Subj : DAY48SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Dec 30 2022 09:51:09 ACUS48 KWNS 300951 SWOD48 SPC AC 300949 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0349 AM CST Fri Dec 30 2022 Valid 021200Z - 071200Z ....DISCUSSION... ....Days 4-5/Mon-Tue -- Eastern OK/TX into the Gulf Coast States Vicinity... A severe thunderstorm episode is expected on Monday into Tuesday across portions of the south-central and southern U.S. Forecast guidance remains bifurcated with regards to the evolution of the large-scale upper trough ejecting over the Plains, as well as the track of the attendant surface low on Monday/Day 4. The ECMWF suite of guidance maintains a slower and more amplified/negative tilt ejecting trough and southerly track for the surface low. Meanwhile the GFS suite of guidance depicts a more neutral large-scale trough with a progressive and northerly surface-low track. This is resulting in uncertainty regarding the northern and eastern extent of severe potential, and severe-area delineations may continue to shift over the coming couple of days. Despite these model differences, guidance continues to paint a broad warm sector from eastern OK/TX toward the Lower MS Valley. How much destabilization occurs will partly be driven by heating and how much convection develops early in convective evolution, though sufficient instability is expected given rich boundary-layer moisture. Strong vertical shear is expected, with 40+ kt southwesterly effective-shear magnitudes overlapping the moist boundary layer ahead of an eastward-advancing cold front. This should result in scattered organized severe convection, and all severe hazards appear possible. The greatest risk potential is focused from northeast TX into central/southern AR and northern LA late Monday afternoon into Monday night. Severe potential is expected to continue eastward ahead of the surface cold front across portions of the central Gulf Coast/southern U.S. on Tuesday/Day 5. Strong midlevel southwesterly flow will overlap a moist boundary layer as the upper trough lifts east/northeast. While stronger large-scale ascent will be ejecting northeast of the region through the period, the eastward-advancing cold front and broad warm sector, amid favorable vertical shear, will focus severe potential from southeast LA into AL and vicinity. ....Days 6-8/Wed-Fri... Some severe potential could persist into parts of the Mid-Atlantic and Southeast vicinity on Wednesday/Day 6. However, uncertainty is high for this period and potential appears lower compared to Day 4/5. By Thursday/Day 7 the surface cold front should have moved offshore the Atlantic coast, leaving a dearth of boundary-layer moisture and increasing surface high pressure in its wake across much of the U.S. Severe potential is expected to be low Thursday-Friday/Days 7-8. ...Leitman.. 12/30/2022 = = = 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) .