Severe Storms

WW 0664 Status Updates
STATUS REPORT ON WW 664 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 45 WSW U31 TO U31 TO 35 NNE U31 TO 35 ESE BAM TO 5 NW EKO TO 45 N EKO TO 40 NE OWY. FOR ADDITIONAL INFORMATION SEE MESOSCALE DISCUSSION 2077 ..JEWELL..09/03/23 ATTN...WFO...LKN...VEF...SLC... STATUS REPORT FOR WS 664 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS NVC007-011-015-017-023-033-032340- NV . NEVADA COUNTIES INCLUDED ARE ELKO EUREKA LANDER LINCOLN NYE WHITE PINE UTC003-005-011-023-027-029-033-035-045-049-057-032340- UT . UTAH COUNTIES INCLUDED ARE BOX ELDER CACHE DAVIS JUAB MILLARD MORGAN RICH SALT LAKE TOOELE UTAH WEBER THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL Read more

WW 664 SEVERE TSTM NV UT 031930Z - 040300Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 664 NWS Storm Prediction Center Norman OK 1230 PM PDT Sun Sep 3 2023 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Central and Eastern Nevada Western and Northern Utah * Effective this Sunday afternoon and evening from 1230 PM until 800 PM PDT. * Primary threats include... Scattered damaging wind gusts to 70 mph possible Isolated large hail events to 1.5 inches in diameter possible SUMMARY...Strong to severe thunderstorms will continue to increase across the region, supported by a very moist air mass and strong winds aloft ahead of an approaching upper-level system. The severe thunderstorm watch area is approximately along and 120 statute miles east and west of a line from 85 miles north of Wendover UT to 80 miles east southeast of Tonopah NV. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU4). 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 1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 23030. ...Guyer Read more

MD 2077 CONCERNING SEVERE THUNDERSTORM WATCH 664...665... FOR FAR NORTHEAST NEVADA AND NORTHERN UTAH INTO EASTERN IDAHO
Mesoscale Discussion 2077 NWS Storm Prediction Center Norman OK 0520 PM CDT Sun Sep 03 2023 Areas affected...far northeast Nevada and northern Utah into eastern Idaho Concerning...Severe Thunderstorm Watch 664...665... Valid 032220Z - 040145Z The severe weather threat for Severe Thunderstorm Watch 664, 665 continues. SUMMARY...Strong to severe storms will move out of Utah and into eastern Idaho producing a few damaging gusts or marginal hail. DISCUSSION...A cluster of storms is currently moving rapidly northward across Box Elder County UT, with indications of severe gust and marginal hail potential. Visible imagery shows an area of relatively better heating extending into eastern ID, with is also within the surface theta-e plume. Given the meridional deep-layer shear vector orientation and values over 40 kt, the severe threat is expected to increase through this corridor over the next few hours. ..Jewell.. 09/03/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...RIW...SLC...PIH...LKN... LAT...LON 41471415 41751408 42001361 42281323 43031272 43711245 44091235 44311202 44371165 44221111 43461085 42161131 41761155 41371196 41241239 41141292 41121329 41071362 41111389 41471415 Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0312 PM CDT Sun Sep 03 2023 Valid 051200Z - 111200Z The potential for widespread critical fire weather conditions appears limited through the extended period, though regional concerns may emerge across the southern Plains on D3/Tuesday. Long-range guidance depicts reasonably good agreement in the evolution of the synoptic regime through the middle/late work week as upper-level ridging becomes re-established over northern Mexico into NM/TX. This will displace stronger mid-level flow over the northern CONUS with sporadic rain chances across the Rockies into the central and eastern U.S. Ensemble guidance shows low probability for wetting rainfall and warm temperatures across TX into the Four Corners region, which should facilitate fuel drying through the week. However, the building ridge will also limit the potential for strong pressure-gradient winds with few strong wind signals noted in ensemble guidance after D3/Tuesday. Additionally, fuels to the west of the Plains likely require several days of drying in order to support a robust fire weather threat. While localized fire weather concerns may emerge across parts of the southern Plains and perhaps northern MT (where fuels are also fairly dry), confidence in critical fire weather conditions for any one day is fairly low. ...D3/Tuesday - Southern High Plains... A cold front is expected to push southeast across KS into OK and perhaps far north TX through D3/Tuesday. Breezy winds immediately ahead and behind the front may support a few hours of elevated fire weather conditions from north TX into northeast OK and eastern KS. However, deterministic solutions hint at a displacement of the stronger winds across KS with the hotter/drier conditions across TX/OK. Ensemble guidance supports this idea with relatively low probabilities for combined 15+ mph winds and sub-25% RH across this region. While confidence in the overall threat is limited for this outlook, highlights may be needed in subsequent updates if guidance trends towards a better overlap of dry/windy conditions. ..Moore.. 09/03/2023 ...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 0300 PM CDT Sun Sep 03 2023 Valid 032000Z - 041200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE GREAT BASIN/INTERMOUNTAIN WEST... ...SUMMARY... Thunderstorms capable of severe wind gusts and hail remain possible across much of the Great Basin and Intermountain West this afternoon and evening, especially across parts of Nevada and Utah into southeast Idaho. ...20Z Update... The Slight Risk has been expanded slightly into a larger part of southeast ID and far western WY. Also, a small 15% hail area has been added where somewhat greater potential for supercells is expected later this afternoon. Otherwise, no changes have been made. Thunderstorms will continue to gradually increase in coverage and intensity this afternoon from NV into northwest UT and southern ID, as a seasonably strong mid/upper-level shortwave trough moves across the northern Great Basin. Moderate deep-layer shear and sufficient instability will continue to support the potential for organized storm clusters and a few supercells, with a threat of strong/severe gusts and some hail. See the previous discussion below for more information. Also refer to MCD 2076, WW 664, and WW 665 for more information regarding the short-term threat. ..Dean.. 09/03/2023 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sun Sep 03 2023/ ...Great Basin/Intermountain West... An upper trough centered over northern California early today will continue to spread east-northeastward over the Great Basin. Preceding the upper trough, 12z observed soundings from locations such as Elko NV, Boise ID, and Salt Lake City UT sampled a very moist air mass with Precipitable Water values generally ranging from 0.80-1.25 inches. Some stronger thunderstorms are already evident early today across western Nevada, and a further increase in coverage and intensity is likely regionally into the afternoon as the boundary layer heats, with plentiful cloud breaks noted across eastern Nevada into Utah this morning. Hail and strong/severe-caliber winds will be possible across a broad region, but the most organized and sustained storms, including some supercells, should occur across the eastern half of Nevada into western/north Utah and possibly southeast Idaho where effective shear should be around 35-45 kt. ...North Texas... Thunderstorms should increase this afternoon, at least in a widely scattered sense, on the immediate eastern periphery of an upper low centered across north Texas. Vertical shear will be weak, and overall buoyancy will be limited as compared to typical summertime standards. However, a pocket of cool mid-level temperatures (around -10C at 500 mb) could support some stronger (low-topped but high-based) storms as the boundary layer heats. A few storms could produce severe-caliber wind gusts. Read more

WW 0665 Status Updates
STATUS FOR WATCH 0665 HAS NOT BEEN ISSUED YET Read more

WW 665 SEVERE TSTM ID WY 031955Z - 040400Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 665 NWS Storm Prediction Center Norman OK 155 PM MDT Sun Sep 3 2023 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Southern and Eastern Idaho Western Wyoming * Effective this Sunday afternoon and evening from 155 PM until 1000 PM MDT. * Primary threats include... Scattered damaging wind gusts to 70 mph possible Scattered large hail events to 1.5 inches in diameter possible SUMMARY...Widely scattered thunderstorms will continue to intensify across the region, potentially including a few supercells given a very moist air mass and strong winds aloft. Storms should become more scattered/numerous by late afternoon and early evening, with continued large hail and severe wind gust potential as storms move northeastward across the region. The severe thunderstorm watch area is approximately along and 70 statute miles east and west of a line from 45 miles north of Jackson WY to 20 miles southwest of Malad City ID. 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. && OTHER WATCH INFORMATION...CONTINUE...WW 664... AVIATION...A few severe thunderstorms with hail surface and aloft to 1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 24030. ...Guyer Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0117 PM CDT Sun Sep 03 2023 Valid 041200Z - 051200Z The Elevated risk area has been expanded to include portions of western KS, and an isolated dry thunderstorm risk area has been introduced to the TX Panhandle region. Latest forecast guidance continues to show reasonably good agreement in increasing winds across the Plains with high probability for 15+ mph sustained winds from west TX into parts of the upper MS River Valley. Additionally, a slight drying trend has been noted across western KS in most solutions over the past 6-12 hours, which increases confidence in more locations maintaining 20-25% RH. Consequently, the risk areas have been conjoined to include areas of western KS where elevated fire weather conditions appear probable. Recent CAM guidance has also begun to show a stronger signal for very isolated convection across the greater TX Panhandle region Monday afternoon. Forecast thermodynamic profiles still appear only marginally supportive for convection, but feature deep, well-mixed boundary layers conducive for dry lightning. This factor, along with the potential for strong thunderstorm outflows and antecedent dry fuels, supports introducing a dry-thunderstorm risk area. ..Moore.. 09/03/2023 .PREV DISCUSSION... /ISSUED 0130 AM CDT Sun Sep 03 2023/ ...Synopsis... On Monday, the upper-level trough within the Four Corners will continue to move eastward while beginning to lift northward as well. The surface trough will sharpen across the Plains. ...Southern High Plains... Fuels have continued to dry with the hot temperatures and lack of precipitation. Surface winds near the surface trough will increase to 15-20 mph (perhaps locally higher) with some gust potential given stronger flow at 850 mb. RH will fall to 15-20%. There is a weak signal for mid-level convection to occur along the trough. Profiles are not overly conducive to lightning production, so the threat for lightning ignitions appears low at this time. However, gusty outflow winds are still possible from this activity. Fire weather concerns will be elevated for a few hours during the afternoon. ...Missouri Valley Vicinity... Winds are expected to be slightly stronger in the region Monday as compared to Sunday. 15-20 mph will be most common, but locally stronger sustained winds are possible as well as a few gusts. RH will remain the biggest question once again. Areas of 15-25% are possible, but the northward and eastward extents are still uncertain. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1228 PM CDT Sun Sep 03 2023 Valid 041200Z - 051200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF NORTHWEST SD...SOUTHWEST ND...EXTREME NORTHEAST WY...EXTREME SOUTHEAST MT... ...SUMMARY... Thunderstorms capable of producing isolated to widely scattered severe wind and hail will be possible Monday afternoon and evening across parts of the northern Plains. ...Northern Plains... Multiple rounds of strong to potentially severe thunderstorms will be possible across parts of the northern Plains Monday afternoon/evening, as a mid/upper-level shortwave trough ejects northeastward out of the Intermountain West. Initial diurnal storm development is expected across the higher terrain of WY, which will spread northeastward into an increasingly warm and unstable environment across the Dakotas. Low-level moisture is expected to remain somewhat limited, which will result in a tendency for convection to be relatively high-based, but increasing deep-layer shear will support organized storm structures, including the potential for organized clusters and potentially a few supercells. The greatest coverage of storms is expected near and just north of a frontal zone draped from western SD into southern ND, with a more conditional risk of isolated storm development near a surface low that will be located near the ND/MN/MB border Monday afternoon. Severe gusts may be the most prominent hazard, given the potential for relatively organized and high-based convection. However, any sustained supercells will also pose some hail potential, especially near the front where buoyancy will be maximized. Convection may tend to be more disorganized with southward extent, but strong pre-convective heating/mixing will support a threat of isolated outflow-driven severe gusts into southern SD and western NE. ...AR into southern MO... An upper-level low initially over north TX is forecast to move northeastward toward the Ozarks through the day on Monday. This will result in somewhat colder temperatures aloft and steeper midlevel lapse rates overspreading relatively rich low-level moisture across parts of AR and southern MO. MLCAPE will increase to near or above 2000 J/kg, in conjunction with a modest increase in deep-layer southerly flow east of the upper low track. A few stronger multicell clusters will be possible during the afternoon and evening, posing a threat of isolated damaging gusts and perhaps some hail. ..Dean.. 09/03/2023 Read more

No watches are valid as of Sat Sep 2 22:19:01 UTC 2023.

MD 2075 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR CENTRAL AND NORTHERN NEVADA INTO SOUTHWEST IDAHO
Mesoscale Discussion 2075 NWS Storm Prediction Center Norman OK 0516 PM CDT Sat Sep 02 2023 Areas affected...central and northern Nevada into southwest Idaho Concerning...Severe potential...Watch unlikely Valid 022216Z - 030045Z Probability of Watch Issuance...5 percent SUMMARY...Strong to marginally severe storms may persist for a few hours into central and northern Nevada, and possibly into far southwest Idaho this evening. Hail up to 1.25" diameter will be possible, along with sporadic strong gusts. DISCUSSION...Storms are increasing near the cold front/midlevel temperature gradient over west-central NV, beneath 35-40 kt midlevel southerlies. Wind speeds increase further with height, which is elongating hodographs and supporting a conditional hail threat. Visible satellite imagery shows clearing/heating ahead of the front, with low-level theta-e advection present. Given the time of day, a few hours of strong storms are expected within a corridor from Lander County NV toward Owyhee County ID through evening. Relatively cool profiles may preclude much wind threat, unless storms evolve into small bows. Otherwise, isolated hail of 1.00-1.25" appears most likely. ..Jewell/Grams.. 09/02/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BOI...LKN...REV... LAT...LON 39031771 39791750 40471743 41151743 41841750 42201758 42421737 42551667 42471596 42221569 41651560 40811563 40081584 39571601 38951676 38881748 39031771 Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0323 PM CDT Sat Sep 02 2023 Valid 041200Z - 101200Z Fire weather concerns will likely remain focused through the central and southern CONUS through the extended period. Long-range guidance continues to show good agreement in the weakening of the upper ridge over the central U.S. as the West Coast upper wave de-amplifies and migrates east. This will establish a broad southwest flow regime over the middle of the country by early next week that will be conducive for pronounced lee troughing and strengthening low-level winds through the Plains. ...D3/Monday - Southern to central Plains... A strong lee trough (by early September standards) is expected to gradually become established over the next 72 hours along the High Plains. The resulting mass response will yield widespread 15-25 mph winds through the southern to central Plains - a region with antecedent dry fuels and minimal rain chances until late next week. The coverage and severity of the fire weather threat will likely be determined by the degree of diurnal mixing and boundary-layer moisture quality. Currently, a plume of 60+ F dewpoints exists through the eastern Plains and MS River Valley, and should remain in the region through D3/Monday. Areas on the western fringe of this moisture will see a higher probability for sub-20% RH and a corresponding greater chance for critical fire weather conditions. Ensemble guidance hints that areas across NE to MN and northwest TX/western OK - which should be in closer proximity to regional surface lows - will see the highest potential for sustained elevated (and potentially critical) conditions, but more localized/transient elevated conditions may develop through much of KS. ...D4/Tuesday and beyond - southern Plains... Hot conditions are expected to persist across the southern Plains and into the Southwest region through the middle of the work week. The southwesterly flow regime will eventually give way to a re-consolidation of the upper ridge over the southern US by late week. This synoptic pattern is not overly favorable for widespread/critical fire weather conditions. However, several days of 100+ F high temperatures across OK/TX will promote further curing of already dry fuels. While predictability of regional winds remains limited in this regime, localized fire weather concerns could emerge through the end of the work week prior to a slight increase in rain chances. ..Moore.. 09/02/2023 ...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 0259 PM CDT Sat Sep 02 2023 Valid 022000Z - 031200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are not expected through tonight. ...20Z Update... Thunderstorms are gradually increasing in coverage this afternoon from southeast CA/western AZ into NV. A marginal supercell or two cannot be ruled out later this afternoon across parts of central/northern NV, given the presence of 30-40 kt effective shear to the east of a stationary upper low across northern CA/southern OR, but generally weak midlevel lapse rates and limited buoyancy are expected to limit the potential for severe hail/wind. Other strong storms remain possible into the lower CO Valley region, where weaker shear but stronger instability is in place compared to areas farther north. See the previous discussion below for more information. ..Dean.. 09/02/2023 .PREV DISCUSSION... /ISSUED 1127 AM CDT Sat Sep 02 2023/ ...Lower Colorado Valley region... A very moist environment will remain in place with PW values of 1.75 to 2 inches. Diurnal heating will contribute to moderate/locally strong MLCAPE (1500-2500 J/kg) this afternoon with negligible CINH. Thunderstorms are expected to develop or increase in coverage, aided by diffluent upper-level flow downstream of an upper low over the northwest CA coast, and ascent with a weak mid-level impulse lifting northeast from northern Baja Peninsula. Despite overall weak shear through the cloud-bearing layer, an isolated stronger storm will be capable of strong gusts. ...Central/northern Nevada... Morning cloud cover/precipitation persists across the area, however some heating/destabilization is expected this afternoon in the vicinity of a stationary front where MLCAPE of 400-800 J/kg should develop. Scattered thunderstorms are expected to redevelop in the vicinity of the front, where mid-level flow of 35-45 kts east of the upper low will contribute to a couple more organized cells. Localized strong wind gusts will be possible, but the lack of greater buoyancy casts doubt on the overall magnitude of the severe risk. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0122 PM CDT Sat Sep 02 2023 Valid 031200Z - 041200Z Confidence in reaching elevated/critical RH criteria across eastern NE into IA remains fairly low, which casts considerable uncertainty onto the overall fire threat for Sunday. Recent RAP and HRRR solutions, which typically exhibit deeper boundary-layer mixing, depict only modest RH reductions into the 25-35% range. This may be attributed to anomalously warm 850-700 mb temperatures at the base of a pronounced EML over the region that is stunting the depth of diurnal mixing, as well as a reservoir of low to mid-60s dewpoints already in place over IA. Regardless, there is a sufficiently consistent signal across guidance (including ensemble guidance) to warrant bifurcating the Elevated risk area, highlighting the regions most likely to experience sustained/widespread fire weather concerns (predominantly western to central KS and southwest WI). Localized elevated conditions may still materialize across NE into IA, but should be transient in nature. ..Moore.. 09/02/2023 .PREV DISCUSSION... /ISSUED 1228 AM CDT Sat Sep 02 2023/ ...Synopsis... The upper-level trough in the West will eject into the Great Basin on Sunday. Eastward into the Plains, some deepening of the surface trough can be expected as the synoptic system approaches. ...Central Plains into the upper Mississippi Valley... Stronger winds are expected within the boundary layer on Sunday as low-level pressure gradients increase in strength. Models continue to show variability in the degree of mixing by the afternoon given differences in moisture return northward. However, it does seem probable that an area of dry and breezy conditions will exist along the western/northern periphery of the surface ridge in the Southeast. RH of 15-20% (locally lower) is most probable in parts of Kansas/Nebraska. RH could fall to similar levels into the upper Midwest, but uncertainty is high. RH of 20-25% becomes more likely into Iowa/Minnesota/Wisconsin. Winds of 15-20 mph (with areas of higher gusts) are expected. Elevated fire weather is possible for a few hours. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No Mesoscale Discussions are in effect as of Fri Sep 1 22:01:01 UTC 2023.

No watches are valid as of Fri Sep 1 22:01:01 UTC 2023.

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0337 PM CDT Fri Sep 01 2023 Valid 031200Z - 091200Z Fire weather concerns will primarily be focused across the Plains and into the upper Mississippi River Valley through the extended period. Long-range guidance shows reasonably good agreement in the gradual weakening of the upper ridge over the central CONUS through the weekend and into early next week as a West Coast trough migrates east into the northern Rockies. Surface pressure falls in response to this feature will strengthen low-level winds, which should promote an increase in fire weather concerns given several preceding days of warm/dry conditions and antecedent dry fuels. ...D3/Sunday - Central Plains to the Upper MS River Valley... The 850-700 mb thermal ridge currently over the central High Plains is expected to gradually spread northeast over the next several days as a broad southwesterly flow regime becomes established. This will place anomalously warm temperatures (near to above the 90th percentile for early September) across the central Plains and the upper MS River Valley. Concurrently, a gradually deepening surface low over the northern High Plains will establish a broad southerly flow regime at the surface. Ensemble guidance suggests that surface winds will likely reach 15 mph by peak heating with RH values in the 20-25% range. While drier solutions hint that critical conditions are possible, elevated conditions appear more likely across a somewhat large swath of the region. However, considerable spread in the moisture return is noted, which casts uncertainty into the north/northeastern extent of the threat. ...D4/Monday - Southern to Central Plains... Further deepening of the lee surface trough is expected heading into D4/Monday. Nearly all guidance depicts a stronger wind signal across the Plains compared to D3/Sunday as southerly winds increase to 20-25 mph. Fire weather concerns will likely emerge across the Plains, but the quality of moisture return may determine the spatial coverage and severity. Recent GEFS guidance shows the highest probability for sub-20% RH across NE into SD/MN, as well as across parts of northwest TX into southwest OK in the vicinity of a secondary surface low. However, these solutions may be influenced by a noted GFS dry bias. While the potential for critical conditions and/or more widespread elevated conditions is noted, confidence remains too limited to introduce higher probabilities or more extensive risk areas. ...Beyond D4/Monday - Southern Plains... The upper ridge will gradually de-amplify and shift into the southern Plains/Southwest through the upcoming work week. This will maintain hot, dry weather across a region that already has receptive fuels. Consequently, fire weather concerns are most likely to emerge across this region after D4/Monday, though confidence in the evolution of the low-level winds field under the upper ridge is too low to introduce additional risk areas at this time. ..Moore.. 09/01/2023 ...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 0255 PM CDT Fri Sep 01 2023 Valid 012000Z - 021200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM SOUTHERN AZ AND SOUTHEASTERN CA INTO SOUTHEAST ID... ...SUMMARY... Isolated severe gusts and hail will remain possible into this evening, from southern Arizona and southeastern California to southern Idaho. ...20Z Update... No changes have been made to the severe probabilities. Thunderstorms capable of producing localized severe gusts and isolated hail will persist through the afternoon across parts of the Desert Southwest, and increase in coverage later this afternoon into parts of the eastern Great Basin. See the previous discussion below for more information, and MCD 2074 for information regarding the short-term threat across parts of southeast CA and the lower CO River Valley vicinity. ..Dean.. 09/01/2023 .PREV DISCUSSION... /ISSUED 1116 AM CDT Fri Sep 01 2023/ ...AZ/Southeastern CA into Eastern Great Basin... Morning satellite and radar imagery shows showers and isolated thunderstorms from southern NV into western UT, within a band of clouds arcing from western AZ through eastern NV/western UT and into WY. This band and associated showers are expected to gradually shift eastward/northeastward throughout the day. Additional thunderstorm development is anticipated later this afternoon to the west of this band, where the airmass is expected to destabilize amid daytime heating and ample low/mid-level moisture. Ascent for this thunderstorm development will be provide by broad low-level convergence between the upper low drifting southwestward towards northern CA and the persistent upper ridging over the central/southern Plains. Moderate mid-level flow will exist between these two features, supporting enough vertical shear for some briefly organized storm structures, and any stronger/more persistent updrafts could produce isolated hail. Cloud bases are not expected to be high by western CONUS standards, but steep low-level lapse rates could still support strong downbursts in areas where clouds clear and some heating is realized. ...Elsewhere... Scattered to numerous thunderstorms are expected across the Southeast, where ample low-level moisture and strong heating will destabilize the airmass in the vicinity of an easterly wave moving across the region. Weak vertical shear will limit storm organization and severity, with an outflow-dominant, multicell mode anticipated. Even so, a damaging gust or two is possible amid strong water loading and forward-propagating storm structures. Ongoing cluster of showers and thunderstorms across SD may persist for the next hour or two, before dissipating as it the low-level jet weakens and the cluster continues northeastward. A few elevated thunderstorms are also possible early tomorrow morning across the Upper Midwest, forced by a strong low-level jet and related warm-air advection (and perhaps weak ascent attendant to a convectively augmented shortwave trough). Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0157 PM CDT Fri Sep 01 2023 Valid 021200Z - 031200Z An Elevated risk area is introduced for portions of northwest KS into central NE. Ensemble guidance has trended towards higher probability of several hours of sub-20% RH with 15-20 mph winds across this region. Although winds are still expected to be slightly weaker than today, temperatures will be several degrees warmer with corresponding lower afternoon RH. Given antecedent dry fuels (exacerbated by today's dry, windy conditions), fire weather concerns seems probable. Elevated conditions may also materialize across northeast WY within a modest downslope flow regime, but considerable ensemble spread limits confidence in the spatial/temporal extent of the threat. ..Moore.. 09/01/2023 .PREV DISCUSSION... /ISSUED 1237 AM CDT Fri Sep 01 2023/ ...Synopsis... The closed low off the northern California coast will begin a transition to an open wave on Saturday. The upper ridge will remain entrenched in the Plains. A similar surface pattern is expected to Friday across the central U.S., though features (and winds) are likely to be weaker. Locally elevated conditions appear possible in parts of the central Plains again. There is considerable spread within guidance as to how dry conditions will be by the afternoon. Though conditions may tend towards the drier guidance, as they often do with trajectories generally out of the surface high, sustained winds (and gusts) are expected to be lighter on Saturday. ...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 1231 PM CDT Fri Sep 01 2023 Valid 021200Z - 031200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected across the continental United States on Saturday. ...Synopsis and Discussion... An upper low will remain situated near coastal northern CA on Saturday, with an upper high over the central Plains. Between the two features, southerly flow will maintain moisture over the Great basin and parts of the Southwest, with daytime showers and thunderstorms common. Areas of clouds and ongoing precipitation early in the day will inhibit heating in many areas, and as such MLCAPE is likely to be limited to 500 J/kg over much of the region. Activity is likely during the morning from northwest AZ across much of NV, with thunderstorm probabilities maximized during the late afternoon with the aid of heating. Forecast soundings show limited lapse rates relative to Friday, but modest deep-layer shear does exist with around 35 kt. Sporadic strong gusts may occur anywhere within the region, but overall severe probabilities appear low. Straight hodographs and cooler air aloft closer to the upper low from northern NV into southern ID may support small hail. ..Jewell.. 09/01/2023 Read more