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The January 16th, 2018, snow-maker was another installment of an active winter season across Central Alabama, including surges of arctic air and frozen precipitation. This event was a rather uncommon snow setup for Central Alabama, with temperature profiles favorable for snow arriving just ahead of the precipitation vs. cold air chasing the last bit of departing precipitation. The main uncertainty with this system was with the extent of accumulating snowfall; however, it was evident that even light snow accumulations would result in travel impacts given temperatures falling into the 20s and then 10s across Central Alabama. Due to arctic origins, snow to liquid ratios were on the higher side for this region of the country, at least 15:1 with this event.
During the morning of January 16th, a band of light snowfall moved into Northwest Alabama, and then progressed toward the I-20 corridor during the afternoon as it trended toward a weakened state. Due to limited moisture content, a trace to less than 1” of snow resulted from the band on average. At the same time, an upstream 500mb trough continued its trend of digging southward, with a lobe of energy and associated swath of higher moisture content that would ultimately be aimed on areas along and either side of the I-85 corridor. For these areas, between 2” to 4” of snow fell during the evening of January 16th and into the early-morning hours of the 17th.
Interestingly, the upper trough was still driving periods of banded snowfall as far northwest as the I-20 corridor into the evening. Here, the leading edge of drier low-level air was advecting into the area, but sufficient moisture aloft remained. Higher tilts of RADAR scans showed relatively enhanced echoes, but nothing was reaching the surface until snow broke through the dry layer. This happened very suddenly near the I-20 corridor, resulting in a quick burst of accumulating snowfall with snow rates near 1”/hour. These bands then advanced southeast toward the I-85 corridor, combining with the ongoing shield of snow.
Some portions of Central Alabama ended up bottoming out in the single digits on the morning of the 17th, and northerly breezes behind the front pushed wind chill values into the single digits and even just below zero across the board. The most significant travel impacts were along and either side of the I-85 corridor and along a stretch of I-65 in Chilton and Autauga Counties, where ice-covered roadways resulted in road closures and stuck vehicles and big rigs. Elsewhere, icy roadways were reported as well, though lighter snow totals and blowing of snow from road surfaces helped limit the overall scope of impacts.
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