Strong to severe thunderstorms continue this evening for areas near and east of I-65 as a dryline and cold front progresses eastward across the middle of the state.
The storms are forming and then moving into an instability axis which is just east of Biringham. This is allowing them to intensify and become severe, with high wind shear allowing the storms to remain organized.
The storms are taking advantage of very high lapse rates that are in the low and mid levels of the atmosphere. Low level lapse rates are off the charts at 8-8.5C/KM. This is about as high as you will see in Alabama. The steep lapse rates and high instability are allowing the storms to go from formation to severity in short periods and are leading to very large hail. Hail to the size of tennis balls has been observed at Leeds in eastern Jefferson County. Baseball sized hail was reported in Cleburne County. That same hail threat will continue with the stronger storms.
The storm near Lincoln has large hail in it. The storm near Ashville is severe warned as well.
The tornado threat is still there for counties along the Georgia border, including Jackson, DeKalb, Marshall, Etowah, Cherokee, Calhoun Cleburne and Randolph as helicity values in the 0-1 km layer are still over 250 m2/s2. Helicity values over 150 m2/s2 extend back to just east of I-65.
A tornado watch continues for Autauga, Barbour, Bibb, Blount, Bullock, Calhoun, Chambers, Cherokee, Chilton, Clay, Cleburne, Coosa, Elmore, Etowah, Jefferson, Lee, Lowndes, Macon, Montgomery, Pike, Randolph, Russell, Shelby, St. Clair, Talladega and Tallapoosa Counties till 9:00 PM.
The dryline will continue east this evening, pushing the storms into Georgia by 10 p.m. for areas at or north of Auburn.
A wind advisory is in effect for much of Central Alabama for tonight and Thursday. Winds will average 20-30 mph with gusts to 30-40 mph at times. This can bring down weakened trees.
That has already happened at Guin in Marion County, where winds were estimated to 45 mph a short time ago, with no thunderstorms involved. Trees downed powerlines, when started a grass fire.
It will be much colder through Saturday, with lows in the middle 40s tonight lower 40s tomorrow night and 30s Friday night. There will be a chance of frost over the normally colder locations and protected valleys of North and North Central Alabama.
Things will warm up later in the weekend, with 70s Sunday through Wednesday. Lows will get back into the 50s.
from The Alabama Weather Blog http://ift.tt/2oF0Mqt
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