The National Weather Service has issued a new PDS (Particularly Dangerous Situation) Tornado Watch for the following counties in central and south Alabama: Autauga, Baldwin, Bibb, Blount, Butler, Calhoun, Chambers, Cherokee, Chilton, Choctaw, Clarke, Clay, Cleburne, Conecuh, Coosa, Crenshaw, Dallas, Elmore, Escambia, Etowah, Fayette, Greene, Hale, Jefferson, Lamar, Lee, Lowndes, Macon, Marengo, Marion, Mobile, Monroe, Montgomery, Perry, Pickens, Randolph, Shelby, St. Clair, Sumter, Talladega, Tallapoosa, Tuscaloosa, Walker, Washington, Wilcox and Winston. This new watch is set to expire at 3 a.m.

Meanwhile, National Weather Service Huntsville has issued a Tornado Watch for the following counties in north Alabama: Colbert, Cullman, Franklin, Lauderdale, Lawrence, Limestone, Madison, Marshall and Morgan. This watch is set to expire at midnight.

Here is the latest from the Storm Prediction Center’s Mesoscale Discussion.

SUMMARY: The risk for tornadoes, a couple of which could become strong and particularly damaging, is expected to continue to increase through mid to late evening as an organizing squall line overspreads the region. This may also be accompanied by more general strong to severe surface gusts.

DISCUSSION (excerpts): Support continues for discrete thunderstorm development within a relatively broad warm sector. This environment remains potentially conducive to long-lived supercells with strong low-level mesocyclones posing a risk for tornadoes.

While the onset of diurnal cooling could result in at least some decrease in instability, favorable large-scale forcing for ascent seems likely to maintain discrete storm development across central Alabama, as a linear convective system continues to evolve upstream across southeastern Louisiana through southern and eastern Mississippi. This is occurring ahead of a vigorous short-wave trough turning east-northeast of the southern Great Plains. As this feature progresses into the lower/middle Mississippi Valley through mid to late evening, south-southwesterly 850 millibar flow is forecast to strengthen in a corridor along/ahead of the evolving squall line.

This will include the potential for strong tornadoes. Otherwise, corridors of potentially damaging wind gusts will probably begin to increase as the evolving squall line continues to organize and accelerate northeastward.

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