102
FXUS64 KMRX 171117
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
717 AM EDT Thu Jul 17 2025

...New UPDATE, AVIATION...

.UPDATE...
Issued at 715 AM EDT Thu Jul 17 2025

With the ground already saturated in many locations across our
northern counties, and additional showers and thunderstorms likely
with the best coverage across the  north, have issued a flood
watch for flash flooding across our northern tier of TN counties
and SW VA for this afternoon and evening.

&&

.SHORT TERM...
(Today and tonight)
Issued at 137 AM EDT Thu Jul 17 2025

Key Messages:

1. Scattered storms are expected again later this afternoon into the
evening hours, especially north of I-40, with damaging winds and
isolated flooding possible.

2. Hot and humid conditions will continue with highs rising into the
90s and heat index values around 100 degrees for many Valley
locations.

Discussion:

Currently early this morning, broad upper-level ridging remains in
place across the southeastern U.S. A weak tropical disturbance is
also moving towards southern Mississippi and Louisiana. Abundant
moisture is evidenced in PWAT values ranging from 1.7 to 2 inches.
When combined with the surface heating, a similar thermodynamic
environment can be expected with MLCAPE values expected to reach
1,500 to over 2,000 J/kg during peak heating. This will make for
another day of scattered storms with the latest CAMs suggesting the
greatest coverage to be north of I-40. Some sources even show a
potential MCS diving down from the Ohio River Valley into the region
by early evening. Regardless, the environment will continue to lack
any notable shear due to weak winds aloft. Regardless, the threat
for locally strong winds and isolated flooding will remain,
especially after the repeated rainfall that was seen this past
night. However, if an MCS does develop and progress into the region,
more widespread damaging winds are possible. But this is still
uncertain due to the strength of high pressure to our south. Some
activity could linger overnight with fog development possible in
places that see rainfall.

&&

.LONG TERM...
(Friday through Wednesday)
Issued at 137 AM EDT Thu Jul 17 2025

Key Messages:

1. Scattered storms will continue through much of the extended
period with chances for strong winds and localized flooding in some
storms.

2. Hot and humid conditions are expected through the period with
high temperatures in the 90s and heat index values around 100
degrees across the Valley. More significant heat is possible by the
middle of next week.

Friday through Sunday

Upper-level ridging will remain in place across the region on Friday
with the remnants of the tropical system expected to progress into
the southern Mississippi River Valley. This setup will continue hot
and humid conditions with even more abundant moisture moving into
the region through the weekend, following the progression of
tropical remnants. PWAT values could exceed 2 inches, which is above
the 90th percentile, even for this time of year. This does indicate
even better coverage of convection through the weekend, in
comparison to recent days. Overall, the convective environment will
be similar to previous days with MLCAPE of around 1,500 to 2,000
J/kg with minimal shear. Strong winds are possible in some of the
storms, along with localized flooding. The flooding threat will
depend on how much coverage is seen in the short term period, but
many places north of I-40 did pick up decent rainfall yesterday.

Monday through Wednesday

Heading into the next week, the upper-level ridge axis will shift to
our west as ridging slowly retrogrades. This will allow for more
northwesterly flow aloft, which may slightly cool temperatures in
the upper-levels. When combined with remaining heat and abundant
moisture, the convective environment may become more favorable than
in recent days. Some sources suggest mid-level lapse rates to reach
around 6 C/km, above the near 5 C/km values in the next couple of
days. This setup could also set the stage for an MCS early in the
week. By Wednesday, upper-level ridging is expected to progress back
eastward and possibly expand to 500mb heights above 5,950m. This
would lessen chances for convection and increase the focus on heat.

&&

.AVIATION...
(12Z TAFS)
Issued at 715 AM EDT Thu Jul 17 2025


Will see showers and thunderstorms around again, and will try to
time highest probability period with prob30 thunder groups all
sites. Outside of any convection, will have a VFR forecast all
sites with the exception of brief fog to start at TRI.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             94  74  93  75 /  40  40  60  30
Knoxville McGhee Tyson Airport, TN  93  74  91  74 /  60  40  70  40
Oak Ridge, TN                       92  73  90  72 /  60  40  80  40
Tri Cities Airport, TN              88  70  87  70 /  70  40  90  40

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...Flood Watch from 2 PM EDT this afternoon through this evening
     for Campbell-Claiborne-Hancock-Hawkins-Johnson-Northwest
     Carter-Scott TN-Sullivan.

VA...Flood Watch from 2 PM EDT this afternoon through this evening
     for Lee-Russell-Scott VA-Washington VA-Wise.

&&

$$

SHORT TERM...
LONG TERM....BW
AVIATION...