Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Apr 14 2023 17:47:18 ACUS02 KWNS 141747 SWODY2 SPC AC 141745 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1245 PM CDT Fri Apr 14 2023 Valid 151200Z - 161200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM CENTRAL MISSOURI SOUTHWARD TO NORTHERN LOUISIANA... ....SUMMARY... Severe thunderstorms -- capable of producing large to very large hail and damaging wind gusts, as well as a couple of tornadoes -- are possible from Missouri and the Mid-Mississippi Valley, southward to the Lower Mississippi and Sabine Valleys. ....Synopsis... As a weakening upper low over the Mid-Atlantic region shifts northeastward, a larger trough exiting the Rockies is forecast to move steadily eastward across the Plains, gradually acquiring negative tilt as it advances. At the surface, a cold front associated with the western U.S. upper trough should lie initially from the western Upper Great Lakes region southwestward into the southern Plains. The boundary is forecast to advance eastward with time, with cyclogenesis forecast to occur along the baroclinic zone across the Mid-Mississippi Valley area during the second half of the period. As the low moves northward toward Lake Michigan overnight, the trailing portion of the cold front is progged to surge southeastward across Missouri/Arkansas/Louisiana through the evening. By Saturday morning, the front should extend from the Lower Ohio and Tennessee Valleys to the central Gulf Coast states. ....Missouri and the Mid-Mississippi Valley south to the Sabine and lower Mississippi Valleys... A complex convective evolution is apparent for Friday across a region centered near/just west of the middle and lower Mississippi Valleys. This will be in part due to a series of perturbations in the southern-stream flow field that are progged to be moving out of Texas, across the western Gulf of Mexico and Lower Mississippi Valley into the central Gulf Coast states through the first half of the period. Lingering convection associated with these perturbations may be ongoing at the start of the period across portions of eastern Texas and Louisiana into southern Arkansas, though CAM guidance differs on the exact location -- and degree -- of convective coverage early. Despite these differences, CAMs generally depict a midday increase in storms across the Lower Mississippi Valley to the central Gulf Coastal region, which seems reasonable as daytime heating helps boost surface-based CAPE, owing in part to steep mid-level lapse rates. Deep-layer shear is progged to decrease with southward extent, hence the gradient in probability lines across Louisiana. However, potential for large hail and damaging winds -- and possibly a tornado -- should evolve across this area. Uncertainty precludes substantial changes to the existing outlook across the area. Adjustments in later outlooks may be needed, once Day 1 convective development across Texas -- associated with the aforementioned southern-stream energy -- becomes more clear. Farther north, as the upper system advances, the combination of very steep lapse rates aloft, and diurnal heating of a seasonably moist boundary layer (low 60s dewpoints into northern Missouri, to near 70 into the southern Arkansas/Louisiana area) will occur. This will result in a strongly unstable environment (2000 to 3000 J/kg mixed-layer CAPE). Storm development is expected to occur by mid afternoon, near and just ahead of the advancing cold front, from western and central Missouri southward into Arkansas. Aided by roughly 30 kt south-southwesterlies at low levels veering weakly and increasing to 35 to 45 kt from the southwest at mid levels, shear will favor supercells -- which will quickly become capable of producing very large hail in excess of tennis ball to baseball size. While low-level shear is not progged to be excessive, a couple of these supercells may become capable of producing tornadoes. With time, convective development both northward and southward along the front is expected. Upscale growth into an at least loosely-organized band or line is anticipated, extending from southeastern Iowa/western Illinois south-southwestward along the advancing front into the Sabine River Valley area. As a result of this anticipated evolution, have expanded higher all-hazard probabilities northward in this outlook, into much of Missouri. Along with continued risk for hail, damaging wind potential should increase during the evening -- particularly across the Missouri/Arkansas area. Storms should diminish in intensity later in the evening, as they cross the Mid-Mississippi Valley, but farther south, may remain severe across Louisiana and into Mississippi through the evening and possibly into the overnight hours. ...Goss.. 04/14/2023 $$ = = = 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) .