February 29, 2012 Leave a comment
Good Wednesday evening! The severe weather threat tonight is over, as instability levels continue to decrease. There’s plenty of speed shear over our area, but high shear with weak instability can disrupt a thunderstorm’s updraft. You’ll get more of disorganized thunderstorms. While a band of showers and weak thunderstorms move across the area tonight, don’t be surprised to see some lightning at times and a period of moderate to heavy rain. I do not see any indication of anything becoming severe tonight. Plus, the upper air dynamics have lifted well to the north of Alabama by this point.
As I like to say when a severe weather event ends… “And another one bites the dust.” With an old stationary front hanging around over the next 18 to 20 hours, look for periods of showers and thunderstorms at times through the rest of the night and during the day on Thursday. Don’t expect rain all day. This activity will come and go; it’s impossible to tell what time it will rain at your house tomorrow, so keep the rain gear handy all day. It will be a very warm and muggy day, with highs in the upper 70s. If a little sun can peak out at times, some spots could reach 80. I think there’s a better chance of spots reaching 80 on Friday.
Once a warm front lifts north of the area early Friday, some sun will arrive at times. This will take the best rain chances north of the area during the day. We could still see an isolated shower or storm, but the atmosphere will be capped off for much of the day. I expect the cap to break during the mid to late afternoon hours as some large scale lift moves over central and west Alabama. This will allow storms to develop ahead of a squall line. While the best severe weather parameters will remain over north Alabama and Tennessee, there is still a good mix of shear and instability across our central counties. If cells are able to form out ahead of the main line Friday afternoon and evening, they stand the best chance of producing damaging winds, hail and tornadoes. We will know much more about the severe weather ingredients tomorrow morning, so be sure to look for a full update. Meanwhile, I think this will be a fairly robust storm system that has the chance of producing widespread severe weather across central Alabama. The main threat will occur near and north of HWY 80 and an even higher threat will occur north of Interstate 20/59. The threats include damaging winds, hail and isolated tornadoes. As for the time frame, storms could start in our northwest counties as early as 3pm and end in southeast Alabama Saturday morning. Model data is still questionable on the exact timing of this event. Data does decrease instability values after midnight, so that would reduce our risk as we approach the daylight hours. A squall line will bring an end to the threat gradually from northwest to southeast through the night.
There is an outside chance of a secondary surface low developing over Tennessee. If that does happen, our tornado threat may actually increase a bit. There are still a lot of questions regarding the chance of that happening. Again, I’ll have much more on that idea tomorrow morning. The Storm Prediction Center has much of central and north Alabama under a slight risk, with higher chances north of Interstate 20/59. The SPC will come out with a new update late tonight.
Temperatures will cool a bit once the front passes central Alabama late Friday night or Saturday morning. Highs will fall into the lower 60s Saturday through Monday afternoons, with lows in the 30s. Skies will also become sunny during the day Saturday and remain sunny through Monday. A quick warming trend is likely on Tuesday and Wednesday, with highs in the 70s.
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