475
FXUS64 KMRX 241715
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
115 PM EDT Sat May 24 2025

...New AVIATION...

.UPDATE...
Issued at 1119 AM EDT Sat May 24 2025

Only minor changes were made to the forecast for this afternoon.
Highs were bumped up just a smidge. Some thinning of clouds can
already be seen on satellite and guidance has gone up on temps
for this afternoon. Still expected to be below normal with some
clouds remaining and a cool air mass in place. Latest surface
analysis has the stationary boundary farther south over Southern
AL/GA. Guidance still suggests a wave of rain and maybe isolated
thunder moving through the region late this afternoon and evening.
Although this activity will be mainly confined to south of I-40
and the Cumberland Plateau. CAMs confirm this activity.

&&

.SHORT TERM...
(Today and tonight)
Issued at 255 AM EDT Sat May 24 2025

Key Messages:

1. Today is a transition day from a dry to a wet pattern that will
continue into at least midweek.

2. Isolated to scattered showers possible south of I-40 today,
with mostly dry conditions north. Better rain chances expected
tonight though.

Discussion:

Northwest upper flow will transition to more zonal flow today as
an upper low over the eastern Great Lakes and New England areas
shifts further northeast. Regional radar and satellite imagery
show an embedded disturbance moving ESE from the Missouri
bootheel area this morning. This may bring some isolated to
scattered rain showers to the southern areas through mid afternoon
but confidence is low as high res CAM guidance continues to keep
the precip southwest of our CWA. Better agreement is seen in rain
chances increasing in magnitude and coverage overnight night as
another convectively driven disturbance moves in. Current PoPs
reflect NBM trends through the day, but I may need to go and
amend the forecast by the end of the shift based on how radar
trends over the next few hours.

&&

.LONG TERM...
(Sunday through Friday)
Issued at 255 AM EDT Sat May 24 2025

Key Messages:

1. Chances for showers and embedded thunderstorms essentially
every day.

2. The threat of severe storms seems low through the period.

3. Repeated rounds of rainfall could result in a low-end flash
flooding threat by Tue/Wed. Will be monitoring this over the
coming days.

Discussion:

The main story for the long term is the pattern will be active,
with repeated chances for showers and embedded thunderstorms
from Sunday through much of the coming week. A couple of more
distinct features currently noted in guidance would be the
possibility of remnant MCS activity moving in from the west late
Sunday, and another being a shortwave ejecting northeast from the
Arklatex region into the Ohio valley Monday night into Tuesday.
Both show promise for widespread convection across the region. In
general, chances for severe storms seems low during the long term
period. Depending on the trajectory of that Arklatex shortwave,
that could present some opportunity for more organized convection,
but as it stands chances seem low through the period. This is
supported by long range HREF probabilistic data showing less than
a 20 percent chance of CAPE and bulk shear exceeding 1,000 J/kg
and 30 kts respectively at any point in the next week. Even the
chances for just CAPE exceeding 1,000 J/kg alone are less than
40-50 percent for almost the entirety of the CWA. Believe any
severe threat will be the exception as opposed to the norm. The
other concern might be flooding, as PWATs will be fairly high and
there will be repeated rounds of rainfall over the next week. The
90th percentile rainfall amounts off of the HREF as well as NBM
show totals exceeding 4" in mainly the southern half of the CWA by
Wednesday afternoon. While not extremely concerning, the threat of
localized flash flooding isn`t zero and the pattern suggests it`s
worth monitoring.

&&

.AVIATION...
(18Z TAFS)
Issued at 108 PM EDT Sat May 24 2025

Showers are likely near CHA mainly late this afternoon and
evening. Thunder chances are low. The cloud deck will lower
tonight. Some MVFR CIGs will be possible mainly near CHA in the
morning hours but confidence is low. Showers will be more
widespread tomorrow mainly after this forecast period. Winds will
be light and variable.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             60  79  63  78 /  60  80  60  70
Knoxville McGhee Tyson Airport, TN  57  74  60  77 /  40  80  70  70
Oak Ridge, TN                       56  73  59  76 /  40  80  70  60
Tri Cities Airport, TN              52  72  56  73 /  20  60  60  40

&&

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

$$

SHORT TERM...CD
LONG TERM....CD
AVIATION...McD