A slow moving upper level low pressure has the potential to bring snow to most of the Carolinas on Tuesday evening through Wednesday.
A large scale upper level trough is digging across the central United States. At the surface, a cold front will push across the Carolinas Tuesday, bringing cooler temperatures Tuesday night. Behind the front, the upper level trough will strengthen and the jet stream will begin to sharpen, allowing for upper level divergence to increase east of the mountains.
Snow is expected in the mountains Tuesday afternoon with the foothills and I-77 seeing snow around midnight. The snow continues to push eastward through the morning hours, reaching Raleigh around daybreak. A rain/snow mix is possible in the piedmont before changing to snow for most areas. Snow will taper from west to east on Wednesday.
Southern counties of NC may be too warm for snow; however, I would not be shocked to see a rain/snow mix in this area.
The system will be extremely slow moving, with most models keeping the band of moisture over the central and eastern parts of the Carolinas through Wednesday afternoon.
This is a very complicated and difficult storm to forecast. There are numerous variables that can occur as we move east of the mountains and models continue to differ on the total precipitation.
The NAM computer model has the highest precipitation totals with the GFS having the lowest precipitation totals. The GFS Ensemble is a good middle ground, and that is what I will use as the basis for my forecast.
The image below is the NAM, GFS, and GFS Ensemble 18z runs on Monday evening.
There is moderately high confidence (60-80% chance) that a winter storm will affect the Carolinas Tuesday evening through Wednesday.
The greatest questions remaining are the amount of moisture involved, the strength and the exact track of the upper level low, and the set up of any mesoscale features.
The confidence level on the snow accumulation map below is low (20-30%). Confidence will increase as the day progresses on Tuesday.
I will continue to monitor the latest trends and I will keep you updated on my Facebook page, WxJordan.