Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Dec 14 2022 05:22:10 ACUS01 KWNS 140522 SWODY1 SPC AC 140520 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1120 PM CST Tue Dec 13 2022 Valid 141200Z - 151200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS TODAY INTO TONIGHT ACROSS PARTS OF SOUTHERN AND EASTERN LOUISIANA AND MISSISSIPPI...SOUTHWESTERN ALABAMA AND MUCH OF THE FLORIDA PANHANDLE... ....SUMMARY... Severe thunderstorms are expected to develop across parts of the central and eastern Gulf Coast states today through tonight. Some will become capable of producing locally damaging wind gusts and tornadoes, a few of which could be strong. ....Synopsis... It appears that blocking will become a bit more prominent within the westerlies across the mid-latitude eastern Pacific through the western Atlantic during this period, with mid-level highs forecast to continue to build offshore of the British Columbia coast and across the northern Quebec vicinity. Several mid-level lows will linger at slightly lower latitudes, including one which may continue to deepen across the middle Missouri Valley vicinity, within larger scale cyclonic flow encompassing much of the interior U.S. An occluding surface cyclone may slowly weaken beneath the mid-level low, which may only very slowly shift eastward today through tonight. It appears that this will mostly be in response to a vigorous short wave perturbation rapidly pivoting around its southern and eastern periphery, from west Texas through the Upper Midwest/Great Lakes vicinity. Models suggest that this will be accompanied by secondary cyclogenesis along a lead surface front advancing east of the lower Mississippi Valley by midday. The surface low is generally forecast to track from central Mississippi northward through the Ohio Valley, with a more significant cold front overtaking the weaker lead front in its wake. Additional cyclogenesis may initiate across the Piedmont of Alabama into Georgia late this evening into the overnight hours. It appears that this will be focused near the intersection of the eastward advancing cold front and a developing warm front, as a wedge of potentially cold air boundary-layer air over the Southeast gradually erodes from the southwest. The cool, dry air is still expected to be entrenched across much of Georgia, northern Florida and Alabama into eastern Mississippi at 12Z this morning. However, beneath a strengthening southerly low-level jet (including 40-50+ kt around 850 mb) off the northern Gulf of Mexico, substantive northeastward boundary-layer moistening appears possible in a narrow pre-frontal plume across southeastern Mississippi, toward west central Alabama, by this afternoon, and perhaps across the Florida Panhandle toward the Georgia Piedmont tonight. ....Lower Mississippi Valley/Eastern Gulf Coast states... Aided by at least the glancing influence of the short wave impulse emerging from west Texas, thunderstorm development, which probably will be ongoing at 12Z this morning across the northwest Gulf Coast and lower Mississippi Valley vicinity, is expected to persist and perhaps increase through midday. This likely will include both along the initially slow moving lead cold front, from northern Mississippi into southwestern Louisiana coastal areas, and ahead of the front near the intensifying low-level jet axis. Clockwise-curved low-level hodographs conducive to tornadic development probably will be maximized within the unstable boundary-layer air across parts of southeastern Louisiana through the Hattiesburg and Meridian vicinities of southeastern Mississippi by mid to late afternoon. This is where potential for a couple of longer-lived/longer track supercells currently appears greatest, accompanied by the potential to produce a strong tornado or two, before gradually spreading eastward into portions of southern Alabama. Upstream, along the cold front, which may begin to surge east of the lower Mississippi Valley by this afternoon, a more widespread line/cluster of thunderstorms may gradually evolve. However, tornadic and damaging wind potential with this activity is more uncertain, as forecast soundings suggest that this convection may tend to be increasingly undercut by cold surface-based air. Farther east, across the Florida Panhandle, northward into the Georgia Piedmont, strengthening wind fields/shear and large-scale forcing for ascent may maintain convection with potential to produce locally damaging wind gusts and tornadoes late this evening into the overnight hours. The extent of this potential will hinge on the degree of northeastward boundary-layer destabilization, which remains unclear at this time. ...Kerr/Lyons.. 12/14/2022 $$ = = = 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) .