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

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FXUS64 KMRX 060828

Area Forecast Discussion
National Weather Service Morristown TN
328 AM EST Tue Dec 6 2016

.SHORT TERM (Today through Thursday night)...
The low pressure system over the lower MS Valley region will track
NE across middle TN this morning to OH by this afternoon. The
strongest forcing in the coupled jet zone will move across our area
this morning, along with some elevated instability ahead of the
midlevel shortwave trough. The trough axis will be to our east by
21z, and POPs will drop sharply through the afternoon. A 30 kt NW
flow may keep some precip going in the mountains this evening, but
soundings appear too dry to support and precip after midnight.

The Wind Advisory will be maintained, but so far observations have
been well below criteria. The LLJ is expected to pick up later this
morning, and higher elevations may approach the advisory thresholds
of 40 mph gusts. The Flash Flood Watch for Sevier County due to the
burn scar will also be maintained, although expected rainfall rates
look marginal at best.

Models agree on a dry day on Wednesday, but diverge significantly
beginning Wednesday night. NAM and SREF spread rain into the area
from the west after midnight, continuing into Thursday morning ahead
of a cold front passage around midday. The GFS is much drier and
quicker to bring in the cold front early Thursday morning. The GFS
has not performed well of late, and has tended to move toward the
NAM solution with the last few systems. Will lean toward the NAM
timing but cut back on its QPF and POPs. Strong cold advection
behind the fropa will result in temps falling through the afternoon
on Thursday, producing a change to snow for northern sections and
higher elevations Thursday afternoon and evening before precip ends
by midnight. Much of the area will have lows in the teens Thursday

.LONG TERM (Friday through Sunday)...
An arctic airmass will be in place on Friday with the coldest air
of the season; and yes, it will be cold. The day starts out mostly
in the teens and ends up in the 20s across Southwest Virginia and
30s across much of the remainder of the lower elevations of East
Tennessee and Southwest North Carolina despite a return to some
sunshine. The good news is that the cold upper level trough will be
on its way out of the area for the weekend with a southerly
component to the flow developing in advance of another system due
in the region on Sunday. There will still be some sub-freezing air
in place early in the day Sunday, and depending on the timing of
precipitation building back northeast across the Southern
Appalachian region; some of the morning precip could be in a mixed
state with a wee bit of freezing rain, sleet and snow before
temperatures quickly rise above freezing around mid to late
morning. This late extended period event is broadbrushed across two
days because the superblend concept merges the faster GFS solution
with a slower ECMWF. Future forecasts of course, should be able to
depict greater temporal resolution during this early week time
period. Some most pleasant warming should be realized toward the
end of the extended on Monday with high temperatures warming in the
lower to middle 50s across almost the entire forecast area.


Chattanooga Airport, TN             57  39  55  40 / 100  10   0  40
Knoxville McGhee Tyson Airport, TN  57  37  53  38 / 100  10   0  40
Oak Ridge, TN                       57  38  53  38 / 100  10   0  40
Tri Cities Airport, TN              55  36  52  38 / 100  30   0  30


TN...Wind Advisory until 4 PM EST this afternoon for Blount Smoky
     Mountains-Cocke Smoky Mountains-Johnson-Sevier Smoky
     Mountains-Southeast Carter-Southeast Greene-Southeast

     Flash Flood Watch through this afternoon for North Sevier-Sevier
     Smoky Mountains.


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