Today’s Severe Weather Zone

William’s Severe Weather Zone for Monday:

At the surface, 11Z analysis showed a low over eastern ND, with occluded front southeastward to a triple-point low over north- central IL, and a warm front from there across central IN, southwestern OH, eastern KY, and western NC. A cold front was drawn from central IL to southwestern MO, south-central OK, to between MAF-LBB, and over southeastern NM. By 00Z the triple point should reach east-central/northeastern OH, with warm front southeastward over northern VA and cold front over western KY, central AR and west-central TX. By 12Z, the occlusion triple point should move offshore from the Mid-Atlantic. The cold front will extend over central/southwestern VA to middle TN, becoming a quasistationary front and weakening from there across northeastern/west-central AR, as a surface cyclone develops/deepens over the central Plains. …Mid/upper Ohio Valley… Isolated to widely scattered thunderstorms are expected into early afternoon, within the western part of a swath of low-level warm advection, moisture transport and related precip — near and north of the warm front. The bulk of this activity will occur prior to the passage of the Great Lakes shortwave trough, above a stable near-surface layer. Behind this convection and the trough aloft, and in between warm- and cold-frontal passages, the northern fringe of the warm sector will yield weak surface-based buoyancy (MLCAPE of 300-700 J/kg based on modified model soundings). Despite veered/ southwesterly to west-southwesterly surface winds following the warm front, sufficient midlevel flow will persist to yield 50-60 kt effective-shear magnitudes. Given those conditions, some concern exists for a conditional severe-gust potential over southern OH, northeastern KY and western WV, for any daytime convection that can form in the warm sector or on the cold front. A marginal/5% wind area was considered. However, current indications are that most, if not all, of that favorable parameter space will lag behind the substantial convection and shortwave trough during daylight hours. Progged low-level convergence and mid/upper support each remain too weak to justify an unconditional risk area while warm-sector parcels still are surface-based. ..Edwards/Gleason.. 12/27/2021 $$