Thursday, December 23, 2010

White Christmas in Alabama?







It is really funny how we get all worked up at the prospect of getting a dusting of snow on Christmas here in Alabama. It seems to be on everyone's mind and in conversations from the water cooler at work all the way to the last minute shoppers at the mall. It's possibly more discussed around here than when the Storm Prediction Center issues a High Risk for severe weather. I guess we Alabamians can be excused, though. Official records in Birmingham, which date back to the late 1800's, reveal that there has never been a true White Christmas (defined by 1" of snow on the ground on Christmas morning). The most snow I remember seeing on Christmas in my lifetime was a dusting on cars and rooftops in Huntsville many years ago.

The system approaching does not appear to be a classic snow-maker for Alabama. Snow in Alabama usually comes in one of three general ways:

1. A cold front moves through and a few flurries or snow showers occur in the cold air after frontal passage in the backwash from the low pressure to our north. This usually results in no accumulation or at most 2" in higher elevations.

2. An upper level low pressure system moves in from the northwest into an existing very cold air mass in place over the state. Usually this results in snow showers that can be briefly heavy. The snow is usually dry and accumulations are usually light (dusting to 1"). Occasionally these systems can tap into enough moisture to surprise a small geographic area with higher accumulations 2-6", but that is very rare.

3. A deep cold air mass is in place over the South while at the same time a low pressure system develops in the Northwest Gulf of Mexico. The cold air has to be deep and well-supported from the north. The low has to be positioned just right, track through the Northern Gulf, and strengthen rapidly. When this scenario phases up just right, Alabama can experience some major snowfall totals. This is the most "ideal" yet rarest scenario for snow in the South. Two examples include Huntsville receiving 21" of snow in 1963 (leading the nation on New Year's Day) and the Blizzard of 1993, which was the textbook example of this scenario. There have been numerous times when I have witnessed 6 or more inches of snow at various places in Alabama and most of them occurred in this kind of set-up. These storms are most likely in January, February, or early March.

Saturday (Christmas Day) will probably most resemble scenario number one. Confidence is high that snowflakes will be in the air in North Alabama on Christmas Day as temperatures will be cold enough to support snow thousands of feet up into the atmosphere and at the surface. Confidence is low that there will be enough moisture to support much, if any accumulation south of the Tennessee River.

No one really knows what will happen, but it is fun to look at the models, sprinkle in a little common sense that comes from many years of watching Alabama weather, and take an educated guess at what might happen. So, a little over 48 hours out, I am predicting a slight chance of very light accumulations roughly north of a line from Hamilton to Anniston. The best chance of light accumulation will be in Northeast Alabama. A dusting is most likely there, but a few of the higher elevations have a slight chance of getting 2 inches.

Bottom line: Snow will fall in North Alabama on Christmas Day, but it will not be significant enough to cause many serious problems. A few communities may be lucky enough to see snow on the ground and may get about as close to a White Christmas as most Alabamians have been in our lifetimes.

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1 comment:

Anonymous said...

Well, it happened! Beautiful White Christmas in Gadsden, AL. I would like to know when the last time in the history of Gadsden, AL. did it ever have a White Christmas. If anyone can help, email me at kayleepitts@rocketmail.com.