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A WEATHER SMORGASBORD: You name it, we’ve got it in this forecast package. As always, I encourage you to watch the Weather Xtreme video for all of the graphics associated with this discussion.
SEVERE WEATHER POTENTIAL FOR TONIGHT: A significant severe weather event is underway to the west of Alabama, where a tornado watch is in effect until 5:00 for much of Central and West Mississippi, and much of Louisiana. Look for this watch to be extended eastward later this afternoon or this evening.
Over in the watch area, surface based CAPE values have soared to 3,000 j/kg over South-Central Louisiana. While we won’t see instability like that, we do expect a sliver of CAPEs between 200 and 400 as far north as Birmingham later tonight, with dewpoints in the low to mid 60s.
Wind fields are screaming; the latest model data suggests 850 mb winds (around 5,000 feet) of 70 knots around Birmingham tonight! Won’t take much for this to translate down to the surface.
TIMING: Severe storms could enter West Alabama as early as 8:00… the storms will then progress slowly across the state during the late night hours, into early tomorrow morning. While the main threat will come from damaging straight line winds, we sure can’t rule out a few isolated tornadoes based on the forecast hodographs we are seeing. The threat will run from around 8:00 p.m. until 4:00 a.m. Be sure you have a NOAA Weather Radio with the alarm available in case late night warnings are required.
The rain will slowly push to the south during the day tomorrow, and we should have a break in the rain tomorrow afternoon and tomorrow night.
SNOW ON THURSDAY? The models are trending colder with a cold core upper low moving right over us Thursday. You can’t ignore the possibility of dynamic cooling with this feature, and the 18Z runs just in are showing 850 mb temperatures well below freezing. At this point we pretty much have to mention a chance of rain Thursday, changing to snow Thursday afternoon and early Thursday night before ending.
A few points to consider:
*The ground is warm and temperatures will be above freezing; so accumulation or travel problems most likely won’t be an issue if we do see a change to snow. The only way we get serious accumulation is if the snow becomes heavy under the cold core upper low, which is not out of the question. The December 1997 event comes to mind.
*Snow as a result of dynamic cooling is a very complicated set-up, and skill in forecasting this kind of event is not the best. But, we have seen enough evidence that it could very well happen this time.
*This won’t be a long lasting event since no real Arctic air is involved with the system; sunshine returns Friday with a high around 50.
WEEKEND AND BEYOND: The weekend will be dry with ample sunshine and highs in the 50s. Next week looks relatively mild as the cold upper trough shifts to the western half of the nation, and the GFS continues the idea of the coldest weather in the nation out west during the latter half of the month. This certainly doesn’t bode well for any hope of a White Christmas in Alabama. But, voodoo is voodoo, you know. That could change.
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We will keep the blog updated with fresh information through tonight’s event, so stay tuned…..
