766
FXUS64 KMRX 170233
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
1033 PM EDT Mon Jun 16 2025

...New UPDATE...

.UPDATE...
Issued at 1029 PM EDT Mon Jun 16 2025

Albeit weak, a jet entrance region on the eastern periphary of an
upper trough is promoting broad ageostrohic circulation across
portions of the southern Appalanchians into the Tennessee Valley.
Upper divergence associated with this circulation is combining with
a weak and eleveated qasui-warm front, noted by an enhanced area of
925mb frontogenesis within SPC mesoanalysis page, to produce
scattered convection across the region. A downward trend in
lightning activity and overall storm intensity has been observed
over the last 30 to 60 minutes as instability wanes behind the now
set sun.

SPC meso forecast trends really knock down the MLCAPE values to
1000J/kg or less around midnight and later. While a stronger storm
and isolated hydro issues may arise for a little while longer,
activity should lessen into the AM hours. Continous days of
showers/tstorms promote a moist boundary layer and soils, with HREF
probabilities of fog(30-50%) focused on the northern Cumberland
Plateau into southwest Virginia so take caution for some patchy fog
early Tuesday morning in these areas - especially sheltered
locations along area waterways.

&&

.SHORT TERM...
(This evening through Tuesday)
Issued at 227 PM EDT Mon Jun 16 2025

Key Message:

Showers and thunderstorms continue today bringing gusty winds and
brief heavy downpours.

Discussion:

Currently scattered showers and few thunderstorms are ongoing across
the southern Appalachian region. Temperatures south of the front
held up near the Ohio River Valley have climbed been steadily
climbing and with a slow moving shortwave/trough moving ever closer
we`re seeing another day of shower and thunderstorm activity.
Instability is still limited with generally 1,000 J/kg or less of
MLCAPE across the region which should limit convective growth. Even
though the storms may be limited in strength, they will be able to
tap into the 1.5+ inches of PWAT in the atmosphere causing brief
heavy downpours. As has been the case for this past week these heavy
rainfalls can quickly cause flooding or water over roadways of urban
and other low lying areas. Expect patchy fog to develop in the
morning hours on Tuesday in areas that get rain heading into the
evening hours.

&&

.LONG TERM...
(Tuesday night through next Monday)
Issued at 227 PM EDT Mon Jun 16 2025

Key Messages:

1. Storms are possible mainly each afternoon the rest of the week
with peak heating. Gusty winds and heavy rainfall are the main
concerns.

2. With above normal moisture available, several inches of rain will
likely occur in some locations over the period. Isolated flooding is
possible in areas that see repeated or prolonged periods of heavy
rainfall.

Discussion:

At the start of the period, the slow moving shortwave will be
centered near the Mississippi River Valley with broad southwesterly
flow locally. Extra Gulf moisture will push PWATs up to around 2
inches... Well above normal for mid-June. MLCAPE should top out near
1,500 J/kg Tuesday afternoon, and the passing shortwave will nudge
winds aloft so deep-layer shear runs about 20+ kts. The hi-res
models (CAMs) fire up storms late-day along the plateau and southern
Appalachians and slide them into the Valley during the evening. The
strongest of these storms may dump heavier downpours, and create a
few strong wind gusts.

Heading into Wednesday, the shortwave lifts north while another,
deeper trough digs to our west. We stay locked in a humid
southwesterly flow with plenty of instability, so scattered showers
and storms linger. Surface low pressure spinning toward the Great
Lakes will tighten the pressure gradient and sharpen a front to our
west. By Thursday, that front and its attendant shortwave slide
overhead, likely sparking a more organized, widespread round of
storms. Current timing (afternoon/evening) lines up with max
heating, so the strongest storms will be capable of damaging winds
and isolated flooding.

By Friday, the trough scoots east and high pressure builds in,
drying us out nicely. After that, eyes turn to what looks like our
first heat wave for much of the eastern U.S. Guidance strengthens a
500-mb Saturday and Sunday. Knoxville hasn`t cracked 90 yet this
year, but that streak is in jeopardy. If the current forecast
verify`s everywhere from Chattanooga up into the Tri-Cities will
break the 90 degree threshold this weekend.

As it will be our first big heat wave of the year after a mild
spring/early summer some heat safety reminders:
-Hydrate early and often.
-Take breaks in the shade or A/C...Check on kids, pets, and
 neighbors who dont have reliable cooling.
-Look before you lock: never leave people or pets in a parked car.

&&

.AVIATION...
(00Z TAFS)
Issued at 736 PM EDT Mon Jun 16 2025

Scattered showers and storms linger around the region and will
continue to do so near midnight as a weak and elevated warm front
drifts northeastward. Coverage will wane overnight as instability
weakens though isolated activity cannot be totally ruled out
during the night. SPC HREF depicts 30-50% probabilities of short-
lived MVFR cigs at TRI and CHA Tuesday morning. Otherwise,
conditions will be predominately VFR outside of any convection.
SSW winds increase to around 10kts Tuesday afternoon, with
additional showers and storms expected to develop.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             71  85  71  87 /  30  80  70  70
Knoxville McGhee Tyson Airport, TN  70  86  70  85 /  40  80  70  70
Oak Ridge, TN                       69  84  69  84 /  40  90  70  70
Tri Cities Airport, TN              67  86  67  84 /  30  80  50  70

&&

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

$$

SHORT TERM...
AVIATION...KRS