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

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FXUS64 KMRX 240741

Area Forecast Discussion
National Weather Service Morristown TN
341 AM EDT Tue Apr 24 2018

.SHORT TERM...(Today and Tonight)...An area of low pressure will
be rotating through the region today and will begin to exit east
tonight. Through the first half of the day the best chances of
rain will be across the central valley/northern valley as well as
the central/northern plateau as this is where the strongest lift
will be. The lift is in response to the leading edge of a strong
vort max associated with the upper low, along with a strong 850
jet directly underneath. Northeast TN and southwest VA will stay
drier as downsloping continues into the early afternoon hours. As
the center of the low slowly pushes eastward these downsloping
winds will diminish by mid/late afternoon and precip chances will
increases across these areas. Also, soundings show some
instability developing this afteroon as we have steep lapse rates
in place due to the low overhead. So have slight chance for a few
thunderstorms in for the afternoon. Small hail is possible with
any of these storms due to the steep lapse rates in place.
Temperatures will be 5 to 10 degrees below normal with highs in
the low to mid 60s.

Tonight, valley locations will see precip chances drop as the low
pushes east and the deeper moisture exits. However, as the low
moves east, winds will shift and be out of the northwest. This
will cause the orographic lift to kick in. Though moisture is
shallow the upslope flow will keep precip chances
likely/categorical across the favored upslope areas through the
night but the precip will be light. Lows tonight will be mild with
temps in the lower 50s.

.LONG TERM...(Wednesday through Monday)...At the beginning of this
period the first upper low has exited the area into the Carolinas,
while our next upper low heading toward us is in the Central Plains
heading southeast.  The surface low will be in the Carolinas as well
with the northerly wind component continuing.  So, this next short
wave and upper low will pass through the area around Thursday, then
a final weak clipper shortwave will race through on Saturday
(looking mostly dry).  During this whole time we will generally have
a northerly component to the surface wind and the warm-up will be
very slow. Finally, after this final shortwave passes, an upper
ridge starts to build in by Sunday, and the winds finally get a
south component, and by Monday we should definitely get some bona
fide warming.  For precip, Wednesday looks wet north tapering off to
low POPs in the southern valley, then all precip moves out Wed
night, only to return Thursday with the upper low/trough moving
through. Precip for most of the area should be moving out on Friday
and continue dry through the weekend, although keeping some minimal
POPs in the mountains Friday night and Saturday.  The airmass looks
too stable for thunder in any of these periods.


Chattanooga Airport, TN             67  53  67  52 /  50  40  10  10
Knoxville McGhee Tyson Airport, TN  65  54  66  50 /  90  50  40  20
Oak Ridge, TN                       66  53  67  49 /  90  50  40  10
Tri Cities Airport, TN              66  51  63  46 /  60  60  60  30




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