SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0130 AM CDT Sat Aug 24 2024 Valid 251200Z - 261200Z ...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. ..Karstens.. 08/24/2024 ...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 0129 AM CDT Sat Aug 24 2024 Valid 241200Z - 251200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF NORTHERN/CENTRAL WYOMING... ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF WESTERN UTAH INTO SOUTHEAST NEVADA... ...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. ..Karstens.. 08/24/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook CORR 1 NWS Storm Prediction Center Norman OK 0127 AM CDT Sat Aug 24 2024 Valid 241200Z - 251200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE FOUR CORNERS REGION INTO THE CENTRAL HIGH PLAINS...PARTS OF WESTERN MO...AND PARTS OF THE SOUTHERN PLAINS... CORRECTED FOR THUNDER LINES ...SUMMARY... Strong to locally severe storms are possible today from the Four Corners region northeastward into the central High Plains. Strong to severe storms are also possible across western Missouri and also across western Oklahoma. ...Synopsis... A deep mid/upper-level trough will remain in place over the West today. An embedded mid/upper cyclone is forecast to move southeastward from northern CA into the Great Basin. Downstream, an upper-level anticyclone will remain anchored over the southern Great Plains. One surface low is forecast to gradually deepen across the northern High Plains, while another weak surface low may develop across the south-central High Plains. ...Four Corners region into the central High Plains... The eastern fringe of stronger southwesterly flow aloft (associated with the deep upper trough) will overspread a plume of midlevel moisture from the Four Corners region into the central Rockies. Scattered thunderstorm development is expected across the region this afternoon. Effective shear of 30-40 kt and modest but sufficient buoyancy will support potential for a few loosely organized cells and/or clusters, with a threat of isolated strong to severe gusts. Richer low-level moisture and stronger instability will develop this afternoon across parts of the central High Plains, where moist easterly flow is maintained to the north of a nearly stationary surface boundary. With capping and weaker large-scale ascent expected, storm initiation within this more-unstable regime may be suppressed. However, high-based convection that develops over the higher terrain could spread into the central High Plains by early evening, potentially accompanied by an isolated strong to severe gusts and perhaps some hail. ...Western MO and vicinity... Most guidance suggests an increase in elevated convection near and after 12Z across parts of western MO, driven by low-level warm advection and moistening in the 850-700 mb layer. Effective shear will not be particularly strong, but relatively steep midlevel lapse rates and moderate elevated buoyancy will support potential for a few robust storms. Isolated hail cannot be ruled out with the strongest storms. Also, despite the elevated nature of the convection, initially rather dry profiles below the moist layer could support locally strong gusts. Depending on the coverage and intensity of morning convection, cold-pool development will be possible, which could lead to a southward-propagating cluster across western MO. This scenario remains quite uncertain, but there will be some potential for an isolated damaging-gust threat to spread into southwest MO from late morning into the afternoon. ...Parts of western OK into northwest TX... Despite generally weak large-scale ascent, some guidance suggests potential for isolated to widely scattered thunderstorm development within a very hot/well-mixed environment across parts of western OK into northwest TX late this afternoon into the early evening. With weak deep-layer shear and the influence of the upper ridge, storms will likely remain disorganized, and coverage of storms remains uncertain. However, any stronger storm within this environment would pose a conditional microburst threat. A 5% wind area has been added where relative confidence in storm development is currently greatest. ...Northeast MT into northwest ND... Moderate to locally strong instability may develop this afternoon from far northeast MT into northwest ND, with sufficient deep-layer shear to support storm organization. However, large-scale ascent is expected to remain rather weak across the region, and there is only a very weak signal for diurnal storm development. Some threat for severe hail and/or wind could accompany any robust storm within this regime, but confidence in storm coverage is too low for probabilities at this time. ..Dean/Karstens.. 08/24/2024 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0110 AM CDT Sat Aug 24 2024 Valid 251200Z - 261200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE EASTERN DAKOTAS INTO NORTHWESTERN MINNESOTA... ...SUMMARY... Scattered severe storms may develop across the northern Plains area on Sunday, with more isolated severe potential southwestward into the southern Rockies on Sunday. A couple of strong/marginally severe storms may also occur across the Lower Great Lakes/Upper Ohio Valley vicinity. ...Synopsis... A progressing western U.S. upper trough is forecast to gradually weaken, as it impinges on a persistent central U.S. ridge. The result will be that the trough gets shunted northeastward toward Montana/Wyoming with time. Meanwhile, weak upper troughing will persist over the Northeast. At the surface, a cold front will progress eastward across the Canadian Prairie, and the north-central U.S. with time. By the end of the period, the front should stretch from Minnesota southwestward to northeastern Colorado. ...Northern Plains southwestward to the Four Corners region... As the western U.S. trough advances eastward, large-scale ascent will support scattered thunderstorm development across the Intermountain Region, within a diurnally destabilizing airmass. While CAPE will remain limited, moderate southwesterly flow aloft ahead of the trough will allow some storm organization/longevity at time. This, combined with a deep mixed layer providing support for enhanced downdrafts with the stronger cells, will result in risk for locally severe wind gusts. More substantial severe risk could evolve across portions of the north-central states, where much greater instability will evolve. Though the airmass should remain capped in most areas, ascent may be sufficient to support local cap breaches by late afternoon to allow isolated storm development. If storms develop, upscale growth near convective outflows would be expected, possibly resulting in evening/overnight MCS development. Large hail would be possible with the initial storms, though with locally damaging gusts likely to be the dominant risk. Still, given the capping that is anticipated, and questions whether ascent will be sufficient to allow storm development, will maintain only conditional 15%/SLGT risk at this time. ...Lower Great Lakes/Upper Ohio Valley area... On the western fringe of the northeastern U.S. trough, moderate northwesterly flow aloft may combine with modest afternoon destabilization to support isolated storm development. Assuming this occurs, a few strong gusts would be possible as storms would move rather quickly southeastward. The main question remains the degree of destabilization which may occur, and thus will introduce only 5%/MRGL risk at this time. ..Goss.. 08/24/2024 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0800 PM CDT Fri Aug 23 2024 Valid 240100Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR A SMALL PART OF NORTHWEST/NORTH-CENTRAL MT... ...SUMMARY... A threat for severe gusts will continue across parts of Montana through mid evening. Other strong to severe storms remain possible across eastern Utah and western Colorado, and also across the central High Plains. ...Montana... Scattered thunderstorms with a history of producing measured severe gusts are quickly moving northward across northwest MT early this evening, and will soon move across the international border. Farther east, a storm cluster across central MT may continue to pose a threat of severe gusts as it moves through a relatively warm and well-mixed environment. A separate cluster of storms across northeast MT may continue to pose a short-term threat of isolated hail and severe gusts, before increasing MLCINH reduces convective potential later tonight. ...Central High Plains into western MO... A small outflow-driven cluster of storms is moving across parts of the central High Plains early this evening. A short-term threat for isolated severe gusts and hail may spread eastward through mid evening, as the cluster moves through a moderately unstable and marginally sheared environment. Increasing MLCINH with time may eventually result in a weakening trend, though stronger elevated convection may persist through the night as the remnant cluster moves eastward. Some increase in elevated storms will also be possible near the end of the period across western MO, within a low-level warm-advection regime. Moderate MUCAPE could support a few stronger storms with small hail and gusty winds, but severe potential prior to 12Z within this regime appears relatively limited. ...Eastern UT into western CO... A couple stronger storms may persist through at least part of the evening from eastern UT into western CO, where MLCAPE in excess of 500 J/kg and favorable deep-layer shear may support transient supercell structures capable of isolated hail and strong/severe gusts. ..Dean.. 08/24/2024 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0800 PM CDT Fri Aug 23 2024 Valid 240100Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR A SMALL PART OF NORTHWEST/NORTH-CENTRAL MT... ...SUMMARY... A threat for severe gusts will continue across parts of Montana through mid evening. Other strong to severe storms remain possible across eastern Utah and western Colorado, and also across the central High Plains. ...Montana... Scattered thunderstorms with a history of producing measured severe gusts are quickly moving northward across northwest MT early this evening, and will soon move across the international border. Farther east, a storm cluster across central MT may continue to pose a threat of severe gusts as it moves through a relatively warm and well-mixed environment. A separate cluster of storms across northeast MT may continue to pose a short-term threat of isolated hail and severe gusts, before increasing MLCINH reduces convective potential later tonight. ...Central High Plains into western MO... A small outflow-driven cluster of storms is moving across parts of the central High Plains early this evening. A short-term threat for isolated severe gusts and hail may spread eastward through mid evening, as the cluster moves through a moderately unstable and marginally sheared environment. Increasing MLCINH with time may eventually result in a weakening trend, though stronger elevated convection may persist through the night as the remnant cluster moves eastward. Some increase in elevated storms will also be possible near the end of the period across western MO, within a low-level warm-advection regime. Moderate MUCAPE could support a few stronger storms with small hail and gusty winds, but severe potential prior to 12Z within this regime appears relatively limited. ...Eastern UT into western CO... A couple stronger storms may persist through at least part of the evening from eastern UT into western CO, where MLCAPE in excess of 500 J/kg and favorable deep-layer shear may support transient supercell structures capable of isolated hail and strong/severe gusts. ..Dean.. 08/24/2024 Read more

WW 0645 Status Updates
STATUS REPORT ON WW 645 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 15 NNW LVM TO 25 SSW GTF TO 45 SSW CTB TO 40 SE GPI TO 35 SSW GPI. ..SPC..08/24/24 ATTN...WFO...TFX...MSO... STATUS REPORT FOR WS 645 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS MTC005-013-015-027-029-035-041-045-051-053-059-073-099-101- 240140- MT . MONTANA COUNTIES INCLUDED ARE BLAINE CASCADE CHOUTEAU FERGUS FLATHEAD GLACIER HILL JUDITH BASIN LIBERTY LINCOLN MEAGHER PONDERA TETON TOOLE THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES. Read more

WW 645 SEVERE TSTM MT 232055Z - 240300Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 645 NWS Storm Prediction Center Norman OK 255 PM MDT Fri Aug 23 2024 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Western and Central Montana * Effective this Friday afternoon and evening from 255 PM until 900 PM MDT. * Primary threats include... Isolated significant damaging wind gusts to 75 mph possible SUMMARY...Scattered thunderstorms will continue to develop and move north-northeastward across the region through early evening, with severe-caliber wind gusts a possibility. The severe thunderstorm watch area is approximately along and 95 statute miles east and west of a line from 25 miles north of Cut Bank MT to 40 miles south of Dillon MT. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU5). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && AVIATION...A few severe thunderstorms with hail surface and aloft to 1 inch. Extreme turbulence and surface wind gusts to 65 knots. A few cumulonimbi with maximum tops to 450. Mean storm motion vector 20030. ...Guyer Read more

MD 1978 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PORTIONS OF WESTERN AND CENTRAL MONTANA
Mesoscale Discussion 1978 NWS Storm Prediction Center Norman OK 0313 PM CDT Fri Aug 23 2024 Areas affected...portions of western and central Montana Concerning...Severe potential...Watch possible Valid 232013Z - 232215Z Probability of Watch Issuance...60 percent SUMMARY...Thunderstorms will increase in coverage and intensity over the next few hours across western and central Montana. Isolated damaging gust of 55-70 mph are possible, along with a few instances of hail to near one inch diameter. DISCUSSION...Gradual destabilization is occurring over the MCD area as temperatures have warmed into the 80s F this afternoon. Boundary-layer moisture will remain meager, but steep midlevel lapse rates/cool temperatures aloft will support MLCAPE increasing to around 500-1000 J/kg through early evening. Deepening cumulus is noted over the mountains and thunderstorms are expected to increase in coverage over the next couple of hours as stronger ascent overspreads the region. Favorable vertical shear will support organized updrafts/clusters, while dry low-levels and very steep low-level lapse rates support strong/severe gusts. Elongated/straight hodographs in conjunction with favorable midlevel instability/shear will also support isolated marginally severe hail with more intense/longer-lived updrafts. While some MLCIN remains over the region, additional heating and increasing ascent should gradually erode inhibition, but overall poor vertical moisture profiles will limit instability. Nevertheless, a severe thunderstorm watch may become necessary, especially if convection across southwest MT/eastern ID sufficiently organizes into forward propagating clusters with time as this activity shifts north/northeast. ..Leitman/Guyer.. 08/23/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BYZ...TFX...MSO... LAT...LON 47561510 48721479 48931407 49031285 48991101 48061016 47261004 46551016 46311028 45981076 45781140 45591292 45911393 46921475 47561510 Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0500 PM CDT Fri Aug 23 2024 Valid 251200Z - 311200Z A large-scale trough will advance eastward across the northern Rockies on Day 3/Sunday. Preceding the trough, moderate deep-layer southwesterly flow will overspread a deep/dry boundary layer across WY -- favoring dry and breezy conditions. Given modestly receptive fuels, elevated to locally critical conditions are expected. Additionally, a mix of wet/dry thunderstorms, aided by ascent accompanying the trough, will develop across portions of the northern Rockies on Day 3/Sunday. While this will pose some risk for lightning-induced fire-starts, the threat appears too localized/marginal for Isolated Dry Thunderstorm probabilities at this time. Thereafter, surface high pressure will build across the West, in the wake of the aforementioned large-scale trough. This will temporarily reduce surface winds and fire-weather concerns across much of the West. On Day 5/Tuesday, a midlevel trough/low and related strong westerly flow will cross the Pacific Northwest. This will promote dry/breezy conditions across portions of the Northwest into the northern Rockies. However, considerable disagreement among the medium-range guidance regarding the strength of surface winds casts uncertainty on the overall threat -- precluding Critical probabilities at this time. These dry/breezy conditions should spread eastward across the northern Rockies on Day 6/Wednesday, with similar uncertainty regarding the development of critical conditions. ..Weinman.. 08/23/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0500 PM CDT Fri Aug 23 2024 Valid 251200Z - 311200Z A large-scale trough will advance eastward across the northern Rockies on Day 3/Sunday. Preceding the trough, moderate deep-layer southwesterly flow will overspread a deep/dry boundary layer across WY -- favoring dry and breezy conditions. Given modestly receptive fuels, elevated to locally critical conditions are expected. Additionally, a mix of wet/dry thunderstorms, aided by ascent accompanying the trough, will develop across portions of the northern Rockies on Day 3/Sunday. While this will pose some risk for lightning-induced fire-starts, the threat appears too localized/marginal for Isolated Dry Thunderstorm probabilities at this time. Thereafter, surface high pressure will build across the West, in the wake of the aforementioned large-scale trough. This will temporarily reduce surface winds and fire-weather concerns across much of the West. On Day 5/Tuesday, a midlevel trough/low and related strong westerly flow will cross the Pacific Northwest. This will promote dry/breezy conditions across portions of the Northwest into the northern Rockies. However, considerable disagreement among the medium-range guidance regarding the strength of surface winds casts uncertainty on the overall threat -- precluding Critical probabilities at this time. These dry/breezy conditions should spread eastward across the northern Rockies on Day 6/Wednesday, with similar uncertainty regarding the development of critical conditions. ..Weinman.. 08/23/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

MD 1979 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF SOUTHERN/EASTERN UTAH INTO FAR WESTERN COLORADO
Mesoscale Discussion 1979 NWS Storm Prediction Center Norman OK 0353 PM CDT Fri Aug 23 2024 Areas affected...Portions of southern/eastern Utah into far western Colorado Concerning...Severe potential...Watch unlikely Valid 232053Z - 232300Z Probability of Watch Issuance...20 percent SUMMARY...Scattered storms, some capable of severe winds and large hail, will occur this afternoon. A watch is not currently anticipated. DISCUSSION...Early cloud cover within the Colorado Plateau has kept temperatures in the mid/upper 70s F thus far. Even so, colder air aloft has promoted around 1000 J/kg MLCAPE in southeastern Utah. Convection has shown signs of deepening on MRMS CAPPI imagery. Some further intensification of this activity is possible as temperatures will still rise this afternoon. Moderate mid-level flow on the eastern flank of the upper low will foster 45-50 kts of effective shear and at least marginal supercell structures. Storms will be capable of severe wind gusts and possibly large hail. ..Wendt/Guyer.. 08/23/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...GJT...FGZ...SLC... LAT...LON 37461224 38391155 39331063 39590951 39220889 38200878 37400900 36991014 36741130 36771203 36981233 37461224 Read more

WW 0645 Status Updates
STATUS FOR WATCH 0645 HAS NOT BEEN ISSUED YET Read more

WW 645 SEVERE TSTM MT 232055Z - 240300Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 645 NWS Storm Prediction Center Norman OK 255 PM MDT Fri Aug 23 2024 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Western and Central Montana * Effective this Friday afternoon and evening from 255 PM until 900 PM MDT. * Primary threats include... Isolated significant damaging wind gusts to 75 mph possible SUMMARY...Scattered thunderstorms will continue to develop and move north-northeastward across the region through early evening, with severe-caliber wind gusts a possibility. The severe thunderstorm watch area is approximately along and 95 statute miles east and west of a line from 25 miles north of Cut Bank MT to 40 miles south of Dillon MT. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU5). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && AVIATION...A few severe thunderstorms with hail surface and aloft to 1 inch. Extreme turbulence and surface wind gusts to 65 knots. A few cumulonimbi with maximum tops to 450. Mean storm motion vector 20030. ...Guyer Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0300 PM CDT Fri Aug 23 2024 Valid 241200Z - 251200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF NORTHERN/CENTRAL WYOMING... ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF WESTERN UTAH INTO SOUTHEAST NEVADA... The primary change with this update was the addition of a Critical area over portions of western UT into southeast NV. Here, A tightening pressure gradient, and deep boundary-layer mixing into strong southwesterly flow aloft, will support 25-35 mph sustained southwesterly surface winds and single-digit RH. While fuels appear modestly receptive over the area, the strong/gusty winds will still support the potential for large-fire spread. For additional details, see the previous discussion below. ..Weinman.. 08/23/2024 .PREV DISCUSSION... /ISSUED 0148 AM CDT Fri Aug 23 2024/ ...Synopsis... A mid-level trough over the Pacific Northwest will shift east and allow a belt of enhanced mid-level flow to overspread parts of the eastern Great Basin and the Northern Rockies. Afternoon heating/mixing will allow for sustained winds of 20-25 mph across the region while RH values fall into the upper teens and low 20s F. Fuels across portions far eastern Great Basin appear marginally receptive, and Elevated highlights have been maintained for this region, whereas fuels across parts of Wyoming appear more receptive where a Critical delineation has been added. In addition, potential for isolated dry thunderstorms has been introduced for the northern Great Basin in association with forcing from the advancing trough. Fuels in this region remain receptive to large-fire spread amid PWAT values that are projected to remain below 0.75 inches. ...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 0246 PM CDT Fri Aug 23 2024 Valid 232000Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF WESTERN MONTANA... ...SUMMARY... Strong to severe storms with severe wind gusts and some hail are possible across Montana, the Intermountain West and central Rockies, southeast Arizona to extreme southwestern New Mexico, and parts of the High Plains. ...20z Update... The primary adjustment for this update was an expansion of the Slight risk/15% wind probability southward to include more of western MT. Slowly intensifying convection across eastern ID is expected to remain relatively benign for the near-term (see MCD #1976 for additional details regarding short-term trends), but may pose a more robust severe wind threat later this afternoon/evening as convection spreads north into a deeply mixed environment across western MT. The last several HRRR solutions have captured recent convective and environmental trends well and consistently suggest the best potential for severe wind will be associated with this activity as it spreads north. The adjustment to the Slight risk area should better reflect this potential. Elsewhere, the forecast remains on track per the previous discussion (below). See MCD #1977 for the latest details regarding the severe threat across southern Arizona. ..Moore.. 08/23/2024 .PREV DISCUSSION... /ISSUED 1127 AM CDT Fri Aug 23 2024/ ...Intermountain West to northern Rockies... The lead portion of an upper trough centered along the coastal Pacific Northwest will shift north-northeastward over the northern Intermountain region in tandem with the exit region of a strengthening mid/upper-level jet. Scattered thunderstorms are expected in this regime preceding the Pacific Coast trough, with initial development over the higher terrain ahead of the surface cold front. Isolated severe gusts and marginally severe hail will be possible, with the potential for a more focused corridor of stronger wind gusts across northwest/north-central Montana late this afternoon through early evening. Additional thunderstorms should form this afternoon across east/northeast Oregon, northern/eastern Idaho, to western Wyoming, and southeastward into Utah/western Colorado, as eastern fringes of large-scale ascent preceding the Pacific Northwest trough and embedded shortwaves overlie destabilizing, elevated terrain. Throughout the corridor, sufficient deep-layer shear (30-45 kt) should exist for organized multicells and small bowing/outflow-driven clusters, and perhaps a few supercells, with some hail and severe-caliber wind gusts possible. ...High Plains... Isolated to widely scattered thunderstorms are expected to form over the central/northern Rockies, as well as near the lee trough over eastern Montana this afternoon, with another favored corridor across the central High Plains including northeast Colorado/western Nebraska. Activity should move east-northeastward across the adjoining High Plains. This convection will encounter a diurnally destabilizing, well-mixed boundary layer with steep low-level lapse rates, supporting isolated severe wind gusts. Isolated large hail also will be possible. Strongly difluent mid/upper-level flow will exist over most of this corridor, between the Pacific Northwest cyclone and the southern Plains anticyclone, with speeds generally increasing northwestward and low-level moisture greater southward across the central High Plains. Still, sufficient moisture should persist near the Montana lee trough, along with enough veering with height over the entire area to yield enough deep shear (30+ kt effective-shear magnitudes) for organized convection. ...Southeast Arizona/far southwest New Mexico... Widely scattered to scattered thunderstorms are expected to develop this afternoon with a relatively moist air mass and ample insolation. Increasing mid-level southerlies around the western rim of the anticyclone should enable 20-30 kt effective-shear magnitudes, and enough northward storm motion to augment already strong downbursts from the most intense cells locally. An instance or two of marginally severe hail could also occur. Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0231 PM CDT Fri Aug 23 2024 Valid 251200Z - 261200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE NORTHERN PLAINS... ...SUMMARY... Scattered severe storms appear likely across the northern Plains area on Sunday, with weaker and more isolated severe potential southwestward into the southern Rockies on Sunday. ...Northern Plains... An upper trough will generally weaken as it moves from the Intermountain Region during the day and into the northern Plains through Monday morning. As the parent upper low moves from ID across MT, it will fill, with steadily decreasing flow aloft into the Plains. Despite this, sufficient shear and lift will materialize to support a severe risk centered over the northern Plains. Effective deep-layer shear on the order of 35-40 kt is forecast east of the cold front, which will exist over the central Dakotas. Heating and a moist air mass will yield 3500+ J/kg MUCAPE, and as such, severe storms are likely to develop along the cold front during the late afternoon. Overall shear looks to be marginal for supercells, given the lack of an appreciable low-level jet. However, veering winds with height may yield transient supercell structures capable of large hail. Clustering or even an MCS may develop with time as storms increase in coverage, with hodographs supporting east/southeast motion. ...Central Rockies/Plains... Modest instability and moisture will extend southwestward along the front and beneath the periphery of the stronger mid/high level winds, from western NE into CO and northern NM. Given both marginal instability and shear, only localized severe gusts are expected. Storms timed during the peak heating hours will likely have a greater risk of strong winds where the boundary layer is deeply mixed. Small hail cannot be ruled out with the strongest cells over the higher terrain of NM/CO. ..Jewell.. 08/23/2024 Read more

MD 1976 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF CENTRAL/EASTERN ID...NORTHWEST WY...AND SOUTHWEST MT
Mesoscale Discussion 1976 NWS Storm Prediction Center Norman OK 0131 PM CDT Fri Aug 23 2024 Areas affected...portions of central/eastern ID...northwest WY...and southwest MT Concerning...Severe potential...Watch unlikely Valid 231831Z - 232030Z Probability of Watch Issuance...20 percent SUMMARY...Isolated strong to severe thunderstorms are possible through the afternoon across parts of central/eastern Idaho, northwest Wyoming, and southwest Montana. Locally strong gusts of 50-65 mph and hail to near 1 inch diameter may occur with strongest cells. DISCUSSION...Temperatures have quickly warmed into the mid 70s to mid 80s F across the region. Steep midlevel lapse rates/cool temperatures aloft are aiding in weak destabilization early this afternoon. As a result scattered convection has already developed over higher terrain. This activity should gradually increase/strengthen with time as additional destabilization occurs through the afternoon within a moderately sheared environment. Boundary-layer moisture will remain modest, but very steep low-level lapse rates and inverted-v sub-cloud thermodynamic profiles will support strong outflow winds. Regional VWP data and forecast soundings show elongated/straight hodographs. Coupled with cool midlevel temps and favorable vertical shear, this could support marginally severe hail from stronger/longer-lived updrafts. The somewhat moisture-starved environment should limit a greater/more widespread severe risk, and a watch is not currently expected for the MCD area. ..Leitman/Guyer.. 08/23/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BYZ...RIW...TFX...SLC...PIH...MSO...BOI... LAT...LON 46091515 46141312 45981081 45820966 45330912 44920906 44340897 42950936 42511022 42011118 41961231 42161328 44581520 45571565 46091515 Read more

No watches are valid as of Fri Aug 23 18:34:02 UTC 2024.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1224 PM CDT Fri Aug 23 2024 Valid 241200Z - 251200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE FOUR CORNERS REGION INTO THE CENTRAL HIGH PLAINS...AND OVER MAINLY WESTERN MISSOURI... ...SUMMARY... Marginally severe storms will be possible on Saturday across the Four Corners region eastward across the central High Plains. A small area of wind or small hail potential may also develop early over parts of western Missouri. ...Synopsis... On Saturday, a large upper trough will affect much of the West, with the primary vorticity max moving across the Great Basin. Southwest 500 mb winds in excess of 50 kt will overspread much of that area, extending into northern Rockies Meanwhile, an upper high will hold from the central and southern Plains to the mid MS Valley through Sunday morning. At the surface, a cold front will roughly stretch from central MT into central NV during the late afternoon, pushing east into the western Dakotas and southeast across UT and southern NV into Sunday morning. The better moisture and instability will be shunted east across far eastern UT and into CO, as low-level drying occurs over AZ and UT with persistent southwesterly winds. Farther east into the Plains, a plume of mid to upper 60s F dewpoints will develop northward across the MO Valley and toward the upper MS Valley late, aided by a heating/deepening boundary layer and around 30 kt southerly winds at 850 mb. This will also result an unstable air mass, with early-day thunderstorms expected over western MO and toward the mid MO Valley. ...Four Corners to the central High Plains... A fetch of midlevel moisture will remain over the area, which is also on the eastern fringe of the stronger flow aloft. Deep-layer effective shear will average 35-40 kt, a will conditionally favor scattered fast-moving cells. Storms are likely to form my early afternoon over far eastern UT into western CO, and extending southward across western NM. Sufficient shear and instability will favor marginal hail with the strongest cells, while favorable diurnal timing will and steep low-level lapse rates will be conducive for strong wind gusts. ...Parts of central and western MO early... Models are in good agreement with the development of a robust cluster of storms in the early-day warm advection regime centered over western MO. Given weak northwest flow aloft and a moistening low-level air mass, it is conceivable that any large cluster of storms could potentially forward-propagate southward across much of western MO. As such, low severe probabilities have been added. Shear will remain weak, but moderate instability may allow for very brief hail. ..Jewell.. 08/23/2024 Read more