Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Sep 06 2023 16:17:32 ACUS01 KWNS 061617 SWODY1 SPC AC 061615 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1115 AM CDT Wed Sep 06 2023 Valid 061630Z - 071200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON AND EVENING ACROSS PARTS OF SOUTHWESTERN TENNESSEE...NORTHWESTERN ALABAMA...NORTHERN AND CENTRAL MISSISSIPPI...SOUTHEASTERN ARKANSAS...AND NORTHERN LOUISIANA... ....SUMMARY... Scattered strong thunderstorms, and perhaps a consolidating cluster of thunderstorms, are possible across parts of the lower Mississippi Valley late this afternoon and evening, accompanied by a risk for potentially damaging wind gusts and some hail. ....Synopsis... Amplified, but weak, mid-level troughing lingers offshore of the Atlantic Seaboard, with a modest cyclone, slowly migrating northeastward to the south of Nova Scotia, the most prominent embedded perturbation. Upstream, models indicate that mid-level troughing may also begin to amplify across and east of the Mississippi Valley, downstream of building short wave ridging to the north of a prominent subtropical high centered over southeastern New Mexico. The amplifying trough will include one generally weakening short wave impulse progressing across the Great Lakes region today through tonight, while an additional couple of perturbations dig within northwesterly flow southeast of the Black Hills vicinity through the Ozark Plateau/lower Mississippi Valley. Stronger wind fields are becoming largely confined to the northwesterly regime upstream of the evolving larger-scale mid-level trough axis, though a remnant belt of modest southwesterly flow (including 30+ kt in the 850-700 mb layer) downstream of the trough axis is forecast to nose northeast of lower Michigan through Ontario by mid/late afternoon. The latter speed maximum will accompany a weakening migratory low within weak surface troughing, along a cold front forecast to slowly advance eastward across the upper Great Lakes region, Ontario and central Quebec. An initial cold frontal surge already has reached the lower Ohio Valley, Ozark Plateau and Texas South Plains vicinity. Across parts of western Kentucky and Tennessee into northeastern Arkansas, the front is preceded by a remnant MCV and convective outflow associated with a dissipating cluster of thunderstorms. ....Great Lakes through southern Great Plains... While deep-layer mean wind fields and vertical shear have generally weakened ahead/south of the cold front, modestly steep lapse rates in lower through mid-levels, coupled with residual boundary-layer moisture, may contribute to areas of sizable mixed-layer CAPE in excess of 2000 J/kg by late afternoon. From the Tennessee Valley into the Great Lakes region, this may be more sparse in nature due to early day cloud cover and weak low-level focus for convective development. However, it seems probable that a more prominent zone of differential surface heating, across parts of central Arkansas into western Tennessee, will become a focus for at least scattered strong thunderstorm development by late this afternoon. Given thermodynamic profiles characterized by large CAPE and a very warm well-mixed boundary layer, various guidance has been suggestive that an upscale growing cluster could eventually evolve along consolidating, south/southwestward propagating cold pools into this evening. If this occurs, a hail/downburst threat in stronger initial storms may transition to a more widespread marginal severe wind threat. Other more widely scattered strong thunderstorm development is possible west-southwestward into a hotter, drier and more deeply mixed boundary layer across parts of west central Texas. ...Kerr/Weinman.. 09/06/2023 $$ = = = 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) .