Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jun 02 2023 12:52:13 ACUS01 KWNS 021252 SWODY1 SPC AC 021250 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0750 AM CDT Fri Jun 02 2023 Valid 021300Z - 031200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE TEXAS SOUTH PLAINS AND PERMIAN BASIN REGIONS TOWARD WEST-CENTRAL TEXAS... ....SUMMARY... Very large hail, severe gusts and a couple of tornadoes are possible this afternoon and evening across parts of the southern High Plains. ....Synopsis... High-amplitude, mid/upper-level blocking will continue over much of North America today, and well into the next week. Before some retrogression of the blocking high now over the Upper Great Lakes, broad cyclonic flow will exist off the southwestern and southwestern flanks of the anticyclone, with troughing over the Intermountain West and Southeast/eastern Gulf. A strong northern-stream shortwave trough initially over Labrador and north-central QC will dig southward across New England and eastern NY overnight. Some precursory/diurnal thunder potential with strong gusts is possible in those areas, as large-scale ascent/cooling aloft spreads over modest low-level moisture and a diurnally warm, well-mixed boundary layer. However, weak deep-layer flow/shear should preclude organized severe potential in that region. A notable southern-stream shortwave trough, that has tracked across the central eastern Pacific for several days, is apparent on moisture-channel imagery near the southern AZ/NM line and southward over portions of eastern Sonora and western Chihuahua. This feature will weaken slightly, but still maintain good definition as it moves east-northeastward today to a 00Z position near the eastern NM/TX line and lower Pecos Valley in west TX. Meanwhile, this perturbation also will phase with a negatively tilted, slower-moving trough over CO. Convectively induced/enhanced vorticity maxima will be entrained into the trough(s) tonight, with the net 12Z/tomorrow 500-mb trough position near an axis from LND-DEN-CDS-AUS. At the surface, 11Z analysis showed a rather muddled, low-gradient pattern east of the Rockies, save for two thermodynamic features: 1. A dryline analyzed over far west TX, east-central NM and east- central CO, and forecast to shift eastward to eastern parts of CO/NM and just west of the TX Pecos Valley by mid-afternoon. 2. An outflow-reinforced baroclinic zone, acting effectively as a warm front, from a low near ELP to near GDP, SWW and DFW. This feature should shift northward over the southern High Plains today and become more diffuse in a regime of broad low-level warm/moist advection, throughout the preconvective hours today. ....Southern High Plains... Widely scattered to locally numerous thunderstorms are expected to develop this afternoon along and east of the dryline. Activity may erupt as soon as midday to early afternoon over parts of the Panhandle/South Plains and adjoining NM where MLCINH is weak -- and by mid/late afternoon toward the Permian Basin and lower Pecos River area where a better-developed EML will be evident, with slightly stronger capping. Any relatively discrete convection that has time to mature may become supercellular will offer a threat of all severe modes (including significant/2+ inch hail and a couple tornadoes). Some potential exists for very large/destructive hail exceeding 3 inches from any sustained supercells, especially in southern parts of the outlook area, where long hodographs will be present amidst the greatest inflow-layer moisture and storm-relative low-level flow. Later this afternoon into evening, activity should aggregate into one or more complexes composed of multicells, supercells and bow echoes, offering an increasing threat for severe, perhaps significant (65+ kt) gusts. Convection then should diminish late this evening and overnight into a stabilizing air mass with time and eastward extent over western/central OK, the Low Rolling Plains/ Concho Valley region, and Edwards Plateau. The southern-stream shortwave trough will be well-timed to support development today, with precursory field of DCVA/ascent aloft and strongly difluent mid/upper winds spreading across the dryline during strong diurnal heating. To its east, surface dewpoints commonly will reach the 60s F, with values in the mid-60s to near 70 already are evident south of I-10 over southwest TX. Moisture advection is expected to offset mixing enough to maintain favorably high-theta-e inflow layers, despite characteristically overexuberant mixing apparent in a few models (especially RAP). 2500-3500 J/kg MLCAPE (locally near 4000 J/kg) is expected across parts of the TX Panhandle southward to the Rio Grande around the northern rim of Coahuila, with effective-shear magnitudes reaching 45-55 kt by mi/late afternoon. Slightly weaker deep shear, earlier in the afternoon before potential major upscale growth of convection, still favors early supercellular modes. Analog-sounding data, 2-D hail models, and the overall character of the vertical wind/buoyancy profiles each support potential for very large hail in the early stages of the event. ....Central High Plains... Isolated to widely scattered thunderstorms are expected to develop near the dryline/lee trough this afternoon, as diurnal heating in the presence of 50s moist-sector dewpoints weakens MLCINH substantially. Weak large-scale ascent aloft -- preceding the CO mid/upper trough -- also may contribute to a favorable convective environment. Although low-level shear should remain modest over most of this region, somewhat stronger flow aloft is forecast as compared to prior days, lending to potential for at least transient supercells, as well as multicell clusters. MLCAPE in the 1500-2000 J/kg range is possible, along with effective-shear magnitudes increasing from less than 20 kt over northern areas to around 45-40 kt over parts of western KS and southeastern CO. ...Edwards/Smith.. 06/02/2023 $$ = = = To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .