Instability values (CAPE or Convective Available Potential Energy) are high across Central Alabama with the amount of heat and moisture available this afternoon. Readings from the SPC Hourly Mesoscale Analysis page shows CAPE values in the 2500-4000 J/kg range across Central Alabama.
The bad news is that we are seeing Downdraft CAPE values in the 900-1100 J/kg range across the area. With these higher values, strong downdrafts are possible which could lead to damaging winds from downbursts.
This is why the National Weather Service office in Birmingham has a good bit of Central Alabama in a Marginal Risk of severe storms through the remainder of the afternoon and evening hours. The main window for stronger to severe storms will be from now until 9:00 pm tonight and mainly south of a line from Haleyville to Birmingham to Phenix City.
The Microburst Composite shows that as the case as the higher values will be in the Marginal Risk locations drawn out by NWS Birmingham. Values of 3-4 mean a slight chance of microbursts, 5-8 infers to a chance of microbursts, and values of 9 or greater infer that microbursts are likely. We see values in the 3-6 range on the latest mesoscale analysis, so microbursts are possible.
Winds have already brought down a few trees today, with several downed along with power lines on Wednesday. Please pay attention to the weather through the day today and on Friday as the Storm Prediction Center already has a Marginal Risk out for nearly all of Central Alabama.