First, a disclaimer: this is NOT the final word on the forecast for this weekend and early next week. The storm system that will bring rain, freezing rain, sleet and snow to Middle Tennessee and southern Kentucky is just now starting to get itself organized…we’ve got 48 more hours of new computer runs, new analyses, and new forecasts before things really get complicated in our neck of the woods.
That said…things are looking messy.
First, the rain. Showers and a few thunderstorms will spread out and intensify throughout the day on Thursday the 5th. Severe weather isn’t a great concern, although a few incidences of gusty winds will be possible in southern Middle Tennessee. The rain will add up, totaling anywhere from 2″ to 4″:
That’s enough to cause localized flooding problems, so if you live in a low-lying or flood-prone location, stay aware of water levels by Thursday night and Friday (and again on Sunday).
The specifics of our winter-weather situation on Friday and Friday night are still VERY uncertain (thus, the disclaimer at the top of this post). Even our in-house Futurecast computer models are of split opinions regarding what will happen around here. Sometime on Friday, the rain will change to ice (either freezing rain or sleet). There’s not much of a difference in the weather conditions that produce those forms of precipitation:
Current computer model forecasts are more supportive of freezing rain (produced when liquid rain falls into a shallow layer of sub-freezing air near the ground, then freezes on contact). If that cold air is just slightly thicker, we’d see sleet — still a pain, but not quite as awful. So, let’s take it time-frame by time-frame and split things into best-case and worst-case scenarios. Right now, my forecast leans toward the worst-case scenario, although I’m obviously hoping for the best-case!
Midnight Friday Night
Worst-case: precipitation winding down. Significant ice accumulations west and north of Nashville (enough to cause widespread power outages and hazardous driving conditions), with a layer of snow on top of the ice. Enough ice in Nashville for slippery bridges and overpasses, some power outages. Minimal ice southeast of Nashville.
Factoring together the various computer models, plus the thoughts of our colleagues at the National Weather Service and the Hydrometeorological Prediction Center (yes, that’s a real thing), here’s the current forecast for ice accumulations through Friday night:
Right now, the heaviest ice accumulations look to be in northwestern Middle Tennessee and the western half of southern Kentucky…but Nashville is going to be right on the dividing line between “nothing” and “a lot”. The National Weather Service has issued a Winter Storm Watch for the counties likeliest to get more than a quarter-inch of ice.
And that’s just ROUND ONE of icy weather. Another wave of moisture will head up towards us Saturday night, and once again the stage is set for a period of freezing rain. It’s a little too soon at this point to get into an ice accumulation forecast with that wave — a lot will depend on what the atmosphere is doing in the wake of Round One. But the same locations that are forecast to receive the most ice on Friday will also receive the most ice Saturday night into early Sunday.
The freezing rain will change over to cold rain on Sunday and Sunday night. Then on Monday, enough cold air will catch up to change the rain to a brief period of snow! Doesn’t look like much at this point, but that’s still 120+ hours away — a relative eternity in forecasting time. You can count on a lot of cold air invading the Midstate by Tuesday the 10th and onward — single-digit low temperatures Wednesday and Thursday???
1) It’s going to rain Thursday into Friday. A lot, in some spots.
2) Sometime Friday, the rain will change to ice…either sleet or freezing rain
3) Significant ice could accumulate to the north and west of Nashville
4) More freezing rain will likely fall Saturday night
5) A slight change in the path of this storm would spell major changes to this forecast
Plan on staying-weather aware Friday all the way through early next week. Travel by road to the north and west of Nashville doesn’t look like a good idea through the weekend. I’ll post another update around this time Thursday morning, and we’ll keep you updated more frequently as things develop Friday.