Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Sep 07 2023 06:01:06 ACUS02 KWNS 070601 SWODY2 SPC AC 070559 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1259 AM CDT Thu Sep 07 2023 Valid 081200Z - 091200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHEAST...MID-ATLANTIC AND SOUTHERN PLAINS... ....SUMMARY... Thunderstorms, associated with a marginal severe threat, will be possible on Friday across parts of the Northeast, Central Appalachians, Mid-Atlantic, Ark-La-Tex and Northern High Plains. ....Northeast/Central Appalachians/Mid-Atlantic... An upper-level trough will remain over the Ohio and Tennessee Valleys on Friday, as mid-level flow continues from the southwest across much of the northeastern U.S. At the surface, a cold front will advance southeastward into the central and northern Appalachians. Ahead of the front, surface dewpoints will likely range from the mid 60s to lower 70s F. Much of the airmass will become moderately unstable by afternoon as surface temperatures warm. Scattered thunderstorms appear likely to develop along and ahead of the front from the Mid-Atlantic into the Northeast by afternoon. Several multicell clusters or line segments are expected to organize in the mid afternoon and persist through much of the late afternoon and early evening. The latest model runs suggest that the most favorable environment for severe storms on Friday will be in southeast Pennsylvania and southeast New York. Along this corridor, NAM forecast soundings have MLCAPE to peaking near 2000 J/kg, with 0-3 km lapse rates reaching the 7.0 to 7.5 C/km range by mid to late afternoon. This, combined with 0-6 deep-layer shear around 30 knots, should support a wind-damage threat. Wind damage will be most likely with organized line segments that move northeastward out of the higher terrain and into the lower elevations from the Mid-Atlantic northeastward into southwestern New England. ....Southern Plains/Ark-La-Tex... A mid-level anticyclone will remain over the southwestern U.S. on Friday, as flow remains northwesterly across much of the southern Plains, Ark-La-Tex and lower Mississippi Valley. A shortwave trough is forecast to move southeastward into the Ark-La-Tex during the afternoon. At the surface, an axis of maximized low-level moisture is forecast from east Texas extending northwestward into southern and western Oklahoma. As surface heating takes place during the day, convective development will be possible near this shortwave trough, and along and to the northeast of the instability axis. Thunderstorms are expected to form and move southward across northeast Texas during the afternoon. NAM forecast soundings in northeast Texas Friday afternoon have MLCAPE peaking near 2500 J/kg, with lapse rates reaching 8 C/km. Moderate deep-layer shear is also forecast, suggesting that supercells will be possible. Supercells, along with the more organized multicells, could be associated with a large-hail and wind-damage threat. ....Montana... Mid-level west-southwesterly flow will remain over much of the western U.S. on Friday. At the surface, a cold front is forecast to move southward into the northern High Plains during the afternoon. A pocket of moderate instability may develop ahead of the front in southern Montana during the day. Convection is expected to first initiate along the western edge of the stronger instability in the higher terrain of southwest Montana during the late afternoon. Additional storms will be possible further east across the northern High Plains. It appears that the combination of instability and shear will support a marginal severe threat, with the stronger cells being accompanied by hail and strong winds. ...Broyles.. 09/07/2023 $$ = = = 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) .