136
FXUS64 KMRX 240126 AAA
AFDMRX

Area Forecast Discussion...UPDATED
National Weather Service Morristown TN
926 PM EDT Sun Jun 23 2024

...New UPDATE...

.UPDATE...
Issued at 918 PM EDT Sun Jun 23 2024

A storm did become severe earlier this evening due to the high
DCAPES (1200 J/Kg) along the west-most region of better
instability. Also just enough broad effective shear of 30 knots to
produce rotation with the storm. Trees down were reported across
western Claiborne.

Scattered convection associated with a weak shear axis moving
across the Tennessee valley. Best instability is west of the
Tennessee valley. This axis of better instability will move into
the area overnight continuing the potential of showers and
possibly a thunderstorm through early morning. MLCAPEs increase to
1000-1500 so can not rule out showers until 4-6 am Monday morning
especially across the far east Tennessee mountains.

Overall, current forecast looks good with limited changes.

&&

.SHORT TERM...
(This evening through Monday)
Issued at 149 PM EDT Sun Jun 23 2024

Key Messages:

1. Thunderstorms arrive from the northwest this evening. A few
could pose a damaging wind risk mainly over the northern plateau
region, but most will be run of the mill storms.

2. Monday will be dry and slightly cooler with dew points in the
60s by afternoon.

Discussion:

A trough is moving into the region from the Ohio Valley this
afternoon. The surface cold front is currently (215 PM EDT) near
SE Missouri/NE Arkansas. Hi-res guidance suggests isolated
showers and storms developing early this evening. The best chance
for strong showers and storms and the most coverage will be mid
to late evening as the cold front moves into Middle Tennessee. The
threat for severe storms looks marginal with CAPE less than 1000
and the front approaching the region after sunset. A few strong to
severe storms cannot be ruled out mainly in the Plateau Counties.
Showers and storms will likely be scattered and some locations
may not even get any rain.

The cold front will move through in the early morning hours.
Monday will be dry with slightly cooler temps. Humidity will be
lower with dew points dropping to the 60s by tomorrow afternoon
with northerly flow and good mixing conditions.

&&

.LONG TERM...
(Monday night through next Sunday)
Issued at 149 PM EDT Sun Jun 23 2024

Key Messages:

1. Rain chances arrive on Wednesday through Wednesday night with a
weak frontal passage. Another front may bring showers and storms
next weekend.

2. Above normal temperatures continue through the period, although
humidity may be moderated on Tuesday and Thursday behind frontal
passages.

Discussion:

We will be in a deep northerly flow pattern to start the period,
with a cold front across central AL/GA and high pressure centered
over WV. Dry air near the surface behind the front will provide
comfortable low temperatures Tuesday morning, in the upper 50s to
mid 60s. Highs will reach the 90s again under full sun, but
dewpoints in the low to mid 60s will take the edge off the heat a
bit.

Low level moisture will increase somewhat on Wednesday as a cold
front moves into the OH Valley region. A pre-frontal trough may
bring some scattered showers and storms Wednesday afternoon, with
greater coverage expected Wednesday night with the frontal zone
and upper trough passage. CAPE will be generous with the NAM
showing MLCAPE around 2000 J/kg, which should support some strong
pulse convection, but the lack of shear will limit any organized
threat of severe storms. Low probability wording in the HWO will
continue for now.

Dry conditions are likely on Thursday, although the NBM holds
some chance PoPs in the area behind the front and upper trough.
This appears overdone and will be lowered to a slight chance.
Temps and dewpoints will drop slightly on Thursday behind the
front, with highs in the mid 80s to lower 90s, and dewpoints in
the lower to mid 60s. High pressure off the Atlantic coast becomes
dominant again on Friday, which will bring rising temperatures
and humidity. Models differ on timing of an approaching cold front
over the weekend, which will bring some increasing rain chances
either Saturday or Sunday.

&&

.AVIATION...
(00Z TAFS)
Issued at 717 PM EDT Sun Jun 23 2024

Main question is the scattered convection across the Plateau and
middle Tennessee will be able to survive the limited initial
instability across the Tennessee valley. Will maintain likely
probability for the TAF sites for mainly 03-06Z but confidence is
low. SPC meso-analysis shows MLCAPE drop significantly into valley
even though models show increasing instability into this evening
before frontal passage early Monday morning.

Besides the convection broken 3500 feet ceiling is expected across
TRI by early Monday morning along with FROPA with scattered to
broken at TYS and CHA.

For Monday, flight conditions are/become VFR with breezy west to
northwest winds.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             74  94  67  95 /  40   0   0   0
Knoxville McGhee Tyson Airport, TN  72  89  64  92 /  60   0   0   0
Oak Ridge, TN                       70  89  64  92 /  60   0   0   0
Tri Cities Airport, TN              69  85  59  90 /  60  10   0   0

&&

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

$$

SHORT TERM...DH
LONG TERM....DGS
AVIATION...DH