Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Mar 03 2023 12:57:02 ACUS01 KWNS 031256 SWODY1 SPC AC 031255 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0655 AM CST Fri Mar 03 2023 Valid 031300Z - 041200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF NORTHEASTERN ALABAMA...NORTHWESTERN GEORGIA...MIDDLE/EASTERN TENNESSEE...CENTRAL/EASTERN KENTUCKY...AND AREAS NEAR THE OHIO RIVER IN SOUTHEASTERN INDIANA AND SOUTHWESTERN OHIO... ....SUMMARY... Severe thunderstorm gusts and a few tornadoes are expected today across parts of the Southeast into the Tennessee and Ohio Valleys. A couple strong tornadoes are possible. ....Synopsis... In mid/upper levels, a progressive, split-flow pattern will shift northeastward from the central CONUS and deamplify, in step with the trough now apparent in moisture-channel imagery over eastern parts of NE, KS, OK, and TX. The embedded 500-mb low over eastern OK should move northeastward to northern IN by 00Z, with trough across southern IN, central KY and middle TN. By 12Z, the perturbation should become an open wave with broader cyclonic flow over the north-central Appalachians, upper Ohio Valley, and northern Mid-Atlantic. The associated surface low was analyzed at 11Z from a low over eastern AR south-southwestward across central LA and over the western Gulf. A synoptic warm front was drawn northeastward through the MO Bootheel then eastward near the KY/TN border. The warm front should proceed northeastward across the Ohio River through the day. The low will move northeastward, reaching the eastern IN/western OH area by 00Z, with occludes/cold front arching out across southern parts of OH/WV, the western Carolinas, western GA, southern AL, to near the Mississippi River mouth. By 12Z tomorrow, the occluded low should be weakening near the PA/NY state line, wile a triple-point low organizes off Long Island. The cold front should trail across Atlantic waters just east of the coastline, across northern FL, to the central Gulf. ....Southeast to Ohio Valley... Convection across parts of the Mid-South region has entered a relative lull in severe risk, but with isolated severe gusts and a tornado or two still possible the next couple hours, amidst weak but still surface-based buoyancy. Activity should strengthen/reorganize substantially later this morning into afternoon as it sweeps northeastward across the remainder of the Tennessee and lower Ohio Valley regions. See SPC tornado watch 60 and related mesoscale discussions for near-term details. A combination of low-level warm/moist advection and muted diurnal heating will destabilize the boundary layer in a narrow zone ahead of the convective corridor, as far north as the Ohio River vicinity and perhaps across southern IN/OH. The projected surface-low track serves as the northwestern bound of the outlook area. Meanwhile, despite slow deamplification of the mid/upper trough, flow aloft and deep shear should increase substantially in a location-relative sense across the region. Forecast soundings suggest around 100-700 J/kg MLCAPE from middle/eastern TN northward, but with 80-110-kt midlevel winds contributing to extreme deep shear (effective shear magnitudes of 80-90 kt possible across the "Enhanced" and nearby parts of the "Slight" areas). Such shear may be too much for some updrafts, given the modest buoyancy, but sufficient deep-layer forcing is apparent that both quasi-linear segments and supercells are possible. Surface-based inflow, collocated with a broad area of 500-800 J/kg effective SRH and very large hodographs, suggest tornado potential for any sustained supercells or line-embedded mesovortices. Similarly to a few nights ago in OK, but with weaker buoyancy and stronger shear, any more than a very weak/brief tornadic spinup may have the potential to produce significant damage in its right side, due to very fast (50-70-kt) ground-relative forward motion. Severe potential today will be limited on the southern part by weakening DCVA and frontal convergence with southward extent, on the northern end, by northward loss of boundary-layer destabilization away from the warm-frontal zone, and to the east, by loss of both daytime heating and overall lift. Neither end appears hard-edged or spatially confident, given 1. Uncertainties on the south side related to warm 700-800-mb temperatures/capping observed in Gulf Coast regional RAOBs at 06-12Z, and how much frontal lift will be needed to overcome that; and 2. How far into the warm-frontal zone and area of antecedent precip that intense wind fields' momentum, transferred downward by downdrafts in the MCS, can penetrate the near-surface stable layer. As such, the unconditional probability gradient is kept rather broad on both sides, though the actual southern and northern cutoffs of severe could be abrupt. ...Edwards/Leitman.. 03/03/2023 $$ = = = 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) .