 08/24/2024 Read more