Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Mar 13 2024 06:01:36 ACUS02 KWNS 130601 SWODY2 SPC AC 130559 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1259 AM CDT Wed Mar 13 2024 Valid 141200Z - 151200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM SOUTHEAST OK INTO WESTERN AR AND FAR SOUTHWEST MO... ....SUMMARY... Strong to severe thunderstorms are possible across a large area from the Middle Mississippi Valley into eastern Oklahoma, East Texas, and the Lower Mississippi Valley on Thursday. Greatest threat is currently expected to be from southeast Oklahoma into western Arkansas. ....Synopsis... A surface low is forecast to be over the NE/IA/MO border intersection vicinity early Thursday morning. A cold front will extend from this low southwestward through southeast KS and central OK into the TX Hill Country. A warm front will extend from this low east-northeastward through central IL. A broad warm sector will exist ahead of the cold front Thursday morning, characterized by dewpoints ranging from the mid/upper 60s over east TX to the mid 50s near the IA/MO border. This reservoir of low-level moisture will exist beneath steep mid-level lapse rates, resulting in moderate to strong buoyancy as heating destabilizes the air mass. As such, thunderstorms are anticipated across much of the warm sector as the cold front gradually shifts eastward throughout the day. Some strong to severe storms are possible, particularly in the corridor from northern MO into the Arklatex. ....Mid MS Valley Thursday morning into late afternoon/early evening... Showers and thunderstorms will likely be ongoing near the surface low and warm front early Thursday morning. General expectation is for most of this activity to be north of the warm front, with an attendant threat for isolated hail. However, there is some potential for the southern edge of these storms (and associated outflow) to move within the far northern corridor of the warm sector, resulting in some threat for damaging gusts as well as hail. This activity is expected to continue eastward, reaching the Middle OH Valley by the afternoon. The presence of these early morning storms could act to shift the position of entire the frontal zone southward, with an attendant shift of the afternoon severe threat as well. Additionally, if strong outflow is realized, the resulting boundary could act as a focus for afternoon development across MO. Evolution of these mesoscale details varies within the guidance, but the more favorable area for afternoon development does appear to be over central MO, which is farther south than forecast yesterday when the area just south of the warm front looked more plausible. Given steep mid-level lapse rates and strong deep-layer vertical shear, large to very large hail is still anticipated with the initial more cellular late afternoon storms. Strong downdrafts are possible as well, with potential for upscale growth into one or more bowing clusters. Veered low-level flow is forecast to limit the tornado potential, although interaction with any boundaries could lead to mesoscale corridors of slightly greater tornado threat. ....Middle OH Valley during the afternoon and evening... As the activity initially over the Mid MS Valley continues eastward, there is some potential it transitions from elevated to surface based (or at least near-surface based) as it interacts with the warm front progressing northward across the region. Buoyancy will be modest, but moderate southerly low-level flow beneath strong westerlies will result in vertically veering low-level hodographs that could support updraft organization and even a few tornadoes. Uncertainties regarding the position of the front as well as how the convection evolves out of the Mid MS Valley limit forecast confidence with this outlook, but future guidance will be evaluated closely, and upgrades may be considered in later outlooks. ....Far Northeast TX and eastern OK into AR during the afternoon and evening... Large-scale forcing for ascent will be nebulous over the region, with some guidance even showing height rises during the afternoon. Even so, weak surface troughing is expected to interact with an increasingly unstable airmass across the region during the afternoon, resulting scattered thunderstorms from far northeast TX into eastern OK and western AR between 18Z and 21Z. Given robust buoyancy and moderate vertical shear, initial development will likely be supercellular and capable of all severe hazards, including very large hail. Low-level southerly flow (perhaps even southeasterly) is also anticipated, resulting in low-level hodographs that support tornadogenesis, particularly from far southeast OK into western AR. Even with favorable hodographs, storm interactions could prevent the discreteness needed for updraft organization. ....Mid MS Valley into the Mid-South during evening and overnight... After the initial development described above, some upscale growth into one or more clusters appears plausible, with an attendant threat for damaging gusts as these clusters move eastward. Buoyancy will gradually decrease with eastward extent, leading to the expectation that whatever line segments do develop will lose intensity as they continue eastward overnight. ...Mosier.. 03/13/2024 $$ = = = To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. 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