-- Discussion containing changed information from previous version are highlighted. --
511
FXUS64 KMRX 270517
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
117 AM EDT Mon May 27 2024

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

.SHORT TERM...
-- Changed Discussion --
(Today and tonight)
Issued at 106 AM EDT Mon May 27 2024

Currently a line of severe thunderstorms is moving through Middle TN
and central KY. Ahead of the line the biggest concern will be the
possibilty of some isolated cells developing into an more untapped
environment across the southern Valley. This area has not been
worked over/stabilized from the afternoon/evening convection and dew
points and instability remain elevated south of Interstate 40.
Special soundings launched this evening show a fairly capped
environment at observation, but if storms break the cap they`ll have
ample instability and shear to tap into with the aid of the strong
southwest LLJ. These discrete cells ahead of the main line would
likely have the greatest chance to strengthen into supercells
capable of all types of severe weather including tornadoes.
Eventually the main line should catch up with any developed
supercells and overtake them.

The main line will quickly move through the area, likely going from
the Cumberland Plateau and then being east of the Appalachians within
a 5 hour window overnight tonight. The primary threat with this main
line will be damaging straight line winds up to 70mph, hail the size
of a quarter, and a quick tornado spin up is possible within notches
of the primary line. In addition the flood risk remains elevated as
we`ve seen pockets of 1-3 inches of rain during the
afternoon/evening convection. Areas north of Interstate 40 have seen
the most widespread and heaviest precipitation, meaning that these
locations are most primed to see additional flooding of low lying
areas, but the flood risk is still present area-wide.
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&&

.LONG TERM...
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(Tuesday through Sunday)
Issued at 106 AM EDT Mon May 27 2024

Key Messages:

1. Another round of afternoon/evening storms possible on Monday

2. Drier and cooler weather to begin Tuesday through the end of the
week. with a gradual warming trend into the weekend.

Discussion:

Monday afternoon/evening will see one more round of more isolated
thunderstorms over the southern Appalachian region as a weaker
shortwave traverses the base of the larger trough. The biggest
question will be how much clearing and destabilization occurs during
the daytime on Monday, which would create an unstable atmosphere for
the afternoon storms to tap into. As of this writing the main line
has not moved through overnight, so there is still much uncertainty
on the cloud coverage behind it. At this point the strongest storms
could bring with them strong straight line winds and hail as the
primary threats. And after the heavy rains overnight the flooding
threat will remain for low lying areas that got several rounds on
Sunday.

After Monday we`ll make a turn for drier and cooler weather for much
of the rest of the work week. We`ll sit underneath some broad
troughing over the eastern third of the United States, helping to
keep temperatures at or below seasonal normals into the weekend.
Over the weekend strong ridging begins to build in ahead of an
approaching system over the northern plains. We`ll have some shower
and thunderstorm chances in the forecast for the weekend, but there
is still much uncertainty with regards to how far east storms are
able to push into the ridge at this time.
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&&

.AVIATION...
-- Changed Discussion --
(06Z TAFS)
Issued at 106 AM EDT Mon May 27 2024

We are still expecting a squall line to move through the region
late tonight/early morning hours. Gusty winds are likely along the
leading edge of the storms. Moderate rain and thunder will
continue after the worst of the storms move through. Monday
morning storms and rain will be moving out. MVFR CIGs will lift
by late morning or early afternoon and westerly winds will be a
tad gusty.
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&&

.PRELIMINARY POINT TEMPS/POPS...
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Chattanooga Airport, TN             87  63  86  62 /  50   0   0   0
Knoxville McGhee Tyson Airport, TN  82  61  81  59 /  70  10  10   0
Oak Ridge, TN                       82  60  82  58 /  60   0  10   0
Tri Cities Airport, TN              80  59  77  55 /  80  10  10   0
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&&

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

$$

SHORT TERM...
AVIATION...McD