Lets use this space tonight to be specific about the storm system that will impact the Deep South Friday night and Saturday morning. The computer models are now in relatively good agreement, making for a reasonably high confidence forecast. Of course, having said that winter weather forecasting in Alabama is very difficult, and some changes in this scenario might be needed.

Rain should enter West Alabama Friday evening, sometime between 4:00 and 7:00 p.m. Rain should become widespread by 9:00 p.m. For communities in extreme North Alabama (the Tennessee Valley), the precipitation should begin as a wintry mix, and change to all snow before midnight.

As colder air pulls in behind a surface low that will move from near Mobile to Dothan, the rain should change to snow over the central part of the state during the night. For the I-20 corridor, including Tuscaloosa, Birmingham, and Anniston, we believe snow accumulation POTENTIAL of 1 to 2 inches is possible from about midnight through 6:00 a.m.

There could be a band of heavier snow accumulation (over two inches) near U.S. 278, or along a line from Hamilton to Cullman to Gadsden. The ultimate track of the surface low will determine where the strip of heaviest snow will fall, and that strip is only about 20 to 40 miles wide in most cases here in Alabama with winter storm events. It is very hard to nail down that strip more than 24 hours in advance.

We need to mention that the models are suggest liquid equivalent amounts of about 3/4 inch with this system from 9:00 p.m. tomorrow through 6:00 a.m. Saturday; if by chance that all falls as snow some spots could see 7 inches. But, we don’t expect that to happen, and for now we will go with the more conservative forecast based on a large part of that 3/4 inch falling as rain.

As always, a few surprises are likely with any kind of system like this. And, of course, this forecast is subject to change.

Very cold air settles into the state for the weekend, and temperatures could reach the teens both Sunday and Monday morning. Stay tuned!

TENNESSEE
Nashville...32, light snow, visibility 1 mile
Clarksville...34, light snow
Smyrna...34, light snow, visibility 1 mile
Knoxville...34, light snow
Oak Ridge...34, light snow
Chattanooga...37, light rain
Fort Campbell (Ky.)...32, light snow

NORTH ALABAMA
Huntsville...41, light rain
Decatur...42, light rain
Meridianville...41, drizzle (north of Huntsville)
Fort Payne...37, light rain
Cullman...37, rain

* One to two inches of snow expected tonight across the Cumberland Plateu of East Tennessee, places like Crossville.

* One to three inches expected in the Smoky Mountain counties, with 4 inches in the highest elevations.

The Wednesday afternoon map discussion video is on the server:

http://beta.abc3340.com/weather/video.hrb

J.B. Elliott has lost Internet service this afternoon... hopefully he will be back on with us tomorrow. I am writing the afternoon forecast package that will be posted over on the seven day discussion page along with this blog post. Lots to disuss...

THIS EVENING: Our clipper is producing light rain over parts of North Alabama this afternoon. I would imagine some of this is beginning to reach the ground... but not all of it. We will continue to mention the chance of a few sprinkles this evening, and flurries later tonight. Dry air near the surface should keep this system from getting out of hand.

GFS JOINS THE PARTY: I have been concerned the American models didn't recognize the potential for an early weekend storm system in recent days. Well... the GFS is now on the same page with the rest of the global models, and is forecasting a significant storm to form near Mobile Friday night.

FRIDAY NIGHT: I think we will deal with a soaking rain at the beginning of the event, perhaps something similar to this past Monday. Rain should begin to fall sometime between 6:00 p.m. and midnight Friday night. Then, as the surface low moves from Mobile over to a point near Dothan, there is a chance that the rain could change to snow over North Alabama overnight, sometime between midnight and 6:00 a.m. Saturday.

Lets take a look at the 00Z model data before we get too specific here. Is there a chance of accumulating snow over North Alabama? Yes. But I am not ready to jump on that with the GFS just now seeing the setup.

**I need to note the new 18Z NAM just into the office is colder than the GFS for Friday night. But, the GFS was more accurate with Monday's system**

WEEKEND CHILL: There is no doubt this will be the coldest air so far this season rolling here this weekend. Who was that forecasting highs in the 50s for the weekend a few days ago? That 50s/30s thing in the longer ranges rarely works this time of the year.

Saturday will be windy and cold with temperatures in the 30s much of the day. We should drop to near 20 degrees early Sunday, with teens possible in colder spots. Sunday will be dry but cold; the GFS MOS, my usual enemy, is actually forecasting a high of only 36 degrees for Birmingham now. The 540 line extends southward into South Florida. This is a very cold airmass. Sure looks like we go into the 15 to 19 degree range early Monday morning.

We begin to dig out of the deep freeze early next week, but I still say the rest of the month will be colder than normal with more threats of wintry weather down the line.

I enjoyed speaking at Career Day today at Pelham High School... good to see my pal Jeff Speegle there as well. I need to write the afternoon discussion now for the seven day page along with the forecast update; that should be ready by 3:30 or so...

I will try to post some additional notes here this evening as new data rolls into the office..

The 12Z GFS run now understands the situation for Friday night/Saturday... it develops a wet storm near Mobile. This is the solution I have been waiting for, and sure looks like we will have to ramp up the chance of precipitation Friday night into Saturday morning.

Looks like the surface low runs from Mobile to Dothan... not really unlike Monday's storm.

Snow or rain?

First glance looks like we might have a soaking rain Friday night with a change to snow on the back side of the storm Saturday morning. But that is sure not set in stone...

Now that the American models understand the situation we can deal with it with a little more accuracy.

I have to run handle the career day duties at Pelham High School, and will have the video with a full post here by 3:30 on the situation. Should be very interesting reading.

Below freezing over most of the state. These lows are from official stations, 3340 WeatherWatchers and amateur stations

18 in Rainbow City (plenty of free hot chocolate for everyone)
21 in Pinson, Gadsden and Fort Payne
22 in Alabaster, heavy frost (Low for all of February last year was 25)
23 in Cullman, Helena and Gadsden
24 in West Hueytown and Vinemont (North Cullman County)
25 in Huntsville, Anniston and Tuscaloosa
26 in Muscle Shoals, Troy, Decatur, Birmingham
27 at Desoto State Park
28 in Auburn, Evergreen, Montgomery and at Shelby County Airport
29 in Mobile
30 in Selma

The Wednesday morning map discussion video is on the server:

http://beta.abc3340.com/weather/video.hrb

I love these days of difficult forecasts... I would much prefer this to the long, hot days of summer where our daily forecast doesn't change much from June through August.

TODAY/TONIGHT: Our system coming down the back side of the long wave trough over the eastern U.S. will bring clouds today, and the risk of some sprinkles this afternoon and flurries tonight. As usual with a "Clipper" type system, it will be starved for moisture and the precipition probably won't amount to much. The 06Z NAM shows a whopping 0.02" of liquid equivalent with this system.

TOMORROW: Lots of sun, but cold. Highs in the 40 to 45 degree range.

FRIDAY NIGHT: An Arctic front moves through here, and the models are now showing enough moisture for some light rain or light snow with the frontal passage between 6:00 p.m. Friday and 8:00 a.m. Sunday.

WEEKEND: There remains a great deal of uncertainty over events Friday night and Saturday. It all involves some energy coming out of Mexico in the sub-tropical jet, and most models have no idea what is going on.

Will the energy simply enhance the precipitation with the frontal passage Friday night and early Saturday morning?

Or, will the energy form a wave on the front Saturday when it is on the Gulf coast and run a low from Mobile to Augusta?

Or, will the energy pass to the south and not phase at all with the Polar jet?

Ah, questions with no really good answers.

For now we will go with chance of light rain or snow Friday night, and a chance of some light snow Saturday morning, and adjust the forecast as needed. I think the telling model run will be the 00Z versions tonight...

One way or another, the weekend will be COLD. If we have a clear sky Sunday morning, look out for teens around here.

LONG RANGE: I still believe temperatures will stay colder than normal, generally speaking, over much of the Deep South through the rest of February. We have the usual model madness... details are impossible to deal with here.

TODAY: Headed out to the annual career day at Pelham High School... I will do two sessions for them. I will be back in the office for the afternoon video feed should be posted by 3:30.

WEATHER BRAINS: We taped our second version of the Weather Brains podcast last night... David Black has it finished and I will post it over on iTunes and the Weather Brains web site within the hour:

http://www.weatherbrains.com/

This week's topic is winter weather forecasting!

STORM ALERT 2006: We will see you tomorrow night at 7:00 at Homewood High School for Storm Alert 2006... this is the only Birmingham metro show this year!