Severe Storms

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook CORR 1 NWS Storm Prediction Center Norman OK 0848 AM CDT Tue May 10 2022 Valid 101300Z - 111200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF NORTHWEST TEXAS AND SOUTHWESTERN OKLAHOMA... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE ENHANCED AREA OVER THE SOUTHERN HIGH PLAINS...AND OVER PARTS OF WISCONSIN AND SOUTHERN UPPER MICHIGAN... CORRECTED FOR REMOVAL OF DOUBLED OUTLOOK LINES ...SUMMARY... Severe thunderstorm winds will be a hazard over parts of the southern High Plains today into this evening, along with isolated hail. Very large hail, isolated severe gusts and a tornado threat will develop this afternoon over parts of Wisconsin and vicinity. ...Synopsis... Little change is expected through this period in the highly amplified, positively tilted, mid/upper-level pattern across the CONUS. Mean troughing will persist from northern Canada, west of Hudson Bay, across the U.S. Northwest and CA. A broad, intermittently closed cyclone -- initially located over parts of northern CA, western OR and adjoining Pacific waters -- is expected to move slowly southeastward, its 500-mb low reaching central CA near FAT by 12Z tomorrow. As that occurs, height rises are expected over the northern Plains and Upper Midwest. A southern-stream perturbation is evident in moisture-channel imagery over western Chihuahua and parts of Sinaloa in northwestern MX. This feature will move northeastward today, reaching parts of far west TX and NM, the proceed to the southern High Plains by the end of the period. Elsewhere, a large, long-lasting, cut-off synoptic cyclone east of the Carolinas will begin to retrograde southwestward today, while its center remains well offshore. A very long ridge will persist from central MX across the Arklatex, lower Ohio Valley, southern ON, and southern QC. The 11Z surface analysis showed a low over north-central KS between HYS-CNK, with a warm to quasistationary front northeastward to a weak low and outflow-boundary intersection over southwestern WI. The outflow boundary extended eastward from there across southern Lake Michigan, and should retreat northward over southern/central WI today while becoming more poorly defined. Farther north, the front was drawn north-northeastward from southwestern WI across western Upper MI, and should move little through most of the day before settling southward tonight. A weak cold to stationary front trailed from the KS low across the northern TX Panhandle to southeastern CO, and should move little through the period. The dryline intersected that front near P28, and extended across the western OK/TX border region, to near LBB, FST and the Big Bend region. The dryline may retreat somewhat westward/northwestward across the Panhandle, South Plains and Permian Basin today. ...Southern High Plains... Highly variable thunderstorm coverage (from isolated to numerous) is possible in the outlook area today. The most probable area for a relatively dense concentration of convection should begin with early/organizing stages this afternoon over the South Plains/southern Panhandle/Permian Basin area. Activity then should aggregate upscale and move eastward to northeastward off the Caprock, then and across parts of northwest TX and southwestern OK this evening. Severe wind -- with at least isolated downdrafts potentially reaching 65-kt significant criteria, should accompany this activity. Despite a lack of stronger flow aloft, thermodynamically supported potential exists for cold-pool mergers and forward propagation to drive severe-thunderstorm clusters eastward into a slowly stabilizing nocturnal boundary layer over more of northwest TX and western OK this evening, before activity weakens with continued inflow-layer stabilization. Initiation will be supported by a combination of dryline lift, intense surface heating and related MLCINH removal along/east of the dryline, steep low/middle-level lapse rates ahead of the ejecting MX perturbation, and favorable low-level moisture. Surface dew points ranging from the mid 50s F just east of the dryline, to the mid-60s east of the Caprock, will support MLCAPE commonly 3000-4000 J/kg, atop a deep, well-mixed subcloud layer supporting around 1500 J/kg DCAPE. Modest mid/upper winds and related lack of more-robust vertical shear will keep activity predominantly multicellular in mode, though large hail may be noted, mainly in earlier stages of the convective process while convection is still rather discrete. ...WI and vicinity... Scattered thunderstorms are expected to develop this afternoon across western/northern parts of the outlook area and move roughly eastward into an increasingly favorable environment for supercells, with severe hail (some of it very large/damaging at 2+ inches diameter), a tornado threat, and sporadic damaging gusts. Amidst ambient, weak height rises, large-scale support aloft will be minimal at most. However, that should be more than offset for the purpose of severe potential by moderately to strongly unstable thermodynamic profiles, weak capping, boundaries, and favorable deep shear. As the outflow boundary retreats northward today and diffuses, a combination of diurnal heating and most advection will contribute to substantial low-level destabilization, with surface dew points increasing to the mid/upper 60s at least into southern/central WI. This will support peak/preconvective MLCAPE increasing into the 2500-4000 J/kg range over southern and central WI, diminishing northward into southern Upper MI. Forecast orientation and strength of deep-shear vectors suggests convection can maintain discrete to semi-discrete modes well into maturation, with supercell potential in the thermodynamically favorably modified outflow environment. Two-dimensional hail models applied to forecast soundings reasonably suggest any supercells over the region could produce very large and damaging hail. Considerable uncertainty, and inconsistency in guidance, remains as to the potential for upscale growth of convection across the region, and the potential for any such activity to coalesce cold pools enough to transition to a forward-propagational complex. Should that occur, severe potential may extend across Lake Michigan into western Lower MI and/or northern IL, aside from any isolated convection that may develop over those areas during the daytime. ..Edwards/Gleason.. 05/10/2022 Read more

No watches are valid as of Tue May 10 13:53:01 UTC 2022.

No Mesoscale Discussions are in effect as of Tue May 10 13:53:02 UTC 2022.

No Mesoscale Discussions are in effect as of Mon May 9 15:16:10 UTC 2022.

WW 0193 Status Updates
STATUS FOR WATCH 0193 HAS NOT BEEN ISSUED YET Read more

WW 193 SEVERE TSTM MN WI 091425Z - 092000Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 193 NWS Storm Prediction Center Norman OK 925 AM CDT Mon May 9 2022 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Far East-Central Minnesota Northwest Wisconsin * Effective this Monday morning and afternoon from 925 AM until 300 PM CDT. * Primary threats include... Scattered large hail and isolated very large hail events to 2 inches in diameter possible Isolated damaging wind gusts to 70 mph possible SUMMARY...A cluster of strong to severe thunderstorms is currently moving east across east-central Minnesota. These storms should continue moving into northwest Wisconsin within the next hour or so, with at least some threat for large hail. The severe thunderstorm watch area is approximately along and 40 statute miles east and west of a line from 30 miles west southwest of Eau Claire WI to 75 miles north of Eau Claire WI. 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. && OTHER WATCH INFORMATION...CONTINUE...WW 192... AVIATION...A few severe thunderstorms with hail surface and aloft to 2 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 24045. ...Mosier/Guyer Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0755 AM CDT Mon May 09 2022 Valid 091300Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER THE UPPER MISSISSIPPI VALLEY REGION... ...SUMMARY... Large hail, damaging gusts, and a few tornadoes are all possible over the upper Mississippi Valley region today into this evening. ...Synopsis... The basic mid/upper-level pattern through the period will feature a positively tilted mean trough over western parts of Canada and the CONUS, with numerous embedded shortwaves/vorticity maxima. Meanwhile, an already high-amplitude downstream ridge -- now extending from central MX across the Arklatex, lower Ohio Valley, southern ON, and southern QC -- will amplify further, while moving little. A long-lived synoptic cyclone will remain over Atlantic waters east of the Carolinas. The southwest-flow belt downstream from the western mean trough will cover most of the Rockies, Great Plains, mid/upper Mississippi Valley, and Upper Midwest. An embedded/leading shortwave trough with convective vorticity augmentation -- now apparent in moisture-channel imagery and composited radar fields over SD -- will eject northeastward across ND and northern MN today. By 00Z, a closed 500-mb low should develop along the shortwave trough, over southern MB, with the trough extending southeastward to northern MN. The perturbation will eject northeastward over MB and northwesternmost ON tonight, leaving behind rising heights across the central/northern Plains and Upper Midwest. At the surface, 11Z analysis showed a low over northern NE near ONL, with cold front southwestward across northwestern KS, becoming quasistationary over east-central CO. A warm front was drawn southeastward across eastern NE, northeastern KS, southwestern MO, and eastern AR. A dryline intersected the cold front over southern NE, and extended southward to western OK, then south-southwestward across the TX Permian Basin. That low is expected to move north-northeastward across southeastern MB by 00Z, with cold front trailing through eastern MN, southwestern IA, southeastern NE, and northwestern KS, to another low related to both lee troughing and baroclinic processes over northeastern CO. By 12Z, the cold front should be decelerating across parts of Lake Superior, Upper MI, WI, and southern IA, then quasistationary to a low over central or north-central KS, then a cold front again southwestward across parts of the OK/TX Panhandles. By mid/late afternoon, the dryline should shift eastward to eastern KS, central OK, western north TX, and the Edwards Plateau, before retreating westward/northwestward overnight. ...Upper Mississippi Valley region... Multiple convective episodes are expected over the region through late evening, collectively contributing to the potential for large hail, damaging gusts and a few tornadoes. The initial episode is manifest as an arc of strong/isolated severe thunderstorms with mainly a hail threat over portions of northeastern SD, southeastern ND and west-central/southwestern MN. This activity is occurring in a zone of strong low-level warm advection and moisture transport, occurring as part of the mass response to the deepening low-level cyclone. See SPC mesoscale discussion 697 and severe-thunderstorm watch 192 for near-term details. For at least a few hours, this activity will move over a relatively stable boundary layer left from the nocturnal near-surface cooling, reinforced by precip. However, with favorable effective shear and buoyancy above the boundary layer, sporadic large hail will remain possible. A conditional threat will develop for some of this complex's gusts to penetrate to the surface later this morning, as a combination of warm advection, vertical mixing and weak diurnal heating destabilize the boundary layer. Behind the initial activity, a narrow, fairly fast-moving plume of superimposed low- and middle-level destabilization may develop this afternoon. Activity could be strongly tilted amidst effective-shear magnitudes of 60-75 kt, based on modified forecast soundings. Meanwhile, even with only meager low-level airmass recovery via warm advection and brief diurnal heating, cooling aloft should steepen deep-layer lapse rates enough for surface-based convection as far north as at least some of northern MN, with weak CINH and frontal lift forcing convection. Offering specifics on buoyancy always is a low-predictability endeavor in these limited-recovery, fast-flow, "bent-back arc" scenarios. Still, 250-500 J/kg MLCAPE appears possible in a narrow plume just ahead of the front over northern MN, increasing to 1500-3000 J/kg in a narrow corridor shifting eastward across southern MN and western WI. This may support a mix of multicells and supercells in an arc over MN, perhaps shifting/backbuilding into northwestern WI. A few tornadoes, occasional hail, and strong-damaging gusts all will be possible. Either backbuilding of the MN/WI arc, or initially separate development, will be possible late this afternoon into this evening along the cold front, over parts of WI into IA, also offering a multi-hazard severe threat. Boundary-layer moisture and lapse rates will be most favorable in this regime, but with only glancing influence of large-scale support aloft from the shortwave trough, before large-scale subsidence increases. Still, a line of convection may build along the boundary for a few hours, as frontal lift takes advantage of MLCINH minimized by both theta-e advection and residual diurnal warmth. 35-50 kt effective-shear magnitudes suggest blended supercell/multicell modes within the convective band, with well-mixed subcloud layers supporting survival of strong-severe gusts and large hail to the surface, before activity diminishes overnight. ..Edwards/Gleason.. 05/09/2022 Read more

WW 0192 Status Updates
STATUS FOR WATCH 0192 HAS NOT BEEN ISSUED YET Read more

WW 192 SEVERE TSTM MN 091255Z - 091800Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 192 NWS Storm Prediction Center Norman OK 755 AM CDT Mon May 9 2022 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Central Minnesota * Effective this Monday morning and afternoon from 755 AM until 100 PM CDT. * Primary threats include... Scattered large hail likely with isolated very large hail events to 2.5 inches in diameter possible Isolated damaging wind gusts to 70 mph possible SUMMARY...Thunderstorms, moving rapidly northeastward across the watch area this morning, will continue to offer occasional severe hail -- some potentially significant (2+ inches in diameter). The severe thunderstorm watch area is approximately along and 50 statute miles either side of a line from 40 miles northwest of Redwood Falls MN to 60 miles east of Brainerd MN. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU2). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && AVIATION...A few severe thunderstorms with hail surface and aloft to 2.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 22045. ...Edwards Read more

WW 0191 Status Updates
STATUS REPORT ON WW 191 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 20 E MHE TO 5 NNW MHE TO 25 SW HON TO 60 SW ABR. FOR ADDITIONAL INFORMATION SEE MESOSCALE DISCUSSION 0696 ..GLEASON..05/09/22 ATTN...WFO...LBF...FSD...UNR...ABR... STATUS REPORT FOR WS 191 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS SDC005-025-029-037-039-051-057-059-073-077-091-097-109-111-115- 091140- SD . SOUTH DAKOTA COUNTIES INCLUDED ARE BEADLE CLARK CODINGTON DAY DEUEL GRANT HAMLIN HAND JERAULD KINGSBURY MARSHALL MINER ROBERTS SANBORN SPINK THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES. Read more

No watches are valid as of Sun May 8 14:03:01 UTC 2022.

No Mesoscale Discussions are in effect as of Sun May 8 14:03:01 UTC 2022.

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0750 AM CDT Sun May 08 2022 Valid 081300Z - 091200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF THE NORTHERN PLAINS AND NORTH TX... ...SUMMARY... Isolated severe hail and/or gusts may occur this afternoon over portions of the north-central Plains and north Texas, with the potential persisting into tonight over the northern Plains. ...Synopsis... A high-amplitude mid-upper-level pattern is forecast to persist through the period. A leading cyclone -- initially located over the Delmarva peninsula -- is forecast to move slowly out to sea through 12Z tomorrow. An upstream ridge -- analyzed from central MX across the Mid-South region to the lower Ohio Valley and southwestern QC -- will amplify but exhibit little lateral movement. A longwave trough over western North America will be anchored by a large, complex cyclonic gyre, orbited by numerous vorticity maxima and smaller-scale circulations, and covering most of western Canada and the northwestern CONUS. One of those circulations -- evident in moisture-channel imagery west of the OR coastline -- should move inland around 18Z today then devolve into an open-wave trough across the northern Great Basin and ID by 12Z. Ahead of it, several smaller-scale perturbations will eject northeastward over the central/northern Rockies and northern Plains. The 11Z surface analysis showed a low over west-central KS, with warm front arching across north-central KS then southeastward over eastern OK and northwestern to southeastern LA. A weak cold front was drawn from the low over the northern TX Panhandle and northeastern NM. A separate cold-frontal zone, with weak attached low(s), was evident from eastern ND across east-central SD, the southwestern NE Panhandle, and southeastern WY. Surface cyclogenesis is expected this afternoon over central to northeastern CO, rendering the southern boundary a warm front by 00Z east-southeastward across parts of KS, as the northern frontal zone becomes quasistationary and more diffuse. By 12Z, the low should eject across the central Plains to near the VTN-9V9 corridor, with cold front southwestward over east-central/southeastern CO and warm front across western IA to central MO. A dryline -- now over the eastern TX Panhandle, northwest TX, and the lowest parts of the Pecos River, should shift eastward this afternoon as far as west-central/central OK, western north TX, to near SJT and north- central Coahuila, before retreating northwestward overnight. ...North-central Plains States... Isolated to widely scattered thunderstorms are possible this afternoon into the overnight hours near the low-level frontal zone, with some supercell evolution possible. Occasional potential will exist for severe gusts/hail. A more-uncertain but non-negligible threat also is apparent, in some guidance, for the development of a loosely organized cluster or complex of elevated thunderstorms with severe hail potential tonight, particularly over the eastern SD/southwestern MN area. Surface dewpoints in the 50s F and lack of a substantial EML influence at these latitudes will render minimal MLCINH, amidst pockets of 500-1000 J/kg peak/afternoon MLCAPE. Surface-based effective-inflow parcels may remain essentially uncapped well into the evening, given some low-level theta-e advection to offset slow nocturnal cooling. Weak low-level flow is forecast before sundown (generally 10 kt or less below the 700-mb level before sunset), but around 90-100 kt anvil-level flow, and 50 kt at 500 mb, should render strong cloud-layer shear and aid in storm organization. After about 02Z, a strengthening northwestern branch of the LLJ, featuring southeast flow, will serve several favorable purposes, including: * Increased low-level shear with enlarging hodographs, even for elevated storms, * Stronger storm-relative winds in at least part of the effective-inflow layer, and * Increasing low-level moisture above the surface, with warming/ saturating parcels in the 8000-850-mb layer, beneath slightly cooling midlevel conditions preceding ejecting vorticity maxima. This may support elevated MUCAPE of more than 2000 J/kg, with 50-70-kt effective-shear vectors. Confidence in timing and breadth of any nocturnal complex(es) remains too low to introduce an unconditional upgrade at this still-early hour. However, one may be needed if better mesoscale foci and/or greater guidance consistency become apparent. ...North TX... Another strongly conditional setting for severe-thunderstorm potential is evident for just 2-3 hours late this afternoon -- slightly northward from yesterday, and along/ahead of the dryline. Any sustained convection that develops through the diurnally weakened EML inversion in this area will pose a threat for severe downdrafts and large hail. Slightly greater confidence exists in this scenario compared to yesterday's, given the more-cyclonic nature of the flow aloft, height falls, rich low-level moisture, and near-record surface temperatures near the dryline to eliminate MLCINH, potentially for long enough to sustain deep convection to maturity. Still, a stout EML inversion, sampled by the 12Z FWD RAOB, renders highly uncertain (but likely isolated) coverage and duration of potential, in turn keeping the unconditional probabilities at marginal levels for now. Upper 60s to low 70s F surface dewpoints should remain over the region ahead of the dryline, underlying steep low/middle-level lapse rates. This contributes to projected peak/preconvective MLCAPE in the 3000-4000 J/kg range (locally/briefly larger), atop a well-mixed subcloud layer with DCAPE exceeding 1500 J/kg. Modest mid/upper flow is expected, substantially restricting deep shear, with effective-shear magnitudes struggling to exceed 30 kt in forecast soundings. However, strong veering of winds with height is forecast in low levels, along with enlarging hodographs from late afternoon into early evening, as the southwestern rim of a broad LLJ develops over the area. This, amidst the very strong and deep buoyancy, indicates transient/messy supercell structures and organized multicells are favored. Any severe threat should diminish rapidly after sunset in the absence of appreciable large-scale forcing, and as the layer of near-surface static stability strengthens/deepens. ..Edwards/Gleason.. 05/08/2022 Read more

No watches are valid as of Sat May 7 14:04:02 UTC 2022.

No Mesoscale Discussions are in effect as of Sat May 7 14:04:02 UTC 2022.

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0753 AM CDT Sat May 07 2022 Valid 071300Z - 081200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF WESTERN/CENTRAL NEBRASKA TO THE CENTRAL SOUTH/NORTH DAKOTA BORDER AREA... ...SUMMARY... Scattered severe storms capable of large hail and isolated severe gusts are possible across western and central Nebraska, mainly this evening and tonight. Other isolated severe storms are possible across parts of North Dakota, north and central Texas, and the Florida Peninsula. ...Synopsis... Two substantial, slow-moving cyclones will be the dominant mid/upper-level features this period, for convective purposes: 1. A vortex now appears over the eastern WV/southern PA/northern VA area, with troughing south-southwestward to the northwestern Gulf. The 500-mb low should move slowly eastward to the Delmarva Peninsula through the overnight hours, with trough across eastern NC, central/southern FL and intervening Atlantic waters by 12Z tomorrow. 2. A very large, complex gyre will arise from two initially well- separated cyclone centers now apparent in moisture-channel imagery over northern AB and over the northeast Pacific near 50N148W. The Pacific portion will approach coastal OR by 12Z, while vorticity maxima consolidate around the erratically drifting AB center. Cyclonic flow and height falls will expand across most of the western half of the CONUS, as a series of vorticity maxima pivot from the Great Basin to the northern Plains. In between those cyclones, a high-amplitude mid/upper ridge -- initially from the southern High Plains to Lake Superior and far northern ON -- will pivot slowly to near a HOU-LIT-MKE-James Bay axis by the end of the period. At the surface, 11Z analysis depicted an occluded low over WV, nearly stacked with the mid/upper low, and a triple-point low over Atlantic waters east of the Hampton Roads region. A cold front was drawn from there across northern FL to extreme southeastern LA, becoming a warm front across southeast and central TX. Another cold front was drawn from a low in the JDN/GGW area across central WY and northwestern CO. The eastern cold front will proceed slowly southeastward down the FL Peninsula, while becoming quasistationary from northeastern Gulf to LA, and moving back northward as a warm front over east TX and into western/southern OK by 00Z. To its southwest and west, a dryline should develop and mix eastward to a maximum late-afternoon extent (minimum longitudes) in an arc from near DRT-SEP-SPS-CDS, then northward over the eastern TX/OK Panhandles, western KS and western NE. In western NE, the dryline will be overtaken by a cold front that will move eastward/ southeastward across the northern Plains and central High Plains through the period. By 00Z, the cold front should reach the central Dakotas, western NS and extreme northern CO. ...Dakotas, Nebraska... Scattered strong-severe thunderstorms are expected, initially late this afternoon over portions of SD and perhaps ND, then this evening and tonight across parts of western/central NE. The greatest concentration of convective/severe potential should be in the SD/NE corridor, where large hail will be possible from early, relatively discrete and potentially supercellular activity. A transition to upscale clustering with some severe-wind threat also exists this evening before the foregoing boundary layer stabilizes too much. Being well north of the southern Plains warm front, moisture will be limited in both magnitude and lateral extent, with a narrow corridor of mainly 50s F surface dew points extending from central KS to the central Dakotas, east of the dryline and cold front. Still, this and insolation will foster enough late-afternoon/early evening mixing/drying of the boundary layer to boost DCAPE and weaken MLCINH substantially, supporting the gust potential beneath 500-1500 J/kg MLCAPE values. Time series of forecast soundings suggesting an "inverted V" subcloud thermodynamic profile in the short time window before deep convective initiation. Veering and strengthening of flow with height, from surface through midlevels, will support 45-55-kt effective-shear vectors aligned nearly orthogonal to the front in SD, with initial discrete/semi-discrete modes until some mergers and cold-pool processes occur. Activity should transition from a hail-dominant to wind-dominant threat before shifting east and weakening in greater stability this evening. Scattered thunderstorms also are forecast to develop over portions of western into central NE -- but this evening, generally as the front overtakes the dryline, and a combination of height falls and shots of DCVA occur in midlevels. Supported by the southerly LLJ, and its associated combination of increasing moisture and favorable storm-relative winds above the surface, elevated supercells and organized multicellular clusters are expected to offer a large-hail threat. Isolated severe gusts may occur as well, where sufficient downward momentum and cold-pool forcing from mesobeta-scale upscale growth can allow downdrafts to penetrate a near-surface stable layer locally. Continued eastward movement of activity atop progressively more-stable boundary-layer conditions should reduce storm intensity overnight. ...Central/south FL... Widely scattered to scattered thunderstorms are expected to continue, predominantly south of the cold front, offering sporadic, marginally severe hail and damaging gusts to near severe limits. Away from small-scale boundaries (outflows, sea breezes), warm- sector flow generally will be nearly unidirectional from the southwest or west-southwest. While this will limit low-level shear and convergence, convective potential will be supported increasingly by strong surface heating and favorable boundary-layer moisture (with surface dewpoints commonly in the 70s F). MLCAPE of 2000-2500 J/kg should be common, amidst 25-35-kt effective-shear magnitudes, for a dominant, sporadically organized multicellular mode. Convection should weaken by evening as low-level thermodynamic, frontal, and prefrontal-boundary lift all diminish. ...Portions of central/north-central TX... Although this area will be under, or very close to, the upper ridge, an isolated intense thunderstorm or two may erupt by late afternoon with a conditional risk for severe gusts and large hail. Intense diabatic surface heating on both sides of the broad dryline bulge may be sufficient to remove most or all EML-related capping for a few hours, in the presence of roughly 70 F surface dew points, and additional lift support from the dryline. With a deep troposphere and steep low/middle-level lapse rates expected, MLCAPE should exceed 4000 J/kg -- much of that in suitable hail-growth layers with no shortage of inflow-layer moisture for precip generation. A well-mixed subcloud layer also will enable strong-severe downdrafts to the surface in any storms that can develop. Lack of greater mid/ upper-level winds will limit deep shear (e.g., effective-shear magnitudes generally 20-30 kt expected), though flow will veer well with height in the low levels. Any severe threat should wind down quickly this evening as the boundary layer cools, the dryline retreats, and MLCINH increases. ..Edwards/Gleason.. 05/07/2022 Read more

No watches are valid as of Fri May 6 14:52:02 UTC 2022.

MD 0671 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR FAR SOUTHEAST LA INTO THE WESTERN FL PANHANDLE
Mesoscale Discussion 0671 NWS Storm Prediction Center Norman OK 0949 AM CDT Fri May 06 2022 Areas affected...far southeast LA into the western FL Panhandle Concerning...Severe potential...Watch possible Valid 061449Z - 061545Z Probability of Watch Issuance...40 percent SUMMARY...A supercell or two may pose a threat for strong gusts, hail and perhaps a tornado over the next 1-2 hours. DISCUSSION...An outflow boundary from overnight convection extends from far southeast LA to just offshore the MS coast and into the western FL Peninsula as of 1430z. A north to south oriented confluence zone is also noted from eastern Okaloosa County in FL southward into the offshore Gulf waters. Clusters of thunderstorms are ongoing along these boundaries with a couple of supercells noted. A very moist airmass resides across the region with dewpoints in the upper 60s to low 70s amid modest midlevel lapse rates and moderate vertical shear. The VWP data from KEVX shows an enlarged, favorably curved low-level hodograph indicative of rotation. These cells may periodic pose a threat for strong gusts, hail and perhaps a tornado. Much of the activity across southeast LA into the immediate coast/offshore islands of MS/AL will shift offshore as the outflow boundary continues to sag south/southeast. The storms further east along the confluence zone will slowly lift north/northeast but main train across a narrow path over the western FL Peninsula over the next 1-2 hours. MLCINH increases with northward extent into southeast AL due to impacts from an early morning QLCS and convection may tend to weaken with northward extent at least in the short term. However, clearing behind earlier morning showers/cloudiness will allow for airmass recovery over the next few hours. The spatial/temporal threat will remain limited across southeast LA before convection shifts offshore. However, the threat may persist/increase across portions of far southern AL into the FL Peninsula and a watch may be needed across parts of this area. ..Leitman.. 05/06/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...TAE...BMX...MOB...LIX... LAT...LON 29749044 30138962 30418875 30868735 31388667 31708605 31778585 31668547 31318515 30788520 30258551 29968609 29708669 29408773 29098882 28968959 29059020 29509046 29689049 29749044 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0751 AM CDT Fri May 06 2022 Valid 061300Z - 071200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM PARTS OF EASTERN ALABAMA TO PORTIONS OF SOUTHEASTERN VIRGINIA AND NORTHEASTERN NORTH CAROLINA... ...SUMMARY... Scattered severe thunderstorms are expected across parts of the Southeast to Ohio Valley and Tidewater region today. Damaging winds, hail and a few tornadoes will be possible, with the primary threat expected between late morning and early evening. ...Synopsis... A strongly progressive upper-air pattern will continue through the period, over the CONUS, with the main feature pertinent to severe-thunderstorm potential being the cyclone now centered over the Ozarks. The associated 500-mb low is expected to move approximately east-northeastward up the lower Ohio Valley to the area between EVV-CVG by 00Z, with a trough southward over the FL Panhandle. Associated mid/upper-level cyclonic flow will cover most of the CONUS east of the southern Plains and south of the Great Lakes. By 12Z, the center of the cyclone will decelerate and reach WV, while overall troughing amplifies over the East, from the lower Great lakes to the northeast Gulf. Otherwise, height falls aloft are expected over parts of the interior Northwest and northern Rockies regions ahead of a strong shortwave trough moving inland from the Pacific. Associated shots of DCVA/destabilization aloft -- over weak but adequate low/middle-level moisture -- will support general thunderstorm potential. At 11Z, surface analysis showed the primary low over extreme southeastern MO with cold front southward across the Mid-South and central LA. A wavy warm front was drawn from the Atlantic, east of the Outer Banks, across extreme southern NC near ILM, central SC, northeastern GA, eastern portions of TN/KY, to the lower Ohio Valley and the low. The low should migrate eastward to near HTS by 00Z, with cold front across western parts of VA and the Carolinas, western GA, southern AL, and southern LA. The warm front should reach the southern Delmarva Peninsula and southern/central VA by 00Z then decelerate, with a low developing thereon over the southern Chesapeake Bay region by 12Z. By then, the cold front should extend from that low over the Outer Banks to northern FL. The specific cold-frontal position through this afternoon and overnight -- especially over the Gulf Coast States -- may be rendered marginally to not relevant because of prefrontal convective stabilization that has made southwestern parts of the forecast more complex and conditional with time (see below). However, colder air aloft farther north across northern parts of the outlook areas may compensate for weaker boundary-layer theta-e enough to maintain at least a marginal severe threat. ...Southeastern CONUS and Ohio Valley to Tidewater... Scattered to locally numerous thunderstorms are expected through this evening, shifting eastward to northeastward across the region in the form of mixed modes (quasi-linear, clustered/multicellular, and probably a few discrete supercells). Damaging gusts, at least a few tornadoes, and sporadic large hail are all still possible -- with damaging to severe gusts being the most common type of storm report expected. A large area of severe-thunderstorm potential exists, though more uncertain now on the southwest side. That part of the outlook is complicated by a long-lived, quasi-linear convective system now weakening across portions of southwestern GA and the FL Panhandle, leaving behind a substantial theta-e deficit over parts of AL and most of MS. Though now weakening, this activity has progressed across the region faster and/or much better-organized than almost all synoptic and convection-allowing guidance has suggested, from 00Z initializations right to the past few hours. For example, the HRRR overnight consistently has been unable to keep up with reality, in terms of being too slow with convective speed and too fast to dissipate the complex. The few progs that have maintained a better-organized squall line (e.g., the 00Z high-res FV3 CAM) still were a few hours too slow with convective translation -- but in planar thermal/buoyancy guidance, more-reasonably indicate the stabilizing effects of the wake cold pool, when spatially adjusted eastward. Favorable destabilization between the outflow boundary (which arcs well southwestward offshore from AL/MS/LA) and the cold front now appears more uncertain, though some potential still exists for either: 1. Strong-severe convection to form along/ahead of the cold front at some ill-defined southern rim of the favorable large-scale lift/cooling aloft related to the cyclone, but in a moist layer that is weaker and shallower than earlier expected, and 2. The outflow boundary to weaken enough for prefrontal/low-level return flow (especially above the surface) to result in favorable theta-e advection, especially into the near-coastal southeastern LA to western Panhandle corridor closest to the remnant boundary. Given the uncertainties, and the reasonable lack of substantial/ organized activity over the coastal plain behind the MCS in progs that show it better, unconditional severe probabilities accordingly have been reduced (but not eliminated) in much of the post- convective area. Further refinements are likely in this region as mesoscale trends and later, more-reliable guidance warrant. Otherwise, the forecast remains largely the same farther north into 1. The Tennessee/Ohio Valley regions, where the influence of stronger cooling/instability aloft will be more important to convective potential, and 2. Over the eastern lobe of the outlook encompassing portions of eastern AL and GA to the Tidewater area, where a weakened MCS will be less to negligibly influential on destabilization from both diurnal/diabatic and advective processes. The CAPE/shear parameter space, especially near the warm front where enlarged hodographs are probable, still is expected to favor supercells with a relative maxima of tornado potential both away from the most strongly stabilized areas of the morning cold pool, and over parts of the VA/NC Piedmont eastward. ..Edwards/Gleason.. 05/06/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1013 AM CDT Thu May 05 2022 Valid 051700Z - 061200Z The Elevated risk area is expanded southward to encompass portions of the Sacramento, Guadelupe, and Davis mountain ranges in southern NM/southwest TX. Latest surface observations already show RH values near 15% with further reduction likely by late afternoon amid deep boundary-layer mixing. Relatively benign winds at the moment will increase through the day as stronger mid-level flow at around 20-25 mph mixes down to the surface within, and in the lee of, the higher terrain. Persistent elevated conditions appear likely, and brief/localized critical conditions are possible. The forecast regarding central NM and portions of southern NV remain on track. See the previous discussion below for details. ..Moore.. 05/05/2022 .PREV DISCUSSION... /ISSUED 1226 AM CDT Thu May 05 2022/ ...Synopsis... The central/southern Plains mid-level trough will continue its slow progression eastward today. Across the West Coast, broadly cyclonic flow will exist with a strong upper-level jet across the northern Sierra. At the surface, fire weather concerns will be driven by weak surface trough development in the Great Basin and in eastern New Mexico. ...Central New Mexico... Mid-level winds will be decreasing during the day. However, they will be sufficient to induce a weak lee trough in the eastern plains. Winds of 15-20 mph with perhaps some higher speeds in terrain-favored areas. Dry air will once again be present with afternoon RH falling to 10-15%. ...Southern Nevada... Temperatures in the upper 80s to low 90s F will support afternoon RH of 10-20% across much of Nevada. A weak surface trough in the Great Basin will promote 15-20 mph winds. Elevated fire weather concerns will exist where fuels have sufficiently dried. ...Please see www.spc.noaa.gov/fire for graphic product... Read more