SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0129 PM CST Fri Dec 11 2020 Valid 112000Z - 121200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN TEXAS INTO WESTERN LOUISIANA AND SOUTHWEST ARKANSAS... ...SUMMARY... A few strong or damaging wind gusts are possible from eastern Texas into western Louisiana and southwest Arkansas from late afternoon into early evening. Little change was made to the previous outlook, with a continued low-end isolated severe risk later today. The main change from the prior outlook was to remove northwestern parts of the Marginal due to lack of instability. Otherwise, storms are expected to form over eastern TX after 21Z, and persist through evening as they move into LA and southwest AR. Some of the storms may fail to become surface based due to existing rain and cool temperatures, which would minimize tornado threat. The higher theta-e surface air will extend from southeast TX into southwest LA through evening. ..Jewell.. 12/11/2020 .PREV DISCUSSION... /ISSUED 1031 AM CST Fri Dec 11 2020/ ...East Texas into the lower Mississippi Valley... As of late this morning a cold front was situated from a weak surface low in northeast KS southwestward through southeast OK to just north of Midland in west TX. A weakly unstable warm sector is present across central through east TX where surface dewpoints range from mid 50s in north central TX to mid 60s F near the coast. Widespread clouds and ongoing areas of showers with embedded isolated thunderstorms in addition to the modest low-level moisture will considerably limit instability with MLCAPE from 200-400 J/kg. Forcing for ascent along the warm conveyor belt associated with a progressive low-amplitude shortwave trough will maintain this area of precipitation eastward into the lower MS Valley. Vertical wind profiles and the most favorable low-level hodographs for organized severe storms will reside in the warm sector where instability is meager, limiting the overall severe threat. The best chance for a few stronger storms might evolve along the southern portion of the conveyor belt from east central and southeast TX into far western LA by early evening where the influx of higher theta-e air will be greatest. These storms may pose a modest risk for mainly a couple of strong wind gusts. Low-level hodographs will also remain sufficient for a conditional risk for a brief tornado. A narrow corridor of clearing and modest destabilization will occur west of the cloud shield and just east of the cold front where a few thunderstorms might develop along the front from north central into northeast TX. However, weakening and veered low-level winds suggest the severe threat should remain limited to a brief strong wind gust or two at best.
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