...SEVERE THUNDERSTORM WATCH UNTIL 9 PM CDT...
The active weather pattern continues, as an upper-level shortwave trough will pass by to our north over the next 24 hours. SPC has placed much of central Alabama in a slight risk for severe weather, and parts of north Alabama in an enhanced risk, for today and tonight.
So far, we have seen a few scattered heavy showers over central Alabama. One moved past my location in Trussville, dropping heavy rain and maybe some tiny hail, around 115 pm. Hail will continue to be a risk with storms the rest of the day, as upper-level temperatures are cold.
In this case, the air will continue to warm up over Alabama this afternoon, with periods of sunshine. Most of us will reach the lower 80s. It is also rather humid today, unlike Saturday, so the air will become quite unstable this afternoon, with CAPE values up to 3000 J/kg over western and central Alabama. So, thunderstorms will increase in intensity and coverage this afternoon. Luckily, once the sun goes down, much like in summer, the temperature will drop and so will the instability, and by 1 am, CAPE will drop below 1000 J/kg.
Luckily, the main wind shear for storm rotation will stay to our northwest until tonight, when CAPE values have dropped significantly and it will be more difficult for storms to keep going. So, here in central Alabama, the strongest instability will not occur at the same time as the most intense wind shear, making widespread tornadoes unlikely. They will come together a bit more in northeast Mississippi, southern Tennessee, and extreme northwest Alabama, so if we see tornadoes, they are most likely to be in those areas.
Expect thunderstorms to increase in coverage this afternoon, with lightning, heavy rain, hail, and straight line winds all possible, especially from Birmingham west. The storms may continue after sunset as more wind shear and forcing moves in, but we do not expect widespread tornadoes, especially not here in central Alabama, as the wind shear moves in after the instability goes away. But, stay weather aware into the evening hours, as things could always change.
Looks like another chance for severe weather, and more rain, late this week.
Dr. Tim Coleman