A wintry mix in the forecast for Sunday night grabs the headlines, but most of the day Sunday in and of itself looks chilly, breezy and dry. The afternoon will feature another slight warm up, with highs for most of the Valley pushing into the low 40s for the first time this year.
By Sunday evening showers will be moving into Alabama and Tennessee. Areas west of I-65 could see light rain by 9PM. Most of the rain will hold off until the overnight hours as temperatures drop to near freezing, which will set us up for a wintry mix through Monday morning. Because some minor accumulations are possible a Winter Weather Advisory has been issued for Jackson, DeKalb, Cherokee, and Etowah Counties in Alabama and Franklin County in Tennessee. The advisory will go into effect at midnight and last through noon Monday.
Wintry Mix and The Potential for Ice – A wintry mix means we could see some light rain mixed with light sleet or freezing rain. A few of us could even end up seeing a brief window of light snow.
The reason we’ll likely end up with a messy mix of light rain and freezing rain is a shallow layer of ‘warm’ air about 500 to 1500 above the surface. This will probably melt any snow that would form into liquid rain, but with temperatures near or at freezing at the surface this liquid could refreeze as sleet or freezing rain. A mixture means smaller accumulations of snow and sleet alongside some rain; it may not be a winter wonderland Monday morning, but you may still have to endure some short-term icy conditions to start the week.
As the mix moves east, it has a better chance of accumulating especially in the higher elevations of Jackson, DeKalb, Etowah and Cherokee Counties of North Alabama and Franklin in Tennessee. These are the counties that will be under the Winter Weather Advisory from midnight through noon on Monday. Morgan, Madison, and Marshall Counties in Alabama and Lincoln County Tennessee are not currently under the advisory, but a few degrees could make the difference between a cold rain and minor ice accumulations.
A side note: if the warm layer is too thick, it will all fall as rain and become freezing rain in areas where temperatures are 32ºF or lower. If that is the case, some areas of Madison, Morgan, Marshall, DeKalb and Jackson Counties could get more than 0.10″ ice accumulation: enough to cause some power outages.