Wintry Precipitation Wednesday and Again on Friday

By Jim Stefkovich, Meteorologist, Alabama Emergency Management Agency
CLANTON – It will be cold, cloudy and wet through Saturday morning for much of Alabama. As of Wednesday morning, there have been reports of sleet near the I-20 corridor including Tuscaloosa and Birmingham. Some more wintry precipitation is expected on Friday in central and south Alabama in the form of rain mixed with snow.
Let’s first briefly explain the “typical” atmosphere and how you get different types of winter precipitation. Look at the chart above to understand how each of these form.

For sleet, the precipitation falls in an area of temperatures above freezing, then encounters temperatures below freezing. In essence, the rain freezes to form sleet. But, Alabama winters and the atmosphere above our state are rarely “typical” for winter events that others across the US experience.

That’s why we are experiencing sleet today even though temperatures at the ground are above freezing. However, just above the ground, temperatures are below freezing and the sleet doesn’t have enough time to melt before landing. The good news is that no accumulations are expected, due to the warm surface temperatures.
From Friday morning through late Friday night, a mixture of rain and snow will occur as far south as the Mobile region. However, any chance of accumulation is within the National Weather Service Birmingham area, and I’ve included that graphic below.

0113EE91-D647-4871-A63A-72892BBCE000

Even though temperatures will remain above freezing on Friday, the upper atmosphere is cold enough to produce snow and not totally melt before reaching the ground. Surface temperatures will drop below freezing across the region by early Saturday morning, so any accumulation/wet roads have the potential to re-freeze, especially on elevated surfaces.

Exact locations and accumulations of winter precipitation in Alabama is very complicated and subject to change, and this event is no different. Thus, there is likely to be some changes to this forecast over the next 24-36 hours. More to come about this unfolding event!

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