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

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FXUS64 KMRX 201850
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
250 PM EDT Fri Oct 20 2017

.SHORT TERM...-- Changed Discussion --(Tonight and Saturday)...We continue in a rather
stagnant pattern and thus another mostly persistence forecast. High
pressure at the surface and aloft over the region will be shifting
slowly east during the period. The atmosphere will remain on the dry
side. Temperatures running slightly higher again today than
yesterday, so the gradual warming trend is continuing. Some patchy
fog can be expected late tonight especially near bodies of water.
Tomorrow will feature plenty of sunshine despite some high clouds
and temperatures generally near or a bit higher than today.

.LONG TERM...(Saturday night through Friday)...By Saturday evening the
upper ridge moves off the southeast U.S. coast. Meanwhile, a deep
long wave trough and associated cold front will move across the
Midwest. So, expect dry conditions across the forecast area with
prefrontal warming bringing temperatures on Sunday 5 to 10 degrees
above normal.

The high amplitude trough will slow forward/eastward progress of the
entire system. Showers and thunderstorms will remain over West
Tennessee for much of Sunday and early Sunday night. Eventually, a
closed upper low forms over northern Mississippi early Monday
morning. This is where the forecast gets difficult due to location
and evolution of this closed low. Current model progs are having a
tough time not just with timing but also location. Should the low
dive into central Alabama the highest QPF will occur over the
southern TN Valley. Downsloping winds from the east/southeasterly
wind component would limit heavy rainfall over northeast TN...say
from Knoxville east along and north of I-40 and the I-81 corridor.

This upper low is kicked out rather quickly with another following
in its wake by Monday night. This will bring significantly colder
air to the region on Wednesday into Thursday. In fact, some higher
elevations could see snow, perhaps mixed with rain, across northern
parts of Tennessee, mountains of southwest Virginia and the
Appalachians. Precipitation chances diminish by Wednesday night. The
remainder of the week will be below normal with another trough
expected to produce more precipitation by early next weekend.-- End Changed Discussion --

.PRELIMINARY POINT TEMPS/POPS...
-- Changed Discussion --Chattanooga Airport, TN 49 79 56 77 / 0 0 0 10
Knoxville McGhee Tyson Airport, TN 49 77 52 78 / 0 0 0 10
Oak Ridge, TN 49 78 51 77 / 0 0 0 10
Tri Cities Airport, TN 44 78 47 76 / 0 0 0 0-- End Changed Discussion --

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

LW/AC

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