Severe Weather Update 1005 am

Warm air coming in just above the surface overnight allowed the air to become unstable enough for elevated thunderstorms (the updraft begins above the surface), and a number of storms developed early this morning in north and central Alabama and continue now.

A band of showers and thunderstorms extends from Fort Payne, basically just north of I-59 to the Birmingham area and then to Tuscaloosa. The storms are moving rapidly NE, but the overall area of storms is moving little, as new storms keep developing. Incidentally, the environment over much of Alabama is excellent for ducted gravity waves near the surface, which are moving NE faster than the storms today, and may have enhanced the mesocyclone over Blount county earlier (see radar picture). This is a process we are studying closely at UAH.

The band of storms along I-59 may continue for a while. The wind shear is extremely high (0-1 km storm-relative helicity 400-500), and there is some instability aloft. An isolated tornado with these storms is not out of the question, so keep a source of weather information nearby. However, large tornadoes are rare in elevated storms.

Farther south, skies are actually clearing in areas south of MGM and Greenville. With temps there rising into the 70s and the front still approaching from the west, there may be a larger threat of tornadoes in south Alabama this afternoon. However, the threat of additional storms will continue in north and central Alabama through the afternoon also, with the cold front not making it to BHM until 5 or 6 pm. A squall line is developing in Mississippi, and that will bring the threat of isolated tornadoes, and especially wind damage, to Alabama as it moves through later this morning and this afternoon.

Arctic air still on schedule…highs only in the 30s over north Alabama Tuesday through Friday next week, lows in the teens in colder places in north Alabama, lower 20s to MGM.

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