-- Discussion containing changed information from previous version are highlighted. --
642
FXUS64 KMRX 132342
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
742 PM EDT Mon May 13 2024

...New AVIATION...

.SHORT TERM...
-- Changed Discussion --
(This evening through Tuesday)
Issued at 215 PM EDT Mon May 13 2024

Key Messages:

1. Wind Advisory for the far east Tennessee Mountains and
Foothills. Gust up to 45 mph possible.

2. Strong to possibly severe storms late Tuesday afternoon and
evening for the Plateau and southeast Tennessee. Marginal severe
hail up to 1 inch and strong gusty winds to 50 mph are possible.
Low-end threat of tornadoes across southeast Tennessee late in the
day.

Discussion:

Through the rest of the afternoon into the evening, weak
isentropic lift will produce scattered showers with light rain or
sprinkles. Besides the potential of light rain, main concern will
be windy conditions across the far east Tennessee Mountains and
Foothills. Camp Creek currently reporting gusts to around 35 mph
but speeds have decreased at Cove Mountains. The low-level jet is
forecast by HREF to increase this evening and expect the greatest
potential of strong winds between 01-06Z.

The boundary layer jet will enhance the potential for scattered
showers this evening/early morning especially over southwest
Virginia and northeast Tennessee.

For Tuesday, upper forcing from the left exit region of the jet
moving into the northern Gulf Coast states and continued
isentropic lift will pull warm/moist air into the region. The
model soundings show more elevated instability as the warm front
remains south of the area until late. Exact timing of a band of
scattered showers and storms remains uncertain but do expect an
area of convection during the day moving northeast.

By late afternoon, another area of convection will form over
middle Tennessee moving the Plateau and southeast Tennessee. This
second area of showers and storms will be more surface based with
MLCAPES up to 1500-1800. Shear will be strong enough to support
organized multi-cluster storms with effective shear of 35 m2/s2.
Mid-level lapse rates are near 6.5 which also supports decent hail
growth resident time. Overall, marginal severe hail and damaging
winds are the main threat.

The HREF is showing some 2-5km updraft helicity tracks across
southeast Tennessee with latest HRRR depicting 0-1km shear of
15-20kts. There is a low-end probability of tornado development
across these areas late in the day.
-- End Changed Discussion --

&&

.LONG TERM...
(Tuesday night through next Monday)
Issued at 215 PM EDT Mon May 13 2024

Key Messages:

1. Showers and thunderstorms continue through Wednesday.

2. A short break is expected, before another round of storms begins
heading into the weekend.

Discussion:

Tuesday evening/night should be the time-frame when we see the
boundary associated with this early week system move thorugh the
area providing a decent environment for thunderstorms. Forecast
soundings show there could be areas of over 500 J/kg of available
CAPE and some moderate (albeit mostly unidirectional) shear in the
mid and deep layers. This atmosphere should be conducive to seeing
more widespread thunderstorms and maybe even some strong to severe
thunderstorms. In the strongest storms we could possibly see near
severe level winds and marginally severe hail... But the primary
threat for the day continues to be the chances for isolated flooding
under heavy thunderstorms. With the weak and nearly unidirectional
shear the threat for tornadoes looks very low at this time. We
should get a break for much of the night and into early Wednesday
morning before the base of the trough/low moves overhead later in
the day leading to another (but hopefully more tame) round of
showers and thunderstorms.

Much of Wednesday night and Thursday should be dry as we sit between
systems and we should see temperatures climb back up to near or
above normal as we head towards the weekend.

By Friday we`ll see increasing precipitation chances as another
system looks to move out of the southern plains towards the
Ohio/Tennessee Valleys through the weekend. There is high confidence
in showers and thunderstorms across the southeast Friday/Saturday,
but lower confidence on the timing and strength of the storms. Some
models are showing more vigorous thunderstorm activity to our south
near the Gulf Coast which typically inhibits convection in the
southern Appalachian. But if the boundary and storms develop further
to the north we`ll likely see more widespread thunderstorms in our
region.

&&

.AVIATION...
-- Changed Discussion --
(00Z TAFS)
Issued at 736 PM EDT Mon May 13 2024

Expecting CIGs to deteriorate to IFR at CHA tonight, with a return
to VFR by the late afternoon. Given a minor wind event in the
mountains, TYS and TRI should be more resistant to low ceilings.
Two rounds of rain are probable tomorrow, first crossing from SW
to NE in the late morning to early afternoon, second a set of
afternoon TS in the late afternoon to the end of the period. Any
TS will potentially have brief reductions in VIS and gusty winds.
-- End Changed Discussion --

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             63  76  63  78 /  50  90  70  60
Knoxville McGhee Tyson Airport, TN  60  76  61  74 /  50  80  90  90
Oak Ridge, TN                       60  75  61  74 /  40  80  90  90
Tri Cities Airport, TN              58  76  58  71 /  60  60  80 100

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...Wind Advisory until 4 AM EDT Tuesday for Blount Smoky Mountains-
     Cocke Smoky Mountains-Sevier Smoky Mountains-Southeast
     Carter-Southeast Greene-Southeast Monroe-Unicoi.

VA...NONE.
&&

$$

SHORT TERM...DH
AVIATION...Wellington