Severe Storms

No watches are valid as of Mon Aug 21 22:16:01 UTC 2023.

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0256 PM CDT Mon Aug 21 2023 Valid 212000Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF COASTAL TX...AZ TO MT...AND NORTHERN MN/WI... ...SUMMARY... Isolated severe thunderstorms are possible across parts of the Interior West through early evening, and the coastal plain of South Texas as well as northern Minnesota/Wisconsin early Tuesday. ...20Z Update... No changes have been made to the outlook. Isolated strong/severe storms remain possible this afternoon into the evening along a corridor from AZ north-northeastward into MT. See MCD 2019 for more information regarding the short-term threat across parts of UT/ID/WY, and MCD 2020 for more information across parts of AZ. Elsewhere, elevated storms with an isolated severe-hail threat are possible early Tuesday morning across parts of northern MN/WI, and a tornado or two will be possible early Tuesday morning across the coastal Plain of south TX, in association with PTC 9 (which may strengthen into a tropical storm by late tonight). See NHC forecasts/advisories for more information regarding PTC 9, and the previous outlook discussion below for more information regarding the severe-thunderstorm threats. ..Dean.. 08/21/2023 .PREV DISCUSSION... /ISSUED 1129 AM CDT Mon Aug 21 2023/ ...Coastal South TX... PTC 9 is forecast by NHC to become a tropical storm by early Tuesday as it organizes westward towards the south TX coast through 12Z. Strengthening low-level winds in the front right quadrant will result in increasing cyclonic enlargement to the hodograph, especially in the 09-12Z period across the portion of the TX coast centered on CRP to PSX. Some 12Z HREF members indicate potential for intermediate convective bands similarly coincident with adequate low-level SRH to support a brief tornado or two towards dawn. Greater spatial extent of this threat inland is expected after 12Z. ...AZ to MT... Between a stout mid-level anticyclone centered over the Lower MO Valley and a cutoff low anchored near the CA Bay Area, a belt of enhanced mid-level southerlies will persist in a swath from AZ to MT, coincident with a plume of higher PW values. Isolated to scattered thunderstorms are expected along the eastern periphery of this plume where more robust boundary-layer heating will occur, and pose a threat for sporadic severe wind gusts. Relatively larger buoyancy should be confined across the AZ portion near/south of the Mogollon Rim where 60s surface dew points remain common this morning. This may yield a slightly greater threat for isolated severe gusts and perhaps marginally severe hail. ...Upper Midwest... Isolated severe hail will be possible during the early morning as highly elevated convection develops in a west-northwest to east-southeast band across northeast MN to northern WI. Owing to the proximity of the mid-level anticyclone/ridge, mid/upper-level lapse rates will not be particularly steep. But with a belt of strong mid/upper flow across northwest ON through the Upper Great Lakes, adequate effective bulk shear should exist for a few mid-level supercells capable of producing severe hail. Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0255 PM CDT Mon Aug 21 2023 Valid 231200Z - 291200Z An upper-level anticyclone will drift slowly westward from the Mississippi Valley to the central High Plains this week into this weekend. Beneath the upper-level anticyclone, persistent hot and dry conditions will promote the further curing of fuels across the central/southern Plains into the lower Mississippi Valley, with no appreciable forecast rainfall in sight. Surface winds are expected to be relatively light beneath the upper-level anticyclone through most of the period, with any breezy conditions that develop remaining localized, precluding any Critical probabilities this outlook. Meanwhile, moisture will continue to pivot around the western periphery of the upper-level anticyclone, potentially dampening significant wildfire-spread potential across much of the Southwest, Great Basin, and central/northern Rockies areas. However, conditions should remain dry to the west of the Cascades, with fuels remaining anomalously dry from far northwest California into western Washington. After the departure of the tropical remnants of Hilary, additional upper troughing along the Pacific Northwest Coastline may promote at least isolated thunderstorm development west of the Cascades by the end of the week. There are some indications from medium-range guidance that these thunderstorms could be dry. However, consistency among guidance members is needed before dry thunderstorm probabilities are introduced. ..Squitieri.. 08/21/2023 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

MD 2021 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR SOUTHEAST/EAST-CENTRAL AZ
Mesoscale Discussion 2021 NWS Storm Prediction Center Norman OK 0258 PM CDT Mon Aug 21 2023 Areas affected...Southeast/East-Central AZ Concerning...Severe potential...Watch unlikely Valid 211958Z - 212230Z Probability of Watch Issuance...20 percent SUMMARY...Thunderstorms capable of damaging gusts may develop across east-central and southeast Arizona this afternoon. DISCUSSION...Recent visible satellite imagery shows some deepening cumulus across southeast/east-central AZ, between more widespread cumulus over the higher terrain near the AZ/NM border and a more persistent north/south oriented cloud band across central AZ. This persistent cloudiness has tempered heating and destabilization across central AZ thus far, but partly cloudy skies have allow modest destabilization across south-central/southeast AZ. Further destabilization is anticipated throughout the afternoon, and moisture convergence along this differential heating zone is expected to result in convective initiation. Strong low to mid-level flow extends throughout this region as well, with recent mesoanalysis estimating effective bulk shear from 35 to 45 kt. As such, any storms that area able to deepen and persist could become organized/supercellular with the potential to produce damaging gusts. Overall coverage of strong to severe storms appears it will remain isolated, likely precluding the need for a watch. ..Mosier/Grams.. 08/21/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...TWC...FGZ...PSR... LAT...LON 31411103 32831163 34271174 34881159 35241114 35111033 34540989 33500953 32700927 32180920 31470925 31340973 31411103 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0215 PM CDT Mon Aug 21 2023 Valid 221200Z - 231200Z The previous forecast (see below) remains on track, with no changes or additions made. ..Squitieri.. 08/21/2023 .PREV DISCUSSION... /ISSUED 0210 AM CDT Mon Aug 21 2023/ ...Synopsis... Strong low/mid-level flow will continue across much of TX and the central High Plains -- along the southern and western peripheries of a persistent midlevel anticyclone centered over the central CONUS. At the same time, an area of low pressure is forecast to continue westward from the western Gulf of Mexico across south TX, while an additional surface low and trailing surface trough persist over the central High Plains. ...Central Texas... Along the northern periphery of cloud coverage associated with the area of low pressure crossing south TX, diurnal heating should support a corridor of 20-25 percent minimum RH across parts of central TX. Here, a tightening pressure gradient, along with boundary-layer mixing into the strong flow aloft, will yield 15-20 mph sustained easterly surface winds (with higher gusts). Given critically dry fuels over this area (95th+ percentile ERCs), elevated to locally critical fire-weather conditions are expected. If model guidance trends any drier with afternoon RH through this corridor, a Critical area could be needed in future outlooks. ...Central High Plains... Similar to Day 1/Monday, a tightening pressure gradient along the surface trough over the central High Plains will contribute to around 20 mph southwesterly surface winds (with higher gusts). These winds, coupled with 10-15 percent minimum RH, will favor elevated to spotty critical fire-weather conditions during the afternoon. ...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 1229 PM CDT Mon Aug 21 2023 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR SOUTH-CENTRAL INTO DEEP SOUTH TX...PARTS OF THE UPPER GREAT LAKES...NORTHWEST AZ INTO UT AND SOUTHWEST WY... ...SUMMARY... Storms with gusty winds and possibly a tornado or two will be possible across parts of south Texas on Tuesday, in association with a potential tropical cyclone. Isolated strong to severe storms will also be possible from northern Arizona into Utah and southwest Wyoming, and also across the upper Great Lakes region. ...South-central into Deep South TX... PTC 9 is currently forecast by NHC to strengthen into a tropical storm early Tuesday morning. The center of this system is forecast to be approaching the south TX coast at the start of the period. As tropical moisture and increasing low-level flow/shear spreads across south-central into Deep South TX in association with this system, transient low-topped supercells will become possible, potentially posing a threat for a tornado or two and isolated strong/severe gusts. The greatest relative threat is expected across the typically favored northeast quadrant of the cyclone, though the magnitude of the threat remains uncertain, pending the landfall intensity of the system and strength of any notable diurnal destabilization. ...Upper Great Lakes vicinity... One round of elevated convection will be possible Tuesday morning from northern WI into parts of upper MI, with another round possible late Tuesday night into Wednesday morning across the same general region, potentially extending into parts of lower MI. Both rounds will occur to the cool side of a slow-moving warm front and be driven by a moderate to strong nocturnal low-level jet. Midlevel lapse rates and MUCAPE will likely be greater for the second round of convection late in the period (potentially increasing above 2000 J/kg), with moderate northwesterly midlevel flow along the periphery of a strong upper ridge providing sufficient effective shear for organized storms. Isolated hail will be possible with the strongest storms, both early and late in the forecast period. MCS development cannot be ruled out late in the period, but low-level stability should generally tend to limit severe-gust potential. ...Great Basin vicinity... A moisture plume and a belt of somewhat enhanced low/midlevel flow will persist across portions of the Great Basin on Tuesday, along/east of an ejecting upper-level trough that will move from northern CA into the northern Rockies. Scattered thunderstorms will be possible within this regime through the day into the evening. While deep-layer shear will be sufficient to support organized convection, rather weak midlevel lapse rates and potentially limited heating may limit destabilization and the overall severe threat. If MLCAPE can increase into the 500-1000 J/kg range (which remains uncertain), a few organized clusters and/or marginal supercells may evolve, with a threat of isolated severe gusts and possibly a brief tornado. ...Interior Northwest... Scattered thunderstorm development is possible Tuesday afternoon from eastern OR into ID and western MT, associated with a mid/upper-level shortwave trough moving across the Pacific Northwest. Deep-layer shear will be sufficient to support somewhat organized convection, but it remains uncertain as to whether instability will be sufficient to support a severe hail/wind threat. ..Dean.. 08/21/2023 Read more

No watches are valid as of Sun Aug 20 22:24:02 UTC 2023.

No Mesoscale Discussions are in effect as of Sun Aug 20 22:24:02 UTC 2023.

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0239 PM CDT Sun Aug 20 2023 Valid 202000Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHEAST CA INTO THE LOWER CO VALLEY... ...SUMMARY... A couple tornadoes are possible across the Lower Colorado Valley and southern Mojave Desert vicinity through around dusk. ...20z Update... Only minor adjustments have been made to the 2 percent tornado probabilities over AZ. Otherwise, the previous outlook remains on track. See previous discussion below for more details, and reference MCD 2017 for short term severe/tornado hazard information. ..Leitman.. 08/20/2023 .PREV DISCUSSION... /ISSUED 1119 AM CDT Sun Aug 20 2023/ ...Desert Southwest... The conditional TC-tornado environment evident over the northern Gulf of CA and northwest Sonora is expected to spread north-northwest across the Lower CO Valley and southern Mojave Desert vicinity. The primary corridor of concern will be across southeast CA and adjacent portions of western AZ/southern NV this afternoon into early evening. Here, meager MLCAPE from 300-600 J/kg should develop with some thinning of the cloud canopy amid upper 60s to low 70s boundary-layer dewpoints. This will remain coincident with an enlarged low-level hodograph in the northeast quadrant of weakening TC Hilary. Most 12Z HREF guidance struggles to maintain deep convection, but sustained low-topped convection could acquire updraft rotation and be capable of producing a brief tornado. This threat will end from south to north during the evening as low-level drying and decreasing hodograph curvature occurs within the southeast quadrant of the remnant TC. Relatively greater likelihood of deeper convective development is anticipated during the mid to late afternoon along the differential boundary-layer heating corridor from southeast AZ to southwest UT. This zone will be within the pronounced west to east gradient of high to low PW and consequently along the fringe of meager MLCAPE. At least isolated thunderstorms should form off the higher terrain and possess progressively weaker low-level SRH relative to the west/south. Some 12Z HREF members do depict a 2-5 km UH signal which makes sense given adequate shear within this layer. While mid-level rotation will be possible, isolated severe wind gusts should be the primary threat, particularly with any cells/small clusters that can propagate towards the more deeply mixed environment to the north-northeast. Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0232 PM CDT Sun Aug 20 2023 Valid 221200Z - 281200Z A large-scale upper-level anticyclone will meander across the central U.S. through much of the week before slowly drifting westward toward the Rockies by next weekend. Relatively rich deep-layer moisture pivoting around the upper anticyclone will promote overall cooler/moist conditions across much of the Pacific Northwest into the central Rockies. Meanwhile, hot and dry surface conditions will prevail beneath the upper anticyclone over the central and southern CONUS. The latest guidance consensus suggests that some overlap in dry/windy conditions may occur over eastern Colorado Day 3/Tuesday, with 40% Critical probabilities introduced. Thereafter, overall weaker surface winds are expected on a widespread basis across the southern High Plains into the Southeast, with more focused areas of relatively greater wildfire-spread potential confined locally. ..Squitieri.. 08/20/2023 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0157 PM CDT Sun Aug 20 2023 Valid 211200Z - 221200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF CENTRAL TEXAS... The previous forecast (see below) remains generally on track. The two main changes in this outlook were to add Elevated highlights to eastern Wyoming and expand the Elevated in Texas eastward to central Louisiana. In Wyoming, 15-25 mph sustained southwesterly surface winds should overlap with 15-20 percent RH during the late morning to late afternoon hours. Grass-based fuels in this area have been exposed to multiple days of relatively dry conditions and have not received appreciable rainfall for at least the last 1-2 weeks. These fuels have become at least marginally receptive to wildfire spread, necessitating the introduction of Elevated highlights. Meanwhile, prolonged dry conditions have materialized across portions of the mid-south, resulting in the curing of fuels in this region. Elevated highlights have been extended into Louisiana to account for the increasingly receptive fuels, RH dipping below 30 percent, and at least locally gusty conditions expected. ..Squitieri.. 08/20/2023 .PREV DISCUSSION... /ISSUED 0218 AM CDT Sun Aug 20 2023/ ...Synopsis... A midlevel anticyclone over the central Plains will shift slightly northeastward on Day 2/Monday, yielding a slight increase in deep-layer easterlies across much of TX. At the same time, a modest increase in the surface pressure gradient is expected along the northwestern periphery of a weather disturbance moving across the Gulf of Mexico. ...Central and north TX... An anomalously warm/dry air mass will remain in place across much of central and north TX -- where 100+ deg afternoon temperatures and around 20 percent RH are expected. Deep boundary-layer mixing into the enhanced easterly low/mid-level flow, coupled with the tightening pressure gradient, will support 15-20 mph sustained east-southeasterly surface winds and locally higher gusts. Given exceptionally dry fuels over the area (95th+ percentile ERCs), critical fire-weather conditions are expected. ...Central High Plains... Similar to Day 1/Sunday, efficient diurnal heating/mixing will yield 15-20 percent minimum RH. At the same time, 15-20 mph sustained southerly surface winds are expected owing to a tightening pressure gradient, with gusts upwards of 30 mph possible. This dry/breezy combination will favor another day of elevated to spotty critical fire-weather conditions. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Sat Aug 19 22:04:01 UTC 2023.

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0317 PM CDT Sat Aug 19 2023 Valid 211200Z - 271200Z An upper ridge will remain firmly in place across the central/southern CONUS through the upcoming week, promoting hot, dry, and occasionally breezy surface conditions across the central High Plains into Texas. Meanwhile, the remnants of Hilary will traverse the interior west, accompanied and preceded by a rich and deeply moist airmass/precipitation, both of which may prove detrimental to significant, widespread wildfire-spread potential. The best chance for Elevated-equivalent dry/windy surface conditions would be Day 3/Monday across the central High Plains and central Texas, where east-southeasterly winds amid a hot/mixed boundary layer will overspread receptive fuels. Thereafter, medium-range guidance differs on the placement and timing of overlapping favorable surface winds/RH across the south-central CONUS, precluding the addition of Critical probabilities. ..Squitieri.. 08/19/2023 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

MD 2016 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR SAN JOAQUIN VALLEY INTO THE WESTERN MOJAVE DESERT
Mesoscale Discussion 2016 NWS Storm Prediction Center Norman OK 0319 PM CDT Sat Aug 19 2023 Areas affected...San Joaquin Valley into the western Mojave Desert Concerning...Severe potential...Watch unlikely Valid 192019Z - 192245Z Probability of Watch Issuance...5 percent SUMMARY...Storms capable of isolated strong to severe gusts will be possible later this afternoon. DISCUSSION...Initially steep midlevel lapse rates and increasing moisture in advance of Hurricane Hilary will result in widely scattered thunderstorm development this afternoon across parts of the San Joaquin Valley and western Mojave desert region. Recent thunderstorm development has already been noted across northeast Kern County, with storm coverage expected to increase over lower elevation areas with time. With low-level flow/shear expected to remain weak through the afternoon, storms may quickly become outflow dominant. However, increasing mid/upper-level flow (as noted on the KSOX and KEYX VWPs) may support modestly organized and sustained convection, with one or more outflow-driven clusters possible by late afternoon. Strong to locally severe gusts will be possible as storms spread northward through the afternoon into early evening across the San Joaquin Valley. ..Dean/Grams.. 08/19/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...VEF...SGX...HNX...LOX...STO...MTR... LAT...LON 36291776 35181694 34881717 34731770 34651820 35151930 36312069 37072115 37732112 38072037 37501907 36291776 Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0241 PM CDT Sat Aug 19 2023 Valid 192000Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE SAN JOAQUIN VALLEY AND WESTERN MOJAVE DESERT... ...SUMMARY... Isolated severe wind gusts are possible over the San Joaquin Valley and western Mojave Desert vicinity the remainder of the afternoon into early evening. ...20z Update -- San Joaquin Valley/Western Mojave Desert... The previous outlook remains unchanged with the 20z update. Convection will increase in coverage over the next 2-3 hours, and sporadic severe thunderstorm gusts are possible into early evening. For more details, see previous outlook below and any forthcoming MCDs. ..Leitman.. 08/19/2023 .PREV DISCUSSION... /ISSUED 1114 AM CDT Sat Aug 19 2023/ ...San Joaquin Valley and western Mojave Desert... Hot temperatures will persist over the Central Valley this afternoon with abundant insolation underway northwest of the extensive cloud canopy downstream of Hurricane Hilary. Convective temperatures will be breached towards early afternoon over the higher terrain across parts of the Transverse Ranges and southern Sierra NV mountains. Isolated to eventually scattered thunderstorms will occur through the afternoon, spreading north-northwest amid south to southeast steering flow that notably strengthens with height in the upper portion of the buoyancy profile. Deeply mixed, inverted-v thermodynamic profiles beneath the moderate storm motions should support a threat for sporadic severe wind gusts before waning during the early evening. ...West... Elsewhere in the West, very localized severe wind gusts will be possible with several areas of scattered thunderstorms this afternoon. Spatial coverage of the severe wind threat appears likely to remain below the 5 percent threshold needed for an areal delineation. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0219 PM CDT Sat Aug 19 2023 Valid 201200Z - 211200Z The previous forecast (see below) remains on track, with no changes or additions made. ..Squitieri.. 08/19/2023 .PREV DISCUSSION... /ISSUED 0205 AM CDT Sat Aug 19 2023/ ...Synopsis... A broad midlevel anticyclone will remain centered over the central Plains on Day 2/Sunday, with enhanced midlevel flow along its southern and western peripheries. ...West and central TX... Similar to Day 1/Saturday, a continuation of above-average temperatures (100+ deg) and 15-20 percent RH is expected across parts of west and central TX during the afternoon. Boundary-layer mixing into the enhanced easterly flow aloft (along the southern periphery of the midlevel anticyclone) will yield 10-15 mph sustained east-southeasterly surface winds. These winds, coupled with the hot/dry conditions, will support elevated fire-weather conditions given critically dry fuels across the area. ...Central High Plains... Efficient diurnal heating/mixing in the presence of enhanced deep-layer southerly flow (along the western periphery of the midlevel anticyclone) will favor dry/breezy conditions over the central High Plains during the afternoon. 15-20 mph sustained southerly surface winds (with higher gusts) amid 15 percent RH could lead to elevated fire-weather conditions. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Fri Aug 18 22:14:01 UTC 2023.

No Mesoscale Discussions are in effect as of Fri Aug 18 22:14:01 UTC 2023.

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0256 PM CDT Fri Aug 18 2023 Valid 201200Z - 261200Z A large-scale upper ridge will dominate the central and southern U.S. through the forecast period. Through the early part of the upcoming week, the remnants of Hilary will track northward across portions of the Great Basin into the Pacific Northwest and northern Rockies, potentially accompanied by soaking rainfall and a plummet in fuel receptiveness to wildfire spread. To the west of the Cascades though, the eastward passage of Hilary may encourage dry, downslope easterly winds, where fuels are highly receptive to wildfire spread. Details of such a scenario are highly dependent on the placement and timing of Hilary remnants, hence no fire weather highlights have been introduced. However, several days of dry and windy conditions are possible across the central/southern High Plains into central Texas, where fuels have been steadily curing over the last couple of weeks. Multiple days of dry/windy conditions should prime fine fuels for some wildfire spread potential, especially Days 3-4/Sunday-Monday, where 40 percent Critical probabilities have been added. The probabilities were added across portions of Texas and the Central High Plains, where confidence is highest in the need for Elevated highlights by the Days 1-2 period. ..Squitieri.. 08/18/2023 ...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 0256 PM CDT Fri Aug 18 2023 Valid 182000Z - 191200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE DESERT SOUTHWEST...MONTANA...AND NEW ENGLAND... ...SUMMARY... Isolated strong to severe wind gusts are possible, mainly from late afternoon to mid-evening across parts of Montana, the Desert Southwest, and New England. ...20Z Update... The general thunderstorm area has been trimmed across New England, but no changes have been made to the Marginal Risk areas. Uncertainty remains regarding potential for substantial redevelopment of deep convection across New England, but isolated damaging gusts cannot be ruled out if any stronger storms can be sustained. Storms capable of producing localized severe gusts remain possible later this afternoon into this evening across parts of MT and the Southwest. See the previous discussion below for more information, and MCD 2013 regarding the near-term threat across Montana. ..Dean.. 08/18/2023 .PREV DISCUSSION... /ISSUED 1129 AM CDT Fri Aug 18 2023/ ...MT... Despite lingering mid-level clouds tempering insolation to some extent, surface temperatures should still heat into the 90s across eastern MT by late afternoon. Large-scale ascent attendant to a shortwave trough tracking east from southern BC to the lee of the Canadian Rockies should largely hold north of the international border. But low-level speed convergence should increase this evening along a trailing surface cold front and this may aid in sustaining isolated thunderstorms off the higher terrain of southwest MT. While MLCAPE should remain meager (at or below 500 J/kg), very deeply mixed profiles east of the terrain will support a threat for isolated severe wind gusts. ...Desert Southwest.... Weak deep-layer shear will be the primary limiting factor to a more organized severe wind threat, with mainly 15-25 kt 500-mb southerlies between a stout anticyclone over the southern Great Plains and a cutoff low off the southern CA coast. Scattered thunderstorms developing over the higher terrain, aided by a high PW air mass emanating north from the Gulf of CA, will pose a threat for sporadic severe wind gusts as they spread/collide northward within the deeply mixed environment across the lower deserts. ...New England... In the wake of this morning's tornadic supercell, low-level winds have substantially veered and weakened ahead of a north to south-oriented cold front pushing east into western New England. With a wedge of greater insolation between it and cloud cover associated with the early-day convection that is now largely off the coast, MLCAPE of 500-1000 J/kg should redevelop over the next few hours and support deepening convection along the front. While adequate deep-layer shear will remain, the increasingly poor low-level wind fields should mitigate an organized damaging wind threat. Still, a few strong gusts remain possible until the front reaches the coast. Read more