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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS64 KMRX 170708
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
308 AM EDT Tue Jul 17 2018

.SHORT TERM (Today and Tonight)...
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With a weakly unstable air mass
in place...a few isolated thunderstorms have continued over the
region through the night into the early morning. Early morning
coverage will be limited. However...as a weakening cold front
settles south and into the Southern Appalachian Region
today...additional lift and low level moisture will increase and
allow for widespread thunderstorm activity for the late morning
and afternoon. The front should continue to weaken as it pushes
through the area late today into this evening. As a result...
thunderstorm activity will decrease this evening...ending for the
overnight hours. As for temperatures ...highs today will reach
into the mid 80s to around 90 across most valley locations and
fall into the 60s to around 70 for the overnight lows.

.LONG TERM (Wednesday through Monday)...The extended range fcst
period kicks off on Wednesday morning amidst passage of an upper
trough axis over the Appalachians, while at the surface drier high
pressure will be building in from the north in the wake of an
earlier fropa. With that, Wendesday into Thursday looks fairly dry
across the region as instability is limited thanks to dewpoints
in the upper 50s to lower 60s, as well as rising heights amidst
shortwave ridging. The pattern looks to remain progressive into
late week as another northern stream upper low/trough dives
east/southeast across the lower Great Lakes and into the OH Valley
by late day Friday. However, diffluent flow over the southern
Appalachians out ahead combined with veered sly return flow (and
thus rising dewpoints) looks to favor increasing chances for
convection Friday afternoon and overnight, some of which could be
strong. At that point the fcst becomes a bit less uncertain given
range, however guidance does hint at a large nearly 600dm H5
anticyclone over the Atlantic providing some blocking of the mean
flow aloft. Thus, the aforementioned trough and closed/stacked
system is progged to slow/stall over the Appalachians and Mid-
Atlantic through the weekend, which could result in prolonged
periods of showers and thunderstorms and possible heavy rainfall.
In summary, the fcst will remain dry on Wednesday with increased
pops over higher terrain on Thursday. Pops will increase further
for Friday and through the weekend into the high chance to likely
range. Temperatures through the period will remain at or slightly
below normal levels.
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&&

.PRELIMINARY POINT TEMPS/POPS...
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Chattanooga Airport, TN             90  70  91  69 /  50  30  10   0
Knoxville McGhee Tyson Airport, TN  88  68  89  68 /  60  30  10   0
Oak Ridge, TN                       88  68  89  67 /  50  30  10   0
Tri Cities Airport, TN              84  65  85  63 /  70  30  10   0
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&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...None.
TN...None.
VA...None.
&&

$$

MJB/CDG