The National Weather Service has increased its Wednesday night snow forecast for Scott County to a half-inch to one inch of accumulation. Earlier today, the NWS was forecasting only 0.1 inch to half an inch of snow for Scott County and the northern plateau region.
The NWS’s change comes as some modeling data shows more snow accumulating than had previously been shown. Specifically, the HRRR model, a typically reliable (but sometimes wrong) short-range model is showing 3 to 4 inches of snow accumulation for much of the northern Cumberland Plateau region on its latest run. That is in line with the lower-resolution GFS computer model, which had shown appreciable snow accumulation for the region on previous runs and continues to show the same on its more recent runs.
It’s important to keep in mind that snow accumulation projections on both models are likely significantly overdone. However, the HRRR’s increasing snowfall projections lends some credibility to what the GFS has been showing, and suggests that there might be more moisture to work with Wednesday night than had previously been anticipated.
Other models, meanwhile, continue to show very light snow accumulations for the northern plateau region. That includes the ECMWF, a European counterpart to the American-maintained GFS, which is showing generally less than an inch of snow for the plateau region, with greater amounts in upper East Tennessee.
The NWS has issued a Winter Storm Watch for the mountains but has not issued any sort of watch or advisory for the plateau, and it isn’t clear that it will. In Tuesday afternoon’s Forecast Discussion, meteorologists at the NWS’s Morristown office did not take a stab at potential snow totals for the region, except to say that “significant snow accumulations” of four or more inches are possible in the mountains, where the Winter Storm Watch has been issued.
Temperatures will generally be in the 40s on Wednesday — perhaps even getting into the 50s in the valley — after a few very mild days of late. So, ground temperatures will be warm, and that should help limit the potential for widespread travel hazards Wednesday night. However, with temperatures dropping well into the 20s before daybreak on Thursday, it’s certainly possible that isolated to scattered trouble spots will develop, especially on bridges and overpasses. But, as the NWS pointed out in a Hazardous Weather Outlook Wednesday afternoon, “much of the snow accumulations will mainly be over the grassy and elevated surfaces.”
The Wednesday night system will be a quick-hitter, and snow may fall only for a couple of hours or so once the changeover from rain occurs. The latest run of the GFS shows nearly half an inch of liquid-form precipitation, but much of that occurs as rain before temperatures drop below freezing throughout the lower levels of the atmosphere.
Behind the departing system, Thursday will be a raw day with temperatures struggling to rise above freezing.
Another cold front will approach the region towards the end of the upcoming weekend, delivering a couple of days of cold weather to begin next week. Some light snow is once again possible on Monday and perhaps on Tuesday. However, the latest run of the GFS has come in somewhat warmer and also drier than previous runs. Currently, it looks as though temperatures on Monday and Tuesday may top out in the mid to upper 30s.