414
FXUS64 KMRX 251922
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
322 PM EDT Tue Jun 25 2024

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

.SHORT TERM...
(This evening through Wednesday)
Issued at 307 PM EDT Tue Jun 25 2024

Key Message

1. Isolated to scattered showers and storms expected tomorrow
afternoon and early evening. A couple of strong storms will be
possible.

Discussion:

Tonight will be clear and quiet as high pressure remains in place.
Tomorrow, a trough will move into the TN and Ohio Valleys. At the
surface, a cold front will approach the region tomorrow evening.
Showers and storms will develop upstream and over the region
tomorrow afternoon. CAMs have isolated to scattered coverage and
intensity looks mostly weak to moderate for storms. HREF has CAPE
values less than 1000 J/kg tomorrow afternoon/evening. Moisture
will start to rebound by tomorrow evening with PWAT values getting
back to the 1.4 to 1.6 range. Overall, the severe threat looks
marginal but a couple strong to severe storms with gusty winds
cannot be ruled out.

Tomorrow will be hot with highs in the mid to upper 90s in the TN
Valley with sunny skies and most shower activity later in the
day.

&&

.LONG TERM...
(Wednesday night through next Tuesday)
Issued at 307 PM EDT Tue Jun 25 2024

Key Messages:

1. Decent rain chances Wednesday evening into Thursday and then
again Saturday night into Sunday.

2. Otherwise, continued hot and dry conditions through extended
forecast.

3. Ridging aloft rebuilds over the area Monday and Tuesday with
scattered showers and thunderstorms.

 Discussion:

A shortwave moving through the Great Lakes and Ohio Valley Wednesday
will reach the forecast area early Wednesday evening producing
showers and thunderstorms from west to east overnight into Thursday.
A cold front moving through the Ohio Valley will make it through the
southern Appalachians Wednesday night and shifting east of the
Appalachians Thursday. Model guidance is predicting scattered to
numerous showers and thunderstorms across the eastern Tennessee
Valley by evening and then slowly pushing through during the
overnight hours ahead of the front. The NAM model is showing strong
to severe storms to develop along the front mainly during the 00z to
06Z hours Wednesday night. GFS and ECMWF show storms weakening
during the evening as they push southeast. SPC day 2 outlook calls
for marginal risk of strong storms developing due to heating and
high instability during the day and expect a cluster of
strong/severe storms to develop over the higher terrain of eastern
KY/WV and northern VA. This activity could make it into northern TN
and SW VA before weakening. The vertical shear will be weaker as it
move south south, but deeper mixing with very steep lapse rates from
forecast soundings may produce damaging gusts and isolated large
hail during the evening with this convective activity.

Thursday looks somewhat drier and slightly cooler but latest models
showing lingering rain chances behind front with best chances in the
higher terrain areas of east Tennessee and southwest North Carolina.
Temperatures will be several degrees cooler than Wednesday. Thursday
night and Friday ridging builds back over the forecast area.
Afternoon and evening showers and storms will be possible Friday.
Then on the weekend the frontal boundary to the south is forecast to
move north and at the same time another frontal system moves into
the Ohio Valley and approaches the Tennessee Valley early Sunday.
The moist unstable southwest flow ahead of the next front and upper
trough will be conducive to increasing showers and storms late
Saturday from the south and continue through Sunday evening. The
building ridge as southwest flow will push highs back to the lower
to mid 90s and edge heat index values up to around 100 or above
across parts of the central and southern valley. Rain chances will
be high Saturday night into Sunday evening with some good rainfall
amounts across the higher elevations. Generally went below NBM
guidance for NBM dewpoints after Wednesdays front with highest
values on the weekend ahead of next front. Monday rain chances lower
again behind next front and continue Tuesday. Ridging aloft
strengthens again so will not really see a temperature drop but rise
a few degrees again into the lower to mid 90s after brief cool down
Sunday with more clouds and rainfall.

&&

.AVIATION...
(18Z TAFS)
Issued at 120 PM EDT Tue Jun 25 2024

VFR conditions expected this TAF cycle. Light winds will become
more southwesterly tomorrow morning.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             72  99  74  93 /   0  10  40  30
Knoxville McGhee Tyson Airport, TN  69  96  71  91 /   0  20  50  40
Oak Ridge, TN                       69  96  70  90 /   0  20  60  30
Tri Cities Airport, TN              65  94  69  87 /   0  30  60  50

&&

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

$$

SHORT TERM...McD
LONG TERM....TD
AVIATION...McD