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

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FXUS64 KMRX 221925

Area Forecast Discussion
National Weather Service Morristown TN
325 PM EDT Mon Apr 22 2019

.SHORT TERM (Tonight and Tuesday)...An upper level trough will
move east across the Great Lakes while dragging a weak cold front
from the Plains into the Ohio Valley through the short term. Very
few clouds will be around tonight, but there will be an increase
in moisture around 20k feet and higher on Tuesday in association
with a southern stream long wave trough shifting slowly east from
the Sonoran Desert into the Texas Big Bend. The cirrus layer
should be relatively thin, so sunshine will still be abundant on
Tuesday. The surface is warmer this afternoon from the lengthy
period of sunshine but radiation in a calm wind, basically clear
sky environment, should allow temperatures to drop to the upper
40s and lower 50s by daybreak Tuesday. The beautiful ridge over
the eastern states will be suppressed just a bit as that Great
Lakes short wave trough builds east, but it will hold over the
Southeastern U.S. keeping very nice weather in place across the
Southern Appalachian region through the day Tuesday. Highs will be
about five to eight degrees above normal in the upper 70s and
lower 80s.

.LONG TERM (Tuesday night through Monday)...The long term outlook
starts off as a weak ridge continues to move off shore to the
east. The tail end of a cold front originating from an upper level
low over southeastern Canada stalling out over the Ohio Valley.
Models aren`t in great agreement as to where the stationary front
will eventually settle. The ECMWF places it over the Central Ohio
Valley, while the NAM12 and GFS depict it further to the south
over Kentucky and southwest Virginia. In either case, expect
temperatures to be a few degrees warmer than the seasonal norm for
mid week while we are stuck in the warmer airmass. Wednesday
afternoon will be our first chance for some showers over northeast
Tennessee and southwest Virginia as models show a stationary
front dipping towards the south over our area.

On Thursday a developing low over the American southwest will track
eastward across TX which will pull the stationary front northward.
Isentropic lifting will lead to periods of showers over the northern
portion of the CWA. Models indicate limited instability values with
CAPEs between 300 to 500 J/kg. A better chance for thunderstorms
looks to be on Thursday night as the cold front moves through the
area. Increasing jet dynamics and a frontal boundary will increase
coverage of showers and possible thunderstorms.

Typical post frontal CAA will lead to cooler and more seasonal
temperatures for Friday and Saturday with warm, moist southerly flow
returning on Sunday ahead of another broad trough moving through the
Great Lakes region. Another round of showers and possible
thunderstorms for either Sunday or Monday as a frontal boundary
approaches southwestern Virginia and northern Tennessee.


Chattanooga Airport, TN             53  81  57  80 /   0   0   0  10
Knoxville McGhee Tyson Airport, TN  52  80  57  78 /   0   0  10  10
Oak Ridge, TN                       52  81  57  77 /   0   0  10  10
Tri Cities Airport, TN              48  78  54  73 /   0   0  10  20




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