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

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452
FXUS64 KMRX 231932
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
232 PM EST Mon Jan 23 2017

.DISCUSSION...

Current water vapor imagery and RAP upper air analysis indicates a
strong closed low centered across North Carolina. Drier air can be
seen moving into the area from the west as a ridge moves in behind
the departing closed low. Current radar imagery also indicates this
drier air moving in with showers ending from southwest to
northeast. However, elevated rain chances will continue across the
higher elevations along the TN/NC line and in SW VA with good
northwesterly flow behind the exiting system. Regardless, amounts
should be light with up to an additional half an inch of rain
possible across the high terrain this evening and tonight. Winds
across the area are below advisory criteria but there have been a
couple of reports of trees down from the gusty winds and saturated
ground, therefore, will continue with the advisory as is.
Temperatures this afternoon at Newfound Gap have been in the mid to
upper 30s and expect there could be some snow mixing in for
locations above 5 kft, this evening and overnight. For now, expect
amounts of a dusting up to half an inch will be possible for these
locations above 5 kft and no winter weather products are
anticipated due to the low amounts and impacts.

Drier air will move into the Southern Appalachians on Tuesday as a
shortwave ridge builds across the region. The pattern throughout
the forecast period will remain progressive and this ridge will be
short-lived. Southerly to southwesterly flow will return to the
area as the ridge axis passes to the east Tuesday night into
Wednesday. An upper level trough will track across the Central
Plains northeastward towards the Great Lakes during this timeframe.
An associated cold front will move across the Mississippi River
Valley into the Tennessee River Valley late Wednesday. Strong warm
air and moisture advection ahead of the system will push highs on
Wednesday up into the 60s areawide with PW values into the 0.8-1.0
inch range. These values are in the 90th percentile for late-
January. The higher moisture values are in a narrow tongue ahead
of the front late Wednesday and expect the precip. will hold off
until then. In addition, not expecting any instability and have
only mentioned showers in the forecast. The timing of the system
between the models is pretty good so far with late Wednesday/early
Thursday being the best chance for precipitation although amounts
should generally be under a tenth of an inch.

Colder air will advect in behind the system late in the week with
temperatures return to near normal for late January. Both the GFS
and ECMWF indicate a series of shortwaves troughs will traverse the
Southern Appalachians late in the week and into early next week.
The GFS soundings indicate enough low-level moisture for
light precipitation during this timeframe. The ECMWF is not near
as bullish with only some light precip. on Friday with no precip.
over the weekend. With the colder air in place, there will be the
chance for a few light snow shower/flurries during this timeframe
but confidence is low at this time. Regardless, the moisture is
limited late in the forecast period and any precipitation would be
light. For now, have mentioned slight chance PoPs for much of the
extended portion of the forecast. The GFS and ECMWF both indicate a
more robust trough early next week that moves through the
northwesterly flow aloft. The GFS indicates a bit more moisture
with this system and the ECMWF keeps conditions dry. Again, have
continued with low PoPs to account for the uncertainty.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             40  58  42  63 /  10  10   0  20
Knoxville McGhee Tyson Airport, TN  43  56  42  63 /  20  10   0  20
Oak Ridge, TN                       43  56  41  62 /  10  10   0  20
Tri Cities Airport, TN              42  52  36  63 /  50  10  10  10

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...Wind Advisory until 11 AM EST Tuesday for Cherokee-Clay.

TN...Wind Advisory until 7 PM EST /6 PM CST/ this evening for
     Anderson-Bledsoe-Bradley-Hamilton-Knox-Loudon-Marion-McMinn-
     Meigs-Morgan-NW Blount-North Sevier-Northwest Monroe-Rhea-
     Roane-Scott TN-Sequatchie-West Polk.

     Wind Advisory until 11 AM EST Tuesday for Blount Smoky Mountains-
     Cocke Smoky Mountains-East Polk-Sevier Smoky Mountains-
     Southeast Greene-Southeast Monroe.

     Wind Advisory from 7 PM this evening to 11 AM EST Tuesday for
     Johnson-Southeast Carter-Unicoi.

VA...None.
&&

$$

MA



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