Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Sep 09 2023 05:37:50 ACUS01 KWNS 090537 SWODY1 SPC AC 090536 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1236 AM CDT Sat Sep 09 2023 Valid 091200Z - 101200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER MUCH OF THE HIGH PLAINS...CENTRAL AND SOUTHEAST TEXAS...AND OVER MUCH OF THE AREA ALONG AND EAST OF THE APPALACHIANS... ....SUMMARY... Isolated strong to severe thunderstorms are possible today from the northern High Plains into the central Plains, over parts of central and southeastern Texas, and over much of the East along and east of the Appalachians. ....Synopsis... The upper air pattern will begin to weaken today, with an upper high still over AZ and NM, and a weak upper trough centered over the OH/TN Valleys. Midlevel winds in association with the eastern trough will generally average 15-25 kt, with relatively cool 500 mb temperatures around -10 C over a large area. To the west, northwest flow around the northern periphery of the upper high will result in areas of 30-35 kt midlevel winds from the central plains into eastern TX, with similarly cool midlevel temperatures. At the surface, cooler air with high pressure will generally stretch from the northern Plains across the mid and upper MS, OH and TN Valleys, with weak convergence zones and troughing east of the Appalachians, over central TX, and across the central High Plains. Moisture will remain robust over the East Coast states with upper 60s F/lower 70s F, and along the TX Coast. A narrow plume of moistening will push into northwest TX and toward the central High Plains. ....Appalachians into the Mid Atlantic and Northeast... Daytime heating of a moist air mass beneath cool temperatures aloft will again lead to widespread daytime storms, developing earliest over the higher terrain from TN/NC northward into WV/western VA, and expanding into PA, southern NY and parts of southern New England later in the day. Shear will be weak across the entire area, and as such, only diurnally driven, localized damaging gusts are expected. ....Much of the High Plains... A cold front will shift south out of SD and into NE as a surface trough develops over the central High Plains. A plume of steep low-level lapse rates will extend from CO into NE, and this will be a favored zone of afternoon development. Modest effective shear around 35 kt may favor a cluster of cells producing hail or locally strong gusts. To the west, cooler air aloft and a bit stronger flow in the mid to upper levels may also favor cells producing marginal hail or wind despite MLCAPE averaging 500-750 J/kg. A cluster or two of cells may proceed east/southeast out of southern MT and WY toward western NE by evening. ....Much of central/southern TX... Ongoing storms over northern TX late Friday night will likely proceed south/southeastward into southeast TX by Saturday morning, and a few strong gusts may occur. Behind/northwest of this activity, residual boundaries combined with strong heating over central TX may yield new development by late afternoon, with another cluster of storms possibly producing areas of strong to severe gusts. The exact area of any concentrated wind threat will depend on how the early day activity evolves, but a small area could experience severe wind gusts late this afternoon into the evening. ...Jewell/Squitieri.. 09/09/2023 $$ = = = 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) .