Subj : DAY48SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Feb 21 2023 08:46:44 ACUS48 KWNS 210846 SWOD48 SPC AC 210844 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0244 AM CST Tue Feb 21 2023 Valid 241200Z - 011200Z ....DISCUSSION... Strong west/southwest flow aloft will exist over the CONUS on Fri/D4, with an upper high over FL and a large-scale upper trough over the West. High pressure will be centered over the northern Plains in the wake of an upper wave exiting the Northeast, with a cold front roughly from central TX eastward across the Gulf Coast states. Subtle height rises will occur across the frontal region as the FL high retrogrades across the Gulf of Mexico. Scattered showers and weak thunderstorms may occur in this region, mainly north of the surface boundary with weak instability and little severe risk. On Sat/D5, an upper low will move across southern CA, while a wave amplifies in the northwesterly flow over the northern Plains. This will reinforce high pressure over the Plains and upper/middle MS Valley, while the boundary across the Gulf Coast states gradually makes northward progress with a few showers and weak thunderstorms within that east-west zone from TX into the Carolinas. By Sun/D6, models are in relatively good agreement showing the upper low moving east across the Four Corners states with height falls into the central and southern Plains by 00Z Mon. Surface moisture/60s F dewpoints will likely surge northward ahead of the shortwave trough, with low pressure over the central High Plains Sun/D6 afternoon, deepening as it pivots into IA during the evening. MUCAPE around 1000 J/kg appears likely from parts of western KS into OK, and shear will favor supercells beneath a 50 kt low-level jet. Initial supercells from the surface low southward along the dryline will favor large hail and a few tornadoes, with damaging wind threat extending eastward across KS and OK through evening as storms possibly become linear. As such, a 15% severe area has been added. Predictability decreases on Mon/D7 as the upper trough moves toward the Great Lakes, and a surface boundary trails southwestward into the lower MS Valley. Here, a plume of mid to upper 60s F dewpoints will likely remain, beneath 50-60 kt midlevel southwesterlies which will mean a larger component of the deep-layer shear parallel to the boundary. Instability will be less by this time owing to relatively warmer midlevel temperatures, but at least some damaging wind potential may eventually be noted with storms expected along the cold front. This front is expected to push offshore by Tue/D8, with lessening threat of severe storms. ...Jewell.. 02/21/2023 = = = 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) .