Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Feb 05 2024 12:44:40 ACUS01 KWNS 051244 SWODY1 SPC AC 051243 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0643 AM CST Mon Feb 05 2024 Valid 051300Z - 061200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE FLORIDA KEYS AND A SMALL PART OF SOUTH FLORIDA... ....SUMMARY... Isolated severe thunderstorms are expected over parts of south Florida and the Keys today, with a marginal tornado, damaging-gust and large-hail threat. ....Synopsis... The synoptic pattern in mid/upper levels will remain highly amplified through the period, but will become more progressive again. A fairly well-stacked, cold-core cyclone now over the southeastern AL/FL Panhandle region is expected to pivot southeastward over the northeastern Gulf to central FL through 00Z, then eastward over the Atlantic tonight. This will occur as an upstream closed 500-mb high over the upper Mississippi Valley weakens and transitions into the northeastern part of a larger- scale, open-wave ridge. Meanwhile, a north/south-elongated cyclone now near the central/ northern Pacific Coast will drift eastward and become an open-wave trough. In the preceding southwesterly to southerly flow aloft, numerous small vorticity lobes and shortwaves will eject across the West Coast States, northern Rockies, Intermountain region, and Great Basin. By 12Z tomorrow, the main trough should extend over the Cascades, southward over the SFO area and Pacific, well offshore from Baja. At the surface, 11Z analysis showed a low near AAF, with cold front arching southeastward then southward over the northeastern/extreme east-central Gulf. The low should track southeastward across the northeastern Gulf, then eastward over south-central FL through 00Z, with the front to its southeast. An outflow boundary from earlier convection was evident over the Upper Keys, and may shift northward into southernmost portions of the mainland before being overtaken by the front and/or prefrontal convection. ....South FL and Keys... In the westerlies aloft, south of the stacked cyclone, a weak shortwave trough was evident in moisture-channel imagery over the extreme eastern Gulf, approaching south FL and the Keys. The feature has been preceded by a band of thunderstorms with an embedded supercell. The related plume of large-scale ascent will shift eastward across the outlook area through midafternoon, supporting both the eastward shift of existing convection across the area, and the development of additional thunderstorms from Atlantic coastal areas of south FL southwestward across the Keys and adjoining waters. Deep shear and long low-level hodographs will persist across the region, beneath tight midlevel height gradient related to the cyclone. Some progs suggest localized backing of near-surface winds along coastal/convective boundaries -- such as apparent now over parts of the upper Keys and Miami-Dade County north of the outflow boundary -- can persist into a period of low-level destabilization related to both muted diabatic heating and warm advection. The thermodynamic environment -- initially hostile for surface-based parcels over mainland areas per 12Z MFL RAOB, but somewhat more favorably modified in the Keys as sampled by the KEY sounding -- also should improve through cooling aloft and steepening of midlevel lapse rates. Accordingly modified forecast soundings yield MLCAPE peaking in the 500-800 J/kg range over the Keys, and around 300-500 J/kg over the southeasternmost mainland. While climatologically small for severe over FL, this buoyancy (given the favorable wind profiles and cold air aloft) will support a threat for relatively low-topped supercells and small bows, accompanied by hail and gusts near severe limits, and the possibility of a tornado where storm-scale/boundary processes can augment low-level shear locally. ...Edwards/Leitman.. 02/05/2024 $$ = = = 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 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .