427
FXUS64 KMRX 031743
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
143 PM EDT Wed Jul 3 2024

...New AVIATION...

.UPDATE...
Issued at 1114 AM EDT Wed Jul 3 2024

In the nearest term, the sky forecast was updated to reflect
current cloud cover. MVFR ceilings are still being observed at
KCHA. Current conditions show mid 80s late this morning over
places with mostly sunny skies.

KS

&&

.SHORT TERM...
(Today and tonight)
Issued at 309 AM EDT Wed Jul 3 2024

Key Messages:

1. Hot and likely dry day today. Heat indices approaching 100F near
Chattanooga.

Discussion:

Upper ridge reaches its fullest extent across the southeast relative
to our local weather forecast today, with the 594 dm contour
extending into southern Kentucky. Underneath, the southwesterly
low level flow will continue to work to advect warmer and more
humid air northwards across East Tennessee and the region at
large. Not convinced we will see any rain anywhere today, guidance
is struggling to convect in the face of warm midlevel
temperatures acting as a lid on storm development. Seems the best
possibility for an errant shower is in the southern Cumberland
Plateau, where modeled CAPE might be able to overcome the warm
temperatures aloft problem.

Heat indices will range from the 90s up to 100F today, so hydration
and breaks in the shade are important for those spending extensive
time outdoors. Tonight will be another warm night, with temperatures
slowly falling as HREF models some decent cirrus cloud coverage
overnight.

&&

.LONG TERM...
(Thursday through Tuesday)
Issued at 309 AM EDT Wed Jul 3 2024

Key Messages:

1. Hot with a few showers and storms possible Independence Day.

2. Higher chances for showers and storms Friday, then chances
decrease during the weekend before trending up again early in the
week.

3. High temperatures will continue to run around to several degrees
above normal.

Discussion:

We start the period under a flattened upper ridge with an upper
trough moving through the Plains. Moisture will continue to slowly
increase over our area, although the upper ridge parked over the
Southeast and Gulf States will preclude any strong moisture return.
Convective energy still looks modest for Independence Day, but the
HREF ensemble data generally indicates a 60-80% chance of SBCAPES
exceeding 1000 J/kg. Expect some isolated to scattered showers and
thunderstorms, with the highest chances over the higher terrain as
well as our northwest counties which will be closer to some weak
short wave energy passing by to our north. The northern Plateau/SW
VA area will also have the best chance for a stronger storm with
strong gusty winds the primary threat. It will be quite hot as dew
points continue to creep upward and temperatures top out in the 90-
95 degree range across the valleys. This combination of temperatures
and humidity will result in heat index values in the upper 90s to
lower 100s across most valley locations, so following good heat
safety practices will be very important for those spending time
outdoors for the holiday.

The upper trough will swing across the Great Lakes region Friday and
Saturday, with a surface cold front approaching our area Friday and
moving through Friday night/early Saturday.  We will see an increase
in showers and thunderstorms ahead of and near the front Friday into
Friday night with coverage decreasing Saturday once the front exits.
Friday will continue to be quite hot with heat index values in the
upper 90s and lower 100s in many valley locations.

The front looks likely to be stalled just to our south Sunday into
Monday. Somewhat drier air will be over our area, but there still
may be a few isolated to scattered showers and storms around each
day, then an uptick in moisture is expected to bring more coverage
of convection by Tuesday. High temperatures will be around to
slightly above seasonal normals all three days.

&&

.AVIATION...
(18Z TAFS)
Issued at 138 PM EDT Wed Jul 3 2024

VFR generally expected through the period. MVFR at CHA eroded
recently, thus hanging on longer than thought. CIGS should
continue to scatter and lift with time overnight. Winds become
calm overnight. The best outside chance of a shower or storm
tomorrow would be near TRI, but do not have anything in the TAF
due to it being towards the very end of the TAF and model
inconsistency and confidence are on the lower end.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             94  77  95  78 /  10   0  30  20
Knoxville McGhee Tyson Airport, TN  94  75  93  76 /  10   0  30  20
Oak Ridge, TN                       94  74  94  75 /  10   0  30  30
Tri Cities Airport, TN              91  70  93  71 /   0  10  50  20

&&

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

$$

SHORT TERM...Wellington
AVIATION...KS