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FXUS64 KOHX 091010

Area Forecast Discussion
National Weather Service Nashville TN
410 AM CST Mon Dec 9 2019


Besides an isolated rain shower or two, the Mid State is quiet 
for now. Thanks to increasing SSW winds, we have more cloud cover 
and warmer temps than yesterday at this time. Expect those winds 
to ramp up through the morning and early afternoon, gusting as 
high as 35 mph. In response, temperatures will soar into the 60s 
this afternoon, despite the abundant cloud cover. Looking at the 
bigger picture, a longwave trough is getting its act together 
across the western U.S., with mid and upper level wind fields 
increasing across the Midwest and OH/TN Valleys. As a cold front 
approaches from the west tonight, rain will turn from scattered in
nature to more widespread after dark. Tuesday's high temperatures
will likely occur right after midnight, as colder air moves in 
for the remainder of the day.

Speaking of colder air and ongoing precip, a wintry mix is 
looking more likely Tuesday morning into early Wednesday. 
Confidence in timing is moderate to high, with a rain/snow line 
approaching northwestern counties between 6 AM and noon Tuesday. 
The first frozen precip to fall in and around Nashville looks to 
be right around lunchtime into the early afternoon, followed by 
areas south and east by mid to late afternoon. During the evening 
rush hour, most of the Mid State will be transitioning to all 
snow. Plan ahead for at least minor travel impacts through the 
afternoon and evening commute, especially along and north of the 
I-40 corridor.

Keep in mind that with these backdoor-type snow events, 
confidence in total accumulations is lower than normal. Many 
forecast complexities include timing the CAA, assessing the depth 
of cold air, and identifying available moisture in the column. In 
addition, warm surface temperatures will take a reasonable amount 
of time to become supportive of accumulation. Model soundings are 
coming into good agreement that this will be a mainly rain-to-snow
event, though a few sleet pellets are not out of the question 
during the liquid to frozen transition. Final snowfall amounts may
also teeter on model guidance drying out the 900-750mb layer. 
However, some models show low-level dry air could be overcome by 
higher precip rates, in response to increased upper level support 
and frontogenetic forcing. Wrapping all of the data and previous 
considerations into one, this forecast modestly increases snowfall
accumulations. Most locations can expect a few tenths of an inch,
enough to lightly dust elevated and grassy surfaces. Areas along 
and north of I-40 and the Cumberland Plateau could see as much as 
1 to 1.5 inches by early Wednesday. 

As the wintry mix shuts down Wednesday morning, temperatures will
have plummeted into the low and mid 20s. We will rebound into the
low 40s, but any snow on the ground may keep temps a degree or 
two cooler. We warm to near-normal Thursday and Friday, with more 
rainfall possible Friday and Saturday. Cooler air looks to arrive 
once again at the beginning of next week.



Cigs will slowly fall tonight as moisture continues to pile into 
Middle TN. Look for MVFR cigs around 07-09Z. IFR cigs should hold 
off until Monday night when rains pick up in coverage/intensity.

It will continue to be breezy tonight, with gusts becoming 
stronger during the daylight hours Monday. Southerly winds and 
gusts of 20-25 kts can be expected by 15-18Z Monday.


Nashville      67  38  41  25  44 /  60  80  80  40   0 
Clarksville    64  33  36  22  43 /  60  60  60  20   0 
Crossville     61  43  46  23  42 /  40  80  80  70  10 
Columbia       67  40  43  23  45 /  50  80  80  50   0 
Lawrenceburg   66  43  45  25  46 /  40  80  80  60   0 
Waverly        65  34  38  23  45 /  60  70  80  20   0 




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