Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jun 06 2023 12:50:14 ACUS01 KWNS 061250 SWODY1 SPC AC 061248 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0748 AM CDT Tue Jun 06 2023 Valid 061300Z - 071200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE INTERMOUNTAIN WEST...SOUTHERN ROCKIES TO FAR WEST TEXAS...SOUTH FLORIDA...AND CAROLINAS... ....SUMMARY... Isolated strong to severe thunderstorm gusts and hail are expected today over parts of the Intermountain West, southern Rockies to far west Texas, south Florida, and Carolinas. ....Synopsis... In mid/upper levels, a blocking pattern will remain in place through the period, as in previous days, anchored by a stout mean ridge up and down the Great Plains, with a high over the northern Plains. This period, the high will weaken and shift westward very slightly, as a synoptic cyclone now centered over coastal NS retrogrades northwestward toward northeastern ME. That, along with a series of shortwaves pivoting through the western flow field of the cyclone, will lead to a broad area of height falls from the Great Lakes across the Appalachians to much of the Atlantic Coast. A subtropical jet in upper levels will extend from central MX across the southern Gulf and Yucatan, to the Keys and south FL, south of a lingering field of cyclonic flow covering the Gulf Coast States and much of the northern Gulf. Farther west, a 500-mb low now over the SBA area will drift erratically through the period, with very slight eastward motion possible into more of southern CA through the period. Associated mid/upper difluence, between the cyclone's eastern northern rim and the mean ridge, will cover much of the Rockies and Intermountain West. A weak, quasistationary trough aloft will extend across the central Rockies/Plains and Arklatex to the Gulf of Mexico troughing. At the surface, 11Z analysis showed a cold front over Atlantic waters east of the Delmarva Peninsula, decelerating to quasistationary across northern/western NC, the length of TN, and northern parts of AR/OK. The boundary over and east of the Appalachians will move southward again today as a cold front, beneath the height falls aloft. Farther west, a dryline has backed well into the higher terrain of central/northern MX and southern/central NM. ....Intermountain West... Widely scattered thunderstorms are expected to develop across southern parts of this region and fan northward out of northern UT, and northwestward to westward out of northern NV, amid the strong difluence. Isolated severe gusts and hail near severe limits are possible, despite a lack of substantial deep shear. A belt of low-level trough/convergence along the outlook corridor, with local orographic and diurnal-heating support, will contribute to lift over the region. Deep/well-mixed subcloud layers should develop over lower elevations, with very steep lapse rates, and enough remaining moisture to support areas of 500-1000 J/kg MLCAPE, with even larger DCAPE values evident in forecast soundings. Associated "inverted-V" thermodynamic profiles will support deep downdraft cooling/accelerations in the most intense cells. ....Southern Rockies to far west TX... Isolated to scattered thunderstorms are expected to develop this afternoon, predominantly over higher terrain on either side of the Rio Grande Valley in NM, and southeastward across parts of far west TX and adjoining Chihuahua. Strong/isolated severe gusts and hail are possible for a few hours into early evening, before a combination of environmental diabatic cooling and spreading outflow air curtail the convection. Activity should form amid strong heating and favorable moisture at high elevation, then move eastward into adjoining valleys where 500-1000 J/kg MLCAPE and deeply mixed subcloud layers can support strong downdraft production/ acceleration. Organization of the activity will be limited by lack of vertical shear; however, some forward-propagational clustering may boost severe potential on small scales. ....SC/NC... Isolated to scattered thunderstorms are expected to develop along/ ahead of the front from eastern SC southwestward over SC, beneath the southwestern rim of stronger cyclonic flow aloft related to the major/retrograding low over western parts of the Canadian Maritimes. The most intense cells will be capable of damaging, perhaps marginally severe gusts, as well as isolated hail near severe limits. An eastward-tapering corridor of favorable low-level moisture and strong diurnal heating will develop ahead of the front and west of the sounds over SC and parts of central/southern NC, supporting MLCAPE in the 1500-2000 J/kg range atop steep low-level lapse rates and a suitably deep, well-mixed boundary layer for downdraft acceleration. Vertical shear will be weak except through the entire cloud-bearing layer, given the majority westerly directional wind component throughout the troposphere. ....South FL... Scattered thunderstorms will form through afternoon as outflow from ongoing convection, as well as the Gulf and Atlantic sea breezes penetrate inland and interact, and on subsequent outflow boundaries and intersections. The most intense cells will be capable of severe hail or damaging to marginally severe gusts from water-loaded downdrafts. Strong diurnal heating and rich low-level moisture (e.g., surface dewpoints commonly in the low 70s F), along with weak MLCINH, will offset modest mid/upper-level lapse rates in supporting development, with preconvective MLCAPE reaching as much as 2000 J/kg locally. Although near-surface flow and boundary-layer shear should be weak overall, the presence of light easterlies under the subtropical jet will lead to somewhat favorable deep/cloud-layer shear for convective organization. Activity should weaken substantially late afternoon into evening with outflow spread and diabatic surface cooling. ...Edwards/Smith.. 06/06/2023 $$ = = = 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) .