Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Dec 17 2024 19:35:06 ACUS01 KWNS 171935 SWODY1 SPC AC 171933 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0133 PM CST Tue Dec 17 2024 Valid 172000Z - 181200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PARTS OF NORTHEAST TEXAS/SOUTHEAST OKLAHOMA TO WESTERN TENNESSEE... ....SUMMARY... Isolated strong to severe thunderstorms are possible tonight through early Wednesday morning across parts of northeast Texas and vicinity into western Tennessee. ....20z Update... No changes are needed to the D1 Convective Outlook. See previous discussion below for more information. ...Thornton/Gleason.. 12/17/2024 ..PREV DISCUSSION... /ISSUED 1030 AM CST Tue Dec 17 2024/ ....Synopsis... Gradual trough amplification will occur through the period across the Plains into the Midwest, as a shortwave trough digs from the central Rockies to the southern Plains tonight. At the surface, a weak cyclone should develop from the central High Plains to the Mid-South and lower OH Valley by early Wednesday morning. Greater low-level moisture, characterized by upper 50s to mid 60s surface dewpoints, is in place across parts of the ArkLaTex to northern MS along/south of a convective outflow boundary/front. This moisture is forecast to spread gradually northward through tonight ahead of the approaching shortwave trough. A separate cold front will spread east-southeastward over parts of the southern Plains and mid MS Valley/Mid-South this evening and overnight. ....Northeast Texas to Western Tennessee... Robust convective development will likely be delayed until near/after 05Z tonight, as low-level warm advection and large-scale ascent preceding the upper trough gradually overspread the warm sector. Even though steeper mid-level lapse rates should lag/remain generally north of the cold front, weak instability (around 500-1000 J/kg MLCAPE) should be present in a narrow corridor along and just ahead of the front. This instability will become weaker and more limited with northeastward extent into middle TN, with an ill-defined cutoff to isolated severe potential somewhere in the western to middle TN vicinity. Strengthening mid-level southwesterly flow with the amplifying upper trough will eventually move into the ArkLaTex and Mid-South, mainly after 06Z, in tandem with modestly enhanced low-level southwesterlies. Sufficient speed shear should exist to support some updraft organization, although the orientation of the deep-layer shear vector will be nearly parallel to the surface front. Thunderstorm mergers and interactions appear likely, with eventual upscale growth into a line anticipated as the cold front intercepts the greater low-level moisture, especially after 09Z. Isolated hail may occur with initial convective development, before strong to occasionally damaging winds become the main threat in the last few hours of the period with the line. A brief tornado cannot be ruled out. The overall severe threat should remain isolated due to the somewhat marginal thermodynamic environment. $$ = = = 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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .