Severe Storms

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

MD 2112 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF FAR NORTHERN NORTH CAROLINA INTO SOUTHEAST VIRGINIA
Mesoscale Discussion 2112 NWS Storm Prediction Center Norman OK 0420 PM CDT Fri Sep 08 2023 Areas affected...portions of far northern North Carolina into southeast Virginia Concerning...Severe potential...Watch unlikely Valid 082120Z - 082245Z Probability of Watch Issuance...20 percent SUMMARY...A few instances of severe wind or hail remain possible for the rest of the afternoon. The severe threat should be relatively isolated and a Severe Thunderstorm Watch issuance is not expected. DISCUSSION...Multicellular storms are propagating north toward the NC/VA border, and some of these storms have a history of producing severe wind and hail (including a measured gust exceeding 65 kts an hour or so ago). While vertical shear is weak, these storms should continue developing northward and pulse in intensity amid a heated boundary layer (90+ F surface temperatures supporting 2500+ J/kg MLCAPE). Damaging gusts remain the main threat, though an instance or two of severe hail may still occur with the stronger storm cores given 7+ C/km mid-level lapse rates. The severe threat should remain isolated into the evening hours, so a Severe Thunderstorm Watch issuance is not currently anticipated. ..Squitieri/Thompson.. 09/08/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...AKQ...RAH...RNK... LAT...LON 36357912 37077859 37427775 37477736 37267686 36907627 36387626 36197642 36147768 36357912 Read more

WW 0675 Status Updates
STATUS REPORT ON WW 675 THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA. FOR ADDITIONAL INFORMATION SEE MESOSCALE DISCUSSION 2111 ..LYONS..09/08/23 ATTN...WFO...BOX...ALY...GYX... STATUS REPORT FOR WS 675 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS CTC003-005-013-082240- CT . CONNECTICUT COUNTIES INCLUDED ARE HARTFORD LITCHFIELD TOLLAND MEC001-005-007-011-013-015-017-023-025-027-031-082240- ME . MAINE COUNTIES INCLUDED ARE ANDROSCOGGIN CUMBERLAND FRANKLIN KENNEBEC KNOX LINCOLN OXFORD SAGADAHOC SOMERSET WALDO YORK MAC003-009-011-013-015-017-027-082240- MA . MASSACHUSETTS COUNTIES INCLUDED ARE Read more

WW 675 SEVERE TSTM CT MA ME NH NY VT CW 081935Z - 090300Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 675 NWS Storm Prediction Center Norman OK 335 PM EDT Fri Sep 8 2023 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Connecticut Massachusetts Maine New Hampshire Eastern New York Southern Vermont Coastal Waters * Effective this Friday afternoon and evening from 335 PM until 1100 PM EDT. * Primary threats include... Scattered damaging wind gusts to 70 mph likely Isolated large hail events to 1.5 inches in diameter possible SUMMARY...Clusters of storms will continue to develop across the region, with damaging winds and some hail possible with the strongest storms. The severe thunderstorm watch area is approximately along and 80 statute miles east and west of a line from 45 miles west northwest of Bangor ME to 40 miles west southwest of Windsor Locks CT. 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 674... 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 550. Mean storm motion vector 23025. ...Guyer Read more

WW 0674 Status Updates
000-082240- STATUS REPORT ON WW 674 THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA. FOR ADDITIONAL INFORMATION SEE MESOSCALE DISCUSSION 2111 ..LYONS..09/08/23 ATTN...WFO...OKX...LWX...PHI...BGM...CTP...RLX... STATUS REPORT FOR WS 674 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS CTC001-009-082240- CT . CONNECTICUT COUNTIES INCLUDED ARE FAIRFIELD NEW HAVEN DEC001-003-005-082240- DE . DELAWARE COUNTIES INCLUDED ARE KENT NEW CASTLE SUSSEX DCC001-082240- DC . DISTRICT OF COLUMBIA COUNTIES INCLUDED ARE DISTRICT OF COLUMBIA Read more

WW 674 SEVERE TSTM CT DC DE MD NJ NY PA VA WV CW 081910Z - 090300Z
WVZ000-CWZ000-090300- URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 674 NWS Storm Prediction Center Norman OK 310 PM EDT Fri Sep 8 2023 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Southwest Connecticut District Of Columbia Delaware Maryland New Jersey Southern New York Eastern and South-Central Pennsylvania Northern Virginia Eastern West Virginia Coastal Waters * Effective this Friday afternoon and evening from 310 PM until 1100 PM EDT. * Primary threats include... Scattered damaging wind gusts to 65 mph likely Isolated large hail events to 1.5 inches in diameter possible SUMMARY...Multiple corridors of storms will continue to increase and intensify through late afternoon/early evening, including near-coastal areas and the I-95 corridor as well as near the mountains/Blue Ridge. Damaging winds can be expected regionally along with some hail. The severe thunderstorm watch area is approximately along and 105 statute miles east and west of a line from 50 miles east northeast of Wilkesbarre PA to 25 miles east of Staunton VA. 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 55 knots. A few cumulonimbi with maximum tops to 550. Mean storm motion vector 22025. ...Guyer Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Fri Sep 08 2023 Valid 082000Z - 091200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHEAST AND MID-ATLANTIC REGION...AND OVER PARTS OF THE EASTERN TEXAS/SOUTHERN LOUISIANA VICINITY... ...SUMMARY... Scattered damaging winds and isolated large hail remain possible across parts of the Mid-Atlantic States into New England into this evening, and across parts of the South-Central States in multiple rounds through tonight. ...Discussion... Convection, and associated severe-weather risk, continues to evolve largely as anticipated in earlier outlooks. As such, no substantive changes to outlook areas or reasoning appear necessary at this time. The most substantial adjustments were to remove portions of Florida from MRGL risk, in the wake of earlier storms which have moved offshore, and to trim parts of the MRGL and SLGT north of the convective line now moving southward across southern Louisiana. ..Goss.. 09/08/2023 .PREV DISCUSSION... /ISSUED 1123 AM CDT Fri Sep 08 2023/ ...Mid-Atlantic States to New England... Thunderstorms this afternoon through early evening will again be capable of damaging winds and hail, in a scenario somewhat similar to yesterday. Late morning/midday observations continue to suggest that abundant insolation east of the Appalachians, combined with a pervasive plume of 60s to low 70s F surface dew points, will yield a pronounced west/east-oriented gradient in MLCAPE across the region, with peak values approaching 2500-3000 J/kg over the coastal plain. Scattered thunderstorms are expected to develop within the MLCAPE gradient from near the West Virginia/Virginia border northeast into parts of eastern New England. With forecast soundings suggesting nearly unidirectional southwest flow will weaken with height from the mid to upper-levels, multicell clustering will dominate. 700-mb winds in excess of 30 kt from eastern New York to Maine should support slightly more organized clustering. Steeper low-level lapse rates from Virginia to the Delaware Valley should compensate for the weaker flow and support relatively more prolific downburst potential. Scattered damaging winds along with isolated severe hail are expected regionally, mainly from mid-afternoon into evening. ...Texas/Oklahoma Red River vicinity and Sabine Valley... An elevated semi-organized linear cluster of storms persists southward at late morning across northern Louisiana. While boundary layer inhibition still currently exists, relatively cloud-free skies are noted to its south, with some potential that this cluster and/or new development on its western-peripheral outflow could root within a very moist/heating boundary layer. If so, damaging winds would be possible across southern Louisiana/southeast Texas. Farther to the northwest along the Red River Valley, record hot temperatures and a deep-mixed boundary layer should support sporadic downbursts from late afternoon to early evening with isolated thunderstorms that develop near the surface front. Some of this activity may try to congeal and grow upscale south-southeastward into east Texas during the evening/overnight within the persistent northwest flow regime atop the low-level moisture gradient. But low confidence exists in this scenario, with potential effects of the daytime round of storms modulating the downstream environment and ascent. ...Northern High Plains to Black Hills vicinity... Relatively isolated instances of severe wind and hail will be possible across the region. A low-amplitude shortwave impulse along the international border over the northern Rockies will move eastward today toward the northern High Plains. Forcing for ascent attendant to this wave will support isolated to scattered thunderstorms focused primarily across the southern half of Montana, but perhaps also far northeast Wyoming and the Black Hills vicinity as well. While there will be MLCIN concerns to the north and east, 35-45 kt effective bulk shear should support a few organized cells capable of isolated severe wind and hail. A more favorable supercell wind profile will conditionally exist near the Black Hills pending sustained storm development. ...Northern/central Florida... A mid-level low near the Florida/Georgia border should slowly weaken as it drifts south today. Relatively cold mid-level temperatures sampled by the 12Z JAX sounding of -13 C at 500 mb should support enhanced CAPE profiles between 700-300 mb yielding pronounced vertical growth. Effective bulk shear will tend to remain weak, especially near the cold core, suggesting the potential for organized storms is limited. Still, sporadic occurrences of marginally severe hail and wind are possible, mainly this afternoon. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0252 PM CDT Fri Sep 08 2023 Valid 091200Z - 101200Z ...NO CRITICAL AREAS... No changes are needed to the D2 Fire Weather Outlook. See previous discussion below. ..Thornton.. 09/08/2023 .PREV DISCUSSION... /ISSUED 0150 AM CDT Fri Sep 08 2023/ ...Synopsis... Upper ridging will persist across the southwestern into the south-central U.S. tomorrow/Saturday. RH should dip to or just below 20 percent by afternoon peak heating across the southern Plains. However, the upper ridging pattern supports an overall weaker surface wind field, precluding the introduction of Elevated highlights this outlook. Isolated thunderstorms (perhaps some dry) seem more probable closer to the TX/NM border. However, storms in these areas will overspread relatively less receptive fuels, so dry thunderstorm highlights have been withheld. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

MD 2100 CONCERNING SEVERE THUNDERSTORM WATCH 673... FOR FAR EASTERN PENNSYLVANIA...CENTRAL AND EASTERN NEW YORK...WESTERN NEW JERSEY
Mesoscale Discussion 2100 NWS Storm Prediction Center Norman OK 0513 PM CDT Thu Sep 07 2023 Areas affected...Far eastern Pennsylvania...central and eastern New York...western New Jersey Concerning...Severe Thunderstorm Watch 673... Valid 072213Z - 072345Z The severe weather threat for Severe Thunderstorm Watch 673 continues. SUMMARY...The severe threat continues across Severe Thunderstorm Watch 673. Damaging gusts remain the main concern, particularly with bowing segments embedded within the broader line of storms. DISCUSSION...A mature line of thunderstorms continues to move across the Hudson Valley, with a bowing segment (potentially augmented by a subtle MCV located to the west) currently tracking over central NY. Surface temperatures in the 85-90 F range continues to support MLCAPE up to 2500 J/kg, which should support additional damaging gusts into the evening. Damaging gusts may be most common with the bowing line segment in central NY. Isolated instances of hail may continue with the more discrete convection in far eastern NY. ..Squitieri.. 09/07/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BTV...OKX...ALY...PHI...BGM...BUF...CTP...LWX... LAT...LON 42867687 43727586 43997500 43937422 43577372 42637376 41707418 40867447 40167512 39457596 39257660 39327684 39897660 40847607 41307571 41907553 42367610 42867687 Read more

MD 2099 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF WESTERN MAINE
Mesoscale Discussion 2099 NWS Storm Prediction Center Norman OK 0450 PM CDT Thu Sep 07 2023 Areas affected...portions of western Maine Concerning...Severe potential...Watch unlikely Valid 072150Z - 072315Z Probability of Watch Issuance...20 percent SUMMARY...Damaging gusts may accompany a small multicell cluster across western ME over the next couple of hours. Areal coverage is expected to be a limited with this storm cluster and a WW issuance is not anticipated. DISCUSSION...A small MCS is traversing the NH/Canada border, and is propagating eastward toward far western ME, where 2000+ J/kg MLCAPE resides. MRMS mosaic radar shows some slight bowing with the leading-line reflectivity, indicative of an appreciable cold pool contributing to forward propagation. Continued downbursts will both sustain the cold pool and promote damaging gust potential for at least the next couple of hours. Since the severe wind threat should remain isolated and spatially confined to the counties closest to the border, a WW issuance is not expected. ..Squitieri/Thompson.. 09/07/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...CAR...GYX... LAT...LON 45167139 45337115 45477085 45847033 46007004 45886982 45486976 45056991 44747027 44697063 44687095 44727144 45167139 Read more

WW 0673 Status Updates
STATUS REPORT ON WW 673 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 15 SW BWI TO 30 SE BGM TO 20 W ITH. ..SUPINIE..09/07/23 ATTN...WFO...LWX...OKX...PHI...ALY...BGM...CTP... STATUS REPORT FOR WS 673 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS MDC003-015-025-033-510-072240- MD . MARYLAND COUNTIES INCLUDED ARE ANNE ARUNDEL CECIL HARFORD PRINCE GEORGES MARYLAND INDEPENDENT CITIES INCLUDED ARE BALTIMORE CITY NJC013-019-027-031-037-039-041-072240- NJ . NEW JERSEY COUNTIES INCLUDED ARE ESSEX HUNTERDON MORRIS PASSAIC SUSSEX UNION WARREN NYC001-007-017-021-023-025-027-035-039-041-043-053-057-065-067- Read more

WW 673 SEVERE TSTM DC MD NJ NY PA VA WV CW 071705Z - 080100Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 673 NWS Storm Prediction Center Norman OK 105 PM EDT Thu Sep 7 2023 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of District Of Columbia central Maryland northwestern New Jersey central and eastern New York central and eastern Pennsylvania northern Virginia eastern West Virginia Coastal Waters * Effective this Thursday afternoon and evening from 105 PM until 900 PM EDT. * Primary threats include... Scattered damaging wind gusts to 70 mph possible Isolated large hail events to 1.5 inches in diameter possible SUMMARY...Thunderstorms developing east of the Allegheny and Blue Ridge Mountains will gradually develop north-northeastward during the next couple of hours, before eventually growing into one or two larger storm clusters. Thereafter, increasing risk for potentially damaging wind gusts is possible on expanding thunderstorm outflows spreading northeastward and eastward into early evening. The severe thunderstorm watch area is approximately along and 70 statute miles east and west of a line from 40 miles southeast of Hagerstown MD to 40 miles west northwest of Glens Falls NY. 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. && 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 24035. ...Kerr Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook CORR 1 NWS Storm Prediction Center Norman OK 0312 PM CDT Thu Sep 07 2023 Valid 072000Z - 081200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHEAST... CORRECTED THUNDER LINE ...SUMMARY... Thunderstorms -- some capable of producing locally damaging wind gusts and marginally severe hail -- will continue across portions of the Mid-Atlantic region and into New England into this evening. ...Discussion... Current expectations with regard to the convective scenario through tomorrow morning remain in line with prior reasoning. As such, aside from minor line adjustments, the overall forecast will remain unchanged with this outlook update. ..Goss.. 09/07/2023 .PREV DISCUSSION... /ISSUED 1110 AM CDT Thu Sep 07 2023/ ...Synopsis... A mid-level high, centered over the southeastern New Mexico vicinity, appears likely to remain prominent through this period, with large-scale ridging building to its north, through much of the Rockies and adjacent Great Plains today through tonight. Downstream, several perturbations, comprising weak but amplifying larger-scale mid-level troughing east of the Mississippi Valley, are forecast to remain generally progressive, though mid-level ridging may continue to build near/east of the middle and northern Atlantic Seaboard, in the wake of a modest cyclone migrating eastward across portions of the Canadian Maritimes. The two more significant perturbations include a remnant mid-level trough forecast to slowly accelerate northeast of the lower Great Lakes region through southern Ontario and Quebec, and a weak developing mid-level low forecast to dig south-southeast of the lower Ohio Valley through Alabama/Georgia by 12Z Friday. East of these features, and ahead of a cold front which has already advanced into the Appalachians vicinity (while stalling across parts of the lower Mississippi Valley into southern Great Plains), deep-layer southerly mean flow and shear will likely remain mostly rather modest to weak (less than 20 kt). However, models do suggest that a more subtle perturbation migrating north-northeast of the Blue Ridge might contribute to a belt of modest south-southwesterly mid-level flow along the western periphery of the building ridge, with at least some signal that this could also become convectively augmented by tonight. ...Atlantic Seaboard... Seasonably moist air, beneath relatively steep lower/mid-tropospheric lapse rates, likely will contribute to sizable mixed-layer CAPE to the east of developing surface troughing to the lee of the Appalachians. This could become supportive of developing clusters of storms with potential to produce strong wind gusts, as convection initiates and slowly propagates off the higher terrain this afternoon. The most prominent and concentrated area of thunderstorm development still appears likely to be focused with the increasingly sheared short wave impulse and modestly strengthening southerly mid-level flow (30+ kt in the 700-500 mb layer) across eastern Pennsylvania and New York, and adjacent portions of the Mid Atlantic and New England, through early evening. This may include an upscale growing, and gradually organizing, thunderstorm cluster or two which may eventually pose a risk of producing a swath of strong to severe surface gusts. ...Lower Mississippi Valley/Gulf Coast vicinity... Destabilization associated with a corridor of strong pre-frontal daytime heating may become sufficient for thunderstorms capable of producing damaging wind gusts, perhaps aided by modest deep-layer shear near the leading edge of strengthening north-northwesterly mid/upper flow. ...Southern Great Plains... Potential for sustained convective development within a very warm and deeply mixed boundary across the Texas Panhandle into western Oklahoma late this afternoon remains uncertain. However, to the east of the lee surface trough, warm advection and lift associated with a nocturnal strengthening south-southwesterly low-level jet will pose better potential for thunderstorm development across northern/eastern Oklahoma tonight. It is possible that elevated instability and unsaturated sub-cloud air may be sufficient to contribute to potential for hail and gusty surface winds with some of this activity. ...Northern Great Plains... Models suggest that daytime heating may contribute to a deep mixed boundary layer with modest CAPE, along and south of a developing zone of stronger differential surface heating, southeast of the Black Hills into central Nebraska. Aided by forcing for ascent associated with a short wave digging around the northeastern periphery of the building larger-scale ridging, isolated strong thunderstorm development posing a risk for producing strong surface gusts is possible for a period late this afternoon and evening. Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0157 PM CDT Thu Sep 07 2023 Valid 091200Z - 151200Z The potential for critical fire weather conditions remains low across the country through the extended period. Long-range ensemble guidance continues to show a building upper-level ridge over the Southwest/northern Mexico through the weekend, followed by a gradual ridge breakdown and an amplifying longwave trough east of the Rockies. This synoptic regime will favor a continuation of warm, dry conditions from west TX into the Four Corners through D4/Sunday, which should favor a slow curing of fuels and may support local fire weather concerns. Rain chances will increase across the Plains and Southwest beginning D5/Monday, limiting the fire weather potential through the remainder of the week. Ensemble precipitation forecasts show low probability for wetting rainfall across much of the West Coast and Pacific Northwest, suggesting some drying will occur across these regions. However, there are currently no appreciable signals for strong synoptic systems that would support widespread 20+ mph winds, which limits confidence in the fire weather potential. ..Moore.. 09/07/2023 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1256 PM CDT Thu Sep 07 2023 Valid 081200Z - 091200Z An isolated dry-thunderstorm risk area is introduced for portions of west to northwest Texas. Latest CAM ensemble guidance has trended towards a higher probability and coverage of thunderstorms in the vicinity of the surface low over northwest TX tomorrow afternoon. Forecast soundings depict very dry boundary-layer conditions featuring LCL heights between 3.5 to 4 km and 50-60 F dewpoint depressions. These profiles will greatly limit rainfall amounts and promote dry lightning over a region with dry fuels. One conditionality is the potential for thunderstorms over the next 12-18 hours across this region; however, a similar thermodynamic environment today should yield very isolated patches of wetting rain, and is not expected to drastically alter the fuel landscape. ..Moore.. 09/07/2023 .PREV DISCUSSION... /ISSUED 1236 AM CDT Thu Sep 07 2023/ ...Synopsis... A slight westward shift in the upper-level ridge is expected on Friday. The surface pattern will remain relatively similar in the southern High Plains, though the surface low may shift farther south and east. ...Southern High Plains... Dry and breezy conditions will again be possible both north and south of the surface trough. Only marginally elevated conditions are probable to the north of the trough in the Texas Panhandle, as winds will be upslope and temperatures will be cooler than on Thursday. Winds to the south of the trough are expected to be weak. There is some additional potential for a thunderstorm or two to develop within the surface trough. While any storm that develops would likely be dry, coverage appears to be much less than 10% at this time. ...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 1245 PM CDT Thu Sep 07 2023 Valid 081200Z - 091200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN PORTIONS OF THE SOUTHERN PLAINS AND ACROSS THE SABINE RIVER VALLEY...AND OVER PARTS OF THE NORTHEAST AND MID-ATLANTIC REGION... ...SUMMARY... Thunderstorms, associated with a marginal severe threat, will be possible on Friday across parts of the Northeast, Central Appalachians, Mid-Atlantic, Ark-La-Tex and Northern High Plains. ...Southeastern Oklahoma/eastern Texas/southwestern Arkansas/western Louisiana... Thunderstorms are forecast to be ongoing at the start of the period across parts of the eastern Oklahoma/western Arkansas region, possibly accompanied by some ongoing potential for strong winds/hail. A strong model signal remains apparent that storms will shift southward with time, strengthening gradually as daytime heating results in a corridor of moderate instability. Given a belt of 35 to 45 kt mid-level north-northwesterly flow around the eastern fringe of the southwestern U.S. upper ridge, potential for an organized MCS moving quickly southward roughly along the Sabine River Valley through the day may evolve. In this scenario, potential for damaging winds would be expected, along with some hail, with the risk shifting southward and likely reaching the Gulf Coast by late afternoon. While less certain, some hints exist within some models that late evening/overnight redevelopment of storms could occur on the western flank/remnant outflow from this initial band of storms, across the north-central Texas vicinity, with potential for a second/southeastward-moving MCS. These storms -- should they develop/organize, could also pose risk for hail and damaging winds through the overnight period. ...The Northeast and Mid-Atlantic region... Afternoon heating/destabilization is expected along and east of the Appalachians Friday, near a weak/stalled surface front. Terrain-induced ascent, and lift near the front, will result in scattered thunderstorm development during the afternoon, particularly from the mountains of Virginia and West Virginia northeastward into New England. With a belt of 25 to 35 kt south-southwesterly flow across this area, on the eastern fringe of the mid-level trough positioned over the Midwest/Tennessee Valley, shear will support a few organized storms/storm clusters. As these clusters shift northeastward, locally damaging wind gusts can be expected, lingering into the early evening hours before storms begin to nocturnally weaken. ...Northern Intermountain region... Daytime heating across the northern Intermountain region will result in modest destabilization, with mixed-layer CAPE averaging 500 J/kg during the afternoon atop a deep mixed layer. As a short-wave trough at mid levels sweeps eastward across the region, isolated to widely scattered thunderstorm development is expected, with peak convective coverage anticipated from late afternoon through mid evening. With a belt of 30 to 40 kt mid-level westerlies accompanying the short-wave trough, and potential for sub-cloud evaporative effects, a few stronger/longer-lived storms may produce gusty/locally damaging winds. ..Goss.. 09/07/2023 Read more

WW 0672 Status Updates
STATUS FOR WATCH 0672 HAS NOT BEEN ISSUED YET Read more