We continue to track a winter storm system that's slowly approaching. We'll remain on the warm side of the system through Wednesday night with highs in the 70s most places. Off and on showers and even a few storms will be possible during that time frame.
Cooler air filters in from the northwest overnight and lagging precipitation behind the cold front will changeover to freezing rain and sleet. The greatest accumulation and travel impacts are expected across the counties under a winter storm warning including, Marion, Lamar, Fayette, Winston, Walker, Cullman and Blount counties.
Counties to the south and along the I-59/I-20 corridor are under a freezing rain advisory from 3am Thursday through 3pm Thursday.
TIMING THE POTENTIAL CHANGEOVER:
The air will be colder for a longer period of time across the counties under a winter storm watch which means a greater threat for accumulation and problems developing on roadways. Farther southeast, the biggest concern may set up on elevated surfaces and above 1,000 feet elevation where the air will be at or below freezing first and for the longest. Remember, we are coming off of a very mild stretch so it's going to take several hours below freezing for precipitation to really become an issue.
MARION, LAMAR, WINSTON, WEST FAYETTE, WEST WALKER AND WEST CULLMAN COUNTIES:
- Freezing rain and sleet arrives mainly after 3AM.
- First across the higher terrain and then down to the lower elevations by 6AM Thursday.
MARION, LAMAR, WINSTON, FAYETTE, WALKER, CULLMAN, & BLOUNT COUNTIES:
- Freezing rain and sleet arrives as far south as Blount county to Pickens
- Greatest threat for icy spots at higher elevations.
- We'll likely see the mixed precipitation impacting parts of the I-59/20 corridor after 9am and especially by noon.
- Elevated surfaces will see the best chance for possible slick spots
- A glaze may form along the higher terrain with even some sleet possible
ALONG AND SOUTH OF I-20:
- A rain, freezing rain, sleet mix will be possible
- Mainly at higher elevations
- Isolated slick spots can't be ruled out
- Light amounts
HERE'S WHAT'S HAPPENING IN THE ATMOSPHERE REGARDING TEMPERATURES AND IMPACTS ON PRECIPITATION TYPES:
- The air at the surface may be above freezing resulting in just rain
- Above 1,000 feet it will be below freezing resulting in freezing rain or sleet
- So that's why higher elevations are at a greater risk for ice than lower elevations
- Remember that snow will be falling through a warm layer and melting and then either having time to freeze into a glaze on surfaces that are below freezing or having time to freeze back into ice pellets called sleet.
ICY PATCHES ON THURSDAY:
- NUMEROUS IN RED
- SCATTERED IN ORANGE
- ISOLATED IN YELLOW
We are going to continue working on this tricky accumulation of freezing rain and sleet forecast. The heaviest sleet looks to set up for counties under the watch. Perhaps 1" at quick glance, especially across Marion and northwest Winston counties. First on elevated and grassy surfaces. Freezing rain amounts could range from as low as a tenth of an inch to a quarter of an inch. Due to gusty winds and the threat for freezing rain, power outages will be possible. I don't think a widespread threat, but enough of a threat that you should prepare for it.
Ok that's the scoop so far.... We are going to continue to look over data and fine tune the forecast.
Jill Gilardi Fox 6 Meteorologist