Rapidly changing weather situation over Alabama this afternoon. The atmosphere is a little bit colder than we thought, probably because the precip got here faster than expected (evaporational cooling aloft initially overwhelmed everything else) and there was no sunshine. The one type of precipitation I did not expect, snow, fell heavily in many parts of BHM, making the ground white, over the past hour or so. However, now that the precip has continued, some of the warm air aloft is working its way down, and the precip here in Trussville is now mainly freezing rain (rain that falls and freezes on impact, causing ice accumulation). Ice is already accumulating on elevated surfaces now, and bridges will become icy very quickly…some already are even in the Birmingham area. Multiple accidents have already been reported. Even non-bridge roadways may have some ice on them, due to the cold temperatures last night.
Temperatures are below freezing pretty much everywhere in central Alabama, with 28 at BHM airport, 30 in Trussville, and 28 in Hoover. With more precipitation developing in east Mississippi, this could become a serious icing situation this afternoon (not that it’s not already on some bridges and roadways).
Leaving work early today is a very good idea. However, since this has come in so fast, it’s a little like 1982, and roads already have some ice on them. Please drive very carefully on the way home. Leave plenty of distance between you and the car in front of you, go slower than normal, and use common sense.
As for tonight’s heavier precipitation, we are still unsure as to exactly what will happen. I have had a discussion with Dr. Kevin Knupp, who has expertise is in cloud physics, and even he doesn’t know how this will all play out. We have competing physical processes here…with warm air coming in aloft, the raindrops will fall at 32-35 degrees, bringing some warmth down with them. However, our surface winds remain out of the north, bringing in cold, dry air. We should eventually make it above freezing late tonight/tomorrow morning sometime, depending on where you are (earlier SE, later NW), but it is possible that significant icing will occur before then, and some power outages are possible.
