Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Jun 08 2023 12:55:58 ACUS01 KWNS 081255 SWODY1 SPC AC 081254 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0754 AM CDT Thu Jun 08 2023 Valid 081300Z - 091200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF CENTRAL TEXAS SOUTHEASTWARD TO THE MID/UPPER TEXAS COAST... ....SUMMARY... The most concentrated potential for severe thunderstorms today appears to be from portions of central Texas southeastward to the mid/upper Texas Coast. ....Synopsis... A blocky large-scale pattern will persist in mid/upper levels, characterized broadly by ridging over the central CONUS, a large cyclone covering much of the East, and a much weaker but still broad cyclone over parts of the western Great Basin, CA and interior Northwest. As these features will move little through the period, shortwave details -- some rather subtle -- will be the main influences aloft. A longstanding height weakness -- extending from the Great Basin cyclone across the northern/central Rockies, through the mean ridge to troughing over the Gulf -- will persist, but weaken somewhat. However, an embedded shortwave trough, with a convectively enhanced vorticity field, was apparent in moisture- channel imagery over west-central TX. This perturbation is forecast to pivot southeastward to the mid/upper TX Coast by 00Z, before moving offshore over the northwestern Gulf. Elsewhere, a series of low-amplitude shortwave perturbations and related vorticity lobes will pivot across the Ohio Valley and central/southern Appalachians, around the southwestern quadrant of the cyclone centered over new England. Similarly, but in a much weaker height gradient, small perturbations will inhabit the cyclonic-flow field across the Great Basin, ID and parts of OR/WA/western MT. At the surface, 11Z analysis showed a wavy cold front, accompanied by several weak lows, from southeastern VA across eastern NC to central SC, central AL, and northern MS, becoming quasistationary across the Ozarks and up the Missouri Valley around MCI-FSD, to near ABR and DVL. This boundary should move slowly southward from AR eastward, while remaining quasistationary north of the Ozarks. ....Portions of central/south TX... Scattered thunderstorms should form this afternoon over the east-central hill Country region or near I-35 and move southeastward over mainly the middle coastal plain, offering large hail and occasional strong-severe gusts. Hail potential will be skewed somewhat westward in the process, where somewhat discrete mix of multicells and at least transient supercells is possible. As activity aggregates and shifts southeastward toward the coast, wind will become the main concern, with hail still possible. Brief/ isolated significant (2+ inch) hail may occur over western parts of the outlook area, but that threat appears too marginal and uncertain for an unconditional sig-hail area at this time. Following the exit of a morning MCS from the lower Rio Grande Valley region to the Gulf, considerable trailing clouds and occasional precip will delay and reduce diurnal destabilization in the trailing outflow pool. However, in the relatively unaffected air mass from central TX to the mid/upper TX Coast, high theta-e is forecast to remain, with surface dewpoints commonly near 70 F below the Balcones Escarpment. An outflow boundary from earlier/dissipated thunderstorms -- now near the I-35 corridor between SAT-TPL but also weakening -- should decelerate and could focus later development or intensification. Other convection may form in diurnally heated/modified air behind the boundary, above the escarpment, and closer to the pocket of large-scale ascent immediately preceding the vorticity lobe. Resulting convection should move southeastward and expand in scale through the afternoon, taking advantage of a strongly heated/mixed inflow layer supporting MLCAPE near 2500 J/kg. Though low-level winds/shear will be weak, favorable deep shear is expected, with effective-shear magnitudes of 35-45 kt probable. ....Northern Plains... Widely scattered to scattered thunderstorms are expected to develop mainly this afternoon, in and west of the frontal zone to the northern High Plains and eastern fringes of the northern Rockies. Relative coverage maxima may develop: 1. Over eastern ND -- near the front and ahead of a weak mid/upper perturbation now evident over southeastern SK -- and 2. Over central/western MT ahead of a westward-drifting shortwave trough over central MT, embedded in the northernmost fringe of the aforementioned northwest/southeast-aligned height weakness. In each lobe, and perhaps in between (nearer the ridge aloft), weak deep-tropospheric flow and lack of substantial shear should limit organization to pulse in nature accompanying multicells. However, diurnal heating/mixing of preconvective boundary layers may support potential for strong/locally damaging gusts, and in eastern areas, a marginal hail profile. ....Southeast... Isolated to scattered thunderstorms are expected to develop this afternoon in vicinity of the front and perhaps the near-coastal sea breeze, offering locally strong/damaging gusts and small to marginally severe hail in the most vigorous cells. Continuing cyclonic flow and subtle shots of DCVA/ascent aloft will overlie frontal lift and a diurnally destabilizing boundary layer, supporting some multicellular storm organization over the area. Rich warm-sector moisture - with surface dewpoints in the mid 60s to near 70 F -- will foster peak/preconvective MLCAPE reaching the 1500-2500 J/kg range, amid 30-35 kt effective-shear magnitudes. ...Edwards/Smith.. 06/08/2023 $$ = = = 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) .