Here’s a 9:45 p.m. Look at the Alabama Severe Weather Situation

We’re tracking a powerful QLCS, or quasi-linear convective system that is tracking across western Mississippi this evening. We used to call them squall lines, but as they say in the advertising business, it’s all about the branding.

Radar, watches and warnings at 930 p.m.

Our line of storms extends from southern Illinois through western Kentucky and western Tennessee, east of Memphis, into western Mississippi and back into eastern Louisiana. The line is approaching Jackson MS at this hour.

Severe thunderstorm warnings are lined up from Winona to Hazlehurst.

There have been several reports of trees down around Vicksburg and back in Northeast Louisiana around Rayville.

A new severe thunderstorm watch was just posted that goes until 2 a.m. for much of Mississippi. That watch comes right up to the Alabama State Line.

TIMING
The line should approach the Alabama border around or just before midnight. It will approach Tuscaloosa between 1 and 2 a.m. and Birmingham between 2-3 a.m. I fear that it might accelerate though, so please be ready earlier than those times and we can adjust them as it gets closer.

THREATS
The main threat should be from straight line wind damage. The SPC puts the probability of West Alabama points seeing severe winds (58 mph or greater) within 25 miles of their location at 15%. This equates to a slight risk.

There is a 5% tornado probability over West Alabama as well. The hail severe hail probability (1″ or greater) is set at 5%. The official probabilities decrease as you travel east.

BUT, NOT SO FAST MY FRIEND:
The line of storms does look like it will weaken a bit as it traverses Mississippi and take on a more broken line appearance. I think this actually enhances the threat of a tornado or two as it pushes into West Alabama, especially since there will be an increasing low level jet at 5,000 feet with strong winds above the surface and surface winds that are more southeasterly in direction, increasing the helicity. I think it is something that we will have to watch.

And I never trust a trough that is becoming more negatively tilted. That is what our upper lvele trough is doing tonight back over the Arklatex.

PARAMETERS
Surface based CAPE values should increase to 1,000 joules/kg or higher as far north as Tuscaloosa. Lapse rates should be really good, making for some potentially strong updrafts. Shear values will be strong over all of central Alabama. I think the potential overlap will be from Tuscaloosa to Clanton and southward to around Choctaw, Marengo and Dallas Counties.

The significant tornado parameters is as high as 1-1.5 as far north as southern Lamar, Fayette, Jefferson, Shelby, St. Clair, Talladega and Calhoun Counties.

BOTTOM LINE
A line of severe thunderstorms will affect Alabama after midnight. Damaging winds will be the main threat, particular west of I-65. But there will be a tornado threat as well, south of a line from Lamar through Fayette, Jefferson, St. CLair, Talladega and Calhoun Counties. The highest threat may be across Greene, Hale, Marengo, Perry, Dallas, Chilton and Autauga Counties.

STAY WEATHER AWARE TONIGHT
This is one of those nights when you need to have your Weatheradio turned on and in alert mode to wake you. Have a backup warning source as well. And take action if a severe thunderstorm warning is issued. Trees can kill when falling on homes or cars. And they produce tornadoes with little or no warning.

FREQUENT UPDATES
We will have frequent updates through the night and morning until the storms are in Georgia.

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