Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue May 16 2023 19:39:12 ACUS01 KWNS 161939 SWODY1 SPC AC 161937 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0237 PM CDT Tue May 16 2023 Valid 162000Z - 171200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON ACROSS PARTS OF SOUTHEASTERN KENTUCKY...NORTHEASTERN TENNESSEE...NORTHEASTERN NORTH CAROLINA....SOUTHWESTERN VIRGINIA AND ADJACENT SOUTHERN WEST VIRGINIA... ....SUMMARY... An organizing cluster of thunderstorms may continue to gradually intensify, with increasing risk of producing damaging wind gusts while spreading across the Cumberland Plateau and adjacent Appalachians, through the Virginia and North Carolina Piedmont by late evening. ....20Z Update... Primary adjustments to the categorical and probabilistic lines have been made to account for the progression of synoptic/sub-synoptic features and their influence on ongoing trends concerning destabilization. For further details, please refer to the 1630Z outlook discussion (appended below), and the latest SPC mesoscale discussions. ...Kerr.. 05/16/2023 ..PREV DISCUSSION... /ISSUED 1102 AM CDT Tue May 16 2023/ ....KY/TN to VA/NC Vicinity... A shortwave mid/upper trough will move across the Ohio Valley and Central Appalachians today, and into the Mid-Atlantic by this evening. This feature will allow midlevel flow to increase through the day, with a belt of 40-50 kt westerly flow overspreading western KY/TN to coastal VA/NC. At the surface, a weak low was analyzed over western KY at 15z. A composite warm front/outflow boundary extended eastward from the low across northern/central KY. This will likely demarcate the northern extent of greater severe potential/coverage. A weak surface lee trough is also evident across the VA/NC Piedmont. The surface low should track roughly east/northeast through the day with a trailing cold front spreading across the region this afternoon/evening. Dewpoints in the upper 60s to near 70 F (low/mid 60s with eastward extent to the lee of the Appalachians), and strong heating south of the warm front where mostly clear skies exist, will allow for weak to moderate destabilization. Low-level flow will remain somewhat weak through 1-2 km, but increasing speed with height will result in effective shear magnitudes around 35-45 kt, supporting organized convection. Initial semi-discrete cells are expected, posing a risk for hail and damaging gusts. Steep low-level lapse rates will support strong outflow and convection will likely transition toward bows as storms shift east across the spine of the Appalachians. A swath of strong gusts may persist east of the Appalachians in a moist and unstable downstream environment. While low-level flow will remain weak, modestly enlarged forecast hodographs and some increase in effective SRH suggest a few spin-ups along the eastward-advancing gust front will be possible given a favorable low-level thermodynamic environment. For short term severe potential across KY/TN vicinity, see MCD 800. More than one round of strong/severe thunderstorm activity may be possible across the VA/NC Piedmont. Initial activity associated with the lee trough may pose a hail/wind risk, while any emerging bow/MCS by late afternoon/early evening may also result in a damaging wind risk. ....Northern MS/AL/GA into Upstate SC... This area will remain south of strong midlevel flow, with mainly modestly, mostly unidirectional westerly deep-layer flow forecast. Effective shear around 20-25 kt amid moderate instability will allow for some transient/loosely organized cells. Steep low-level lapse rates will foster strong outflows and a few locally strong/damaging gusts are possible. ....High Plains... A shortwave trough currently over SD will track southward today into the high plains of eastern WY/CO and western NE/KS. Strong heating over this region, coupled with dewpoints in the 40s to lower 50s, will result in a deeply mixed boundary layer and CAPE values of 1000-1500 J/kg. Widely scattered diurnal thunderstorms are expected, with sufficient deep-layer shear for high-based supercell structures capable of gusty winds and hail. $$ = = = 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) .