Showers will linger into tonight for the Upstate, while the mountains will continue to see steady light to moderate rain through Wednesday morning. Flooding is still a concern for western NC through noon on Wednesday. We should slowly dry out Wednesday afternoon before our next system arrives Thursday. The next system is a head scratcher and a real soap opera to watch on the models!
An UPPER LOW will move through Thursday, and I put UPPER LOW in all caps because it is a very tough feature to forecast! We have trouble forecast precip types with many systems, but when you deal with the dynamic processes of an upper low it can really be unpredictable. Lessons can be learned from previous experience with these beasts, and I'm trying to apply that toward this forecast, along with what the models say.
First off, an upper low is "cold air aloft" or cold air above our heads.
Here's the scenario... rain will start sometime midday on Thursday. The upper low will be approaching and temps will slowly get cooler toward late day and the evening. Heavy rain will accompany the low as it passes overhead during the evening. The heavy precipitation could help to pull some of the cold air aloft down to the surface, providing a cold enough air column for brief snow during the evening and early night hours. Surface temps would still be just above freezing in the Upstate, and near it in the mountains.
So, this could be a big ole cold rain event for the Upstate and northeast GA, or it would get interesting with some late evening snow. Either way, nothing should stick for the lower elevations as it looks now. We'll be watching for snow between 6pm and midnight on Thursday night. In the mountains we could pick up a few inches of snow out of this.
We'll be dry by Friday morning and temps should stay above freezing in the Upstate (keeping roads wet, but not frozen). Slick roads will be possible in the mountains as temps drop to the upper 20s.
My gut is telling me we'll get some brief snow or a snow/rain mix in the Upstate during the evening, given the nature of this system and my past experience dealing with these things. Upper lows are responsible for unforecasted snow events all the time! Computer models don't do a good job with dynamic cooling, so often the precip is shown as rain.
So, no accumulations are expected in the Upstate or northeast GA. Northern Upstate spots COULD see some snow accumulate on grassy surfaces if it snows long enough, but that might be a stretch. Mountains... brace yourselves for some slick roads Friday morning, and accumulations of 2-4 inches or more.
Andy, Alex and I will be watching this system evolve through tomorrow, and can give you a more confident, official forecast tomorrow evening hopefully. But even 24 hour out, upper lows are still tricky. It may turn into a nowcasting kind of event. Regardless, I don't foresee any reason to get milk and bread in the Upstate or northeast GA at this point. We'll keep you posted!