Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jan 03 2023 12:58:09 ACUS01 KWNS 031258 SWODY1 SPC AC 031256 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0656 AM CST Tue Jan 03 2023 Valid 031300Z - 041200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM SOUTHEAST LOUISIANA INTO SOUTHERN/CENTRAL ALABAMA... ....SUMMARY... Tornadoes, damaging winds and isolated large hail are possible across the central Gulf States into the Tennessee Valley, with the greatest threat for strong tornadoes from southeast Louisiana into southern/central Alabama. ....Synopsis... In mid/upper levels, a prominent cyclone is apparent in moisture- channel imagery over the central Plains, centered over southern NE, with synoptic-scale trough southward then southwestward across parts of OK and west TX to northern/western MX. The 500-mb low is forecast to shift northeastward across the upper Mississippi Valley by late tonight. A series of initially low-amplitude shortwave perturbations/vorticity maxima should phase across the Colorado Plateau and southern Rockies through the day. A more coherently structured shortwave trough should emerge from that process over the southern High Plains to the Big Bend region by 00Z. By 12Z tomorrow, this trough should reach the western Ozarks, eastern OK, and north-central/northeast TX. At the surface, 11Z analysis showed an elongated cyclone from southeastern NE to northwestern MO, with cold front across east- central MO, central AR, and east through deep south TX. A synoptic warm front extended from northeastern MO east-northeastward over north-central portions of IN/OH, and should move slowly northward into the southern Great Lakes through the period. By 00Z, the front should extend from a triple point over northeastern IL south- southwestward, roughly down the MS River from southern IL to northeastern LA, then offshore from the TX Coast. As the aforementioned mid/upper-level shortwave approaches and the then- occluded surface cyclone fills slowly, the cold front should accelerate somewhat overnight, reaching eastern KY, northeastern AL, the Mississippi River mouth, and the west-central Gulf by 12Z. ....Gulf Coast to parts of KY... A swath of prefrontal convection, with widely scattered to scattered thunderstorms in a modestly forced by also weakly capped warm-advection regime, is ongoing from western LA to central KY. A couple tornadoes and isolated damaging gusts are possible with this activity for at least a few more hours, primarily related to embedded supercells and mesovortices attached to surging QLCS segments. See SPC tornado watch 6 and related mesoscale discussion for near-term coverage of this regime -- the northern parts of which will spread into middle/eastern TN, northern AL, and more of central/eastern KY with time during the day. To its south and southwest, the low-level jet will weaken slightly and shift eastward, but not as much as typical in the southeastern fringe of ejecting/filling cyclones, thanks to the mass response ahead of the approaching southern-stream perturbation. Continued warm advection and moisture transport is expected amid favorable hodographs, with a broad area of 200-400 J/kg effective SRH and 45-60-kt effective-shear magnitudes. Thermodynamically, mid 60s to lower 70s surface dewpoints will become pervasive across that part of the warm sector from the TN Valley southward. With slow diurnal heating, muted by cloud cover, MLCAPE should increase to near 2000 J/kg roughly south of I-20 and west of I-65 over prefrontal MS/AL/LA, decreasing northeastward through northern AL and mid TN where the air mass will be slow to recover from the morning/midday convective plume. A broad, low- level confluence/convergence zone, superimposed on a relative max in buoyancy and favorable shear, should support a relatively dense concentration of warm-sector development and potential for persistence of mature supercells this afternoon, from southeast LA to southern/central AL, in and near the "enhanced risk" area. Activity will continue to develop over southwestern areas while moving into more-stable air in parts of GA/SC tonight. However, with continued theta-e advection, surface-based inflow parcels may spread eastward as far as the GA/SC border region before 12Z. ....IL/IN... Widely scattered strong/isolated severe thunderstorms may develop along and ahead of the cold front from midday into the afternoon, as areas of at least marginally favorable moisture, warm advection and some diurnal heating destabilize the boundary layer. This should occur beneath cooling midlevel air and steepening deep-tropospheric lapse rates, fostering a corridor of 500-1000 J/kg MLCAPE that should diminish precipitously after dark. Long hodographs and favorable deep shear are forecast (effective-shear magnitudes 45-60 kt), suggesting some supercell potential, with at least marginal threat for all hazards. ...Edwards/Broyles.. 01/03/2023 $$ = = = 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) .