Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Aug 28 2023 17:29:25 ACUS02 KWNS 281729 SWODY2 SPC AC 281727 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1227 PM CDT Mon Aug 28 2023 Valid 291200Z - 301200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHWEST/WEST-CENTRAL FLORIDA PENINSULA... ....SUMMARY... The potential for a few tornadoes should gradually increase along/near parts of the Florida Gulf Coast and into north Florida through Tuesday night as Tropical Cyclone Idalia approaches. ....Florida into Southeast Georgia... Latest forecast for TC Idalia centers the system northwest of western Cuba early Tuesday morning, with northeastward/north-northeastward motion taking the storm to just off northwestern FL Peninsula by 12Z Wednesday morning. Strong low/mid-level flow associated with this system will gradually spread northward across the FL Peninsula throughout the day, with the strongest winds expected along the western coast after 00Z. Rain bands will likely begin moving across the peninsula during the early afternoon, with a generally northeastward storm motion anticipated. Lapse rates will be poor, but the moist airmass across the region will still support moderate buoyancy and the potential for a few strong updrafts. The most significant increases in low-level shear are not expected under after 00Z, so the severe-gust and tornado potential with these multicellular bands will be low, but not zero. After 00Z through the remainder of the period, strengthening low to mid-level flow will result in a gradually increasing tornado potential, particular along the west-central and northwest portions of the FL Peninsula. TC tornado climatology shows a notable preference for tornadoes between 200-300 km northeast of the center for northeastward progressing major hurricanes. This matches well with the most favorable environmental conditions for tornadogenesis in this case, which are along the northwest/west-central FL coast from 06Z-12Z. ....Interior Pacific Northwest into the Northern Rockies... A negatively tilted shortwave trough is forecast to progress across the Pacific Northwest on Tuesday. Moderate mid-level flow and moisture will spread eastward ahead of this wave across ID and into western MT. Resulting combination of a deeply mixed boundary layer, increasing mid-level moisture, and strengthening ascent is expected to result in afternoon/evening thunderstorm development. 20 to 30 kt of effective shear will help organize some updrafts, with high cloud bases and steep low-level lapse rates supporting the potential for strong outflow. An instance or two of hail is possible as well. ....Great Lakes/OH Valley... A cold front is forecast move southeastward across the Great Lakes and parts of the Midwest/OH Valley, in tandem with an eastward-moving upper trough. Dewpoints will likely be in the upper 50s and low 60s from IL into IN and MI ahead of this front, but mid-level temperatures will be relatively warm, limiting buoyancy and updraft strength/duration. Damaging gusts would be possible with any deep, sustained updrafts, but the overall probability of occurrence currently appears low. ....Appalachians... Scattered thunderstorms should develop across parts of the southern/central Appalachians Tuesday afternoon, as modest ascent associated with an upper trough moving Quebec and the Upper Great Lakes/OH Valley glances the region. Modest deep-layer vertical shear is anticipated amid the southwesterly mid-level flow stretching across the region, supporting potential updraft organization. Even so, poor lapse rates should limit instability and overall updraft strength. A generally multicellular, outflow-dominant storm mode is anticipated, and the potential for a damaging gust or two exists within any bowing segments. However, overall severe coverage is expected to remain too low to include severe probabilities. ...Mosier.. 08/28/2023 $$ = = = 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) .