Severe Storms

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.

MD 0839 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR MUCH OF SOUTHERN FLORIDA
Mesoscale Discussion 0839 NWS Storm Prediction Center Norman OK 1031 AM CDT Fri May 20 2022 Areas affected...much of southern Florida Concerning...Severe potential...Watch unlikely Valid 201531Z - 201800Z Probability of Watch Issuance...20 percent SUMMARY...Scattered to numerous storms are expected by afternoon, with locally damaging wind gusts or marginally severe hail. DISCUSSION...A moist and unstable air mass is already in place across southern FL, with PWAT over 2.00" and no capping inversion. Early day storms have left a cooled air mass across the central Peninsula, with heating continuing to the south, which is resulting in MUCAPE over 3000 J/kg. Storms are already forming off the Gulf and Atlantic coasts, with expanding showers over land. Just 1-2 more hours of heating will likely result in a rapid expansion of convection, perhaps spreading northwestward with strong outflow. However, wind fields are weak and storm motion may be erratic. Water-loaded downdrafts may produce locally damaging gusts, and the strong instability and cool midlevel temperatures may support brief periods of marginal hail. ..Jewell/Hart.. 05/20/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...MFL...MLB...KEY...TBW... LAT...LON 25767999 25148022 25138050 25078112 25208128 25858178 26588233 27288268 27848290 28068278 27938235 27628162 27388055 27258014 26807995 25767999 Read more

MD 0838 CONCERNING SEVERE POTENTIAL...WATCH LIKELY FOR MUCH OF CENTRAL PENNSYLVANIA INTO FAR NORTHERN MARYLAND
Mesoscale Discussion 0838 NWS Storm Prediction Center Norman OK 0939 AM CDT Fri May 20 2022 Areas affected...much of central Pennsylvania into far northern Maryland Concerning...Severe potential...Watch likely Valid 201439Z - 201615Z Probability of Watch Issuance...80 percent SUMMARY...The severe threat is increasing across portions of central PA into MD. Damaging gusts and perhaps a few tornadoes may accompany the strongest, longer lived storms. A WW issuance will be needed within the next couple of hours. DISCUSSION...A remnant mid-level MCV (evident via water vapor imagery and 700-500 mb objective analysis fields) is currently located just west of the OH/PA border and continues to track eastward towards central PA, and is expected to support more robust convective initiation in the next few hours. Immediately ahead of the MCV center lies a highly sheared low-level environment, with recent PBZ VAD data showing relatively long, curved low-level hodographs and over 300 m2/s2 of associated 0-1km SRH. At the moment, buoyancy remains scant across portions of western into central PA. However, modest breaks in the clouds are contributing to modest surface heating, with mid 60s F surface temperatures already noted across central PA, with low 70s F along the PA/MD border. With surface dewpoints around 60F across several locales, RAP forecast soundings suggest temperatures need to warm into the lower 70s for appreciable buoyancy to develop given the presence of relatively poor (5.5-6.5 C/km) low and mid-level lapse rates. While buoyancy is expected to initially be marginal (i.e. at or below 1000 J/kg MLCAPE), localized deep-layer ascent and strong low-level shear associated with the approaching MCV should support at least a few strong to severe storms developing early this afternoon. Damaging gusts and perhaps a few tornadoes will be the primary concerns, though a brief instance or two of marginally severe hail cannot be completely ruled out with the longer-lived, persistent rotating updrafts. A WW issuance will be needed within the next couple of hours to address the severe threat. ..Squitieri/Hart.. 05/20/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...PHI...BGM...CTP...LWX...PBZ... LAT...LON 39507942 40487929 41477881 41867804 42007731 41887681 41487648 40907628 40257618 39787629 39547651 39437720 39317819 39507942 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0756 AM CDT Fri May 20 2022 Valid 201300Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF LOWER MICHIGAN...THE NORTHERN MID-ATLANTIC...AND A SMALL PART OF THE SOUTHERN PLAINS... ...SUMMARY... Severe thunderstorms are expected to be most concentrated over portions of Lower Michigan, the northern Mid-Atlantic, and a small part of the southern Plains. ...Synopsis... In mid/upper levels, positively tilted mean troughing will continue from a cyclone over Hudson Bay southwestward across the northern Plains and northern Great Basin region. A tightening of the height gradient aloft and commensurate increase in southwest flow is expected from the southern Rockies to the upper Great Lakes, as heights rise over the Eastern CONUS. Within those height rises, however, a shortwave trough and accompanying MCV -- arising from south-central High Plains convection a couple days ago and persisting now across OH -- will cross PA today, before reaching the southern NY/NJ region around 00Z, and eastward over southern New England, Long/Block Islands, and the adjoining Atlantic tonight. The 11Z surface analysis showed a seasonally strong cold front from a triple point over southern WI southwestward through a low over south-central KS, then over northwestern OK, the TX Panhandle, and northeastern NM. A wavy warm front -- somewhat diffuse west of the Appalachians thanks to outflow from MCV-related convection to its south -- was drawn from that triple point across central Lower MI, northeastern OH, northeastern WV, and northern VA. This warm front should move northward through Lower MI today prior to cold frontal passage, while also moving northward over southern/eastern PA and NJ. By 00Z the cold front should extend from Lower MI to near a line from ORD-STL-TUL-SPS-LVS. A dryline should intersect the front over northwest TX and extend south-southwestward to the Rio Grande shortly upstream from DRT. By 12Z, the front should reach northwestern OH, southern IL, north-central TX, and southeastern to central NM, overtaking the retreating dryline over west-central TX. Relative maxima in severe potential will occur in two nodes near the front, over Lower MI and the Red River region, with isolated, likely nocturnal severe potential from mostly elevated convection near the front in between. ...Lower MI... Scattered thunderstorms are expected to develop this afternoon -- perhaps in multiple episodes - ahead of the surface cold front, from west of central/northern Lake Michigan across central/northern Lower MI. The most favorable buoyancy/shear parameter space for severe thunderstorms -- including a few supercells with a tornado threat, damaging winds and large to significant hail -- will be across central/northern Lower MI. A combination of convergence near the cold front and boundary-layer heating in the warm sector will contribute to thunderstorm development, along with outflow/differential-heating boundaries on the mesobeta scale. Low-level warm/moist advection will aid in airmass recovery behind a pool of outflow produced by earlier MCV/MCS passage to the south of the area. Surface dew points commonly in the 60s F, diurnal heating, favorable low/middle-level lapse rates, and a deep troposphere will contribute to MLCAPE building into the 2000-3000 J/kg range, amidst supercell-favorable shear. Hail models applied to, and analog data closely associated with, these thermodynamic and wind profiles suggest any supercells will pose a threat of 2+ inch hail; therefore, a significant-hail area was added. Density of the tornado threat is more uncertain, with time series of forecast soundings suggesting some veering of near-surface winds and shrinking of hodographs right as the cap breaks. Still, a mesobeta-scale area of greater potential may develop, and observational trends and 12Z guidance will be monitored for considering ENH-level probabilities in succeeding outlooks. ...Northern Mid-Atlantic... Scattered thunderstorms -- some severe -- should develop just ahead of the MCV and along/south of the warm front, as the MCV moves across PA today. Damaging to severe gusts, isolated large hail, and a few tornadoes are possible. Large-scale lift on a mesoscale spatial scale will immediately precede the MCV, as will a corridor of relatively maximized low-level shear and enhanced 700-500-mb flow. These and relatively backed winds near the warm-frontal zone will contribute to favorable vertical shear for supercell and especially bow-echo organization. Meanwhile, moisture/theta-e advection and diurnal heating -- behind a swath of precursory morning clouds/convection now crossing the region -- should destabilize the boundary layer and weaken MLCINH sufficiently to support the severe threat. Peak preconvective MLCAPE in the 1500-2500 J/kg range is possible in central PA, decreasing eastward toward the Jersey Shore. However, even with lesser buoyancy, a cold-pool-driven, compact MCS may develop and persist eastward to near the coastline, sustained by forced ascent of at least marginally unstable parcels on the leading edge. ...Southern OK/north TX... Scattered strong-severe thunderstorms should develop this afternoon and persist into evening near the front and east of the dryline, over parts of southern OK and adjoining north TX. Severe hail/gusts will be possible. A favorably unstable moist warm-sector boundary layer will develop, with surface dewpoints in the upper 60s to near 70 F, and strong heating yielding a well-mixed subcloud layer despite the moisture content. MLCAPE of 3500-4500 J/kg appears probable, much of it in layers suitable for both hail growth and lightning generation. Low-level and deep shear will be weak, limiting modes to clustered, multicellular, and perhaps temporarily cold-pool-forced in character. With weak mid/upper winds expected, rapidly collapsing cores with considerable precip loading and severe gusts are possible. Overall, the threat should diminish after dark, though a few strong-severe storms may persist well into the evening given available moisture and steep low/middle-level lapse rates away from convectively modified air masses. ..Edwards/Kerr.. 05/20/2022 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0756 AM CDT Fri May 20 2022 Valid 201300Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF LOWER MICHIGAN...THE NORTHERN MID-ATLANTIC...AND A SMALL PART OF THE SOUTHERN PLAINS... ...SUMMARY... Severe thunderstorms are expected to be most concentrated over portions of Lower Michigan, the northern Mid-Atlantic, and a small part of the southern Plains. ...Synopsis... In mid/upper levels, positively tilted mean troughing will continue from a cyclone over Hudson Bay southwestward across the northern Plains and northern Great Basin region. A tightening of the height gradient aloft and commensurate increase in southwest flow is expected from the southern Rockies to the upper Great Lakes, as heights rise over the Eastern CONUS. Within those height rises, however, a shortwave trough and accompanying MCV -- arising from south-central High Plains convection a couple days ago and persisting now across OH -- will cross PA today, before reaching the southern NY/NJ region around 00Z, and eastward over southern New England, Long/Block Islands, and the adjoining Atlantic tonight. The 11Z surface analysis showed a seasonally strong cold front from a triple point over southern WI southwestward through a low over south-central KS, then over northwestern OK, the TX Panhandle, and northeastern NM. A wavy warm front -- somewhat diffuse west of the Appalachians thanks to outflow from MCV-related convection to its south -- was drawn from that triple point across central Lower MI, northeastern OH, northeastern WV, and northern VA. This warm front should move northward through Lower MI today prior to cold frontal passage, while also moving northward over southern/eastern PA and NJ. By 00Z the cold front should extend from Lower MI to near a line from ORD-STL-TUL-SPS-LVS. A dryline should intersect the front over northwest TX and extend south-southwestward to the Rio Grande shortly upstream from DRT. By 12Z, the front should reach northwestern OH, southern IL, north-central TX, and southeastern to central NM, overtaking the retreating dryline over west-central TX. Relative maxima in severe potential will occur in two nodes near the front, over Lower MI and the Red River region, with isolated, likely nocturnal severe potential from mostly elevated convection near the front in between. ...Lower MI... Scattered thunderstorms are expected to develop this afternoon -- perhaps in multiple episodes - ahead of the surface cold front, from west of central/northern Lake Michigan across central/northern Lower MI. The most favorable buoyancy/shear parameter space for severe thunderstorms -- including a few supercells with a tornado threat, damaging winds and large to significant hail -- will be across central/northern Lower MI. A combination of convergence near the cold front and boundary-layer heating in the warm sector will contribute to thunderstorm development, along with outflow/differential-heating boundaries on the mesobeta scale. Low-level warm/moist advection will aid in airmass recovery behind a pool of outflow produced by earlier MCV/MCS passage to the south of the area. Surface dew points commonly in the 60s F, diurnal heating, favorable low/middle-level lapse rates, and a deep troposphere will contribute to MLCAPE building into the 2000-3000 J/kg range, amidst supercell-favorable shear. Hail models applied to, and analog data closely associated with, these thermodynamic and wind profiles suggest any supercells will pose a threat of 2+ inch hail; therefore, a significant-hail area was added. Density of the tornado threat is more uncertain, with time series of forecast soundings suggesting some veering of near-surface winds and shrinking of hodographs right as the cap breaks. Still, a mesobeta-scale area of greater potential may develop, and observational trends and 12Z guidance will be monitored for considering ENH-level probabilities in succeeding outlooks. ...Northern Mid-Atlantic... Scattered thunderstorms -- some severe -- should develop just ahead of the MCV and along/south of the warm front, as the MCV moves across PA today. Damaging to severe gusts, isolated large hail, and a few tornadoes are possible. Large-scale lift on a mesoscale spatial scale will immediately precede the MCV, as will a corridor of relatively maximized low-level shear and enhanced 700-500-mb flow. These and relatively backed winds near the warm-frontal zone will contribute to favorable vertical shear for supercell and especially bow-echo organization. Meanwhile, moisture/theta-e advection and diurnal heating -- behind a swath of precursory morning clouds/convection now crossing the region -- should destabilize the boundary layer and weaken MLCINH sufficiently to support the severe threat. Peak preconvective MLCAPE in the 1500-2500 J/kg range is possible in central PA, decreasing eastward toward the Jersey Shore. However, even with lesser buoyancy, a cold-pool-driven, compact MCS may develop and persist eastward to near the coastline, sustained by forced ascent of at least marginally unstable parcels on the leading edge. ...Southern OK/north TX... Scattered strong-severe thunderstorms should develop this afternoon and persist into evening near the front and east of the dryline, over parts of southern OK and adjoining north TX. Severe hail/gusts will be possible. A favorably unstable moist warm-sector boundary layer will develop, with surface dewpoints in the upper 60s to near 70 F, and strong heating yielding a well-mixed subcloud layer despite the moisture content. MLCAPE of 3500-4500 J/kg appears probable, much of it in layers suitable for both hail growth and lightning generation. Low-level and deep shear will be weak, limiting modes to clustered, multicellular, and perhaps temporarily cold-pool-forced in character. With weak mid/upper winds expected, rapidly collapsing cores with considerable precip loading and severe gusts are possible. Overall, the threat should diminish after dark, though a few strong-severe storms may persist well into the evening given available moisture and steep low/middle-level lapse rates away from convectively modified air masses. ..Edwards/Kerr.. 05/20/2022 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0756 AM CDT Fri May 20 2022 Valid 201300Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF LOWER MICHIGAN...THE NORTHERN MID-ATLANTIC...AND A SMALL PART OF THE SOUTHERN PLAINS... ...SUMMARY... Severe thunderstorms are expected to be most concentrated over portions of Lower Michigan, the northern Mid-Atlantic, and a small part of the southern Plains. ...Synopsis... In mid/upper levels, positively tilted mean troughing will continue from a cyclone over Hudson Bay southwestward across the northern Plains and northern Great Basin region. A tightening of the height gradient aloft and commensurate increase in southwest flow is expected from the southern Rockies to the upper Great Lakes, as heights rise over the Eastern CONUS. Within those height rises, however, a shortwave trough and accompanying MCV -- arising from south-central High Plains convection a couple days ago and persisting now across OH -- will cross PA today, before reaching the southern NY/NJ region around 00Z, and eastward over southern New England, Long/Block Islands, and the adjoining Atlantic tonight. The 11Z surface analysis showed a seasonally strong cold front from a triple point over southern WI southwestward through a low over south-central KS, then over northwestern OK, the TX Panhandle, and northeastern NM. A wavy warm front -- somewhat diffuse west of the Appalachians thanks to outflow from MCV-related convection to its south -- was drawn from that triple point across central Lower MI, northeastern OH, northeastern WV, and northern VA. This warm front should move northward through Lower MI today prior to cold frontal passage, while also moving northward over southern/eastern PA and NJ. By 00Z the cold front should extend from Lower MI to near a line from ORD-STL-TUL-SPS-LVS. A dryline should intersect the front over northwest TX and extend south-southwestward to the Rio Grande shortly upstream from DRT. By 12Z, the front should reach northwestern OH, southern IL, north-central TX, and southeastern to central NM, overtaking the retreating dryline over west-central TX. Relative maxima in severe potential will occur in two nodes near the front, over Lower MI and the Red River region, with isolated, likely nocturnal severe potential from mostly elevated convection near the front in between. ...Lower MI... Scattered thunderstorms are expected to develop this afternoon -- perhaps in multiple episodes - ahead of the surface cold front, from west of central/northern Lake Michigan across central/northern Lower MI. The most favorable buoyancy/shear parameter space for severe thunderstorms -- including a few supercells with a tornado threat, damaging winds and large to significant hail -- will be across central/northern Lower MI. A combination of convergence near the cold front and boundary-layer heating in the warm sector will contribute to thunderstorm development, along with outflow/differential-heating boundaries on the mesobeta scale. Low-level warm/moist advection will aid in airmass recovery behind a pool of outflow produced by earlier MCV/MCS passage to the south of the area. Surface dew points commonly in the 60s F, diurnal heating, favorable low/middle-level lapse rates, and a deep troposphere will contribute to MLCAPE building into the 2000-3000 J/kg range, amidst supercell-favorable shear. Hail models applied to, and analog data closely associated with, these thermodynamic and wind profiles suggest any supercells will pose a threat of 2+ inch hail; therefore, a significant-hail area was added. Density of the tornado threat is more uncertain, with time series of forecast soundings suggesting some veering of near-surface winds and shrinking of hodographs right as the cap breaks. Still, a mesobeta-scale area of greater potential may develop, and observational trends and 12Z guidance will be monitored for considering ENH-level probabilities in succeeding outlooks. ...Northern Mid-Atlantic... Scattered thunderstorms -- some severe -- should develop just ahead of the MCV and along/south of the warm front, as the MCV moves across PA today. Damaging to severe gusts, isolated large hail, and a few tornadoes are possible. Large-scale lift on a mesoscale spatial scale will immediately precede the MCV, as will a corridor of relatively maximized low-level shear and enhanced 700-500-mb flow. These and relatively backed winds near the warm-frontal zone will contribute to favorable vertical shear for supercell and especially bow-echo organization. Meanwhile, moisture/theta-e advection and diurnal heating -- behind a swath of precursory morning clouds/convection now crossing the region -- should destabilize the boundary layer and weaken MLCINH sufficiently to support the severe threat. Peak preconvective MLCAPE in the 1500-2500 J/kg range is possible in central PA, decreasing eastward toward the Jersey Shore. However, even with lesser buoyancy, a cold-pool-driven, compact MCS may develop and persist eastward to near the coastline, sustained by forced ascent of at least marginally unstable parcels on the leading edge. ...Southern OK/north TX... Scattered strong-severe thunderstorms should develop this afternoon and persist into evening near the front and east of the dryline, over parts of southern OK and adjoining north TX. Severe hail/gusts will be possible. A favorably unstable moist warm-sector boundary layer will develop, with surface dewpoints in the upper 60s to near 70 F, and strong heating yielding a well-mixed subcloud layer despite the moisture content. MLCAPE of 3500-4500 J/kg appears probable, much of it in layers suitable for both hail growth and lightning generation. Low-level and deep shear will be weak, limiting modes to clustered, multicellular, and perhaps temporarily cold-pool-forced in character. With weak mid/upper winds expected, rapidly collapsing cores with considerable precip loading and severe gusts are possible. Overall, the threat should diminish after dark, though a few strong-severe storms may persist well into the evening given available moisture and steep low/middle-level lapse rates away from convectively modified air masses. ..Edwards/Kerr.. 05/20/2022 Read more

No watches are valid as of Thu May 19 15:06:06 UTC 2022.

MD 0826 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR CENTRAL INTO EASTERN MISSOURI AND SOUTHWEST ILLINOIS
Mesoscale Discussion 0826 NWS Storm Prediction Center Norman OK 1005 AM CDT Thu May 19 2022 Areas affected...central into eastern Missouri and southwest Illinois Concerning...Severe potential...Watch possible Valid 191505Z - 191730Z Probability of Watch Issuance...40 percent SUMMARY...Storms may produce sporadic hail over the next several hours, eventually affecting the St. Louis area and crossing into Illinois. DISCUSSION...Strong storms persist in the warm advection regime ahead of a prominent MCV, with sporadic hail cores noted. This leading cluster of storms is currently moving east/northeastward, embedded within a larger-scale area of deep theta-e advection, which in itself is also shifting northeast. Therefore, the trend of pulsing hail cores should persist today, and may strengthen later this afternoon as instability is maximized from heating. Steep lapse rates aloft and sufficient deep-layer shear will continue to favor hail cores, but a wind risk could develop out of this activity at which time a watch would become more likely. ..Jewell/Hart.. 05/19/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...PAH...ILX...LSX...SGF... LAT...LON 38459227 38859208 39249159 39589037 39548967 39528913 39328846 38738799 37968796 37618805 37308838 37198953 37348999 37519067 37649122 37669162 37769202 38459227 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0724 AM CDT Thu May 19 2022 Valid 191300Z - 201200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS LATER THIS AFTERNOON INTO EARLY TONIGHT FOR NORTHERN IA...SOUTHEASTERN MN AND WESTERN WI... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS TODAY FROM SOUTHERN MO TO THE LOWER OH VALLEY AND THE CAROLINAS... ...SUMMARY... Isolated very large hail, damaging winds, and a couple of tornadoes will be possible later this afternoon into early tonight across northern Iowa, southeastern Minnesota and western Wisconsin. Occasional large hail, damaging winds, and a couple of tornadoes may also occur this afternoon from southern Missouri into southern Illinois, with at least isolated large hail/damaging winds farther east into the Carolinas. ...IA/MN/WI late this afternoon into tonight... A deep midlevel trough will move generally eastward along the international border from MT to MN by the end of the period. Downstream from the strengthening midlevel jet, initial lee cyclogenesis this morning across southwest SD will develop eastward to southern MN this evening and northwest WI tonight. East of the cyclone, a warm front will develop northward across IA/southern MN/WI through the afternoon/evening. The more probable area for initial storm development late this afternoon/evening will be east of the surface cyclone, along and north of the warm front in the zone of stronger ascent/warm advection with gradually increasing low-level moisture. Other storms will likely form this evening farther southwest along the trailing cold front. Uncertainty in this outlook area is related to the remnant MCS and well-developed MCV moving across northeast OK/southeast KS/southwest MO, which has intercepted the richer (near 70 F) dewpoints along the diffuse baroclinic zone straddling the KS/OK and MO/AR borders. This leaves residual low-mid 60s dewpoints across eastern KS and southeastern NE to the north of the MCS, which is below the more aggressive model forecasts of moisture return. Thus, the low-level moisture spreading into IA/MN/WI through the day is likely to be somewhat marginal for a more substantial tornado threat, when also considering the effects of afternoon mixing. Steep lapse rates and MLCAPE in excess of 2500 J/kg, as well as relatively long hodographs with low-level clockwise turning, will support supercells capable of producing very large hail initially. Storms should tend to evolve into clusters and line segments with more of a damaging wind threat by late evening. As previously discussed, the tornado threat will depend on the degree of low-level moisture return, which at the moment appears more supportive of a typical (5%) outlook area. ...Central/southern MO/IL through late evening... A well-developed MCV from overnight convection is approaching southwest MO, and will likely persist while continuing east-northeastward through the day, in response to gradual backing of midlevel flow related to upstream amplification of the trough over the northern Rockies. The MCV will track along a residual baroclinic zone and corridor of 68-72 F boundary-layer dewpoints with MLCAPE of 3000-4000 J/kg, which will support the potential for continued latent heating and maintenance of the MCV through the day. Associated convection will likely undergo diurnal intensification since the richer low-level moisture is already present in advance of this system. A couple of tornadoes, large hail, and damaging winds will all be possible with embedded clusters/supercells coinciding with MCV-related enhancements to the wind profiles. ...KY/TN into the Carolinas through late afternoon/evening... A midlevel shortwave trough is moving over the southern Appalachians this morning. As the low levels warm/moisten across the Carolinas today, at least isolated thunderstorm development is expected in advance of this trough. Midlevel lapse rates of 7.5-8 C/km, MLCAPE at or above 2000 J/kg and straight hodographs with 30-35 kt effective bulk shear will support a mix of multicell clusters and supercells capable of producing large hail and damaging winds, mainly this afternoon/evening. Farther west, storm development is a bit less certain to the west of the Appalachians shortwave trough, and well east of the MO MCV. Daytime heating/mixing could support isolated storm development across TN/KY this afternoon, and perhaps a few storms this evening/early tonight in the warm advection zone across northern KY/southern IN, east of the weakening MCV. ..Thompson/Leitman.. 05/19/2022 Read more

No watches are valid as of Wed May 18 13:36:01 UTC 2022.