Severe Storms

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0454 PM CDT Sun Sep 10 2023 Valid 121200Z - 181200Z Generally quiescent fire-weather conditions are expected across the CONUS through the extended forecast period. Pacific Northwest troughing is forecast to remain in place through the first part of next week before mid-level ridging builds over the West. Cooler and breezy conditions will give way to warmer and drier weather, with generally poor overlap of critical fire-weather conditions and dry fuels expected across the western states. ...Northwest... Through the first part of next week, the persistent mid-level trough over the Pacific Northwest will remain in place, subtly enhancing west/southwest flow over the Pacific Northwest and northern Rockies. Ensemble forecasts suggest winds will likely be strongest D3/Tues into D4/Wed east of the Cascades and across the Snake River Valley. Isolated thunderstorms may also develop with the passage of the main trough, though coverage is expected to remain low. While surface winds may occasionally reach 15 mph on a localized basis, widespread dry and windy conditions, supporting critical fire-weather concerns, are not expected. Fire-weather concerns shift toward warm, dry and unstable conditions late next week into the first part of next weekend, as a mid-level ridge is forecast to build over the eastern Pacific. With the main ridge axis offshore, weak offshore flow is possible over parts of the Cascades and West Coast. Localized fire-weather concerns are possible, but widespread coverage is not anticipated through the remainder of the extended forecast period. ..Lyons.. 09/10/2023 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

WW 0680 Status Updates
STATUS FOR WATCH 0680 HAS NOT BEEN ISSUED YET Read more

WW 680 SEVERE TSTM CO KS OK 102055Z - 110400Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 680 NWS Storm Prediction Center Norman OK 355 PM CDT Sun Sep 10 2023 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Southeast Colorado Western Kansas Oklahoma Panhandle * Effective this Sunday afternoon and evening from 355 PM until 1100 PM CDT. * Primary threats include... Scattered large hail and isolated very large hail events to 2 inches in diameter possible Scattered damaging wind gusts to 70 mph possible A tornado or two possible SUMMARY...Scattered strong to severe thunderstorms will continue to develop across the region through late afternoon and early evening. The severe thunderstorm watch area is approximately along and 110 statute miles east and west of a line from 70 miles northeast of Lamar CO to 20 miles west of Guymon OK. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU0). 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 550. Mean storm motion vector 29025. ...Guyer Read more

MD 2133 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PARTS OF NORTHEASTERN NEW MEXICO...SOUTHEASTERN COLORADO...AND THE TEXAS AND OKLAHOMA PANHANDLES INTO SOUTHWESTERN KANSAS
Mesoscale Discussion 2133 NWS Storm Prediction Center Norman OK 0313 PM CDT Sun Sep 10 2023 Areas affected...parts of northeastern New Mexico...southeastern Colorado...and the Texas and Oklahoma Panhandles into southwestern Kansas Concerning...Severe potential...Watch possible Valid 102013Z - 102245Z Probability of Watch Issuance...60 percent SUMMARY...Isolated to widely scattered strong thunderstorm development is possible through 5-6 PM CDT. This may include an isolated supercell or two, posing a risk for severe hail, locally strong surface gusts and perhaps a brief tornado. DISCUSSION...Low-level moistening is still ongoing within weak, but slowly deepening surface troughing to the lee of the southern Rockies. This is occurring beneath warm and capping elevated mixed-layer, and mid-level ridging to the north of a still fairly prominent subtropical high centered over the northwestern Mexican Plateau. In response to a series of short wave perturbations progressing around the periphery of the ridge in the near term, and, later, digging mid-level troughing across the northern Great Plains, mid-level heights are gradually beginning to fall. It appears that large-scale forcing for ascent will lead to increasing convective development spreading off the Front Range into the destabilizing boundary layer across and east of northeastern New Mexico and southeastern Colorado by early this evening. Potential for the initiation of sustained thunderstorm development in advance of this activity, through late afternoon, remains more unclear. Based on objective analysis, mixed-layer CAPE remains fairly modest to the north of the Texas Panhandle vicinity, currently maximized around 1000 J/kg near the Colorado/Kansas border. However, shear for boundary-layer based thunderstorm development is sufficient for supercells beneath 30 kt west-northwesterly mid-level flow (around 500 mb). Farther south, mixed-layer CAPE is more substantive, but shear remains weaker. With additional surface heating, it appears possible that weakening of lingering mid-level inhibition may become sufficient for at least widely scattered thunderstorm development. A zone of enhanced lower/mid-tropospheric warm advection, currently centered to the west/northwest of Garden City KS, may provide one potential focus for thunderstorm initiation during the next hour or two. As this activity acquires increasing inflow of destabilizing boundary-layer, it may rapidly intensify and organize, accompanied by increasing potential for severe hail and perhaps some risk for a tornado through 22-23Z. ..Kerr/Guyer.. 09/10/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...OUN...DDC...GLD...LUB...AMA...PUB...ABQ... LAT...LON 37350277 38420253 38800174 38540046 38029982 36909958 33770062 34030194 34280395 35780381 37350277 Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0242 PM CDT Sun Sep 10 2023 Valid 102000Z - 111200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE SOUTH-CENTRAL PLAINS... ...SUMMARY... Scattered severe thunderstorms are expected through this evening across eastern Colorado and western Kansas into the Oklahoma/Texas Panhandles. Large hail and severe wind gusts will be the main threats. ...20z Update... The previous outlook remains on track and no changes have been made with the 20z update. See previous discussion below for more details. ..Leitman.. 09/10/2023 .PREV DISCUSSION... /ISSUED 1138 AM CDT Sun Sep 10 2023/ ...Central High Plains southward to west Texas... A nearly zonal belt of moderately strong westerlies will exist from the central Rockies into the south-central Plains. Weak surface cyclogenesis will occur across southeast Colorado/far southwest Kansas as a cold front shifts southward across the south-central High Plains. A confined plume of modified Gulf air will be maintained across a portion of west Texas into southwest Kansas near and ahead of the front. Robust boundary-layer heating is expected especially to the west/southwest of convection that persists across the region into midday, netting a corridor of moderate buoyancy mainly from northwest Texas into southwest Kansas later today. Afternoon thunderstorm development should be focused within three regimes. One being high-based storms emanating off the southern Rockies, two being along the front and buoyancy plume intersection in west Kansas, and three near the dryline/remnant outflow intersection in the Texas Panhandle. For the latter two, low-level veering of the wind profile with height beneath mid to upper level speed shear should favor at least a few discrete supercells with a primary threat of large hail. Upstream high-based activity should overtake slower-moving supercells and Kansas supercells will also be undercut from north to south by the accelerating cold front. This should yield broader cluster development towards early evening with some uptick in severe wind potential anticipated. ...Southern New England... A weak mid-level disturbance and warm/moist conveyor appears to be influencing a corridor of recently increased thunderstorms at late morning. A moist air mass and cloud breaks/additional heating will lead to modest destabilization, although updraft accelerations will be somewhat tempered by poor mid-level lapse rates. A few microbursts could occur, but overall severe potential should be tempered by the marginal thermodynamic environment and effective shear of 20-25 kt or less. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0244 PM CDT Sun Sep 10 2023 Valid 111200Z - 121200Z ...NO CRITICAL AREAS... ...20z Update... Generally quiet fire-weather conditions are again expected over much of the western CONUS D2/Monday. Locally breezy winds will be possible over parts of the Columbia Gorge and lee of the Cascades coincident with periodic drier surface conditions. However, widespread dry and windy conditions are not expected over the West, precluding broader fire-weather concerns. ..Lyons.. 09/10/2023 .PREV DISCUSSION... /ISSUED 0143 AM CDT Sun Sep 10 2023/ ...Synopsis... A surface cold front will continue to sweep across the southern Plains as a mid-level trough becomes situated over the central U.S. tomorrow/Monday. Cooler, moist conditions will usher in behind the cold front and will overspread much of the Plains states, limiting widespread, significant wildfire-spread potential. Dry conditions should also persist across the western U.S. However, the lack of stronger surface winds should keep wildfire-spread potential localized. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

MD 2126 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PORTIONS OF EASTERN WYOMING INTO FAR SOUTHWESTERN SOUTH DAKOTA AND NORTHWESTERN NEBRASKA PANHANDLE
Mesoscale Discussion 2126 NWS Storm Prediction Center Norman OK 0519 PM CDT Sat Sep 09 2023 Areas affected...portions of eastern Wyoming into far southwestern South Dakota and northwestern Nebraska Panhandle Concerning...Severe potential...Watch possible Valid 092219Z - 092345Z Probability of Watch Issuance...40 percent SUMMARY...The severe threat may be increasing across portions of the northern High Plains. The strongest storms may produce a few bouts of severe hail or wind. A Severe Thunderstorm Watch issuance may be needed if more widespread convective coverage becomes evident. DISCUSSION...Convective initiation has occurred along the lee of the Rockies in eastern WY while multicells/transient supercells have become established across southwestern SD. The SD storms are expected to remain confined to the more favorable terrain, with a persistent but sparse severe wind/hail threat. However, the storms should intensify and move off of the higher terrain in WY as a weak mid-level impulse crests the synoptic ridge and ejects into the central High Plains. Boundary-layer moisture is meager. However, steep low and mid-level lapse rates are contributing to 1000+ J/kg MLCAPE, which is adequate to support some severe wind/hail with supercells that can develop given elongated hodographs and 40-50 kts of effective bulk shear. Nonetheless, discrete storms and their severe threat should be isolated, so convective trends are being closely monitored for greater storm coverage and the need for a Severe Thunderstorm Watch issuance. ..Squitieri/Thompson.. 09/09/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...UNR...CYS...BYZ...RIW... LAT...LON 41550500 43390680 44680696 44980582 44820466 44300337 43710285 43220272 42680299 41760401 41550500 Read more

WW 0677 Status Updates
STATUS REPORT ON WW 677 THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA. ..SPC..09/09/23 ATTN...WFO...LWX...PHI...OKX...BGM...CTP... STATUS REPORT FOR WS 677 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS DCC001-092340- DC . DISTRICT OF COLUMBIA COUNTIES INCLUDED ARE DISTRICT OF COLUMBIA MDC003-005-013-015-021-025-027-031-033-043-510-092340- MD . MARYLAND COUNTIES INCLUDED ARE ANNE ARUNDEL BALTIMORE CARROLL CECIL FREDERICK HARFORD HOWARD MONTGOMERY PRINCE GEORGES WASHINGTON MARYLAND INDEPENDENT CITIES INCLUDED ARE BALTIMORE CITY NJC005-007-015-019-021-027-031-035-037-041-092340- Read more

WW 677 SEVERE TSTM DC MD NJ NY PA VA WV CW 092025Z - 100300Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 677 NWS Storm Prediction Center Norman OK 425 PM EDT Sat Sep 9 2023 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of District Of Columbia Maryland New Jersey Southern New York Central and Eastern Pennsylvania Northern Virginia Far Eastern West Virginia Coastal Waters * Effective this Saturday afternoon and evening from 425 PM until 1100 PM EDT. * Primary threats include... Scattered damaging wind gusts to 65 mph possible Isolated large hail events to 1 inch in diameter possible SUMMARY...Scattered strong to severe thunderstorms will continue across the region through early/mid-evening, with locally damaging winds and some hail occurring. The severe thunderstorm watch area is approximately along and 90 statute miles east and west of a line from 20 miles east of Binghamton NY to 10 miles east southeast of Washington DC. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU7). 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 676... AVIATION...A few severe thunderstorms with hail surface and aloft to 1 inch. Extreme turbulence and surface wind gusts to 55 knots. A few cumulonimbi with maximum tops to 550. Mean storm motion vector 21035. ...Guyer Read more

MD 2125 CONCERNING SEVERE THUNDERSTORM WATCH 677... FOR MIDDLE ATLANTIC
Mesoscale Discussion 2125 NWS Storm Prediction Center Norman OK 0506 PM CDT Sat Sep 09 2023 Areas affected...Middle Atlantic Concerning...Severe Thunderstorm Watch 677... Valid 092206Z - 100000Z The severe weather threat for Severe Thunderstorm Watch 677 continues. SUMMARY...Severe threat continues with robust convection this evening. DISCUSSION...Numerous showers/thunderstorms have developed over the Middle Atlantic early this evening, especially from northern VA, north across central/eastern PA arcing into southern New England. Boundary layer has been overturned across the southern Middle Atlantic with several pockets of modest buoyancy remaining from central/eastern PA into CT. Latest radar imagery suggests a longer-lived MCV over western NY, just south of lake Ontario, is lifting northeast. It appears this feature is having some influence on convection trailing south into central PA along the primary zone of low-level confluence. Over the next few hours much of the greater instability should be overturned as widespread convection/clusters coalesce over central/eastern PA. Locally damaging winds, along with some hail remain possible until this air mass is overturned. ..Darrow.. 09/09/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...OKX...ALY...PHI...BGM...CTP...LWX... LAT...LON 38787851 42187735 42187382 38777519 38787851 Read more

WW 0676 Status Updates
STATUS REPORT ON WW 676 THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA. ..BENTLEY..09/09/23 ATTN...WFO...GID...LBF... STATUS REPORT FOR WS 676 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS NEC019-029-041-047-063-073-085-101-111-113-117-135-137-163-175- 092340- NE . NEBRASKA COUNTIES INCLUDED ARE BUFFALO CHASE CUSTER DAWSON FRONTIER GOSPER HAYES KEITH LINCOLN LOGAN MCPHERSON PERKINS PHELPS SHERMAN VALLEY 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 676 SEVERE TSTM NE 091945Z - 100200Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 676 NWS Storm Prediction Center Norman OK 245 PM CDT Sat Sep 9 2023 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Southwest and South-Central Nebraska * Effective this Saturday afternoon and evening from 245 PM until 900 PM CDT. * Primary threats include... Scattered large hail and isolated very large hail events to 2 inches in diameter possible Isolated damaging wind gusts to 70 mph possible SUMMARY...An unstable environment favorable for severe storms including supercells exists across the region near a weak surface low and front. Some of these storms may produce large hail and locally damaging winds through early evening. The severe thunderstorm watch area is approximately along and 75 statute miles east and west of a line from 25 miles northwest of Broken Bow NE to 50 miles south of North Platte NE. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU6). 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 550. Mean storm motion vector 29025. ...Guyer Read more

MD 2124 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF CENTRAL INTO SOUTHERN TEXAS
Mesoscale Discussion 2124 NWS Storm Prediction Center Norman OK 0459 PM CDT Sat Sep 09 2023 Areas affected...portions of central into southern Texas Concerning...Severe potential...Watch unlikely Valid 092159Z - 092330Z Probability of Watch Issuance...20 percent SUMMARY...A few instances of severe wind and hail may accompany the stronger storms. The severe threat should remain isolated and a WW issuance is not expected. DISCUSSION...Pulse cellular and multicellular storms have been increasing in intensity and coverage across central TX toward the middle TX coast over the past couple of hours. Despite weak vertical shear, these storms continue to intensify atop a hot, well-mixed boundary layer, with surface temperatures well exceeding 100 F, boosting MLCAPE to 1500+ J/kg. Water-loaded downdrafts within the stronger storm cores may support a couple of severe gusts along with an instance or two of hail. Nonetheless, the lack of more appreciable vertical shear should render the severe threat brief and isolated, precluding a Severe Thunderstorm Watch issuance. ..Squitieri/Thompson.. 09/09/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...HGX...FWD...CRP...EWX...SJT... LAT...LON 27729703 29299830 29359841 30339919 30920011 31260040 32119983 32259910 32229840 31579733 30549650 29639598 29129570 28709562 27729703 Read more

MD 2123 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR EXTREME SOUTHWEST NEBRASKA...EXTREME EASTERN COLORADO...EXTREME NORTHWEST KANSAS...EXTREME NORTHEAST COLORADO...WESTERN OKLAHOMA PANHANDLE...EXTREME NORTHWEST TEXAS PANHANDLE
Mesoscale Discussion 2123 NWS Storm Prediction Center Norman OK 0447 PM CDT Sat Sep 09 2023 Areas affected...extreme southwest Nebraska...extreme eastern Colorado...extreme northwest Kansas...extreme northeast Colorado...western Oklahoma Panhandle...extreme northwest Texas Panhandle Concerning...Severe potential...Watch possible Valid 092147Z - 092315Z Probability of Watch Issuance...40 percent SUMMARY...The severe threat may be increasing across portions of the central and southern High Plains, both with storms approaching from central NE, and with the potential for storms to develop along the CO/KS border area. Severe wind and hail are the main concerns. Conditions are being monitored for the need of a Severe Thunderstorm Watch issuance. DISCUSSION...Multiple supercells across central NE have begun to grow upscale into an MCS structure, with the southwest flank of this structure anchoring along the surface lee trough (located from southwest NE and trailing along the CO/KS border). This developing MCS may continue to propagate south-southwestward amid a buoyant and sheared airmass, which in turn may support an increasing severe threat into northwestern KS later this evening. Multiple attempts at convective initiation have also been observed along the lee-trough in extreme eastern CO. Though convective coverage along the lee trough remains questionable, any storms that can develop may become supercellular, supporting severe wind and hail given 7.5-8 C/km mid-level lapse rates and elongated hodographs with slight low-level curvature. Any severe threat that materializes may last for at least a few hours. As such, convective trends are being monitored for the need of a Severe Thunderstorm Watch issuance pending adequate convective coverage, mainly across northwest KS. ..Squitieri/Thompson.. 09/09/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...GID...LBF...DDC...GLD...AMA...PUB...ABQ... LAT...LON 36120368 38060271 39530225 40230212 40480167 40390053 40229965 39879954 39159984 38240026 37400120 36160255 36120368 Read more

MD 2122 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF EASTERN NEW MEXICO INTO FAR WESTERN TEXAS
Mesoscale Discussion 2122 NWS Storm Prediction Center Norman OK 0425 PM CDT Sat Sep 09 2023 Areas affected...portions of eastern New Mexico into far western Texas Concerning...Severe potential...Watch unlikely Valid 092125Z - 092300Z Probability of Watch Issuance...5 percent SUMMARY...An isolated severe gust or instance of hail may accompany the stronger storms this afternoon. A WW issuance is not expected. DISCUSSION...Multicellular and pulse-cellular storms have been gradually intensifying over the higher terrain in central NM, where strong surface heating and boundary-layer mixing has boosted MLCAPE over 1000 J/kg. Given scant low-level moisture, these storms are high-based and are expected to remain so through the rest of the afternoon. 9+ C/km low-level lapse rates (per 21Z mesoanalysis) should support the potential for a severe gust or two. Given steep lapse rates also present in the 700-500 mb layer, some hail may also accompany the most potent storm cores. Nonetheless, the severe threat should remain isolated overall and a Severe Thunderstorm Watch issuance is not expected. ..Squitieri/Thompson.. 09/09/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LUB...AMA...MAF...ABQ... LAT...LON 34050554 35040511 35450475 35680408 35590333 35320302 34640293 33990305 33540329 33370355 33310440 33250488 34050554 Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0359 PM CDT Sat Sep 09 2023 Valid 111200Z - 171200Z Overall fire-weather concerns through the extended forecast period are low. Periodic troughing across the western US and Pacific Northwest this weekend will allow for cooler temperatures with slightly stronger winds through midweek next week. This pattern is forecast to give way to a building ridge late next week into the weekend. Warmer temperatures, but weaker flow and localized fire-weather conditions are expected. Periodic thunderstorms are also possible across the West, though the coverage of dry storms also appears low. ...Northwest... Weak troughing along with a slight increase in mid-level flow will overspread the area through the weekend and into early next week. Periodic gusty west winds are possible over parts of the eastern Cascades, Columbia and Snake River Basins through mid week. While not overly strong, gusts may occasionally reach 15 mph with afternoon RH below 20% on a localized basis. The strongest winds are expected D4/Tuesday into D5/Wed with the passage of a stronger shortwave trough. Isolated thunderstorms may also develop, though coverage is expected to remain low. Fire-weather concerns shift toward warm, dry and unstable conditions late next week into next weekend as a mid-level ridge is forecast to build over the west in the wake of earlier troughing. With the main ridge axis offshore, weak easterly flow is possible over parts of the Cascades. Localized fire-weather concerns are possible but widespread coverage is not anticipated. Thunderstorm chances may increase again toward the end of the period as a series of weak upper-level troughs approach the northwest into the weekend. However, predictability remains low. ..Lyons.. 09/09/2023 ...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 0238 PM CDT Sat Sep 09 2023 Valid 092000Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON AND EVENING ACROSS PARTS OF SOUTHWESTERN THROUGH CENTRAL NEBRASKA...PARTS OF EASTERN WYOMING AND ADJACENT PORTIONS OF THE GREAT PLAINS...EASTERN PENNSYLVANIA AND ADJACENT PORTIONS OF THE MID ATLANTIC... ...SUMMARY... Widely scattered strong to severe thunderstorm development remains possible across parts of the northern Mid Atlantic states into southern New England late this afternoon, and across parts of the Great Plains to the east of the Rockies late this afternoon through this evening. ...20Z Update... Categorical and severe probabilistic outlook lines have been adjusted, mostly to account for the continuing gradual progression of synoptic and sub-synoptic scale features and their influence on trends concerning instability. East of the Mississippi Valley, the boundary-layer remains seasonably moist and characterized by moderately large CAPE, along and southeast of a weak surface frontal zone across parts of the Allegheny Plateau into southern Maine. Southwesterly deep-layer mean flow and shear in the vicinity of the front is rather modest (on the order of 20-25 kt or less), but this might still be enough to contribute to some convective organization and marginally higher probabilities for severe wind and hail than areas elsewhere across the east. To the lee of the Rockies, steep lower/mid-tropospheric lapse rates are contributing to moderately large mixed-layer CAPE, but mostly in a rather narrow corridor east of lee surface troughing, from the northwestern Texas Panhandle into the North Platte NE vicinity. For more details on the severe weather potential, please refer to the prior outlook discussion appended below, and the latest SPC mesoscale discussions. ..Kerr.. 09/09/2023 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sat Sep 09 2023/ ...Nebraska/Kansas and northern High Plains... No changes warranted, with at least widely scattered severe storms including supercells expected across the region later today. Deep-layer wind profiles will be conducive to discrete supercells from late afternoon into this evening, focused along a surface front from central Nebraska to northwest Kansas and within a post-frontal weak low-level upslope regime to the northwest across the northern High Plains. A ribbon of around 1 inch PW values depicted in GOES imagery and sampled by the 12Z LBF sounding should be maintained from western Kansas into central Nebraska. This combined with surface temperatures warming through the 80s along with steep mid-level lapse rates will support a confined corridor of 1000-2000 J/kg MLCAPE. A few to several high-based supercells should develop with large hail as the primary hazard, along with isolated severe wind gusts. This will initially be across central Nebraska and then southwestward into northwest Kansas. A strengthening southerly low-level jet during the evening may support a small cluster evolving south over southwest Nebraska/western Kansas with a continued wind/hail threat. The northern High Plains portion should similarly see a few to several supercells developing off the higher terrain in Wyoming/far southern Montana/southwest South Dakota. While buoyancy will be weaker here and the boundary layer not as deep, 35-45 kt effective shear will be conducive to a few long-track cells capable of producing sporadic hail swaths up to around golf ball size, particularly across east-central/northeast Wyoming. ...Carolinas/Mid-Atlantic/Northeast States.. While overall regional severe coverage will be lesser after a couple of prior active days, along with increasingly meridional and weaker wind profiles, at least isolated damaging winds will again be possible across much of the region. One area of focus for the possibility of a few supercells and slow-moving multicell clustering will be downstream of an MCV over western Pennsylvania. Here, pockets of moderate insolation should support a plume of 1000-2000 J/kg MLCAPE centered on the Delaware Valley. As storms develop and impinge on this buoyancy plume this afternoon, coincident with a mesoscale belt of slightly stronger mid-level flow as sampled by recent KCCX VWP data (30+ kt in lowest 3km AGL), the potential for sporadic damaging winds along with isolated, marginally severe hail should increase. Farther south, a broad plume of weak to moderate buoyancy and steepened low-level lapse rates will support the potential for localized damaging wind gusts. With somewhat weaker mid-level lapse rates and slightly less deep-layer shear relative to farther north, potential for a more organized severe threat appears nebulous at this time. ...South-central/southeast Texas... Hot temperatures in excess of 100 F will again be common to the west of overnight convection outflow (now over the western Gulf of Mexico) and elevated thunderstorms that have redeveloped today across east-central/southeast Texas. While some initial large hail will be possible with storms near the coast, the primary threat should be sporadic severe wind gusts. ...Great Basin... Coincident with a disturbance or two embedded within low-amplitude westerlies, and along the leading periphery of gradually increasing PW values from the southwest, at least isolated high-based thunderstorms are expected to develop later this afternoon. With moderately strong mid-level winds, any of these high-based storms will be capable of producing dry microbursts with severe-caliber wind gusts. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0151 PM CDT Sat Sep 09 2023 Valid 101200Z - 111200Z ...NO CRITICAL AREAS... The previous forecast remains valid with no changes. ..Lyons.. 09/09/2023 .PREV DISCUSSION... /ISSUED 0130 AM CDT Sat Sep 09 2023/ ...Synopsis... Some dampening of the upper ridge is expected across portions of the central and southern U.S. tomorrow/Sunday, as a mid-level impulse ejects into the central Plains. The ejection of this mid-level trough will hasten the southward surge of a cold front across the central U.S., which will ultimately bring about cooler and moist conditions. Locally dry and breezy conditions may precede the approaching cold front across the southern Plains on Sunday afternoon. However, an appreciable overlap of dry and windy conditions, capable of supporting significant wildfire-spread potential, is not expected. ...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 1230 PM CDT Sat Sep 09 2023 Valid 101200Z - 111200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SUNDAY AFTERNOON AND EVENING ACROSS PARTS OF SOUTHEASTERN COLORADO...WESTERN KANSAS...NORTHEASTERN NEW MEXICO AND THE TEXAS AND OKLAHOMA PANHANDLES... ...SUMMARY... Scattered strong thunderstorms are possible across parts of the southern Rockies and adjacent Great Plains Sunday afternoon and evening. Some of these may pose a risk for severe wind and hail. ...Synopsis... Models indicate that the westerlies in the northern mid-latitudes of the eastern Pacific and North America will remain amplified through this period, with one significant trough pivoting inland across the British Columbia and Pacific Northwest coast. Downstream, mid-level ridging will remain strong across the Canadian Prairies and northern U.S. Rockies, while troughing digs across northwestern Ontario southwestward through much of the northern U.S. Great Plains and upper Mississippi Valley by late Sunday night. In the southern mid- and subtropic latitudes, flow is forecast to become less amplified, as a persistent prominent mid-level high substantively weakens to the west-southwest of the Texas Big Bend vicinity. It appears that a weak downstream low will become increasingly sheared and accelerate within confluent flow east-northeast of the southern Appalachians. This may be accompanied by the development of a weak wave along a weak surface frontal zone, across and offshore of the southern Mid Atlantic coast Sunday through Sunday night. On the northeastern periphery of the weakening subtropical high, models indicate that mid-level flow will transition from broadly anticyclonic to cyclonic across the Colorado Rockies into central Great Plains, to the south of the digging troughing across the northern Great Plains. This is forecast to be accompanied by modestly deepening surface troughing to the lee of the southern Rockies during the day Sunday, in advance of cool surface ridging nosing southward to the lee of the northern Rockies. ...Southern Rockies and adjacent Great Plains... Within the deepening lee surface troughing, models indicate that at least modest boundary-layer CAPE may develop with daytime heating, beneath steep lower/mid-tropospheric lapse rates. The NAM appears on the more aggressive side with peak mixed-layer CAPE exceeding 2500 J/kg, but general magnitudes on the order of 1000-2000 J/kg appear probable, beneath a modest (but increasingly favorably sheared) west to northwesterly mid-level flow regime. With the onset of mid-level height falls, possibly aided by an embedded short wave perturbation, scattered vigorous thunderstorms are expected to develop across and to the lee of the southern Rockies late Sunday afternoon and evening. Given the thermodynamic profiles, including the steep lapse rates and a considerable degree of unsaturation in lower/mid-levels, some of this activity may gradually organize and pose a risk for marginally severe wind and hail before weakening Sunday evening. ...Southern Mid Atlantic Coast vicinity... Strong thunderstorm development might become possible near and in advance of the developing frontal wave, particularly across parts of southeastern Virginia/eastern North Carolina late Sunday afternoon and evening. Despite generally weak lower/mid-tropospheric lapse rates, it appears that boundary-layer moisture might be sufficient to support moderate to large mixed-layer CAPE. However, due to lingering uncertainties, including the likely continuing presence of generally weak wind fields and shear, it remains unclear if the severe weather threat will meet or exceed 5 percent severe probabilities. ..Kerr.. 09/09/2023 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 Sep 08 2023 Valid 101200Z - 161200Z A building high across the central/western US will bring dry and warm conditions across much of the western US and keep winds primarily light, tempering the fire weather risk within the extended period. Moisture is expected to return across the Southwest and Central/Southern Plains late D3 Sunday/D4 Monday, bringing a return of wetting rainfall and thunderstorm chances. Very little rainfall is expected across the West Coast and Pacific Northwest which will likely lead to some drying of fuels. By D6 Wednesday - D7 Thursday, a deepening trough across the Great Lakes will lead to a westward shift of the ridge axis. Overall, no widespread signal for sustained 20 mph within receptive fuels precludes the need to include any areas. ..Thornton.. 09/08/2023 ...Please see www.spc.noaa.gov/fire for graphic product... Read more