408
FXUS64 KMRX 151329
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
929 AM EDT Mon Jul 15 2024

...New UPDATE...

.UPDATE...
Issued at 927 AM EDT Mon Jul 15 2024

Forecast is on track this morning with temperatures slightly
cooler than previous days due to the mid-level cloud deck.
However, moisture is on the increase, especially across southern
areas of the forecast area, which will lead to higher heat index
values this afternoon. Isolated diurnal convection continue to be
expected across the plateau and southern counties of the forecast
area this afternoon.

&&

.SHORT TERM...
(Today and tonight)
Issued at 342 AM EDT Mon Jul 15 2024

Key Messages:

1. Hot again today. Heat Indices will range from the mid/upper 90s
north of I-40 and near 100 south of I-40.

2. Better coverage of showers and storms today, but still
isolated to scattered.

Discussion:

A weak, mid-level, shortwave still resides just to our southwest.
Conditions look more favorable today to see isolated to scattered
showers and storms this afternoon. This is mainly due to better
moisture today due to the southerly flow at 850mb. Weak mid-level
vorticity and upper divergence continue to remain in place. Greatest
coverage will be during peak heating and generally south of I-40.
However, even with the increased coverage, many places will still
remain dry today. Not expecting any severe weather today.

Due to the increase in moisture today, I expect greater cloud cover.
This will mainly be in the form of a mid/high cloud deck. The
uncertainty though is how much coverage as models are in very poor
agreement. Best guess as of now is a SCT mid/high deck for much of
the area with some areas seeing BKN. If this plays out, this will
dampen our temperatures by a few degrees compared to yesterday. By
how much depends on the extent of cloud cover. Generally have the
central and southern TN valley a few degrees cooler. While northeast
TN and southwest VA will see similar temps due to lesser cloud cover
that far north. Heat Indices will still range from the mid/upper 90s
to near 100 for this afternoon which is similar to yesterday, due to
the increasing dew points.

Convection peters out this evening with loss of heating. Above
normal temps expected overnight with lows in the lower 70s for most
places.

&&

.LONG TERM...
(Tuesday through Sunday)
Issued at 342 AM EDT Mon Jul 15 2024

Key Messages:

1. Unseasonably hot conditions are expected Tuesday and Wednesday.
Heat indices will range from the upper 90s to lower 100s each
afternoon.

2. Scattered storms are expected on Tuesday with more numerous
coverage Wednesday and Thursday. Lower chances continue into this
weekend with relief from the heat expected Thursday onward.

Discussion:

Overall, there remains pretty minimal change in the messaging and
key points from previous forecast issuance. Increasing moisture
advection and weak disturbances aloft will lead to scattered chances
for showers and storms Tuesday, although, latest hi-resolution
guidance generally highlights areas along and south of I-40 with the
greatest chances for precipitation. While temperatures relative to
the previous days are expected to ever so slightly cool, increasing
humidity will still allow for heat indices to approach the lower
100s across portions of the central and southern valley. There is
potential that a heat advisory may be needed in future forecast
packages but there is a conditional aspect to reaching criteria
revolving around how exactly storm coverage and their timing pans
out.

Humid and muggy conditions will persist into Wednesday as a surface
boundary encroaches on the region, bringing increased chances of
scattered to widespread showers and storms. While temperatures will
be cooler, continuance of favorable moisture advection will promote
heat indices in the lower 100s across portions of the central and
southern valley once more. Advisory criteria currently looks
unlikely this day.

H5 heights fall to ~586-584dam as greater influence from troughing
and persistent clouds bring relief from the heat Thursday into the
weekend. The chance for precipitation will linger each day, however,
there is some uncertainty in the best timing/coverage based on
potential shortwaves and how exactly a surface boundary lingers
across the region. For the Tuesday through Thursday timeframe, there
looks to be pretty minimal threat for any strong to severe concerns
but as is typical of any summertime activity, locally gusty winds
are possible with the tallest storms. We are highlighted by WPC for
a marginal risk in excessive rainfall for Wednesday and Thursday due
to PWAT values around 1.9-2.1 inches and tall/skinny CAPE profiles.
However, the lack of recent rainfall should really limit any flood
threat.

&&

.AVIATION...
(12Z TAFS)
Issued at 709 AM EDT Mon Jul 15 2024

VFR conditions through the period at TYS and TRI with light
southwest winds. Mostly VFR at CHA but a PROB30 MVFR during the
afternoon for thunderstorms. Isolated showers and storms may be
near TYS and TRI this afternoon but not enough confidence to
include VCTS.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             95  74  95  75 /  40  30  50  30
Knoxville McGhee Tyson Airport, TN  95  74  95  75 /  30  10  40  30
Oak Ridge, TN                       95  72  95  74 /  30  10  40  30
Tri Cities Airport, TN              94  70  93  72 /  20  10  40  30

&&

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

$$

SHORT TERM...
LONG TERM....KRS
AVIATION...