Update (01/10/18, 8:23 p.m.) — The National Weather Service has bumped up its start time for this weekend's minor wintry weather event, but is still forecasting only limited accumulations for the northern Cumberland Plateau region.
With its afternoon forecast package, the NWS is now forecasting the transition from rain to snow to begin at 8 p.m. Friday evening, becoming all snow by 10 p.m. The NWS is forecasting an 80 percent chance of snow Friday night and a 50 percent chance of snow Saturday.
In a forecast discussion this afternoon, the NWS's Morristown weather forecast office projected about an inch of snow accumulation for the northern plateau region.
The GFS model continues to show about an inch of snow for the plateau, in line with the NWS's forecast. And, in a major shift, the model is no longer showing significant accumulations in portions of the state to our west. The NAM model has shifted its heaviest accumulations back into West Tennessee, in the Mississippi River Valley. It does have a band of snow setting up further east with several inches of snow, but keeps it west of the plateau. It is showing less than an inch of accumulation for the plateau. The Canadian model is now showing the heaviest accumulation in extreme West Tennessee as well, with an inch or less for the plateau. So there seems to be a model consensus developing.
All in all, it looks like a very minor winter weather event. It will be our most snow of the season, if it pans out, but that's not saying much. However, with temperatures crashing rapidly late Friday, there will likely be slick spots that will develop on the roadways. Temperatures will only get into the mid to upper 20s on Saturday, so some slick spots could persist in shaded areas on untreated secondary roads throughout Saturday and into Sunday.
There have been questions asked about the championship and consolation games of the Scott County Middle School Basketball Tournament, which are scheduled to begin at Scott High School at 1:30 p.m. Saturday. Chances are, roads will be in pretty good shape overall — with state highways being clear — by that point. However, that doesn't mean that some slick conditions won't exist on secondary streets and backroads.
The original post follows...
Confidence is growing that the northern Cumberland Plateau region will experience its first accumulating snow of the season late Friday into Saturday, though amounts still look relatively minor — for now.
The National Weather Service is currently forecasting an 80 percent chance of rain changing to snow Friday night, and a 60 percent chance of snow Saturday. The NWS places the changeover time at around 3 a.m. Saturday morning, meaning anyone who has Friday plans should be in good shape — though this is a dynamic and rapidly changing situation.
The NWS still isn't mentioning accumulation amounts, which isn't surprising at this range. However, in a forecast discussion this morning, the NWS did offer this: "At this point, it looks like most of the area will see at least a dusting of snow with higher amounts across the Plateau, southwest Virginia, and the mountains — but will continue to fine tune this as the event approaches."
The NWS office in Nashville, which covers the western side of the plateau (Crossville, Jamestown) was predicting general totals of 1-2 inches yesterday, but does not mention specifics in its overnight forecast. Instead, meteorologists there had this to say in this morning's forecast discussion: "It is looking more and more like an accumulating snowfall event will occur across the mid state region Fri into Fri night. However caution still needs to be given to amounts, as a quick turnover from liquid, to freezing, to frozen pcpn will more than likely occur, but specifics this far out still hard to pinpoint."
I blogged yesterday that this was looking like a bonafide winter storm for parts of West Tennessee and western Middle Tennessee, and more of a nuisance event this far east. Things are changing, however. While most forecast models do not show significant snowfall this far east, the system is shifting east in general, and Middle Tennessee is now in the bullseye.
As of now, it looks like the actual low pressure system will be too far west for the plateau to receive significant wintry weather. At the moment, it looks like the storm center will move directly up the Tennessee Valley. That will cause quite a dramatic shift in temps from west to east across the state on Friday. Knoxville could be more than 30 degrees warmer than Nashville for much of the day, before the storm system lifts northeast and cold air shifts eastward. As a result, Middle Tennessee could receive wintry precipitation throughout the day on Friday — including freezing rain and sleet before an eventual changeover to snow — before things start to get dicey this far east.
Currently, there are fairly significant differences between the NWS's forecast offices in Nashville and Morristown. NWS-Morristown is forecasting a rain-to-snow transition around 3 a.m. Saturday morning in Oneida, while NWS-Nashville is forecasting rain to begin transitioning to snow and perhaps freezing rain between 9 p.m. and 11 p.m. Friday evening.
As for what the models are showing, we remain far from a consensus. The GFS model has actually reversed its eastward trend of the storm's placement and has moved the heavier snow totals back west. It is generally showing an inch or less of snow for the northern plateau.
The NAM has also shifted back to the west and is showing less than an inch of snow for the northern plateau.
The Canadian model is showing an inch or so of snow for our region, with a localized area of higher snowfall just to our northwest.
The European model is currently a fairly significant winter storm for the Cumberlands.
All models are in agreement with keeping significant freezing rain well to our west.
The bottom line, for now, is it looks like the low placement will be much to close for our region to see significant snowfall, but there are a ton of uncertainties that remain with this system. As precipitation begins to move out late Friday night, it looks like a changeover to snow will occur, and the cold air advection over the terrain change of the plateau should help influence ongoing snow showers on Saturday. We may not see a lot of snow, but it won't take much for this to be our biggest snow of the season — we've seen only a trace thus far.
I'll update this post this evening.
Eye to the Sky is a weather blog by Independent Herald editor Ben Garrett. Garrett is a weather enthusiast who has long blogged about interesting weather on his personal website. He is not a professional forecaster or a meteorologist and information on this blog should not be considered a substitute for forecasts, advisories or other products from the National Weather Service.