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

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FXUS64 KMRX 151948

Area Forecast Discussion
National Weather Service Morristown TN
248 PM EST Fri Dec 15 2017

.SHORT TERM...(Tonight and Saturday)...

Temperatures have struggled today under mostly cloudy skies with
most locations as of 2 pm still in the low to mid 30s. Recent
visible satellite imagery indicates that the cloud cover is
breaking up over Middle TN and could still see a warm up of a few
degrees this afternoon. At the surface, high pressure is building
in behind a departing cold front. In the upper levels, the axis of
the upper level trough is passing to the east with northwesterly
flow developing aloft. For tonight, expect the clouds will
continue to erode with mostly clear skies by daybreak. Light winds
moving in with the surface high will create radiational cooling
conditions. Overnight lows will generally be in the 20s.
Temperatures will begin to rebound on Saturday with light
southerly to southwesterly flow developing as the surface high
shifts eastward. Additionally, higher heights aloft will build in
as a shortwave ridge builds in behind the trough. High
temperatures on Saturday will range from upper 40s to low 50s
across most locations under mostly sunny skies.

.LONG TERM...(Saturday night through Thursday)...

Models remain in very good agreement on the weather system for
Sunday as shortwave energy rides NE out of Texas across a building
middle level ridge over the Southeast US. Low level southerly flow
ahead of this system on Saturday night into Sunday morning should
greatly limit any frozen pcpn to the pre-dawn hours on Sunday with
no accumulations expected before any mixed pcpn becomes all liquid
by mid morning.

Continued low level southerly flow coupled with weak ridging aloft
will help to keep temperatures about 5-10 degrees above normal from
Sunday afternoon through Tuesday. Although bulk of moisture remains
south of the area for the start of the work week, chance pops remain
as the southern branch of the jet remains active with a series of
shortwave troughs moving across the southern quarter of the area
Monday and Tuesday. Given above normal temps and persistent WAA, no
frozen pcpn is expected. Cold front finally pushes through very
early Tuesday evening. Associated cold air lags well behind the
front with temperatures Wednesday still expected to be slightly
above normal for mid December.

Solution to late week system is gaining confidence with the latest
runs as GFS, Canadian, and ECMWF are all in fair agreement on
position of surface cold front into Middle TN by the end of the
forecast period.


Chattanooga Airport, TN             27  52  35  48 /   0   0  10  60
Knoxville McGhee Tyson Airport, TN  27  52  33  48 /   0   0   0  40
Oak Ridge, TN                       26  52  32  47 /   0   0   0  50
Tri Cities Airport, TN              23  50  28  49 /   0   0   0  40




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