Ice update – 1141 am
…FREEZING RAIN ADVISORY IN EFFECT FOR CENTRAL ALABAMA INCLUDING BHM…TCL…ANB…
Rain showers are increasing on radar at this hour across parts of Alabama and Mississippi. Much of the rain you see on radar over Alabama is not hitting the ground yet but evaporating aloft, due to the dry atmosphere in place. But, as rain continues to move in, the atmosphere will saturate this afternoon in some places, allowing this rain/sleet/snow mixture to reach the ground. Since it is showery and not solid, it’s hard to say exactly where this will happen.
Here is the problem. Surface temperatures are around 30 degrees over central Alabama, and the ground is cold, especially elevated surfaces like bridges, after the low in the 20s with wind last night. Aloft, temperatures are above freezing. Here is the balloon data from NWS Calera.
Nptice how temperatures at 850 mb (5,000 feet) are way above freezing (actually in the 40s). This is causing most of the snow to melt aloft, and fall as either rain or sleet. Sleet we can deal with better, but any that falls as freezing rain will begin to accumulate as ice on surfaces, especially bridges, etc. It’s hard to say exactly where or when this will happen, but precipitation is already reaching the ground in some spots, and precipitation will keep coming through the afternoon.
The NWS feels that light ice accumulation will occur in some spots this afternoon, causing possible road icing. So, people may want to consider going home early, before this gets going. We are not expecting a major ice storm, since the very warm temperatures aloft will probably work their way down to the surface and get us above freezing late tonight. But, between now and midnight or so, scattered ice accumulations will be an increasing problem.
Category: Alabama's Weather