We are in the first quarter of a four quarter severe weather event that will unfold between now and early Wednesday morning over Alabama.
(Had to work football in there during the Super Bowl, you know.)
The kickoff has been a passing disturbance that is moving into Georgia tonight. It has combined with an moisture surging off the Gulf of Mexico. The airmass to the west of Alabama is already becoming unstable, especially over Louisiana, but the atmosphere is capped off for now.
A warm front will organize and push northward across Alabama overnight. It will be accompanied by showers and elevated thunderstorms. This activity will be mainly after midnight in Central Alabama, pushing into North Central sections early tomorrow morning and northern sections during the morning. With the warm frontal passage…the rain will end and the sun will eventually breakthrough. A lot of uncertainty about temperatures for tomorrow afternoon. I think the average will be around 68. Where the sun break through for an extended period, highs may warm well into the 70s.
Thunderstorms that develop during the afternoon could be strong. We will call that the second quarter. They will potentially be prolific hail producers. Some could become severe with damaging winds. Lifted indices will go negative tomorrow with around 500j/kg of CAPE available according to the WRF.
The big upper trough will be swinging eastward into Texas by Tuesday morning. At least it will be positively tilted. A negatively tilter trough brings higher energy along with it. Thunderstorms will become severe tomorrow to the west of Alabama, especially over Arkansas and parts of surrounding states, where a Slight Risk Outlook is in effect.
Tuesday will feel like a severe weather day over Alabama. Winds will be increasing out of the south, averaging 10-20 mph. They will increase even further during the evening hours. Temperatures will start off in the upper 50s to lower 60s and the air will have a muggy feel.
Instability will approach 500-750 j/kg during the day, especially over West Alabama. Thunderstorms could become severe, especially west of I-65 during the late morning and afternoon, pushing eastward. That will be the third quarter. The models are fairly consistent in their treatment of the instability fields. Honestly, they are not overly impressive just yet, with dewpoints only progged to be in the lower 60s. We really need middle 60s for a big event. But the helicity values were healthy, with both models showing lwo level helicity of around 150-200 m2/s2 during the day, increasing as we go into the evening hours. Supercell storms with isolated tornadoes will be possible.
Now as we get into the evening, instabilities should creep up and helicities will increase also. A long, powerful squall line will form to the west of Alabama and head our way. Evening storms could be severe, as instabilities edge upward and wind shear increases. Isolated tornadoes will be a possibility. That will be the fourth quarter.
Then the squall line will bring a round of damaging winds to the area through the late evening and overnight hours.
Right now, it is unclear just how warm it will get Tuesday. If highs are in the middle 70s and dewpoints edge toward 65, that would favor a stronger event. The GFS outputs a high of 76 with a dewpoint of 61 at Birmingham. The NAM is cooler, with 68 for the high and dewpoints in the upper 50s.
We will just have to wait and watch the system unfold. It does appear that a significant severe weather scenario is likely Tuesday into Tuesday night for Alabama. I would not be surprised to see a moderate risk outlook issued for us before this is over.
Needless to say, all Alabamians should pay very close attention to the latest information on Monday. No better place for the latest thinking throughout the event than right here.
Make sure that you can hear weather watches and warnings tomorrow just in case and especially on Tuesday. Review your personal severe weather safety plan. Know where you will go when severe storms approach. If you live in manufactured housing, have a plan to move to a sturdy shelter well in advance of the storms.
