Subj : DAY48SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Apr 18 2023 09:00:25 ACUS48 KWNS 180900 SWOD48 SPC AC 180858 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0358 AM CDT Tue Apr 18 2023 Valid 211200Z - 261200Z ....DISCUSSION... ....Friday/Day 4... An upper-level trough will move into the southern Plains on Friday, as a cold front advances southeastward into the western Gulf Coast states. Ahead of the front, surface dewpoints from 65 to 70 F, will contribute to moderate destabilization by midday. Thunderstorms will likely develop along the front during the afternoon, with several clusters or line segments moving east-southeastward across southeast Texas, southwest Louisiana and the lower Mississippi Valley. Moderate instability and 40 to 50 knots of deep-layer shear, combined with steep lapse rates, may result in a wind-damage threat with the stronger multicells. Supercells with large hail will also be possible, but this will depend upon if cells can remain discrete. Any severe threat will likely be greatest during the late afternoon and early evening, when low-level lapse rates will be the steepest. ....Saturday/Day 5 and Sunday/Day 6... The upper-level trough is forecast to become negatively-tilted across the Ohio and Tennessee Valleys on Saturday, as a cold front advances eastward into the Carolinas and central Appalachians. Although the models suggest that instability will remain weak ahead of the front, large-scale ascent associated with the upper-level trough and strong low-level flow, could be enough for an isolated severe threat during the afternoon. An isolated wind-damage threat would be greatest with multicell line segments, but the spatial predictability appears too low for a threat area on Saturday. The front is forecast to move eastward across the Northeast on Sunday. Isolated damaging wind gusts will be possible during the day, along line segments that form ahead of the front. Instability is expected to remain weak in the Northeast, which would minimize any severe threat that develops. ....Monday/Day 7 and Tuesday/Day 8... West-southwesterly mid-level flow is forecast across much of the nation on Monday. Moisture return will probably take place in the southern Plains, around the western periphery of an area of surface high pressure. Dewpoints could increase into the 60s F across parts of Texas. Further north, thunderstorm development will be possible across parts of Oklahoma and Kansas during the day. Any severe threat is expected to remain isolated due to relatively weak instability. The same general setup is expected on Tuesday with a moist airmass in place across the western Gulf Coast region. Strong thunderstorms could develop at the northern end of the moist sector in the Ozarks and mid Mississippi Valley during the day on Tuesday. However, medium-range model forecasts generally have wide spreads for Monday and Tuesday, suggesting predictability is low. ...Broyles.. 04/18/2023 = = = 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) .