466
FXUS64 KMRX 170551
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
151 AM EDT Tue Jun 17 2025

...New AVIATION...

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

Albeit weak, a jet entrance region on the eastern periphery of an
upper trough is promoting broad ageostrophic circulation across
portions of the southern Appalachians into the Tennessee Valley.
Upper divergence associated with this circulation is combining
with a weak and elevated quasi-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. Continuous 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...
(06Z TAFS)
Issued at 146 AM EDT Tue Jun 17 2025

Scattered showers and isolated thunder will fade in coverage
overnight. HREF ensemble paints prob of brief MVFR cigs at TRI and
CHA around the 40-50% range early Tuesday morning before improving
mid to late morning. SSW winds will increase to around 10-15kts
Tuesday afternoon with additional shower and thunderstorms across
the region during the afternoon and evening.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             85  71  87  72 /  80  70  70  30
Knoxville McGhee Tyson Airport, TN  86  70  85  71 /  60  70  70  30
Oak Ridge, TN                       84  69  84  70 /  70  70  70  40
Tri Cities Airport, TN              86  67  84  67 /  60  60  70  20

&&

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

$$

SHORT TERM...
AVIATION...KRS