Severe Storms

WW 274 TORNADO AL FL MS CW 261245Z - 261900Z
URGENT - IMMEDIATE BROADCAST REQUESTED Tornado Watch Number 274 NWS Storm Prediction Center Norman OK 745 AM CDT Thu May 26 2022 The NWS Storm Prediction Center has issued a * Tornado Watch for portions of Southern Alabama Panhandle of Florida Extreme southeastern Mississippi Coastal Waters * Effective this Thursday morning and afternoon from 745 AM until 200 PM CDT. * Primary threats include... A couple tornadoes possible Isolated damaging wind gusts to 70 mph possible SUMMARY...Several areas of thunderstorms, moving/expanding inland from the Gulf, will pose a threat for a couple tornadoes and some damaging gusts through midday. The tornado watch area is approximately along and 45 statute miles north and south of a line from 60 miles northwest of Mobile AL to 20 miles east northeast of Apalachicola FL. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU4). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Tornado Watch means conditions are favorable for tornadoes and 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. && AVIATION...Tornadoes and a few severe thunderstorms with hail surface and aloft to 1 inch. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 22030. ...Edwards Read more

MD 0922 CONCERNING TORNADO WATCH 274... FOR SOUTH AL...FL PANHANDLE
Mesoscale Discussion 0922 NWS Storm Prediction Center Norman OK 0946 AM CDT Thu May 26 2022 Areas affected...South AL...FL Panhandle Concerning...Tornado Watch 274... Valid 261446Z - 261615Z The severe weather threat for Tornado Watch 274 continues. SUMMARY...The threat for a brief tornado or two and locally damaging wind gusts will continue through the morning. DISCUSSION...Extensive convection has organized into multiple clusters across south AL into the FL Panhandle and northern Gulf of Mexico. Several embedded cells within the cluster offshore of Pensacola have shown periodic midlevel rotation, but thus far have weakened before moving onshore. Widespread cloudiness is noted over the FL Peninsula, limiting the potential for destabilization, but 0-1 km SRH in excess of 150 m2/s2 (as noted in KEVX VWP) will support a brief tornado threat near the coast, should any stronger cells make it onshore. Further west, a loosely organized, outflow-driven cluster is ongoing east of Mobile. Locally damaging wind gusts will be possible as this cluster moves eastward through the morning. A brief embedded tornado will also be possible with any embedded circulations, as this cluster merges with the storms ongoing near/south of Pensacola. To the east, another cluster of storms is ongoing near/south of the FL Big Bend. Increasing low-level flow/shear later this morning may result in an uptick in storm organization within this cluster, resulting in a threat of locally damaging wind gusts and/or a brief tornado with any stronger convection that is able to move onshore. ..Dean.. 05/26/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...TAE...MOB... LAT...LON 31228785 31558736 31348631 30578486 30338406 30068359 29758364 29498427 29408530 29748676 30118784 30418831 31048820 31228785 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0746 AM CDT Thu May 26 2022 Valid 261300Z - 271200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM OHIO TO PARTS OF SOUTHERN ALABAMA AND THE FLORIDA PANHANDLE... ...SUMMARY... Isolated to widely scattered severe thunderstorms are possible over parts of the inland Northwest, and from Ohio Valley region to the east-central Gulf Coast and southern Appalachians. ...Synopsis... A pronounced, slowly progressive, deep-layer cyclone was apparent in moisture-channel imagery over parts of KS, MO, OK, AR, southern IA and southeastern NE, centered roughly between JLN-TOP. The accompanying mid/upper-level trough extended southward across the Arklatex region to the northwestern Gulf. By 00Z, the 500-mb low should be over eastern MO, with trough roughly southward down the lower Mississippi Valley and offshore from LA. By 12Z, the low should reach the lower Wabash River area, with trough south-southwestward past BIX. Farther upstream, synoptic-scale ridging will cross the Rocky Mountain States, ahead of a complex, elongated mid/upper cyclone now located west of Vancouver Island and south of the Gulf of Alaska. Associated height falls and southwest flow aloft will spread inland over the Northwest. Embedded in that flow, a lead shortwave perturbation -- initially apparent with positive tilt from just west of the WA coast southwestward to about 600 nm W of SFO, will pivot inland across WA/OR around 00Z. The trough should weaken somewhat overnight as it accelerates toward the northern Rockies and the larger-scale ridge position. At the surface, 11Z analysis depicted a low near SZL, with cold front arching across southeastern MO, northwestern MS, and south-central LA. A warm front was drawn across northern IL, central Lower MI, and eastern OH, becoming quasistationary while wrapping around the Appalachians from Western WV to northeastern TN and northwestern SC. This front extended to another low offshore from HSE. By 00Z, the cold front should curve from the low near UIN across southern portions of IL/IN, middle TN, northern/southwestern AL, to near the mouth of the Mississippi River. By 12Z, it should reach eastern parts of KY/TN, the FL Panhandle, and the central Gulf. The eastern front should shift diffusely and slowly northward across the Carolinas later today. ...Ohio Valley region to Gulf Coast... Multiple rounds and areas of widely scattered to scattered thunderstorms are expected across the outlook area today into this evening -- both in the form of cold-frontal and prefrontal bands aligned roughly parallel to the cold front, and a blend of discrete cells and clusters in the weakly capped warm sector. Damaging to isolated severe gusts, a marginal overall tornado threat, and isolated severe hail are possible across a large swath from the Gulf Coast across the Ohio Valley and into the western Carolinas, with wind likely being the most common severe-report type. Convective coverage has been increasing gradually the last several hours near the Gulf Coast -- primarily over water, and may expand/develop inland with time this morning across AL and the FL Panhandle. This is occurring near a weak surface low between BVE-MOB and a related low-level convergence zone, within a richly moist air mass (low/mid 70s F surface dew points) supporting MLCAPE in the 1500-2500 J/kg range -- diminishing gradually with northward/inland extent across MS and western AL. Farther east, a baroclinic boundary is noted near or just off the FL Panhandle coastline between PAM and western Apalachee Bay, reinforced by precip from a complex extending well offshore (and which has contained occasional supercells appearing to be strengthened by vorticity in the baroclinic zone). That quasistationary boundary may limit inland penetration of favorable boundary-layer air in the near-term. Strongly difluent flow aloft also has been noted, rendering highly variable effective shear (magnitudes generally 25-50 kt, increasing inland into a currently less-unstable environment). See tornado watch 274 and related mesoscale discussions for more-updated near-term info on this region. Inland destabilization is expected later this morning into afternoon, related to both theta-e advection -- recovering west of the Panhandle/Gulf complex and its dissipated northward extension over eastern AL and GA. This may support both an inland growth of the Gulf activity over the next few hours, and later-morning/ afternoon development along/ahead of the front well inland across the Tennessee/Ohio Valleys. 35-50-kt effective-shear magnitudes (with shear and mean-wind vectors obliquely off the frontal alignment) will support mixed convective modes, but mainly linear. The "slight" areas have been connected accordingly, though a relative minimum in severe potential still may exist farther east near the mountains, where effects of the "wedge" front will be more persistent. Backed low-level winds preceding convection closer to the low, over IL/IN, also may support some hodograph enlargement, and marginal tornado probabilities have been expanded into those areas. Conditional, mesoscale to localized maxima in tornado potential also may exist near the Carolinas front (but with considerable uncertainty related to mode and cross-boundary cell motion), and in the weaker-instability arc along/ahead of the front over the IL/IN region. If any of those becomes better-focused and less conditional, an upgrade in those probabilities may be considered in a succeeding outlook. ...Interior Northwest... Isolated to scattered thunderstorms are expected to develop over western portions of OR/WA and central OR late this afternoon, then move northeastward into the evening. Meanwhile, the environment from central/eastern OR and southeastern WA, northeastward across western/northern ID, will best support severe potential, in the form of gusts and hail. Antecedent diurnal heating of lower terrain east of the Cascades will lead to a deep, well-mixed boundary layer beneath increasing midlevel moisture. Preconvective lapse rates aloft are expected to increase as well, related to large-scale DCVA/ascent preceding the shortwave trough. Pockets of MLCAPE near 500 J/kg are possible, with a broad area exceeding 100 J/kg -- nonetheless extending into thermal layers suitable for lightning generation. Although low- level hodograph size and shear-vector magnitudes will be limited by some westerly to northerly near-surface wind components, favorable deep shear will exist for either high-based supercells or organized bowing structures. Any hail associated with the former would be well-maintained to the surface through the subcloud layer, and large DCAPE will support the potential for cold pools to aggregate and produce a wind swath with a northeastward thrust into ID. ..Edwards/Kerr.. 05/26/2022 Read more

WW 0273 Status Updates
STATUS FOR WATCH 0273 HAS NOT BEEN ISSUED YET Read more

WW 273 SEVERE TSTM LA MS 251435Z - 252200Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 273 NWS Storm Prediction Center Norman OK 935 AM CDT Wed May 25 2022 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Eastern Louisiana Central and Southern Mississippi * Effective this Wednesday morning and afternoon from 935 AM until 500 PM CDT. * Primary threats include... Scattered damaging wind gusts to 70 mph likely A tornado or two possible SUMMARY...A line of thunderstorms and isolated cells ahead of the line will track northeastward across the watch area today. Locally damaging wind gusts and an isolated tornado or two are the main threats. The severe thunderstorm watch area is approximately along and 60 statute miles east and west of a line from 45 miles east northeast of Greenwood MS to 30 miles west southwest of Slidell LA. 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 inch. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 23025. ...Hart Read more

MD 0912 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR EASTERN/SOUTHEASTERN LOUISIANA INTO SOUTHERN/CENTRAL MS
Mesoscale Discussion 0912 NWS Storm Prediction Center Norman OK 0923 AM CDT Wed May 25 2022 Areas affected...eastern/southeastern Louisiana into southern/central MS Concerning...Severe potential...Watch possible Valid 251423Z - 251600Z Probability of Watch Issuance...60 percent SUMMARY...Sporadic strong gusts and a tornado or two will be possible the remainder of the morning into the afternoon across parts of far eastern/southeastern Louisiana into southern/central Mississippi. DISCUSSION...A line of storms along a composite outflow and ahead of a surface cold front will continue to shift east/northeast through the remainder of the morning and into the afternoon. Pockets of heating ahead of the line and surface dewpoints in the upper 60s to low/mid 70s F is aiding in moderate destabilization this morning, with MLCAPE values around 1500-2500 J/kg. However, effective shear magnitudes are expected to remain modest through the day at around 30 kt. Furthermore, both low and midlevel lapse rates are expected to remain weak. This will limit storm intensity overall, but the parameter space will adequately support at least brief strong embedded cells or bows along the line. The main hazard with this activity will be strong gusts in the 40-50 kt range. Regional VWP data also shows enlarged, curved low-level hodograph, which could support rotation within the line or in cellular activity ahead of the line. While low-level lapse rates are poor, 0-3 km MLCAPE greater than 100 J/kg and some enhanced low-level vorticity could support a brief spin-up in more intense convection. Convective trends will be monitored and a watch may be needed. ..Leitman/Hart.. 05/25/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...MOB...JAN...LIX...LCH... LAT...LON 30909181 31709177 32519159 32909123 33139038 33108988 32998940 32668896 32308870 31878854 30578846 29608870 29078906 28978977 28959038 29049109 29319143 29729171 30639171 30909181 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0746 AM CDT Wed May 25 2022 Valid 251300Z - 261200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF EASTERN LOUISIANA...MISSISSIPPI...AND WESTERN ALABAMA... ...SUMMARY... Strong to severe thunderstorms are possible from the central Gulf Coast into parts of the lower/mid Mississippi Valley, Southeast, Midwest, and Ohio Valley. ...Synopsis... The main mid/upper-level feature for this forecast will be a well-defined synoptic trough now over the Plains States southward to northeastern MX, with a 500-mb low re-forming across western OK at this time. The low should move erratically northeastward to near the southern part of the KS/MO line by 12Z tomorrow, with trough southward across the Arklatex and western Gulf. Small, convectively induced/augmented vorticity maxima will eject northeastward to northward ahead of the trough, across parts of the lower/mid Mississippi and Ohio Valleys, Tennessee Valley and central Gulf Coast. At the surface, 11Z analysis showed a low over northeastern KS, with a cold front arching across the OK/MO border area, northeast TX, and east-central TX, to near LRD. The cold front was preceded by a convective/outflow boundary from northeastern MX and near BRO northeastward across western LA. A warm front was drawn over northern MO, north-central IL, and central portions of IN/OH, though several areas of convection have altered the sector south of the synoptic warm front. The cold front should move eastward slowly across much of AR and LA through the period, preceded at least into this evening by the convective boundary. Meanwhile, the low should split, with one part moving northeastward along the warm front to WI tonight, and the other stacking more vertically with the mid/upper cyclone center. ...Gulf Coast States, Delta region, Mid-South, TN Valley... Scattered thunderstorms are possible in multiple episodes through the period, the main one likely being associated with a band of convection now extending from western LA across the northwestern Gulf. Sporadic damaging winds and a few line-embedded tornadoes are possible. This activity, and the associated corridor of outflow- aided convective lift, are expected to shift eastward into a low-level air mass destabilized by a combination of: 1. Theta-e advection from the south, with 70s F surface dew points already common south of I-20 between western AL and western LA; 2. Patchy areas of diurnal surface heating, in relative breaks of cloud cover between the convective band and a separate area of thunderstorms initially over AL and the western FL Panhandle. These factors should offset modest midlevel lapse rates enough to support MLCAPE near 2000 J/kg over southern LA/MS, decreasing to around 500-1000 J/kg northward over parts of the Mid-South region. Mid/upper-level winds and deep speed shear will increase with time as the synoptic trough approaches, but with little change in direction in the vertical profile. As such, forecast soundings show peak effective-shear magnitudes only reaching the 30-40-kt range, supporting organized multicells, QLCS mode, short-lived supercell structures, and a few bow/LEWP formations with associated mesocirculations. Additional strong/isolated severe thunderstorms may persist this morning across the east-central Gulf Coast region from the FL Panhandle into AL, as well as develop behind the remnants of original convective line tonight across parts of LA/MS/southern AL. The severe potential with the overnight activity (wind, perhaps tornado) is more uncertain, and dependent on the extent of airmass recovery behind the daytime complex. However, the bulk of any such nocturnal threat should be contained within the upgraded outlook area as drawn. ...Eastern Ozarks, mid Mississippi/lower Ohio Valleys... Widely scattered to scattered thunderstorms are expected to form this afternoon in an arc along/ahead of the front, and northeast through east of the surface low, over parts of northeastern AR and eastern MO. This activity should shift into IL before weakening appreciably. Widely scattered thunderstorms also should develop today in a zone of increasing low-level moisture and slowly eroding MLCINH in the partially modified warm sector across parts of IL/IN/OH/KY ahead of the near-frontal arc. At least a marginal wind/tornado threat may develop, along with isolated hail. The convective arc will be located in a zone of relatively maximized deep-layer lift and low-level convergence ahead of the progressive mid/upper cyclone, with relatively backed near-surface flow aiding boundary-layer shear. However, weak middle-level lapse rates and muted surface heating due to cloud cover (limiting low-level lapse rates) will temper buoyancy in this regime, which will be located well north of the richest Gulf moisture. MLCAPE generally in the 300-800 J/kg range is expected with little to no MLCINH left by midafternoon, enabling development and maintenance of this activity, which may link up with the northern extent of the LA/MS convective band discussed above. If mesoscale trends and subsequent model guidance indicate more destabilization (surface or aloft), or stronger sustained lift, greater severe probabilities may need to be extended north into this region. ..Edwards/Kerr.. 05/25/2022 Read more

No watches are valid as of Tue May 24 14:51:02 UTC 2022.

MD 0897 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR UPPER TEXAS COAST VICINITY
Mesoscale Discussion 0897 NWS Storm Prediction Center Norman OK 0948 AM CDT Tue May 24 2022 Areas affected...Upper Texas Coast vicinity Concerning...Severe potential...Watch unlikely Valid 241448Z - 241615Z Probability of Watch Issuance...20 percent SUMMARY...Locally strong gusts may occur across portions of the Upper Texas Coast the next couple of hours. DISCUSSION...A band of strong storms is lifting northward near the Upper Texas Coast this morning at around 40 kt. Latest radar data indicates a pocket of 45-55 kt velocities around 1-2 kft. Deep-layer flow is rather weak, but some local enhancement is likely occurring as this activity is developing on the east side of an MCV/lead shortwave impulse shifting east toward the Middle Texas Coast. Surface dewpoints in the low 70s are supporting a corridor of 1500-2000 J/kg MLCAPE ahead of the line of convection. However, low and mid-level lapse rates remain weak, while DCAPE values are less than 1000 J/kg. Forecast RAP soundings do indicate a modest dry layer just above the surface, which could aid in stronger outflow as the convection advances quickly northward. Locally strong gusts may accompany this activity the remainder of the morning, but overall severe threat is expected to remain marginal and a watch is not expected at this time. ..Leitman/Hart.. 05/24/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LCH...HGX... LAT...LON 28779529 28969542 29839554 30149551 30329539 30429514 30519450 30479415 30319391 29949381 29409386 29099398 28919412 28799443 28759488 28779529 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0733 AM CDT Tue May 24 2022 Valid 241300Z - 251200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER CENTRAL...NORTH-CENTRAL AND NORTHEAST TEXAS... ...SUMMARY... Numerous thunderstorms are expected from west-central Texas into the ArkLaMiss region, some of which will produce hail, damaging winds, and a few tornadoes. ...Synopsis... The dominant mid/upper-level feature for this period will be a pronounced synoptic-scale trough -- initially located over the Rockies. An embedded vorticity maximum -- evident in moisture-channel imagery over south-central CO -- is expected to strengthen into a closed cyclone over the next several hours. The associated 500-mb low should reach east-central/southeastern CO near the KS border by 00Z, with trough south-southwestward across the TX Big Bend region. The low will move eastward over western KS overnight, while the trough assumes neutral to slightly negative tilt, reaching the TX Hill Country and Rio Grande Valley near LRD by the end of the period. A shortwave trough now evident over the Four Corners region should dig southeastward across NM today, perhaps with some convective vorticity augmentation this afternoon/evening, then become a strong basal shortwave trough tonight over the TX South Plains region, before pivoting east-northeastward toward north-central TX/south-central OK. East of the synoptic trough, a series of small shortwave perturbations -- many of them convectively induced/enhanced vorticity lobes -- will pivot northeastward across the Gulf Coast States, lower Mississippi Valley region, and GA/Carolinas. One of those -- now apparent in reflectivity composites and satellite imagery over west-central/southwestern AL -- should move northeastward to the eastern parts of TN/KY this evening while weakening. Another may arise from an MCS now offshore from deep south TX, and pivot northeastward toward the ArkLaMiss vicinity by this evening. Another -- related to ongoing convection over western OK and northwest TX -- should move northeastward to MO. There likely will be more. At the surface, 11Z analysis showed a low over NC between CLT-POB, with warm front eastward across the southern Outer Banks, and wavy/quasistationary front west-southwestward to northern LA. The boundary continues diffusely into northeast TX and southern OK as a warm front. Warm frontogenesis was evident along a boundary extending near an SPS-OKC-TUL-JLN-OWB line, and that will become the main front today as the Red River-area boundary gets more diffuse. An outflow-reinforced frontal zone extended from the SPS area southwestward to near MAF, then to near CNM and SRR. The NC low should move slowly eastward across that state today, along the front, with only slight northward drift of the boundary expected just ahead of the low. A separate low should develop by afternoon over northern OK/southern KS, becoming better defined and moving northeastward over eastern KS tonight. The trailing, outflow-reinforced cold front will move southeastward across much of OK and west TX through tonight. By 12Z, the boundary should reach from a newer/frontal-wave low over the Arklatex region southwestward across south-central TX to the Rio Grande Valley in the LRD-DRT corridor. ...Southern Plains to lower Mississippi Valley... A complex convective scenario will unfold this period, driven primarily (but not entirely) by activity related to the baroclinic zone and the perturbation(s) aloft pivoting through the synoptic trough. Ongoing convection over OK and near the Red River may pose a marginal wind threat as it impinges on a boundary layer with weak lapse rates, but slowly/advectively strengthening warm-sector moisture and theta-e through the afternoon. The best-organized severe potential appears to be from two other processes: 1. New development along the baroclinic zone across north through west-central TX this afternoon, some of which may be supercellular at first with large to isolated very large hail, localized damaging gusts and a tornado or two. However, this activity should grow upscale to a squall line rapidly as frontal forcing encounters (and increasing large-scale ascent passes over) the very moist warm- sector boundary layer across north, central and perhaps parts of southwest TX. The main threat will evolve to damaging and severe wind -- especially with surging/bowing segments. Localized significant (65+kt) wind corridors may develop, but will depend on mesobeta- and smaller-scale convective/cold-pool processes whose evolution still is uncertain at this point. Some potential for QLCS tornadoes will exist with this MCS as well for several hours this evening, as it encounters a combination of surface-based effective-inflow parcels and enlarging boundary-layer hodographs/SRH beneath a strengthening LLJ. Strengthening mid/upper flow through the day will improve deep-layer shear, with effective- shear magnitudes topping 50 kt near the north-central/ west-central TX frontal segment. Peak/preconvective MLCAPE should increase from around 1000 J/kg over eastern OK and AR to 2000-3000 J/kg across west-central TX and the Edwards Plateau vicinity. 2. A north-south, broken belt of convection forming in the post-frontal upslope-lift regime of east-central NM and moving southeastward. Though this activity will encounter some boundary- layer air processed by prior convection, it will be supported by residual moisture, midlevel cooling/lift near the trough, and modestly diurnally enhanced low-level instability, for a threat of strong-severe gusts and hail. Some of this convection may survive to reach the frontal zone over west-central TX, then either merge with or backbuild upon the above-mentioned MCS. ...Southeastern CONUS... Isolated to scattered thunderstorms are expected to develop, predominantly this afternoon, in a broad area of the Southeast. Damaging gusts will be the main concern. Coverage will vary greatly within this area, but likely greatest along boundaries (outflow, sea-breeze and differential-heating), and where mesoscale areas of lift related to the MCV(s) move atop the generally favorably moist environment across the region. Modest midlevel lapse rates and generally weak mid/upper winds will keep deep shear weak over most of the area, with storms mainly multicellular in nature. Brief supercell structures may develop where mass response to MCV-related processes boosts hodograph size locally. Isolated damaging gusts and perhaps a tornado also may occur over portions of eastern NC, south through east of the low where the moisture/buoyancy parameter space will be maximized today in combination with low-level shear. ..Edwards/Kerr.. 05/24/2022 Read more

No watches are valid as of Mon May 23 15:22:01 UTC 2022.

MD 0879 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF CENTRAL AND NORTHERN SOUTH CAROLINA
Mesoscale Discussion 0879 NWS Storm Prediction Center Norman OK 1020 AM CDT Mon May 23 2022 Areas affected...portions of central and northern South Carolina Concerning...Severe potential...Watch unlikely Valid 231520Z - 231645Z Probability of Watch Issuance...20 percent SUMMARY...A line of storms capable of isolated damaging wind gusts will persist across portions of South Carolina through early afternoon. DISCUSSION...A line of thunderstorms has moved across Georgia this morning on the eastern periphery of a compact warm-core low. These thunderstorms have recently shown a bit more organization as they have moved into South Carolina where temperatures have increased into the upper 70s to low 80s with dewpoints in the upper 60s to low 70s. Mid-level flow around 45 to 50 knots per CAE VWP has proven sufficient for some storm organization along this line. Therefore, at least some isolated damaging wind threat should persist through at least early afternoon. However, these storms are moving further away from the surface low and the compact wind field surrounding it. Therefore, despite improving instability through the afternoon, the damaging wind threat is expected to remain isolated due to the decreasing deep-layer shear and likely reduction in storm organization. ..Bentley/Hart.. 05/23/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...RAH...ILM...CHS...CAE...GSP... LAT...LON 33118098 33158155 33238177 33428196 33648195 34078200 34498204 34628206 35178183 35128111 34888045 34848021 34727961 34177970 33518019 33118098 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0752 AM CDT Mon May 23 2022 Valid 231300Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTHERN PLAINS... ...SUMMARY... Severe thunderstorms will be possible today into tonight across parts of the southern Plains, with large hail, severe wind gusts, and a tornado or two possible. Isolated damaging wind and a tornado may occur across parts of the Southeast. ...Synopsis... In mid/upper levels, broadly cyclonic flow will cover much of the Rockies and Plains, as a series of shortwave perturbations contribute to gradual amplification of a slowly eastward-moving synoptic trough. On the southeastern fringe of that regime, moisture-channel imagery indicates a weak southern-stream perturbation over northeastern Chihuahua and far west TX, east of another small trough over western Chihuahua. The leading feature should move east-northeastward across southwest/west-central TX today, with vorticity augmentation likely from convective processes. That perturbation should reach eastern OK and east TX by 12Z tomorrow. Meanwhile, behind the southern perturbation and over the southern High Plains, height falls will continue as the synoptic trough amplifies. By 12Z, the larger trough should extend nearly over the spine of the Rockies from MT-NM, with a prominent vorticity lobe over northeastern NM. Farther east, a deep-layer trough was apparent over AL, with weak low-level circulation centered near MGM at 11Z. This feature is forecast to move northeastward across northern GA and the western Carolinas through the period, while gradually deamplifying. At the surface, 11Z analysis depicted a cold front over the Atlantic east and south of New England, becoming quasistationary across northern/western NC, southeastern TN and northern AL, then a slow- moving cold front again over central MS, southern LA, and the mid/upper TX coastal-shelf waters. A quasistationary to warm front was drawn from there across south TX to a low near FST. A separate low north of MGM should move northeast and merge with the frontal zone through the day. The TX part of the front will move northward and become diffuse, amid an intensifying, broad, low-level warm- advection plume. A dryline should develop today over eastern NM, along the western edge of the associated moisture return. Another frontal zone will develop farther northeast by 00Z -- from the northern part of a strengthening lee trough/low over northeastern NM across the TX Panhandle and north TX. This boundary should pivot to a position from east-central NM to north-central OK by 12Z. ...Southern Plains... Isolated to scattered thunderstorms are expected to develop this afternoon over the High Plains west of the Caprock, as well as over a swath of weakly capped, moist boundary layer from the southeastern Trans-Pecos/Big Bend regions to the Edwards Plateau and across the northern Serranias Del Burro of Coahuila. The severe threat is not well-focused east of the dryline, but with weak MLCINH and variable large-scale lift aloft expected, a broad area will have the potential for convective initiation and maintenance. Large hail and isolated severe gusts will be the main concerns during the first few hours of the convective cycle. Several supercells are possible, given strong veering of flow with height, and generally 35-45 kt effective-shear magnitudes. Tornado potential appears very conditional and relegated to localized boundary/ storm-scale interactions, given the modest ambient hodographs. Some of the diurnal activity may aggregate into at least a couple loosely organized clusters or small MCSs into this evening, supported by moisture advection/transport associated with a broad, strengthening nocturnal LLJ. Such convection will offer predominantly a wind threat while moving east of the Caprock, and across the southwest/south-central TX region. A combination of moist/theta-e advection and diurnal heating (including heating of higher terrain from the Big Bend region into Coahuila) will erode the cap today, and will contribute to favorable buoyancy. By late afternoon, preconvective surface dew points in the 50s F should be common from the Panhandles to the South Plains, with 60s from the lower Pecos Valley region across the Edwards Plateau, Hill Country, north TX, and southern OK. MLCAPE around 1000-1500 J/kg will be possible over the High Plains east of the dryline, while values of 1500-2000 J/kg may develop prior to convective passage from northwest to southwest TX. Convection should weaken with eastward progress tonight over northwest TX/southern OK, and near the I-35 corridor in central/south TX. ...Southeast... Widely scattered to scattered thunderstorms are expected through this evening, in a northeastward-shifting, low-level convergence arc located east through south of the primary low/middle-level circulation center and vorticity max. A marginal tornado threat is apparent from embedded supercell(s)/mesovortices, and isolated gusts near severe limits may be noted as well. The overall coverage and magnitude of severe potential still appear isolated and marginal, though mesoscale trends will be monitored for better-focused, higher-probability potential within this swath. The boundary layer should destabilize through the afternoon ahead of the primary convergence arc, within a combination of low-level theta-e advection and pockets of variably cloud-muted diurnal heating. Although weak midlevel lapse rates will temper buoyancy somewhat, moisture associated with surface dew points commonly in the mid 60s to lower 70s F will contribute to MLCAPE around 500-1500 J/kg. Despite the slow weakening of the deep-layer trough, a mesoscale belt of enhanced cyclonic flow in the 850-500-mb layer will shift northeastward across GA and parts of the Carolinas through this evening, just south through east of the main midlevel vorticity lobe. This will overlie the main low-level convergence zone, with enough low-level and deep shear to support sporadic organization of associated quasi-linear convection into bows and LEWPs. Occasional, mostly short-lived supercell structures may be noted either within the main convective arc, or in discrete to semi-discrete supercells to its east. Some backbuilding or regeneration of convection is possible late this afternoon from central GA toward southeastern AL and perhaps adjoining parts of the FL Panhandle as well, though shear will be weaker over that area by then. ..Edwards/Kerr.. 05/23/2022 Read more

No watches are valid as of Sun May 22 13:57:01 UTC 2022.

No Mesoscale Discussions are in effect as of Sun May 22 13:57:01 UTC 2022.

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0744 AM CDT Sun May 22 2022 Valid 221300Z - 231200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE NORTHERN MID-ATLANTIC AND NEW ENGLAND... ...SUMMARY... Scattered thunderstorms, some with damaging to severe gusts and large hail, are expected today over parts of the northern Mid-Atlantic and New England. ...Synopsis... In mid/upper levels, mean troughing and related large-scale cyclonic flow will persist from northeastern/Arctic Canada across the northern Plains, with some eastward shift over the Great Basin to central Rockies, and across northwestern MX. Numerous embedded shortwaves will perturb that broader cyclonic-flow pattern on the mesoscale. The most convectively important of those shortwave troughs is apparent initially in moisture-channel imagery from northeastern MN across IA. This feature is expected to stretch northeast/southwest through the day as the northern portion ejects more rapidly, reaching southwestern/central QC by 00Z. As that occurs, height falls, tightening mid/upper height gradient, and accordingly, stronger 500-250-mb southwesterlies will overspread much of the Northeast today on both sides of the front described below. Otherwise, a series of convectively induced/enhanced vorticity maxima will occupy a belt of weaker westerlies and southwesterlies aloft, from south TX to VA. At the surface, 11Z analysis showed a cold front from southern ON across western OH, western KY, southern AR, through a weak frontal- wave low near SHV, to south-central TX and northern Coahuila. As the northern-stream shortwave trough approaches, the front will accelerate eastward, reaching northern/western New England and near the I-95 corridor between NYC and northern VA around 00Z. From there the front should be positioned across western NC, northern AL, central MS, southwestern LA, and deep south TX. By 12Z, the front will move offshore from the Northeast, and extend across central NC, becoming slow-moving to stationary through a weak frontal wave over northern AL, southwestward over southern LA and deep south TX. ...Northeastern CONUS... Scattered thunderstorms are likely in one or more bands, along/ahead of and largely parallel to the surface front. Activity may develop by midday to early afternoon across portions of PA, northern WV and western NY. Mainly multicell bands/clusters, with isolated discrete or embedded supercells over New England, are possible. This activity should move eastward to northeastward into a diurnally destabilizing, favorably moist air mass and intensify while also growing in coverage. Damaging to severe gusts and sporadic hail are possible, and a tornado or two may occur over northeastern portions of the area. Low-level and deep shear each should increase with northward extent under the greater height falls aloft, while moist advection and pockets of sustained diurnal heating contribute to favorable destabilization, particularly over the "slight" area. A corridor of 1000-2000 J/kg MLCAPE may develop ahead of the front across ME and adjoining parts of northern/central New England, with peak surface dew points in the 60s F and surface temps into the mid/upper 80s and 90s (elevation-dependent). Meanwhile, effective-shear magnitudes around 40-50 kt are possible over northern/western ME, decreasing to less than 35 kt over southern NY and eastern PA. While bands or clusters of thunderstorms may develop farther south, overall organization and coverage should be less. Activity should diminish this evening as it moves into areas from Downeast Maine to southern New England where the cold/stable marine-layer influence will be greater. ...Gulf Coast to southern Mid-Atlantic... Isolated to scattered thunderstorms, sometimes in loosely organized multicellular clusters, should occur today in a broad, favorably moist swath from the southern Mid-Atlantic across the Southeast, ahead of the surface front and along/ahead of an aggregate of outflow/differential-heating boundaries left by prior convection and its lingering cloud cover. Additional convection may form along sea-breeze fronts and serial outflows from successive daytime activity. Being well-displaced from substantial midlevel flow and deep shear, this activity should present a marginal, isolated severe concern, mainly for damaging gusts. A convectively active/reinforced midlevel perturbation over the northern Gulf and southeastern LA may contribute some enhancement to low/middle-level flow and shear (e.g., via strengthened 850-500-mb speeds, and some backing of surface winds as well). This suggests transient storm-scale rotation may occur with associated cells near the coast and offshore, particularly this evening into tonight. As such, marginal tornado probabilities are maintained across parts of that region. ..Edwards/Kerr.. 05/22/2022 Read more

No watches are valid as of Sat May 21 15:09:01 UTC 2022.

MD 0848 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PORTIONS OF SOUTHERN IL/IN
Mesoscale Discussion 0848 NWS Storm Prediction Center Norman OK 1006 AM CDT Sat May 21 2022 Areas affected...Portions of southern IL/IN Concerning...Severe potential...Watch possible Valid 211506Z - 211700Z Probability of Watch Issuance...40 percent SUMMARY...A cluster of thunderstorms may strengthen over the next couple of hours and become capable of producing scattered damaging winds. Watch issuance is possible. DISCUSSION...At 15Z, a small cluster of thunderstorms is ongoing along/near the MS River in the vicinity of St. Louis MO. This activity is probably still slightly elevated to the north of a surface boundary and outflow from prior convection. However, the airmass downstream across parts of southern IL/IN is in the process of destabilizing, with diurnal heating promoting surface temperatures to rise generally into the 70s per recent observations. A fairly moist low-level airmass is also in place across this area, along with modestly steepened mid-level lapse rates per 12Z sounding from ILX. This cluster may become surface based over the next couple of hours as it spreads into southern IL/IN and encounters greater instability. Given the already linear mode, scattered damaging winds should be the main threat, although some hail may also occur. Convective trends will be closely monitored for signs of increasing thunderstorm intensity, which may prompt watch issuance in next couple of hours. ..Gleason/Hart.. 05/21/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LMK...IND...PAH...ILX...LSX... LAT...LON 37808962 38428970 38988975 39778776 39878610 39738544 38638550 38228676 37808962 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0751 AM CDT Sat May 21 2022 Valid 211300Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE SOUTHERN PLAINS INTO THE LOWER OHIO VALLEY...LOWER GREAT LAKES AND NORTHEAST... ...SUMMARY... Scattered severe thunderstorms capable of producing both damaging winds and large hail should develop through evening from parts of the southern Plains into the lower Ohio Valley, lower Great Lakes and Northeast. A tornado or two may occur as well. ...Synopsis... The large-scale mid/upper-level pattern will continue to be dominated by a positively tilted trough from northeastern Canada across the northern Plains to the Great Basin and southern CA. Numerous shortwaves will be embedded in the associated cyclonic flow over the northern Plains and western CONUS, and downstream southwest flow across the Midwest and Great Lakes. However, the great majority of these, and of the fastest flow aloft, will remain behind the surface front described below. Exceptions will include MCVs produced by ongoing convection over the Ozarks to IN. A weak but still well-defined southern-stream shortwave trough is apparent in moisture-channel imagery over central/south-central TX, and should weaken further as it moves northeastward to parts of east TX and AR by this evening. The 11Z surface analysis showed a cold front from southwestern QC and southeastern Lower MI across western IN, south-central MO, south-central OK, to between MAF-HOB, northwestward into central NM. The front should move slowly eastward/southeastward by 00Z to southern parts of QC/ON, northern IN, southern IL, southern MO, extreme southeastern OK, and central/southwest TX. By 12Z tomorrow, the front should reach parts of OH, western KY/TN, northern LA, deep south TX, and southern Coahuila. A wavy warm front -- drawn initially across portions of eastern NY/PA and northern NJ -- will shift northeastward over most of New England through today. ...Southern Plains to Northeast... Widely scattered to scattered thunderstorms are expected to develop through the period (including ongoing clusters from parts of IN/OH to northwestern AR). While severe may occur at almost any time from the most intense cells, the greatest concentration of potential should be this afternoon, up and down the over 2000-mile-long swath. Damaging gusts and large hail should be the most common severe threats, though a tornado or two may be possible (especially over parts of western/northern Maine and the Ozarks to lower Ohio Valley). A lengthy corridor of 60s F surface dew points already is observed from southeastern MO northeastward to northern NY, with upper 60s and low 70s over much of AR and TX ahead of the front. Areas of cloud cover will slow diurnal heating over much of the corridor east of the Mississippi River; nonetheless, preconvective MLCAPE of 1000-2000 J/kg should develop. Buoyancy will be greater amidst larger boundary layer theta-e and stronger heating over AR and TX, with 2000-3000 MLCAPE common. Except from near the lower Great Lakes across northern New England, and perhaps parts of northern AR, substantial mid/upper winds and their contribution to deep shear will remain well behind the front. Near the Canadian border, some supercell potential may persist from southern QC into northern and northwestern ME this afternoon/early evening before weakening. [For severe-weather concerns in adjoining parts of Canada, refer to Environment Canada public weather alerts for Quebec-south via weather.gc/ca/warnings.] Clusters of strong-severe thunderstorms also may concentrate along outflow boundaries ahead of the front, left by morning convection from parts of the lower Ohio Valley to AR. Elsewhere, isolated, localized damaging gusts or marginal hail may occur this afternoon from pulse/multicell convection, across a broad area of the South ahead of the cold front. ..Edwards/Kerr.. 05/21/2022 Read more

No watches are valid as of Fri May 20 15:33:02 UTC 2022.