Today’s Severe Weather Zone

William’s Severe Weather Zone for Wednesday:

At the surface, 11Z analysis showed a cold front from far northern ON through a low near STC, southwestward to another low near GBD, then across southern CO. This front will move southeastward to near a DBQ-MKC-PNC-CDS-CVS line by 00Z. By 12Z tomorrow, the front should reach northeastern Lower MI, southern IL, north-central AR, and northeast to south-central TX and northern Coahuila. …Southern Plains to Mid Mississippi Valley… Isolated to scattered thunderstorms are expected to develop this evening and overnight in two primary regimes: 1. Along and behind the cold front, where the boundary (surface through low levels) impinges on a progressively modifying/ moistening warm sector. 2. A belt of broad low-level confluence/convergence ahead of the front in the warm sector, with weak CINH, related to the return-flow/warm-advection regime. Considerable veering with height of low-level flow is expected, along with strong upper/anvil-level winds. However, midlevel flow weaknesses generally will keep effective-shear magnitudes below 35 kt, based on forecast soundings sampling warm-sector/surface-based environments and elevated buoyancy behind the front. A northward- narrowing wedge of 60s F surface dew points should reach eastern OK and perhaps the western Ozarks prior to frontal passage. Beneath modest mid/upper-level lapse rates, this will support MLCAPE in the 500-1000 J/kg range over central/north TX, decreasing to less than 300 J/kg over northwestern AR. Similar values of MLCAPE are expected just behind the front at the same latitudes. The most intense cells may produce small hail or strong gusts, but severe potential appears too minimal for a categorical area at this time. ..Edwards/Jewell.. 11/24/2021 $$