SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1242 AM CDT Thu Aug 22 2024 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE CENTRAL HIGH PLAINS...EASTERN DAKOTAS INTO WESTERN MINNESOTA...NORTHERN ARIZONA INTO PARTS OF UTAH AND EXTREME EASTERN NEVADA... ...SUMMARY... Strong to severe storms capable of hail and localized severe gusts will be possible across the central High Plains this afternoon and evening. Isolated strong to severe storms will also be possible from the eastern Dakotas into Minnesota, and also from northern Arizona into parts of Utah. ...Synopsis... A mid/upper-level trough is forecast to amplify over the West later today, as an embedded midlevel cyclone moves slowly southward off of the Pacific Northwest coast. Downstream of this trough, a midlevel shortwave and related surface low are forecast to move east-northeast across parts of SK/MB, with a trailing cold front moving into parts of the northern Great Plains. Other low-amplitude shortwaves along the eastern periphery of the amplifying mid/upper-level trough may move across parts of the central Rockies/High Plains. ...Central High Plains... Low-level southeasterly flow is expected to persist across parts of the central High Plains today, to the north of a weak surface low over the TX/OK Panhandle region. This will maintain sufficient low-level moisture to support moderate destabilization by late afternoon, in conjunction with diurnal heating. Initially high-based convection that develops near the Front Range may intensify by late afternoon into early evening, as it moves eastward into increasingly favorable instability. While deep-layer flow will remain rather modest, southeasterly low-level flow veering to southwesterly aloft will support effective shear of 30-40 kt, sufficient for somewhat organized convection. Localized severe gusts may be the most prominent hazard, as storms and their related outflows increase in coverage by late afternoon into the evening. Isolated hail will also be possible, especially with any storm that can persist near the stronger instability axis from far eastern CO into western KS/NE. Higher severe probabilities may eventually be needed for parts of the region, if confidence increases in a focused corridor of greater severe potential. ...Eastern Dakotas into Minnesota... Early-day convection and possibly a remnant MCS are expected to move across eastern ND into northwest MN later this morning. Moderate MUCAPE could support an isolated severe threat with the morning storms as they move eastward. Later in the day, moderate destabilization will be possible along/ahead of the weakening cold front, and potentially near any remnant outflow boundaries. With the primary shortwave trough and any MCV related to morning convection expected to move away from the region through the day, coverage of storm redevelopment during the afternoon could be relatively limited. However, deep-layer shear will remain sufficient for some storm organization, and isolated hail/damaging wind could accompany any stronger redevelopment. ...Parts of northern Arizona into Utah... A relatively favorable environment for organized convection may evolve this afternoon from northwest/north-central AZ into UT, where increasing mid/upper-level flow related to the amplifying trough will overlap the western periphery of monsoonal moisture. However, guidance varies regarding the magnitude of heating and destabilization, with potential for relatively early storm development. Effective shear of 30-40 kt may support a few organized cells/clusters through the day, and isolated hail and/or severe gusts will be possible with the strongest storms. ...South-central Texas... High-based convection appears possible across parts of south-central TX this afternoon, in response to strong heating/mixing in the vicinity of a weak surface trough/dryline. Large-scale ascent and deep-layer flow/shear are both expected to remain weak, so any storms will likely remain disorganized, but inverted-v profiles may support isolated downburst winds late this afternoon into the early evening. ..Dean/Squitieri.. 08/22/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1156 PM CDT Wed Aug 21 2024 Valid 231200Z - 241200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF EASTERN NEVADA INTO WESTERN UTAH AND SOUTHERN IDAHO... ...Synopsis... A deepening mid-level trough will progress across the Interior West as upper ridging continues across the Plains to the Eastern Seaboard tomorrow (Friday). Strong mid-level flow aloft and associated upper support, amid a deep, dry boundary layer, will foster Elevated to Critical conditions across the Great Basin, with sustained southwesterly surface winds approaching 25 mph in spots, and RH dipping into the 15-20 percent range. Furthermore, upper support amid adequate buoyancy will promote the development of both wet and dry thunderstorms across portions of the Pacific Northwest (mainly central into eastern Oregon). Given receptive fuels in the area, isolated dry thunderstorm highlights have been added. ..Squitieri.. 08/22/2024 ...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 1148 PM CDT Wed Aug 21 2024 Valid 221200Z - 231200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF CENTRAL INTO EASTERN NEVADA... ...Synopsis... A mid-level trough will amplify across the Interior West as an upper ridge persists across the central U.S. today. Strong mid-level flow from the upper trough, overspreading a deepening boundary layer over the Great Basin, will support dry and windy conditions through the afternoon. 15-20 mph sustained southwesterly surface winds, overlapping with 15-20 percent RH and fuels receptive to fire spread, will result in widespread Elevated conditions for several hours. However, portions of central Nevada may also experience higher sustained southerly surface winds (i.e. over 25 mph), warranting Critical highlights. ..Squitieri.. 08/22/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

MD 1972 CONCERNING SEVERE THUNDERSTORM WATCH 643... FOR EASTERN MONTANA/WESTERN NORTH DAKOTA
Mesoscale Discussion 1972 NWS Storm Prediction Center Norman OK 1113 PM CDT Wed Aug 21 2024 Areas affected...eastern Montana/western North Dakota Concerning...Severe Thunderstorm Watch 643... Valid 220413Z - 220545Z The severe weather threat for Severe Thunderstorm Watch 643 continues. SUMMARY...Severe threat continues to gradually diminish across eastern Montana/WW 643. DISCUSSION...Over the last couple of hours, a noted/gradual decrease in convective coverage -- and particularly intensity -- has occurred, as the low-level airmass gradually stabilizes. While convection will likely linger over the next couple of hours, including a stronger storm or two at times capable of producing marginally severe hail and/or wind, new WW issuance is not anticipated. As storms move eastward into North Dakota with time, WW 643 will likely be able to be cancelled prior to its scheduled 22/07Z expiration. ..Goss.. 08/22/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BIS...UNR...BYZ...GGW... LAT...LON 49000430 48990278 47380222 46400279 45890399 46060468 48000518 49000430 Read more

MD 1970 CONCERNING SEVERE THUNDERSTORM WATCH 642... FOR EASTERN MONTANA...WESTERN NORTH DAKOTA...NORTHEASTERN WYOMING...AND PARTS OF WESTERN SOUTH DAKOTA
Mesoscale Discussion 1970 NWS Storm Prediction Center Norman OK 0616 PM CDT Wed Aug 21 2024 Areas affected...eastern Montana...western North Dakota...northeastern Wyoming...and parts of western South Dakota Concerning...Severe Thunderstorm Watch 642... Valid 212316Z - 220115Z The severe weather threat for Severe Thunderstorm Watch 642 continues. SUMMARY...Isolated severe risk -- ongoing in/near WW 642 -- is forecast to expand across northeastern Montana over the next couple of hours. DISCUSSION...Latest radar/satellite loops show isolated convection -- rather slow to initiate thus far -- increasing across portions of the northeastern Wyoming vicinity. While a couple of strong/severe storms persist east of the Black Hills, the aforementioned convection increasing over northeastern Wyoming should continue to increase, and spread into WW 642 with time. Meanwhile, a minor increase in convection over the past half hour is noted over portions of eastern Montana, in the wake of prior storms which have moved across the border into Saskatchewan. Recent HRRR runs continue to show robust convective development across eastern Montana, as a mid-level short-wave trough now over southern Alberta and western Montana advances slowly east-northeastward. With a favorably unstable airmass in place (mixed-layer CAPE in the 2000 to 3000 J/kg range across east-central and northeastern Montana and into western North Dakota), and moderately strong/increasing flow with height that should strengthen with time with the approach of the mid-level system, the environment within and north/northeast of WW 642 suggests severe potential will persist well into this evening. New WW issuance into portions of northeastern Montana and possibly western North Dakota, currently not included within WW 642, will likely be required within the next 1 to 2 hours. ..Goss.. 08/21/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...ABR...BIS...UNR...BYZ...GGW...TFX... LAT...LON 48970877 48970458 48350405 45170149 43580099 44290392 45570612 47130877 48970877 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0759 PM CDT Wed Aug 21 2024 Valid 220100Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN HIGH PLAINS... ...SUMMARY... Severe storms capable of producing large hail and damaging gusts remain possible this evening into tonight over parts of eastern Montana and the western Dakotas. ...Montana into the western Dakotas... A seasonably strong mid/upper-level shortwave trough is moving across parts of southern AB and western MT this evening. In advance of this system, multiple clusters of strong to severe storms are ongoing across parts of central/eastern MT into western SD. Moderate to strong buoyancy (with MLCAPE of 1500-3000 J/kg) and favorable effective shear (generally in excess of 40 kt) will continue to support severe-thunderstorm potential through the evening as the shortwave trough moves eastward. A general weakening trend is expected overnight as storms encounter increasing MLCINH, but some severe threat is expected to spread across a larger portion of eastern MT into western ND later this evening, including some potential for upscale growth and an increasing severe-wind threat. See MCD 1970 for more information. ...Central High Plains... Strong storms are ongoing this evening across the NE Panhandle into extreme southeast WY, with weaker convection across much of CO. Moderate to strong buoyancy and sufficient deep-layer shear will remain favorable for organized convection across parts of the central High Plains for much of the evening. Some modest upscale growth is possible with time from western NE into northeast CO and western KS, in conjunction with a nocturnally increasing low-level jet. As a result, a threat for localized severe gusts and hail may spread eastward through the evening, before increasing MLCINH results in a weakening trend overnight. ...Southeast AZ... Storms that developed this afternoon across parts of southeast AZ have occasionally exhibited severe-hail and wind potential. A general weakening trend is expected as initially moderate buoyancy diminishes with time, but a short-term threat for a few stronger storms may persist through early evening. ..Dean.. 08/22/2024 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0759 PM CDT Wed Aug 21 2024 Valid 220100Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN HIGH PLAINS... ...SUMMARY... Severe storms capable of producing large hail and damaging gusts remain possible this evening into tonight over parts of eastern Montana and the western Dakotas. ...Montana into the western Dakotas... A seasonably strong mid/upper-level shortwave trough is moving across parts of southern AB and western MT this evening. In advance of this system, multiple clusters of strong to severe storms are ongoing across parts of central/eastern MT into western SD. Moderate to strong buoyancy (with MLCAPE of 1500-3000 J/kg) and favorable effective shear (generally in excess of 40 kt) will continue to support severe-thunderstorm potential through the evening as the shortwave trough moves eastward. A general weakening trend is expected overnight as storms encounter increasing MLCINH, but some severe threat is expected to spread across a larger portion of eastern MT into western ND later this evening, including some potential for upscale growth and an increasing severe-wind threat. See MCD 1970 for more information. ...Central High Plains... Strong storms are ongoing this evening across the NE Panhandle into extreme southeast WY, with weaker convection across much of CO. Moderate to strong buoyancy and sufficient deep-layer shear will remain favorable for organized convection across parts of the central High Plains for much of the evening. Some modest upscale growth is possible with time from western NE into northeast CO and western KS, in conjunction with a nocturnally increasing low-level jet. As a result, a threat for localized severe gusts and hail may spread eastward through the evening, before increasing MLCINH results in a weakening trend overnight. ...Southeast AZ... Storms that developed this afternoon across parts of southeast AZ have occasionally exhibited severe-hail and wind potential. A general weakening trend is expected as initially moderate buoyancy diminishes with time, but a short-term threat for a few stronger storms may persist through early evening. ..Dean.. 08/22/2024 Read more

WW 0642 Status Updates
STATUS REPORT ON WW 642 THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA. ..GOSS..08/22/24 ATTN...WFO...BYZ...UNR... STATUS REPORT FOR WS 642 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS MTC011-017-025-065-075-087-103-220140- MT . MONTANA COUNTIES INCLUDED ARE CARTER CUSTER FALLON MUSSELSHELL POWDER RIVER ROSEBUD TREASURE SDC007-019-033-047-055-063-071-081-093-095-102-103-105-121-137- 220140- SD . SOUTH DAKOTA COUNTIES INCLUDED ARE BENNETT BUTTE CUSTER FALL RIVER HAAKON HARDING JACKSON LAWRENCE MEADE MELLETTE OGLALA LAKOTA PENNINGTON PERKINS TODD ZIEBACH 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 Read more

WW 642 SEVERE TSTM MT SD 212100Z - 220400Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 642 NWS Storm Prediction Center Norman OK 400 PM CDT Wed Aug 21 2024 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Southeast Montana Western South Dakota * Effective this Wednesday afternoon and evening from 400 PM until 1100 PM CDT. * Primary threats include... Scattered damaging wind gusts to 70 mph likely Scattered large hail and isolated very large hail events to 2 inches in diameter possible SUMMARY...Thunderstorms will develop across southeast Montana and western South Dakota through the afternoon and evening. The strongest cells may produce damaging winds and large hail. The severe thunderstorm watch area is approximately along and 55 statute miles north and south of a line from 145 miles west northwest of Broadus MT to 25 miles north northeast of Philip SD. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU2). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && AVIATION...A few severe thunderstorms with hail surface and aloft to 2 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 25030. ...Hart Read more

WW 0643 Status Updates
STATUS FOR WATCH 0643 HAS NOT BEEN ISSUED YET Read more

WW 643 SEVERE TSTM MT 220025Z - 220700Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 643 NWS Storm Prediction Center Norman OK 625 PM MDT Wed Aug 21 2024 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Northeast Montana * Effective this Wednesday night and Thursday morning from 625 PM until 100 AM MDT. * Primary threats include... Scattered damaging winds and isolated significant gusts to 75 mph possible Scattered large hail and isolated very large hail events to 2.5 inches in diameter possible SUMMARY...Thunderstorms should continue to intensify this evening across parts of northeast Montana, while posing a threat for large to very large hail around 1.5-2.5 inches in diameter, along with severe/damaging winds up to 65-75 mph. The severe thunderstorm watch area is approximately along and 120 statute miles east and west of a line from 50 miles north of Glasgow MT to 95 miles south of Glasgow MT. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU3). 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. && OTHER WATCH INFORMATION...CONTINUE...WW 642... AVIATION...A few severe thunderstorms with hail surface and aloft to 2.5 inches. Extreme turbulence and surface wind gusts to 65 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 26025. ...Gleason Read more

MD 1968 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF SOUTHERN ARIZONA
Mesoscale Discussion 1968 NWS Storm Prediction Center Norman OK 0442 PM CDT Wed Aug 21 2024 Areas affected...portions of southern Arizona Concerning...Severe potential...Watch unlikely Valid 212142Z - 212315Z Probability of Watch Issuance...20 percent SUMMARY...A few instances of severe hail/wind gusts are possible through the remainder of the afternoon and evening. The severe threat should remain isolated, and a WW issuance is not anticipated. DISCUSSION...Pulse-cellular storms have been percolating in intensity over the past few hours with approach of peak afternoon heating. These storms are developing atop a low-level airmass characterized by steep low-level lapse rates. Given relatively weak vertical wind shear in place, storms will likely remain pulse-cellular in nature, though a few multicell clusters are possible. Severe gusts are the main threat, though a couple instances of large hail may also accompany the strongest, longest-lived storm cores. ..Squitieri/Gleason.. 08/21/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...TWC...PSR... LAT...LON 31231125 32191173 33041210 33561201 33541125 33221064 32690992 32150936 31550924 31230931 31231125 Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0421 PM CDT Wed Aug 21 2024 Valid 231200Z - 291200Z An upper low over the West Coast is forecast to move south late this weekend into early next week as an omega block breaks down over the central CONUS. Stronger flow aloft east of the low will overspread a dry air mass across parts of the Great Basin and Northwest, supporting elevated to critical fire-weather potential and some risk for isolated dry thunderstorms. Flow aloft returns to more zonal flow later next week with some risk for additional fire-weather concerns, though forecast confidence is low. ...Great Basin and Rockies... Stronger flow aloft on the eastern side of the approaching upper low will overspread a warm and fairly dry air mass across parts of OR/ID and into the Great Basin late this week and through the weekend. Several days of dry and breezy conditions are expected with the potential for elevated to critical fire-weather concerns. The highest confidence in sustained 20-30 mph winds and higher gusts remains D3/Friday over parts of southern NV and western UT. Several preceding days of RH below 15% and gusty winds will allow area fuels to dry. With ERCs continuing to increase, critical fire-weather concerns are probable. Dry and breezy conditions will likely continue into the weekend over parts of the Rockies beneath the stronger upper jet. Elevated to near-critical conditions are possible over parts of central and eastern WY and northern CO D4/Saturday. Less confidence exists D5/Sunday, but there remains some risk for isolated elevated fire-weather concerns with gusty downslope winds over the Front Range. ...Southern Plains... Dry southerly flow is possible over parts of the southern Plains late this week into the weekend as lee low deepens over southern CO. Gusty southerly flow ahead of the upper low to the west may support occasional 10-15 mph winds and RH below 20% over parts of west TX and eastern NM. Additionally, a few thunderstorms with some potential for dry strikes in receptive fuels are possible along a stalled front over west TX into the early weekend. Confidence remains low in the coverage and duration of any significant fire-weather potential for now. ...Dry Thunderstorms... Confidence continues to increase that mixed wet/dry thunderstorms will develop east of the upper low over portions of Northwest and northern Rockies D3/Friday. Model soundings show relatively dry low-levels with storm motions of 30-40 kt. This should support somewhat limited wetting rainfall over parts of eastern OR where fuels are receptive. Showers and thunderstorms will remain possible through the weekend over parts of the Northwest and northern Rockies. However, increasing PWATs and several days of rain chances should keep the risk of dry lightning relatively limited this weekend and beyond. ..Lyons.. 08/21/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0421 PM CDT Wed Aug 21 2024 Valid 231200Z - 291200Z An upper low over the West Coast is forecast to move south late this weekend into early next week as an omega block breaks down over the central CONUS. Stronger flow aloft east of the low will overspread a dry air mass across parts of the Great Basin and Northwest, supporting elevated to critical fire-weather potential and some risk for isolated dry thunderstorms. Flow aloft returns to more zonal flow later next week with some risk for additional fire-weather concerns, though forecast confidence is low. ...Great Basin and Rockies... Stronger flow aloft on the eastern side of the approaching upper low will overspread a warm and fairly dry air mass across parts of OR/ID and into the Great Basin late this week and through the weekend. Several days of dry and breezy conditions are expected with the potential for elevated to critical fire-weather concerns. The highest confidence in sustained 20-30 mph winds and higher gusts remains D3/Friday over parts of southern NV and western UT. Several preceding days of RH below 15% and gusty winds will allow area fuels to dry. With ERCs continuing to increase, critical fire-weather concerns are probable. Dry and breezy conditions will likely continue into the weekend over parts of the Rockies beneath the stronger upper jet. Elevated to near-critical conditions are possible over parts of central and eastern WY and northern CO D4/Saturday. Less confidence exists D5/Sunday, but there remains some risk for isolated elevated fire-weather concerns with gusty downslope winds over the Front Range. ...Southern Plains... Dry southerly flow is possible over parts of the southern Plains late this week into the weekend as lee low deepens over southern CO. Gusty southerly flow ahead of the upper low to the west may support occasional 10-15 mph winds and RH below 20% over parts of west TX and eastern NM. Additionally, a few thunderstorms with some potential for dry strikes in receptive fuels are possible along a stalled front over west TX into the early weekend. Confidence remains low in the coverage and duration of any significant fire-weather potential for now. ...Dry Thunderstorms... Confidence continues to increase that mixed wet/dry thunderstorms will develop east of the upper low over portions of Northwest and northern Rockies D3/Friday. Model soundings show relatively dry low-levels with storm motions of 30-40 kt. This should support somewhat limited wetting rainfall over parts of eastern OR where fuels are receptive. Showers and thunderstorms will remain possible through the weekend over parts of the Northwest and northern Rockies. However, increasing PWATs and several days of rain chances should keep the risk of dry lightning relatively limited this weekend and beyond. ..Lyons.. 08/21/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

WW 0642 Status Updates
STATUS FOR WATCH 0642 HAS NOT BEEN ISSUED YET Read more

WW 642 SEVERE TSTM MT SD 212100Z - 220400Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 642 NWS Storm Prediction Center Norman OK 400 PM CDT Wed Aug 21 2024 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Southeast Montana Western South Dakota * Effective this Wednesday afternoon and evening from 400 PM until 1100 PM CDT. * Primary threats include... Scattered damaging wind gusts to 70 mph likely Scattered large hail and isolated very large hail events to 2 inches in diameter possible SUMMARY...Thunderstorms will develop across southeast Montana and western South Dakota through the afternoon and evening. The strongest cells may produce damaging winds and large hail. The severe thunderstorm watch area is approximately along and 55 statute miles north and south of a line from 145 miles west northwest of Broadus MT to 25 miles north northeast of Philip SD. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU2). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && AVIATION...A few severe thunderstorms with hail surface and aloft to 2 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 25030. ...Hart Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0242 PM CDT Wed Aug 21 2024 Valid 221200Z - 231200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF CENTRAL AND EASTERN NEVADA... ...20z Updated... The previous outlook remains valid with only minor changes for the latest guidance. Sporadic thunderstorms are possible over parts of north-central OR late D2/Thursday into early D3/Friday. While a few of these storms may be on the drier side, confidence in the coverage of storms and lightning over dry fuels remains too low for dry thunder probabilities. See the prior discussion. ..Lyons.. 08/21/2024 .PREV DISCUSSION... /ISSUED 0145 AM CDT Wed Aug 21 2024/ ...Synopsis... A southward-moving shortwave trough is forecast to approach the Oregon/Washington coasts on Thursday, before moving east on Friday. This will result in an intensified height gradient across the Great Basin and a deepening surface low over Oregon that will bring widespread dry/windy conditions to portions of Oregon, Nevada, and Idaho. ...Dry/Windy... Critical fire-weather conditions are forecast across southwestern and central Nevada, where single-digit relative humidity values and winds of 25-30 MPH will overlap with ERC values exceeding the 80th-98th annual percentiles. Uncertainty exists in the eastward extent of the Critical area due to recent wetting rainfall and a tight gradient in fuel receptiveness to wildfire spread, and some areal expansion may be needed in future updates. Elevated fire-weather conditions are expected on the periphery of the Critical highlight area, as well as portions of northwestern Nevada into southeastern Oregon. Southeastern Oregon and northwestern Nevada will have slightly higher boundary-layer relative humidity values of 10-15%, and slightly slower wind speeds of 20-25 MPH. However, fuels in the region are widely receptive to wildfire spread, and if surface winds trend higher, a subsequent upgrade to Critical may be needed in this area. ...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 0227 PM CDT Wed Aug 21 2024 Valid 212000Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN HIGH PLAINS... ...SUMMARY... Severe hail and thunderstorm gusts are most probable today over parts of eastern Montana and the western Dakotas. ...20Z Update... The previous forecast remains on track for the northern and central High Plains based on recent observed trends and latest forecast guidance. The Marginal risk area across south-central AZ has been modified to remove areas that have seen little diurnal destabilization owing to persistent stratiform rain and/or cirrus emanating from a broken line of weak convection. Additionally, wind risk probabilities have been expanded slightly east to account for recent thunderstorm development within a similarly buoyant and deeply-mixed environment as the remainder of the risk area. See the previous discussion for additional details. ..Moore.. 08/21/2024 .PREV DISCUSSION... /ISSUED 1120 AM CDT Wed Aug 21 2024/ ...Northern High Plains... Morning water vapor imagery shows a fast-moving shortwave trough over ID/NV tracking northeastward. Lift associated with this system will overspread parts of MT/WY/Dakotas later this afternoon and evening. This will help to initiate scattered thunderstorms over the higher terrain of southern MT and WY, building eastward into the Plains during the evening. Instability in the mountains is quite weak with dewpoints only in the 40s, but with steep low/mid level lapse rates and moderately strong westerly flow aloft posing a risk of gusty winds. Storms will eventually move/develop eastward into a more moist/unstable air mass across eastern MT and western SD/ND where more robust/severe storms are expected, capable of damaging winds and large hail. ...CO/NE/KS... Ample mid-level moisture will result in scattered afternoon thunderstorms over the mountains of central CO and southern WY. This area will be on the fringe of the stronger westerly flow aloft, and with pockets of strong daytime heating helping to steepen low-level lapse rates. This will promote a risk of gusty/damaging winds in the strongest cells. As the activity spreads eastward into the Plains, further intensification is possible with a few cells continuing a risk of gusty winds and hail during the evening. ...Southeast AZ... Afternoon thunderstorms have been occurring daily over southeast AZ, with isolated strong cells capable of gusty winds. Today will be similar as daytime heating dewpoints in the 60s promote storms over the higher terrain that track slowly northwestward during the late afternoon and early evening. Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0225 PM CDT Wed Aug 21 2024 Valid 231200Z - 241200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF UTAH INTO WESTERN COLORADO...AND OVER THE NORTHERN HIGH PLAINS... ...SUMMARY... Marginally severe storms with hail and isolated severe gusts will be possible on Friday across parts of the northern high Plains, and in parts of the Intermountain West and central Rockies. ...Synopsis... On Friday, a prominent upper ridge will hold across the Plains with an upper trough over much of the West. A lead wave will pivot northeast out of the Great Basin and into MT, with a secondary lobe moving into northern CA into Saturday morning. At the surface, a cold front will push east across ID and NV during the day, with strengthening southerly winds ahead of it. Southeast winds will persist across much of the Plains with a surface trough also extending from central MT into the northern and central High Plains. A low level jet will develop from eastern MT into the western Dakotas in response to the lead wave. ...UT/Western CO and southwest WY... Midlevel winds will increase to over 50 kt as the upper trough nears during the afternoon. Cool temperatures aloft, PWAT over 1.25" and heating will yield over 1000 J/kg MUCAPE, while deep-layer shear increases to over 40 kt. Forecast soundings suggest cells capable of marginal hail and locally severe gusts will be possible. ...Eastern MT into northeast CO... Scattered storms will form during the late afternoon across western WY into southwest MT, and proceed northeastward with the mean wind aloft. Convection will likely arc southeastward across eastern WY and into northeast CO where heating will result in a marginally unstable air mass. Isolated severe gusts appear most probable with this activity. ..Jewell.. 08/21/2024 Read more

No watches are valid as of Wed Aug 21 17:56:02 UTC 2024.