Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Sep 10 2024 05:34:48 ACUS01 KWNS 100534 SWODY1 SPC AC 100533 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1233 AM CDT Tue Sep 10 2024 Valid 101200Z - 111200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE LA COAST... ....SUMMARY... Some tornado threat associated with Tropical Cyclone Francine may approach the Louisiana Coast by early Wednesday morning. ....Synopsis... A shortwave trough is expected to be off the Northeast Coast early Tuesday morning, with continued eastward progression into the northern Atlantic expected thereafter. A relatively zonal pattern is anticipated west of this shortwave trough across the majority of the CONUS throughout much of the period. A low-amplitude shortwave trough is forecast to move within this zonal flow across the northern Plains and the Upper Midwest, but with minimal pattern amplification. Some amplification is expected late Tuesday/early Wednesday across the Pacific Northwest, ahead of a strong shortwave trough approaching the coast. Surface pattern early Tuesday will feature high pressure centered over the central Appalachians and covering much of the OH Valley. This ridging is expected to gradually shift eastward/northeastward throughout the period. Surface troughing associated with the northern Plains shortwave trough will extend across the central Dakotas early Tuesday, before then shifting eastward throughout the day. Farther south across the northwest Gulf of Mexico, TC Francine is expected to reach hurricane strength while gradually progressing northeastward. ....TC Francine - LA Coast... Rainbands from Francine will likely spread across the northwest Gulf Coast throughout the day, but the stronger flow will remain displaced south throughout much of the period. Beginning around 06Z, the stronger flow may be far enough north to influence any deeper updrafts that develop along the LA Coast, with an attendant risk for brief tornadoes. ....Upper Midwest... Moderate low-level moisture, characterized by surface dewpoints in the upper 50s/low 60s, is expected across the region Tuesday afternoon ahead of the approaching shortwave trough and associated surface trough. Steep mid-level lapse rates will aid in the development of strong buoyancy across the region, supporting a conditional severe-thunderstorm risk. However, despite moderate low-level moisture and strong daytime heating, warm mid-level temperatures are forecast to keep capping in place, precluding afternoon thunderstorm development. ....Elsewhere... Afternoon thunderstorms are expected again across the eastern Great Basin and northern/central Rockies, where orographic effects and modest large-scale ascent will combine with modest moisture and buoyancy to support thunderstorm development. Increasing thunderstorm potential is anticipated late Tuesday into early Wednesday across the Pacific Northwest ahead of the approaching shortwave trough. ...Mosier/Lyons.. 09/10/2024 $$ = = = 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) .