Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Nov 26 2023 05:15:13 ACUS01 KWNS 260515 SWODY1 SPC AC 260513 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1113 PM CST Sat Nov 25 2023 Valid 261200Z - 271200Z ....NO SEVERE THUNDERSTORM AREAS FORECAST... ....SUMMARY... The risk of severe thunderstorms appears negligible across the U.S., today through tonight. ....Discussion... Modestly amplified split westerlies near the North American Pacific coast converge across and east of the Rockies, where a pair of significant consolidating short wave troughs are forecast to contribute to the evolution of more prominent larger-scale troughing in the northern stream, as another short wave impulse digs across the central Canadian/U.S. border. As subtropical ridging centered over the Caribbean maintains strength as far north as the southeastern Gulf of Mexico and southern Florida Peninsula, models indicate considerable intensification of westerly flow between the large-scale troughing and ridging today through tonight. Within this regime, a focused area of strengthening upward vertical motion (supported by low-level warm advection beneath an increasingly divergent upper flow field) is forecast to continue to develop through daybreak today, near and south of Gulf coastal areas from southeastern Louisiana toward the Florida Big Bend. Coincident with further gradual modification of the north central and northeastern Gulf boundary layer, models suggest that destabilization may become supportive of an upscale growing convective cluster with embedded thunderstorm activity. It appears that this generally will become rooted above a residual stable boundary layer, to the north of a warm front in advance of a modest developing frontal wave, which likely will persist and overspread the Big Bend and adjacent portions of northern Florida through mid to late afternoon. Thereafter, a relatively compact, but stronger, surface cyclone is forecast to begin to develop offshore of the southern Mid Atlantic coast by early this evening, before migrating toward the Cape Cod vicinity through 12Z Monday. North-northwest of this feature, various model forecast soundings indicate the development of weak CAPE rooted within strengthening lower/mid-tropospheric warm advection. While this may be accompanied by an expanding area of convection across northern Mid Atlantic into New England coastal areas late this evening through the overnight hours, the extent to which this could become capable of producing lightning remains unclear. Due to at least initially limited low-level moisture return, and the lack of stronger forecast cooling aloft, thunderstorm probabilities still appear less than the minimum 10 percent threshold for a categorical thunder area at this time. ....Tampa Bay vicinity... Within the warm sector of the frontal wave, it is possible that hodographs could become supportive of potential for supercells with a risk of tornadoes along coastal areas near/north of Tampa Bay by late this afternoon. However, given lingering questions concerning the depth of the moistening boundary layer, and, particularly, a capping (relatively) warm layer centered around or just below the 500 mb level, unconditional severe probabilities still appear generally negligible (i.e., less than 2/5 percent for tornado/wind, respectively). ...Kerr/Weinman.. 11/26/2023 $$ = = = 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) .