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

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FXUS64 KMRX 221858

Area Forecast Discussion
National Weather Service Morristown TN
258 PM EDT Tue May 22 2018

.SHORT TERM (Tonight and Wednesday)...Still a decent chance of
some showers and possibly a thunderstorm or two across the
forecast area tonight as the advertised Midwest upper trough and
surface frontal wave build east across the Appalachians. Would
expect loss of heating to allow for development to diminish in
coverage later in the evening. Maintained a smaller chance for a
shower or thunderstorm across mainly southern and eastern parts of
the forecast area during the first part of the day Wednesday as
the weak boundary makes progress south. The drier and more stable
air behind the boundary should keep Wednesday night and Thursday
largely precipitation free. Stayed close to guidance mins in the
60s tonight with highs a few degrees warmer on Wednesday; ranging
from the lower 80s north to the middle 80s south.

.LONG TERM (Wednesday night through Tuesday)...A front will be
pushing south across the area to start the period, which will
necessitate a low PoP mention Wednesday evening across southern
sections. High pressure over the Great Lakes will provide a
northeasterly low level flow Thursday morning, but as the high
shifts to the Mid Atlantic region in the afternoon, an easterly
flow develops across the Carolinas with an inverted trough over
our area. This may allow for some scattered convection to develop
in the afternoon hours, mainly in the southern sections.

With the ridge offshore and a northward-moving low over the Gulf of
Mexico, we will have a deep southerly flow developing across the
area on Friday that will persist trough the remainder of the
forecast. The sub-tropical low will move into the Southeast states
on Sunday, then stall over AL (GFS) or MS (ECMWF). Model differences
in its position will affect the finer details of QPF and timing of
the best rain chances, both of which are too uncertain at the time
to specify. However, with general agreement on the pattern, the
forecast will keep high chance to likely PoPs going for each
period, with mostly cloudy skies and temperatures above normal.


Chattanooga Airport, TN             68  86  67  86 /  40  30  20  40
Knoxville McGhee Tyson Airport, TN  66  85  65  86 /  30  30  10  20
Oak Ridge, TN                       66  85  64  86 /  30  20  10  10
Tri Cities Airport, TN              63  81  59  83 /  50  30   0  10



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