Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Apr 25 2023 12:46:21 ACUS01 KWNS 251246 SWODY1 SPC AC 251244 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0744 AM CDT Tue Apr 25 2023 Valid 251300Z - 261200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM CENTRAL TO NORTHWEST TEXAS AND A SMALL PART OF SOUTHWESTERN OK... ....SUMMARY... Severe thunderstorms are possible over parts of the southern Plains, with a risk of large to very large hail, damaging gusts, and perhaps a couple of tornadoes. ....Synopsis... In mid/upper levels, a broad, slowly weakening cyclone -- initially centered over the Georgian Bay area of Lake Huron -- should drift northeastward to southwestern QC through the period. Cyclonic flow to its south over the Lower Great Lakes, Ohio Valley and Northeast will become nearly zonal across the Southeast and FL. Meanwhile, a smaller cyclone -- evident in moisture-channel imagery over the SLC area -- will move southeastward to southwestern CO by 00Z. By 12Z tomorrow, the cyclone center should reach northeastern NM. This feature will be preceded for about 300 nm by substantial height falls and strongly difluent flow aloft, but those height falls should not reach the southern High Plains until late overnight. The 11Z surface analysis showed a warm to quasistationary front across central FL, the north-central and northwest Gulf, to just offshore from BRO. The FL segment should drift northward and become more diffuse, while the northwest Gulf segment moves northwestward into south TX and also loses some definition. Initially separate frontogenesis over northwest and central TX may connect to the remains of the Gulf boundary late today or overnight. As the mid/ upper low approaches the southern Rockies this afternoon, surface cyclogenesis is expected over northeastern NM/northwestern TX Panhandle, and the residual marine/warm front will move northward across west and central TX. By 00Z, a low should exist along the front in the CAO/DHT area, with the boundary extending west- northwestward toward TAD and southeastward across southwestern OK and central TX. By 12Z, the low should strengthen and reach the western/central TX Panhandle, with abundant convection to its north helping to shift the baroclinic zone southward over northwest TX, to central/north-central TX. ....Southern Plains to southeastern CO... Multiple convective regimes/episodes are possible through the period, each with at least marginal potential for supercells and (where inflow is surface-based) the full spectrum of severe types possible. Though substantial height falls preceding the mid/upper cyclone will be delayed until late in the period, the difluence aloft and favorable gradient winds aloft -- on the north rim of the subtropical jet -- will affect most of the outlook area today into tonight. So will a sustained fetch of low-level warm/moist advection east of the dryline, and over the baroclinic zone into a regime of elevated instability and marginal severe-hail potential across parts of OK. Given a weakening of the EML with eastward extent, some potential exists for diurnal to evening development in the warm-advection plume across parts of south-central to north- central TX, on either side of the front. Though weak low-level flow will limit hodograph size, LCL will be low, and enough veering with height will be present beneath the strong mid/upper westerlies to support isolated warm-sector supercell potential, and a threat for all severe types. Farther west, scattered to widely scattered thunderstorms are possible late this afternoon into this evening from portions of southeastern CO across the TX Panhandle, as some cooling/ascent aloft begins to affect these areas. Low-level instability will be limited, but may be surface-based over the High Plains, with a plume of 500-1000 J/kg MLCAPE despite cool surface temperatures. Amid easterly to northeasterly surface flow, strong veering with height and favorable hodographs, sufficient shear will exist for supercells with isolated severe hail/gusts or a tornado possible. Diurnal dryline development over west-central/northwest TX is far from guaranteed, but with colder air aloft and greater low-level convergence than farther south, any storms that do form will be capable of becoming supercells. Severe gusts and large to very large hail may occur, with upper 50s to low 60s F dewpoints supporting 1500-2000 J/kg MLCAPE, long hodographs, and 35-50 kt effective-shear magnitudes. A time window of a couple hours or so of tornado potential may develop late afternoon into early evening for any relatively discrete dryline/frontal supercells, when surface-based inflow is still possible, but while hodographs grow enough to support 150-300 J/kg effective SRH. The regional LLJ will strengthen throughout the night with the approach of the cyclone aloft, helping to support upscale expansion of convection along and mainly north of the front over northwest TX and OK. Diurnal initiation and maintenance of deep-convective plumes along the dryline is in greater doubt with southward extent across west- central/southwest TX, given expected EML-related capping and lack of substantial large-scale support. ...East-central/southeastern FL... Scattered thunderstorms are expected to develop from midday through the afternoon, predominantly along: 1. The Atlantic sea breeze near the coast, and perhaps a little sooner than 2. On a Gulf sea-breeze front displaced further inland than its eastern counterpart. This development should move eastward to southeastward, with access to the most buoyant, diurnally-heated, moist boundary layer (peak/preconvective MLCAPE reaching the 1500-2000 J/kg range). Despite weak low-level winds, enough deep shear should exist beneath strong upper westerlies (under the subtropical jet) to yield 35-45-kt effective-shear magnitudes. This will support both organized multicells and at least transient supercell potential. Subsequent outflows and boundary interactions down to the storm scale will dictate specific convective growth/intensity maxima locally. In general, isolated large hail and damaging to severe gusts are possible. Convective coverage/intensity will decrease through this evening, amidst nocturnal cooling and maximized outflow area. ...Edwards/Leitman.. 04/25/2023 $$ = = = 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) .