I don’t think I have ever seen so much of the country under a Winter Storm Warning in my 29 years in meteorology! This Arctic air mass just never quits. Check out 3 am temperatures. 34 here in BHM, but 30 in HSV, 30 in Meridian, MS, 21 in Natchez (with snow), and 31 in Baton Rouge (with freezing rain). Memphis has snow with 14 degrees.
The big upper system is digging in and a low is forming in the Gulf, bringing precipitation into the southeastern US.
Note the heavy precip near Baton Rouge and New Orleans…a lot of that is sleet and freezing rain…same near Jackson, MS and approaching Columbus, MS. Up near Memphis it is all snow. The low will continue to develop tonight, bringing more widespread precipitation to MS and AL. It should reach western AL by 5:00 am, and BHM by 9:00 am. Temperatures are key, as the air over most of MS and AL is too warm aloft for snow, but instead it will fall as rain then either refreeze before reaching the ground (sleet) or freeze on impact forming ice glaze (freezing rain). This will likely be a major ice storm from northern LA through central/eastern MS and northwest AL, with trees going down and power outages during extreme cold.
But, low pressure areas tend to follow temperature gradients, and the Arctic air has gotten so far south into Mississippi and Louisiana that it looks like the Gulf low will track more northeast than east, allowing warmer air to flow into central and eastern Alabama just above the shallow Arctic surface air, out ahead of the low. Winds are already out of the south at just 3,000 feet over central Alabama according to VAD wind profiles from the NWS Doppler Radar at Calera, AL at 3:00 am. Note the surface low position at 21Z (3 pm CST)…near Gadsden. Not at all classic for a winter storm in central Alabama. More for one in Mississippi and northwest Alabama, where the Winter Storm Warning is.
Things could still change, as we are dealing with a shallow, extremely cold air mass (20 degrees and snow in south MS?). But it looks like warm air will flow into Tuscaloosa, Birmingham, and even Cullman just above the surface. With any wind mixing, plus rain drops bringing warmth to the ground, temperatures will probably stay steady or rise today, maybe as high as 40 degrees, as rain moves in. In northwest Alabama, and especially back into Mississippi and Louisiana, up to 0.5″ of ice will accumulate.
The big problem here in Birmingham could be Monday night and Tuesday, when temperatures will plummet below freezing by sunset, and into the upper teens by morning. Any water left around from the rain will freeze quickly, forming black ice on roads and causing traffic problems Tuesday, especially in the morning hours. It will stay very cold on Tuesday (maybe below freezing all day), with wind chills Tuesday morning near 10 at times. It looks like we will finally start to get out of this Arctic air, as it continues to spread out and slowly modify, by next weekend.
Dr. Tim Coleman
Coleman and Knupp, LLC