Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Mar 12 2023 16:32:09 ACUS01 KWNS 121632 SWODY1 SPC AC 121630 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sun Mar 12 2023 Valid 121630Z - 131200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS NEAR THE NORTH-CENTRAL/NORTHEASTERN GULF COAST AND SOUTHERN GEORGIA... ....SUMMARY... Severe hail, damaging winds and a couple tornadoes are possible today across parts of the Southeast. A few strong/severe storms are also possible in the California Central Valley. ....Synopsis... In mid/upper levels, a progressive pattern is forecast to continue across the CONUS, characterized by 1. Essentially conjoined northern and southern streams, and 2. Lower-amplitude perturbations with southward extent, amidst nearly zonal flow. The most intense features -- a cyclone/trough now over MN and another over the Pacific well west of Vancouver Island -- will remain removed from areas of potentially strong-severe convection. Instead, to their south, a series of vorticity maxima and weak shortwaves will traverse the westerlies from offshore of CA, across CA/NV/AZ to the southern Rockies and southern Plains, to the TN Valley and Gulf Coast States. At the surface, an occluded low was analyzed at 15Z near the eastern portion of the KY/TN line, with occluded/cold front southwestward across northern AL, western MS, central LA, and south-central TX. A warm front was drawn across parts of southern SC and south-central GA to southeastern AL, where it was being overtaken by convective outflow. The latter process will continue, as the bulk of surface-based convection should remain well ahead of the cold front. By 00Z, the cold front should reach from a triple point over western GA across southern AL to southeastern LA, then across extreme southeastern GA and northwestern FL by 12Z. ....Southeast... Scattered thunderstorms are expected to occur along and behind a progressive, aggregate outflow boundary that is evident across south-central GA, southern AL and extreme southern MS. Large hail, damaging gusts and a couple tornadoes are possible. Refer to SPC mesoscale discussion 280 for the near-term scenario. The progress of this boundary -- and the trailing area of stabilizing precip -- has reduced severe potential from the northwest, and outlook lines have been adjusted accordingly. However, as the boundary and associated convection move into a destabilizing environment across parts of southern MS/AL/GA and the FL Panhandle, a gradual increase in severe potential is possible through early afternoon. This will be supported by a combination of low-level theta-e advection -- which will warm/moisten parts of southern GA now under the more-stable influence of drier FL Peninsular trajectories -- and cloud-tempered diabatic surface heating. Peak/preconvective MLCAPE around 1500 J/kg should spread/expand eastward across the remaining parts of the outlook area through the afternoon, while the outflow continues to shunt the western bounds of substantial severe potential southeastward. Modified RAOBs and forecast soundings indicate 40-50-kt effective-shear vectors, aligned nearly parallel to the middle/western parts of the outflow boundary, and slightly across it over the eastern (currently southeastern AL/GA) section. This will occur amidst broadly difluent mid/upper-level flow and subtle shots of DCVA from aforementioned minor southern-stream perturbations. As such, episodic but gradual net increase in convective intensity/coverage appears to be supported into the afternoon, over the remaining areas ahead of the boundary. Potential should diminish this evening in step with decrease of lift and available inflow-layer instability. ....Central CA... Widely scattered to scattered thunderstorms should cross the region during mid-late afternoon, offering a marginal hail and tornado threat. Activity will be supported by destabilization from a combination of cold midlevel temperatures and gradual diurnal heating. This will reduce already meager MLCINH and support relatively deep for this area (300-350-mb equilibrium levels) MLCAPE in the 500-1000 J/kg range. With near-surface flow weak, but backed due to orographic forcing, sufficient veering of modest low-level winds with height will be present to contribute to 35-40 kt effective-shear magnitudes. Hodographs are not forecast to be particularly large, but will be well-curved, with at least marginally favorable deep shear to support potential for a few supercells to mature across the valley before weakening deeper into in the foothills/Sierra. ...Edwards/Squitieri.. 03/12/2023 $$ = = = 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) .