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Area Forecast Discussion

FXUS64 KMRX 251915

Area Forecast Discussion
National Weather Service Morristown TN
315 PM EDT SAT JUN 25 2016

.Short Term (Tonight and Sunday)...Surface ridge now over the area
with associated light winds this afternoon and should drop to near
calm this evening. As the ridge slides east, a southerly return
flow will begin on Sunday allowing more moisture into the
area...but also allowing the strong capping inversion to wane.
Expecting showers/storms to develop in the western areas in the
afternoon...as well as the elevated terrain along the Appalachians.
Upper flow will be quite weak from the North and Northwest...so
keeping less chances of precip from the west making it into the
central and eastern parts of the valley...and precip from the
Appalachians should drift S/SE into the Carolinas. Keeping some
patchy fog late tonight in low spots near lakes. For temperatures
went very close to Guidance values both tonight and Sunday.

.Long term (Sunday night through Saturday)...The main feature of
interest for this part of the forecast will be Monday into Monday
night as the advertised cold front moves across the Southern
Appalachian region. Likely pops were applied for convection with the
a pre-frontal trough/outflow boundary which appears to move onto the
plateau during the mid to late afternoon hours and continues
southeast through the rest of the forecast area during the evening.
There will be a marginal risk for severe convection for the event.
Instability should be no problem with moderate to high cape values
however, shear will be less impressive. The actual cold frontal
boundary will lag well behind the convective outflow so will keep
the chance pops going into the morning hours on Tuesday. A period of
mainly dry weather will begin later Tuesday afternoon all the way
through approximately Thursday. Higher pressure and sufficient dry
advection and limited instability should keep any shower or
thunderstorm from forming across most of the region. The added
benefit of orographic lifting could allow for isolated precipitation
across some of the higher terrain. Model solutions diverge at the
end of the long term (Friday and Saturday) with the ECMWF trying to
bring a weak short wave and associated slightly higher pop for
convection into the region while the GFS picks up on a short wave
feature but doesn`t bring the perturbation into the Southern
Appalachians until about Sunday. Therefore, just added a slight
chance for showers and thunderstorms for the entire forecast area
for Friday and Saturday while awaiting better model agreement in
later runs.


Chattanooga Airport, TN             73  95  74  92 /  10  30  30  60
Knoxville McGhee Tyson Airport, TN  70  91  71  87 /   0  20  20  70
Oak Ridge, TN                       70  93  71  87 /   0  20  40  70
Tri Cities Airport, TN              66  89  67  84 /  10  10  20  70




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