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

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FXUS64 KMRX 221904
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
304 PM EDT Fri Mar 22 2024

...New SHORT TERM, LONG TERM...

.SHORT TERM...
(This evening through Saturday)
Issued at 257 PM EDT Fri Mar 22 2024

Key Messages:

1. Light to moderate rain becomes widespread this evening and
through the overnight.

2. Strong, gusty winds in the East Tennessee mountains and
foothills continue through the evening.

3. Saturday will be breezy, with temperatures roughly 10-15
degrees cooler.

Discussion:

Satellite imagery shows clouds gradually spreading northward as
surface low pressure spins southwest of the forecast area. Potent
warm air-advection has won the battle over high clouds, with
temperatures over-performing and reaching into the low to mid 70s
for much of the area this afternoon. As rain continues to spread
north it will take some time to erode low level dewpoint depressions
ranging from 15-25 degrees F, thus, any better looking radar returns
may even lead to just a light sprinkle/rain at the surface for the
next couple of hours. Light to moderate rain becomes widespread this
evening, with amounts of half an inch to one inch generally expected
through early Saturday.

Regarding winds, the advisory remains in good shape. Camp Creek has
maintained 40-45mph gusts most of the day, with Cove Mountain wind
tower also showing sporadic observations at advisory criteria. Based
on the most recent run HREF guidance will trim back the end time to
midnight. Otherwise, rain tapers off west-east throughout the day
Saturday, lingering  the longest in higher elevations of East
Tennessee mountains and southwest Virginia. The surface low-pressure
system is expected to deepen as it lifts up the eastern coastline. A
continued strong pressure gradient will lead to a breezy afternoon
Saturday, although, winds will now be from the north. NAM model
guidance suggest the northerly H85 flow will reach 30-35 knots which
could lead to some gusts just shy of advisory criteria for the
higher elevations of the mountains once more. The northerly flow
will bring about temperatures near 10-15 degrees cooler.

&&

.LONG TERM...
(Saturday night through next Friday)
Issued at 257 PM EDT Fri Mar 22 2024

Key Messages:

1. Breezy and cold Saturday night. Temps 5 to 10 degrees below
normal. Chances of below freezing temps likely for areas north of I-
40. Little to no chance down around Chattanooga.

2. Breezy winds and low RH values expected on Monday, which will
allow for elevated fire weather concerns.

3. Mountain wave winds possible on Monday night and Tuesday. Showers
Tuesday into Wednesday.


Discussion:

The combination of clearing skies and northerly flow behind
Saturday`s system will allow for below normal temps on Saturday
night. Temps will be 5 to 10 degrees below normal with freezing to
subfreezing temps likely north of I-40. NBM prob for temps to hit 32
deg are greater than 90% for northeast TN, southwest VA, southwest
NC, and the northern Cumberland Plateau. Areas just north of I-40
are in the 60 to 75% range. Areas just south of I-40 are in the 30
to 40% range, with little to no chance of reaching 32 degrees down
around Chattanooga. Additionally, winds will remain breezy through
the night. This will allow Wind Chill values to be in the 20s for
most areas, with teens expected across the higher elevations of the
east TN mountains and across southwest VA. So Sunday morning will be
quite unpleasant.

Dry and warmer Sunday afternoon through Monday with high pressure in
place across the area. With our next system approaching Tuesday, the
pressure gradient begins to strengthen on Monday. This will cause
winds to be breezy for most areas by Monday afternoon. With dry air
still in place, min RH values will be low during the afternoon hours
which will elevate fire weather concerns.

Models still in good agreement that showers hold off until Monday
night as the cold front slows down as it progresses eastward. It may
even be until Tuesday afternoon until rain arrives to northeast TN
and southwest VA. Mountain wave winds still look probable from
Monday night through Tuesday due to southeast flow across the
mountains around 40 to 50 kts at 850 mb. One change from yesterday
is that now it looks like the front will push east of our area by
Wednesday. This means lesser chances for rain compared to what
models showed yesterday. NBM now just showing slight chance to
chance POPs. Thursday and Friday look dry behind the cold front as
high pressure begins to build back into the region.

&&

.AVIATION...
(18Z TAFS)
Issued at 132 PM EDT Fri Mar 22 2024

Unsettled weather returns with rain chances increasing south to
north late this afternoon through tonight. Expect MFVR conditions
to settle in for all sites, but IFR conditions cannot be ruled
out(both cigs and vis). Have opted to include a scattered IFR
deck to cover the uncertainty at this time. In addition to the
rain, a wind shift is expected over the period. Gusts will settle
tonight as winds back, becoming more easterly. Winds will
continue to back and become more northerly for tomorrow afternoon,
in which breezy conditions will return. Turbulent low-level winds
near the mountains and western foothills will persist through the
evening.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             53  62  37  68 / 100  30   0   0
Knoxville McGhee Tyson Airport, TN  52  58  33  65 / 100  70   0   0
Oak Ridge, TN                       52  60  33  65 / 100  40   0   0
Tri Cities Airport, TN              49  56  28  65 / 100  80   0   0

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...Wind Advisory until 2 AM EDT Saturday for Blount Smoky Mountains-
     Cocke Smoky Mountains-Johnson-Sevier Smoky Mountains-
     Southeast Carter-Southeast Greene-Southeast Monroe-Unicoi.

VA...NONE.
&&

$$

SHORT TERM...KRS
AVIATION...KRS


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