Subj : DAY3SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu May 15 2025 19:22:27 ACUS03 KWNS 151922 SWODY3 SPC AC 151920 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0220 PM CDT Thu May 15 2025 Valid 171200Z - 181200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE SOUTHERN PLAINS INTO ARKANSAS...AND OVER PARTS OF THE MID-ATLANTIC AND NORTHEAST... ....SUMMARY... Severe thunderstorms are possible Saturday across parts of the Mid Atlantic and Northeast, and across parts of the southeastern Great Plains to Lower Mississippi Valley. ....Synopsis... An upper cyclone and attendant shortwave trough over the upper Great Lakes to the TN Valley will shift east on Saturday, becoming positioned from NY to offshore the Mid-Atlantic coast by Sunday morning. Meanwhile, an upper trough will dig across the western U.S. while upper ridging develops over much of the Plains. A belt of strong westerly flow associated with the eastern upper trough will overspread much of eastern U.S., while a sub-tropical jet streak moves across the southern Plain into the Lower MS Valley. At the surface, a cold front will surge east across the Ohio Valley through early afternoon, and the Mid-Atlantic and Northeast during the evening/overnight. The southwest extent of this surface boundary will extend from the Lower OH Valley into central OK Saturday morning. The boundary may sag southward across portions of the TN Valley, while the Plains portion of the boundary lifts northward into KS and southern MO during the evening/overnight. Meanwhile, a surface dryline will extend south/southwest from near western OK to the TX Big Bend vicinity. ....Southern Plains to Lower MS Valley... The building upper ridge over the Plains will likely suppress convection across portions of the region as an EML will be difficult to overcome without stronger large-scale ascent/height falls. However, low-level convergence along the dryline amid persistent low-level warm advection and forecast shortwave perturbations migrating through the upper ridge from the southern Rockies into the Red River vicinity may aid in isolated to widely scattered storm development during the afternoon. A very moist airmass will be in place (upper 60s/low 70s F dewpoints) beneath 7.5-8.5 C/km midlevel lapse rates. This will result in strong instability across the warm sector (MLCAPE greater than 2500 J/kg). Furthermore, supercell wind profiles are apparent in forecast soundings, with curved low-level hodographs become elongated/straight above 2-3 km. Any discrete cells that develop will pose a risk for large to very large hail. If sufficient storm coverage occurs, some clustering could result in upscale developing into an MCS moving across the ArkLaTex vicinity and into the Lower MS Valley during the evening/nighttime hours. If this occurs, a risk for damaging gusts will increase. ....Southeast... Convection may be ongoing/weakening across portions of MS/AL/GA/SC/NC Saturday morning. It is unclear how this activity may evolve, but an outflow boundary will likely extend across portions of MS/AL/GA. Given a very moist and unstable airmass by afternoon some redevelopment of thunderstorms is possible. Forcing for ascent will be nebulous across the Deep South, so coverage may remain sparse. Nevertheless, any storm that develops could produce strong gusts or hail. ....NC/VA into the Northeast... Convection may be ongoing across portions of NC/VA Saturday morning but likely will be weakening as outflow is expected to be surging across the Piedmont. It is unclear if redevelopment may occur ahead of the surface cold front during the afternoon/evening. While a very moist and unstable airmass will reside across the region, large-scale ascent will remain weak and focused further north toward the Northeast. If storms can develop, a risk for large hail and damaging gusts will be possible. Additional storms are expected to develop with northward extent into the Northeast beneath the upper low and ahead of the surface cold front. While boundary layer moisture will be more modest with northward extent, cool temperatures aloft will foster modest destabilization. Isolated to widely scattered storms will pose a risk for hail and gusty winds through early evening. ...Leitman.. 05/15/2025 $$ = = = 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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .