Severe weather update – 412 pm

…First big severe weather threat of 2011 season facing Alabama overnight…

…See James’ post below for more details on the forecast…

A low pressure area now over western Arkansas will move east-northeastward tonight, toward west TN and central KY.  It will drag a cold front through Alabama, and a line of severe thunderstorms (storms are already lined up from NE AR to east TX).  Also, along a warm front east of the low, in parts of west TN, some isolated supercell storms have developed, and tornado warnings were issued.  Often storms that form near boundaries have enhanced rotation due to the increased convergence and wind shear along the boundary. 

A few scattered storms may develop over Alabama during the evening hours out ahead of the main line.  The intense line of storms should move into NW Alabama around 11 pm, then move SE across the state, probably weakening some.  Given the limited instability, tornadoes are not the main threat with this system, but isolated ones can’t be ruled out.  The main threat will be widespread damaging wind.  The wind fields tonight will be very strong around the intensifying low to our northwest, with 850 mb winds (at about 5,000 feet) reaching near 80 mph.  The storms’ downdraft will bring some of this momentum down to the ground, producing wind gusts over 60 mph in many locations, especially from BHM NW.  If there is enough instability to maintain these storms well into the night, widespread wind damage and power outages may occur. 

This will be a night to have a NOAA Weather Radio turned on.  If a 70 mph wind pushes a tree on your house, that’s about as dangerous as a tornado.  We’ll have to see how strong the storms can remain late at night to see how much potential there is for widespread wind damage.  I think it’s almost sure that trees will go down over Alabama tonight.

Category: Severe Weather