Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN

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FXUS64 KMRX 141946
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
246 PM EST Thu Dec 14 2017

.SHORT TERM...(Tonight and Friday)...

The cold front is now to the south and east of the area with a
reinforcing shot of cold air arriving across the Southern
Appalachians. PW values remain low behind the front with values in
the 0.3-0.4 inch range. There is an area of low-level post frontal
clouds across NE TN and SW VA. Expect these will persist
throughout the afternoon and into the evening hours. The heart of
the cold air advection will arrive late tonight into Friday and
overnight lows will generally be in the 20s as surface high
pressure builds in behind the departing front. This cold and dry
airmass will continue into Friday with highs in the upper 30s to
mid 40s.

.LONG TERM...(Friday night through Wednesday)...

Models continue to be in good agreement early in the long term
period with diverging solutions late in the period. Surface ridging
on Saturday will keep things dry with low boundary layer moisture
resulting in large diurnal temperature variation through the day. As
a shortwave trough moves eastward across the Southern Plains on
Saturday night, southerly flow and moisture will increase ahead of
it on Sunday. Model soundings indicate very dry air within the
boundary layer on Sunday morning even though mid-levels are nearly
saturated. This will likely limit precipitation on Sunday,
especially during the early onset of precipitation. Cannot rule out
a slight chance of brief light mixed precipitation early on Sunday
morning with lingering cool air in the valleys and evaporational
cooling. However, temperature profiles show warm air advection will
keep any mixed precip brief and switch to all liquid rain by mid-
morning Sunday. We stay in a southwesterly flow on Monday and
Tuesday with most moisture expected to remain to our south. A cold
front sweeps through late Tuesday with lingering moisture across the
higher elevations of the mountains and northeast TN on Tuesday
night. Surface ridging expected to keep us dry on Wednesday and
Thursday. Model solutions diverge late week with increased
uncertainty regarding strength and position of trough and expected
position of the surface cold front.


&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             29  44  28  53 /   0   0   0   0
Knoxville McGhee Tyson Airport, TN  27  42  27  52 /   0   0   0   0
Oak Ridge, TN                       27  42  27  51 /   0   0   0   0
Tri Cities Airport, TN              25  40  24  50 /   0   0   0   0

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...None.
TN...None.
VA...None.
&&

$$

MA/JB



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