After midnight and early Christmas Eve, a powerhouse cold front will sweep through North Alabama. Expect heavy rain with embedded thunderstorms. Regardless of any storms wind gusts with the front could peak at 40-45 mph.
Around sunrise, the temperatures crash from the 40s to the 30s very quickly.
Towards the tail end of the precipitation, several snowflakes are possible in north Alabama on Christmas Eve morning. The best chance will be in northeast Alabama over the higher elevations. Accumulations, if any should be a coating at most on grassy areas.
For the last few days models have been keying in on a second round of snow showers in the afternoon and evening Christmas Eve. One area of note will be areas downwind of Wheeler Lake and Tennessee River. A highly localized narrow snowband could develop: this would be a lake effect snowband. The water is still near 50°F and air just a couple of hundred feet off the ground will be 20°F. Northwest winds could line up perfectly with the shape of the lake/river. This wind fetch over 30+ miles of water fluxes heat/moisture off the lake into a narrow band of air. That air must rise because it is significantly warmer/less dense than the surrounding air. This creates a snowband, similar process as an afternoon thunderstorm in the summer.