Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Feb 16 2024 12:35:25 ACUS01 KWNS 161235 SWODY1 SPC AC 161233 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0633 AM CST Fri Feb 16 2024 Valid 161300Z - 171200Z ....NO SEVERE THUNDERSTORM AREAS FORECAST... ....SUMMARY... No areas of organized severe thunderstorms are forecast over the conterminous U.S. ....Synopsis... A highly amplified mid/upper-level pattern will persist over the CONUS today, as an initial high-latitude omega configuration over western Canada evolves into a full-latitude, open-wave, synoptic ridge. That ridge will extend southward over the western U.S. as well. The eastern portion of a shortwave trough -- initially over the northern Rockies -- will break away from the remainder of the height weakness footing the omega pattern and reach parts of southwestern WY, southern ID and northern UT by 00Z. The trough then should dig southeastward to parts of CO/UT by the end of the period. As that occurs, a weaker, downstream perturbation -- evident in moisture-channel imagery near an axis from HLC-AMA-INK -- will weaken gradually as it moves eastward across OK and AR, reaching the lower Ohio Valley and western TN by 00Z. What is left of this feature should accelerate eastward over the central Appalachians by 12Z tomorrow. At the surface, 11Z analysis showed a frontal-wave low near FDR, with wavy warm front across central parts of OK/AR to northern MS. An initial/weak cold front was drawn from the low southwestward over southern NM and an Arctic front across the southeastern TX Panhandle to northeastern NM. These fronts should merge through the day, while the low ripples rapidly east-northeastward along the warm front. The low should reach south-central/southeastern KY by 00Z, with trailing cold front across middle TN, northern MS, the Arklatex region, and south-central TX. By 12Z, the low should move offshore from Hampton Roads, with cold front over central NC, north-central GA, south-central AL, to parts of the north-central/northwestern Gulf. ....AR/Mid-South... Scattered thunderstorms are expected to form this afternoon into evening over AR, along/ahead of the surface cold front, then shift eastward while backbuilding southward. A resultant band of thunderstorms should cross parts of western TN, northern MS and northern LA before weakening substantially late this evening. The strongest cells within the band -- especially early in the convective cycle when discrete storms still are possible -- may produce hail approaching severe limits and strong gusts. Severe potential still appears too low and conditional for a categorical risk area; however, an isolated, marginally severe hail report or damaging subsevere gust cannot be ruled out. Surface dewpoints in the 50s F already extend from the Gulf into the warm sector across parts of this region, and should remain in place as moist advection offsets any diurnal mixing. The return-flow regime will remain incompletely modified, so that the convective plume will outrun already modest moisture this evening while diabatic cooling takes hold. Time series of forecast soundings depict two simultaneous processes: 1. Effective-inflow parcels becoming surface-based this afternoon, in a narrow prefrontal corridor, due to warm advection and cloud-slowed diurnal surface warming. This should contribute to peak preconvective MLCAPE in the 300-800 J/kg range. 2. Veering of surface winds with time, reducing hodograph size, low-level SRH and low-level bulk shear. Deep shear will be marginal to favorable, even with veering of low-level flow. 0-6-km shear magnitudes in the 45-55-kt range are expected. However, effective- shear magnitudes are only around 1/2-2/3 that range, because the low-topped/compressed nature of the buoyant layer shunts the upper reaches of the calculation to below the strongest mid/upper winds. With the favorable kinematic and thermodynamic factors trending oppositely through the afternoon, and the regime already being somewhat moisture/buoyancy-starved, unconditional probabilities will be held below MRGL categorical levels for the time being. ...Edwards.. 02/16/2024 $$ = = = 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) .