First up, the rest of today…the main rain area is moving out of the state as it weakens, and we are left with low clouds, some patchy drizzle, and breezy conditions for the rest of today.  We have already reached our high for the day, and temperatures will continue to fall for the rest of the the afternoon and evening as clouds decrease.

Tuesday:  Easily the nicest day of the week.  Plenty of sun, and mild, with temps around 60…winds will begin to shift out of the south and pick up late in the day into the evening.

Wednesday:  Will be as ugly as Tuesday is nice. Rain begins early, and persists for a while.  Surface low pressure develops in the Gulf and moves northeast across the state; the latest data has the low tracking over Birmingham as it heads NE.  On this track, the most unstable air would be limited to along and south of a line from Jackson, AL to Montgomery to Anniston; severe weather would be likely be limited to South AL and NW Florida.  However, this assumes that the computer model forecasts are correct.  The TREND for the models, which is just as important as the actual model data itself, is for the low to be somewhat slower and further west, which would open up more of the state to a greater chance of severe weather.  Regardless of the severe weather threat it is going to be a very wet, and very windy day; there is forecast to be a tremendous amount of wind energy aloft with this system, and this should translate down to the surface.

Thursday: The system will be exiting the area during the day, and a very cold airmass will trail behind it…this could be some of the coldest air of the year so far, and temperatures will struggle (and probably fail) to reach 50 in the afternoon, with very brisk north winds.  Clouds should clear late, but it would not shock me if we got a report of a flurry or two Thursday night across the Tennessee Valley before the clouds finally clear.

Friday:  Prior to about 11am this morning, this was a pretty easy forecast, but some changes in the modelling from this morning has made this forecast at least trickier…here is why.

This is output from the US GFS (Global Forecast System) model from this morning for this Friday.  The colored areas are precip over the previous 12 hrs (in this case Friday morning), the black line are lines of equal pressure (isobars) and the colored lines are the temperatures at 850 millibars (roughly 5000 ft above the earth’s surface).  Notice that most of Alabama is between 0 and -10 degrees (C) at 5000 feet with precip being recorded.  What is happening is a weak wave of low pressure is redeveloping in the Gulf, and is creating an overrunning event over Alabama.  This is the most common scenario for winter type weather generation in the south:  A cold airmass in place is overrun by warm moist air aloft which can generate various types of precipitation.  In this case, if this model is correct, we would see some sort of light wintery mix across the state during the late day Friday.  However, while there is some support from some other modelling this morning for this solution, this is JUST ONE SET OF DATA.  The first hint of this was this morning; the previous modelling holds off precip until the late weekend after we warm back up.  I am not prepared to call for winter weather in the state Friday…it’s just not very likely at all…but we will have to monitor new data as it arrives to see if these models are really on to something, or is this is just a bad run of data.  Regardless, it’s going to be cold Friday, with morning lows in the upper 20’s.

I will post more this evening if the model data lends more support to the ideas for Friday.

Jason Kelley
Fox 6 Meteorologist
jkelley@wbrc.com
Twitter: Fox6WxJason
Facebook: wxman007

Filed under: Birmingham, Flooding, Rain, Thunderstorms, Tornadoes, Winter Weather