Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Jan 09 2023 12:40:29 ACUS01 KWNS 091240 SWODY1 SPC AC 091238 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0638 AM CST Mon Jan 09 2023 Valid 091300Z - 101200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS NEAR THE CENTRAL/NORTHERN COAST OF CALIFORNIA... ....SUMMARY... Isolated strong to marginally severe thunderstorms are possible near the central/northern coast of California early Tuesday morning. ....Synopsis... In mid/upper levels, a mostly low-amplitude, shortwave-dominant pattern will persist over the CONUS this period. That will change with the approach of the feature that will have the most substantial convective influence late overnight into tomorrow: a shortwave trough apparent in moisture-channel imagery about halfway between HI and the southwest coastline of mainland AK. This perturbation is part of a very large, complex area of low heights and cyclonic flow covering much of the northeast Pacific, and containing numerous small cyclonic gyres and vorticity maxima. The aforementioned perturbation should phase temporarily with a couple smaller vorticity lobes/maxima to its north and amplify, as it moves rapidly east-southeastward through the period. By 12Z tomorrow, the resulting strong shortwave trough should extend from just offshore north-central CA (near the Farallon Islands) south-southwestward to near 30N130W. A surface/low-level cold front should arch cyclonically ahead of this trough, with its apex nearing the central CA coastline by 12Z. ....Coastal CA... Episodic, isolated thunderstorms are possible, with isolated damaging gusts. A brief tornado also cannot be ruled out, mainly late overnight into tomorrow morning with the near-frontal convective band amidst weak buoyancy but strengthening deep-layer flow/shear. The bulk of strong-severe convective potential appears to be on day 2/Tuesday (see that outlook for more details); however, the episode may begin in the last few hours of this period (i.e., around 09-12Z). Warm/theta-e advection preceding the frontal band will destabilize low levels, with the strongest cooling/ destabilization aloft likely to be near and behind the cold front. Pockets of 100-500 J/kg MLCAPE are possible, with 40-50-kt southwest flow through most of the 850-500-mb layer. One potential caveat is timing -- which is trending later for arrival of the main convective regime in each outlook cycle. Accordingly, the outlook has been shifted seaward some, again -- such that any further mesoscale slowing of the arrival would remove the pre-12Z risk area from the mainland in entirety. ...Edwards/Broyles.. 01/09/2023 $$ = = = 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) .