Slight Risk for Severe Storms Issued for Much of North/Central Alabama

The Storm Prediction Center has upgraded the severe risk across much of North/Central Alabama to a Slight Risk for severe storms. The Slight Risk includes the cities of Russellville, Athens, Decatur, Huntsville, Hartselle, Cullman, Guntersville, Hamilton, Birmingham, Hoover, Tuscaloosa, Demopolis, and Selma. A Marginal Risk for severe storms continue for Scottsboro, Rainsville, Gadsden, Anniston, Talladega, Clanton, Alexander City, Auburn, Montgomery, and Troy.

Severe threat will continue across the area from northwest to southeast from now until at least 1 pm today. Damaging winds up to 60 mph will be the main threat, but there is also a small, non-zero, threat of a brief spin-up tornado.

Here is the latest text from the Storm Prediction Center:

Scattered strong to severe storms are expected today from east Texas to portions of the Tennessee Valley. Damaging wind gusts will be the primary hazard, with a tornado or two possible.

A broadly cyclonic pattern has developed in mid/upper levels over most of the CONUS, with the dominant feature being a strong shortwave trough initially located from Lake Superior across southern WI to northeastern KS. This trough is forecast to pivot across the upper Great Lakes and lower/mid-Ohio Valley today, while assuming less-positive tilt. Related 500-mb height falls should extend about as far south as TN today, before the trough ejects across QC and the Northeast overnight. Meanwhile, a weak southern-stream perturbation — apparent in moisture-channel imagery over central TX and the Edwards Plateau — will move eastward across east TX and LA/MS through 00Z, while slowly weakening. Upstream, a small, weak, closed cyclone over coastal southern Sonora will devolve to an open wave and move east-northeastward across northern MX, reaching the Big Bend region and adjoining western Coahuila by 12Z tomorrow.

At the surface, a cold front related to the northern-stream mid/upper trough was drawn at 11Z from OH across western portions of KY/TN to southern AR and central/southwest TX. Around 00Z, the front should reach western New England, coastal NJ/Delmarva, western NC, northern GA, southern portions of MS/LA, and the shelf waters off most of the TX coast. By 12Z, the front should reach coastal SC, southern GA, the FL Panhandle, and open waters of the northwest Gulf.

…East TX to portions of the TN Valley…
Frontal and prefrontal bands of thunderstorms are expected to offer a threat for damaging to isolated severe gusts, as well as a brief tornado or two, through mid/late afternoon. Very isolated, conditional, weakly forced supercell potential will persist in the warm sector to its south as well. Activity should shift generally southeastward (with embedded convective elements such as LEWPs, small bows and brief supercells) moving eastward to east-northeastward. A relative max in favorable parameter space will exist broadly over the “slight” area today, with the front and prefrontal convergence line(s) impinging on 60s F surface dew points, boundary- layer theta-e advection, and fragmented areas of diabatic heating beneath broken, variably thick cloud cover. Peak MLCAPE of around 1500 J/kg is expected in the southwestern parts of the outlook area, decreasing/tapering to less than 500 J/kg in the northeast. Effective-shear magnitudes, by contrast, should increase from around 30-40 kt near the Sabine River to 50-55 kt in the Tennessee Valley region.

The eastern part of the severe potential will be limited by a more-stable air mass left behind the prior cold frontal passage, with incomplete airmass recovery in return flow. To the south, closer to the coast, large-scale support aloft will be more limited with time this evening and tonight, and deep shear will diminish southward. To the south and west, despite relatively maximized moisture and some large-scale ascent aloft preceding the approaching southern-stream perturbation, an anafrontal regime and shallower frontal density current will limit organization.

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