Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Apr 26 2023 12:50:00 ACUS01 KWNS 261249 SWODY1 SPC AC 261248 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0748 AM CDT Wed Apr 26 2023 Valid 261300Z - 271200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF NORTH TEXAS AND CENTRAL FLORIDA... ....SUMMARY... A few tornadoes, along with very large/destructive hail, and severe thunderstorm gusts, are expected over parts of north Texas this afternoon and evening. Very large hail and damaging winds also are expected over parts of central Florida. ....Synopsis... The primary mid/upper-level feature influencing this forecast is a compact cyclone -- apparent in moisture-channel imagery over the southern Rockies and centered near SKX. A trough extends from the low southwestward across southeastern AZ, and northeastward to near IML. The 500-mb low should move southeastward across northeastern NM today, then by 00Z, pivot eastward to the TX Panhandle, with through southwestward past ELP. By 12Z, the perturbation should devolve to an open-wave trough with primary vorticity lobe over OK, and trough across west-central/far west TX. A broad area of difluent, somewhat cyclonic flow will spread across the southern Plains to its southeast. Several embedded, convectively induced/ reinforced vorticity maxima will eject eastward across the Arklatex and Mid-South regions ahead of this feature. A continuing fetch of strong upper-level westerlies -- with weak/embedded perturbations -- will overlie the northern Gulf and FL. One such weak shortwave trough is apparent over the north- central/northeastern Gulf, associated with a few thunderstorms southeast of LA. This feature should reach peninsular FL by this evening. At the surface, a quasistationary front was drawn at 11Z across north-central FL and the northern Gulf, becoming a warm front over southeast through central TX, to a low between SWW-LBB. A cold front extended from there southwestward over the lower Pecos Valley. The cold front will shift eastward over central/north TX through the period, while the warm front shifts northward today to near the DFW Metroplex, before being overtaken by convection. The FL frontal segment should remain near its present position. ....North TX and vicinity... Widely scattered to scattered thunderstorms are expected to occur along and south of the warm front this afternoon, with all severe modes possible. The main concern at first may be large to giant hail, with ideal conditions progged for generation of hailstones above 3 inches in diameter from any sustained supercell(s). As early supercells move east-southeastward to southeastward across the region into greater low-level moisture and weak CINH along/south of the effective warm front, two processes should occur in tandem: 1. Enlargement of low-level hodographs during late afternoon into early evening, 2. Growth in convective coverage, ultimately leading to a line of strong-severe thunderstorms moving southeastward across central and northeast TX. The resulting QLCS this evening will be mainly a damaging-wind threat with potential for significant/65+ kt gusts, but with a couple tornadoes and isolated large hail still possible. While supercells still are present -- and especially along the warm front where low-level shear/vorticity will be maximized -- so will be the potential for tornadoes (some possibly capable of significant/EF2+ damage). Uncertainties remain on mesoscale specifics of boundary position and mode-transition timing, but both giant hail and tornadoes are possible with the boundary potentially lying across some part of the Metroplex. North of the boundary, isolated large hail still may occur from the most vigorous elevated convection across mainly the Red River region into parts of OK/AR. This includes an ongoing, elevated cluster of thunderstorms over northwest TX and southwestern OK, which should move astride the Red River across southern OK and parts of north TX through the day. A corridor of 2500-3500 J/kg peak/preconvective MLCAPE should develop east of the cold front and southwest of the warm front through central TX, narrowing northward. Strong veering of flow with height -- especially near the warm front -- will contribute to 45-60 kt effective-shear magnitudes. The largest hodograph sizes and SRH for surface-based, effective-inflow parcels should be along the warm front, but still will favor supercells in the warm sector. Once the modal transition occurs, wind and tornado potential will be maximized near embedded mesocirculations and bow/LEWP features. ....FL Peninsula... Scattered, mainly afternoon to early-evening thunderstorms are expected across central and south FL, offering large hail and isolated damaging to severe gusts. The greatest convective coverage potential and most-favorable environmental parameter space for significantly severe hail appears to be over portions of central/ east-central FL this afternoon, where supercells with significant hail (2+ inches diameter) may occur. Isolated damaging/severe downbursts also may occur, and a tornado is possible with help from storm-scale/boundary processes. Initial foci for convection will be sea-breeze boundaries near the East Coast, and farther inland from the Gulf. With strong surface heating and abundant low-level moisture expected to minimize MLCINH by midday, outflow and differential-heating boundaries also may support storm initiation throughout the afternoon. The coldest midlevel temperatures and steepest low/middle-level lapse rates are expected over central FL, associated with a remnant Mexican EML plume. With surface dewpoints in the upper 60s to low 70s F, preconvective MLCAPE should reach 2500-3000 J/kg (locally higher). Low-level flow will be weak, keeping hodographs small for the most part. However, flow will veer strongly with height beneath favorable mid/upper winds of the subtropical jet, contributing to 40-50-kt effective-shear magnitudes. This, along with boundary interactions, will support supercell potential to maximize updraft strength and efficiency of hail production. Hail-growth models applied to forecast soundings indicate potential for hailstones 2-3 inches in diameter, perhaps from multiple storms. The overall convective coverage/intensity should decrease markedly after about 03Z, when outflow coverage is maximized and nocturnal boundary-layer stabilization is underway. ...Edwards/Leitman.. 04/26/2023 $$ = = = 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) .