UPDATE: A Winter Weather Advisory has been issued for Chesterfield, Lancaster, York, and Cherokee counties, valid from early Thursday morning through late Thursday night.
It has been a mild and wet winter thus far in the Palmetto State. The “wet” is not likely to go away this week, but enough “cold” could make the weather interesting Thursday into Thursday night.
A cold front will make a clean pass through the state by midday Wednesday. Chilly air from a high pressure area plunging south out of Canada into the Dakotas will begin to make its presence felt tonight. Temperatures are expected to bottom out in the 30s for much of the Upstate and parts of the Midlands by first thing Thursday morning, with lower to mid 40s over the Lowcountry and Pee Dee regions. A wave of low pressure forming near the Texas Gulf coast is expected to stay south of the state as it moves offshore Thursday night. Moisture from the low is likely to overspread most of the state Thursday and Thursday evening, but the question is whether the air will be cold enough for snow.
Computer model guidance has been differing on this question. Models run in the U.S. — including the “GFS” (Global Forecast System) and higher-resolution simulations that receive initial conditions from the GFS — are forecasting rain gradually changing to snow on Thursday. If these models are correct, snow is possible in the Upstate region Thursday morning, spreading to the Rock Hill area in the afternoon, and then eventually the Darlington, Dillon, Aynor, and Florence areas Thursday evening. Models run in Europe — including the “ECMWF” (European Center for Medium Range Weather Forecasting) and the Canadian global model — say little or no accumulating snow will occur, except over the mountains of South Carolina and for a brief period Thursday afternoon and early evening.
At this time, the most likely scenario is for either no accumulating snow or a light dusting on grassy areas within about 30 miles of the North Carolina state line, and for no accumulation over the remainder of the state. The worst case scenario is for 1 to 2 inches of snow in these same areas, and a light dusting as far south as the Sumter, Columbia, and Anderson areas. If snow manages to accumulate, roadway surfaces are likely to remain wet because of a warm ground. No snow is presently anticipated over the Lowcountry.
The storm producing the rain (and possibly snow) is expected to move away from the state after midnight Thursday night. In its wake will be a chilly and breezy Friday with lows in the 20s and highs only topping out in the 40s over much of the state. A few patches of black ice are possible, especially on bridges, early Friday morning, but it is not expected to be widespread. A gradual warming trend is likely over the weekend.