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

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FXUS64 KMRX 230736
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
336 AM EDT Mon Apr 23 2018

.SHORT TERM...(Today and Tonight)...

The main story for the short term period continues to be the rain
chances, and also the expected high winds over the mountainous
areas.

Mid and upper level GOES16 water vapor imagery show a fairly well
defined dry slot working east through northern MS/AL and central
TN this morning. The eastern edge of this dry slot is situated
along the GA/AL border north into central TN, which lines up very
well with the precip shield to the east of that line and very
limited and light precipitation back to the west. As such, expect
the PoP forecast to be somewhat complicated today as the forecast
area is likely to see a few distinct waves of rainfall associated
with vort lobes that rotate around the parent upper low and
through eastern Tennessee. The first will move through much of the
area before dawn, or by the time most folks read this discussion,
with another wave developing by early afternoon and rotating
through the forecast area this afternoon/evening. The complicated
part is really in regards to nailing down any of the waves of
rainfall to a 3-6hr block of time for the forecast. Regardless,
expect most people across eastern Tennessee, southwest Virginia,
and far southwest North Carolina to see rainfall at various times
today. With regards to amounts, the plateau and Tennessee
mountains should get somewhere around an inch when all is said and
done (which would cover a time frame extending into the long term
period) with notably lighter amounts in the valley where downslope
effects will negatively impact rainfall amounts.

Speaking of downsloping winds, have left the wind advisory and
high wind warnings as is. Winds have been a little sluggish to
respond thus far, which concerns me a little bit. But the tightest
pressure gradients are yet to come, and the pattern is that of a
high wind event. Guidance is still insistent on these high winds
developing, and some mountain locations are gusting into the
+30mph range. Will leave those headlines as is for the time being
and continue to monitor the situation.

.LONG TERM...(Tuesday through Sunday)...

The pesky upper low will be centered near Nashville at the start
of this period. It will be slow to move across East Tennessee and
weaken through Tuesday night. Expect showers and a few isolated
thunderstorms to occur Tuesday. Rain chances should diminish later
Tuesday night as the trough translates into North Carolina and
Virginia.

A shortwave ridge follows in its wake on Wednesday which would
normally bring drier weather, however, models are producing low end
PoPs and minimal QPF coinciding with the northwest flow. Confidence
is rather low for any measurable rainfall during the Wednesday time
period.

The next shortwave trough appears to dig farther south Thursday and
Thursday night. The southern Tennessee Valley and extreme eastern
portions of the forecast will have the better chances of measurable
rainfall - at least with the 00Z runs of ECMWF/GFS. Obviously this
will become better defined in the upcoming days and newer runs.

The ECMWF and GFS begin to diverge in their solutions toward the end
of the week. They do agree on the deep trough over the eastern U.S.
which will bring cooler than normal temperatures to the region for
the weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             68  55  70  54 /  70  70  60  20
Knoxville McGhee Tyson Airport, TN  67  54  67  53 /  80  80  70  30
Oak Ridge, TN                       65  54  68  52 /  80  80  70  30
Tri Cities Airport, TN              62  51  67  50 /  80  70  70  60

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...Wind Advisory until 7 AM EDT this morning for Cherokee-Clay.

TN...Wind Advisory until 2 AM EDT Tuesday for Jefferson-NW Blount-
     North Sevier-Northwest Carter-Northwest Cocke-Northwest
     Greene-Northwest Monroe-Sullivan-Washington TN.

     High Wind Warning until 2 AM EDT Tuesday for Blount Smoky
     Mountains-Cocke Smoky Mountains-Johnson-Sevier Smoky
     Mountains-Southeast Carter-Southeast Greene-Southeast
     Monroe-Unicoi.

     Wind Advisory until 7 AM EDT /6 AM CDT/ this morning for Bledsoe-
     Bradley-East Polk-Hamilton-Marion-McMinn-Meigs-Rhea-
     Sequatchie-West Polk.

VA...Wind Advisory until 2 AM EDT Tuesday for Russell-Washington.

&&

$$

CD/AC



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