Subj : DAY3SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Jun 24 2023 20:13:10 ACUS03 KWNS 242013 SWODY3 SPC AC 242012 Day 3 Convective Outlook AMEND 1 NWS Storm Prediction Center Norman OK 0312 PM CDT Sat Jun 24 2023 Valid 261200Z - 271200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR THE MID-ATLANTIC STATES AND CAROLINAS... AMENDED FOR EXPANSION/UPGRADING OF SEVERE PROBABILITIES IN THE MID-ATLANTIC AND SOUTHEAST ....SUMMARY... A severe threat is expected to develop on Monday from the Carolinas into the Mid-Atlantic, where damaging winds and hail will be possible. An isolated severe threat will also be possible in the northern High Plains. ....Amended discussion for the Eastern U.S.... A mid to upper-level low will meander slowly eastward over the central Great Lakes during the period. An associated trough initially over the OH Valley/southern Appalachians is forecast to gradually shift eastward into the central Appalachians/Carolinas. A belt of moderate southwesterly 500-mb flow (25-40 kt) will overspread a destabilizing warm sector ahead of a front/composite outflow over the Appalachians. Strong heating ahead of the front and very moist low levels (66-74 deg F surface dewpoints) will likely result in a moderate to very unstable airmass from the Southeast northward into the Mid-Atlantic states. Several linear clusters of intensifying thunderstorms are forecast to develop by early afternoon in the immediate lee of the higher terrain. Further upscale growth into a more expansive band of linear segments is expected by late afternoon/early evening from the Mid-Atlantic states southward into the Carolinas. Damaging gusts appear to be the primary hazard due to 50-70 mph gusts. Isolated large hail may accompany the stronger cores. Have added 5-percent severe probabilities across the northeast Gulf Coast for the possibility of 1) at least isolated strong/severe thunderstorms pushing off the coast during the morning, and 2) diurnal storms rejuvenating on the composite outflow/front as it may provide a focus for additional storms. ---Previous Discussion--- ....Eastern U.S... An upper-level low is forecast to move through the Great Lakes region on Monday, as an associated trough moves into the southern Appalachians. At the surface, a front will move into the Appalachians as a pre-frontal trough develops from the Carolinas into the Mid-Atlantic. Moderate to strong instability is expected by afternoon along and near the surface trough. Convection will initiate in the higher terrain of the Appalachians and spread eastward into the Piedmont. It appears that an isolated severe threat will develop with storms that move into the stronger instability during the late afternoon from eastern Pennsylvania southward into the Carolinas. The greatest severe threat could be from southern Virginia into central North Carolina, where model forecasts suggest the combination of instability and shear will be maximized. Storms that form in this more favorable zone could have a threat for wind damage and hail, mainly during the late afternoon and early evening. ....Northern High Plains... An upper-level ridge will remain over the High Plains on Monday. At the surface, a narrow corridor of maximized low-level moisture is forecast across the central and northern High Plains. As instability increases during the day, isolated to scattered thunderstorms will likely develop. The strongest storms may form from eastern Wyoming southeastward into western Nebraska, along and near the instability axis. NAM forecast soundings by late afternoon near Scottsbluff, Nebraska have MLCAPE near 1500 J/kg and 0-6 km shear of 50 to 60 knots. This, combined with 700-500 mb lapse rates approaching 8 C/km should be sufficient for an isolated severe threat. The large temperature-dewpoint spreads are expected to result in high storm bases. The storms could be associated with strong wind gusts and hail. ...Smith.. 06/24/2023 $$ = = = 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) .