Potential Winter Storm SundayKey Points:- Fresh cold air will trickle into South Carolina Saturday night, then a storm system will arrive early Sunday to bring precipitation. There’s a chance it’s cold enough for snow, at least at the end of the precipitation or on the northwestern part of the area that sees precipitation.
- The latest computer model trends as of late Thursday evening are toward a mostly rain event, but it’s a close call and we’re not out of the woods yet. Models sometimes flip-flop, even within a couple of days of an event.
I said y’all would probably be hearing from me again sooner rather than later, and here we go (now that Verizon has its act together and I can use 2-factor authentication to access the system that composes these … been trying to send y’all of these since Wednesday morning). I wanted to get something out now that I finally can, so enjoy this waiting for you when you wake up or something to read during the downtime of your graveyard shift. We’re at risk of seeing a winter storm on Sunday, though nothing is set in stone yet due to uncertainties. First, let me set the table for the potential Sunday snow dinner: - Winds are diminishing tonight, but aside from a bitterly cold morning, Friday won’t be as harsh as Thursday was.
- Another cold front will move through late Friday night into Saturday morning, causing a period of light rain in the Upstate. It may be cold enough for snow north of Highway 11, but you’d have to be on a high spot for a chance at an accumulation.
- Reinforcing cold moves in behind the front for Sunday, and the front will turn stationary along our coast late Saturday night.
This Weather Prediction Center weather map for Saturday evening shows a cold front moving through South Carolina and precipitation breaking out along the Gulf Coast. Here are the uncertainties for Sunday’s storm: - We know a storm will track along the front, moving along the Gulf Coast and then along our coast late Saturday night through Sunday. However, the storm could track farther inland or farther offshore, which will affect where the heaviest precipitation falls.
- The storm’s intensity is uncertain; a stronger storm would lead to more widespread and heavier precipitation.
- We’re not sure how well the cold air will penetrate South Carolina; it may not be cold enough for snow in areas where significant precipitation falls.
- Even if it snows, the storm will mostly occur during the daytime, which makes it harder for the snow to stick.
To illustrate the point, here’s output from one of the computer models, the GEFS (Global Ensemble Forecast System). It’s an ensemble model based on our GFS model. The GFS is one of the ensemble members, and the other members are the same model run with 30 slightly altered inputs, for a total of 31 variations. That simulates potential input errors. It also allows us to see the range of possibilities with an upcoming weather event and to gauge how well the model is performing. 
Total snowfall to forecast hour ending at 7 a.m. Monday from the GEFS using weather observations from 7 p.m. Thursday as the model’s starting point. Image Source: WeatherBELL The late-breaking information is that the overnight model runs available as of 11:30 p.m. Thursday (my bedtime!) show more moisture available but less cold air, resulting in not much snow in the Palmetto State on Sunday. We’re not out of the woods yet, but this trend favors snow haters. We’ll have the rest of the overnight models available when we wake up Friday morning, and the next round of models will start trickling in by late morning. You can see that there is a wide range of possibilities, ranging from little or no snow in the state to a part of the state receiving a significant snowstorm. Also, this is just one model. There are also models from Canada, Europe, the United Kingdom, Japan, Korea, and others to consider, plus a few newfangled artificial intelligence-based models. Meteorologists spend a ton of time looking at computer model output! As we get closer to the event, we’ll be able to start nailing down more details. The picture usually steadily improves once we’re within 72 hours of the event, as we are now. But we can say that the risk is there. Also, chilly days behind the storm, should it come to pass, could mean it takes a couple of days for the snow to melt. So, you’ll want to think about getting ready. That does not imply a stampede toward the bread and milk aisles of your favorite grocery store (though if you need bread or milk, buy it; even if it doesn’t snow, it seems milk sandwiches are haute cuisine according to YouTube). Start by reviewing SCEMD’s SC Winter Weather Guide, see which preps fit your situation best, and go from there. Frank Strait
Severe Weather Liaison
S.C. State Climate Office | 
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