611
FXUS64 KMRX 081900
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
300 PM EDT Mon Jul 8 2024

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

.SHORT TERM...
(This evening through Tuesday)
Issued at 258 PM EDT Mon Jul 8 2024

Key Messages:

1. Heat Index of 100-105 expected tomorrow afternoon in the central
and southern TN Valley.

2. Isolated to scattered showers/storms tomorrow in a very moist air
mass.

Discussion:

Through the rest of the afternoon, isolated to scattered showers and
thunderstorms will affect portions of the area, mainly in the
Pleatau and mountains. A few of these could move into the TN Valley,
or put out outflow boundaries that lead to new cells. The CAMS show
some showers persisting until 06Z in southern areas, possibly due to
increasing moisture advection near 850 mb with an increasing
southerly flow. Will hold onto some slight chance PoPs until around
06Z south of I-40.

The remnants of Beryl will track across AR to the central MS
Valley region tomorrow. In East TN, it will have little impact
other than maintaining a very moist air mass and PW values around
2 inches. With very little in the way of forcing mechanisms
present, convective development will likely favor the higher
terrain areas of the mountains and Plateau. As usual, the NBM PoPs
appear way too high, and will be cut back to isolated/scattered
coverage.

High clouds associated with Beryl`s remnants will spread across the
area, but the uncertainty lies with how much this will impact high
temperatures. Dewpoints are likely to be in the 70-75 range, and if
highs can reach 95-98, the heat index will meet or exceed Heat
Advisory criteria of 105 or higher in the central and southern
Valley. However, the questions about cloud cover lower confidence on
the temperature forecast , and so will hold off on a Heat Advisory
for now, and let the mid shift decide with additional data.

&&

.LONG TERM...
(Tuesday night through next Monday)
Issued at 258 PM EDT Mon Jul 8 2024

Key Messages:

1. Best chance for precip is Tuesday night as the remnants of Beryl
pass to our northwest. Otherwise, little chance for any widespread
precip through the rest of the long term.

2. Breezy east TN mountain winds Tuesday night into Wednesday early
morning, with gusts to around 30 to 35 mph.

Discussion:

Isolated to scattered showers and storms are likely to be ongoing
Tuesday night as we begin the long term period. This is due to the
remnants of Beryl moving through the MS River Valley. At best,
convection will be scattered. This means that most locations won`t
see rain, but some will.

Noticed that the NAM 850mb winds looked fairly strong for this time
of year Tuesday night, with roughly 30kts from out of the south.
This makes sense though due to a tightening pressure gradient across
our area with the remnants of Beryl to our northwest and high
pressure to our east. This would yield gusts from 30 to 35 mph
across our highest east TN mountain peaks Tuesday night. HREF ens
guidance supports this and shows mean wind gusts values from 30 to
35 mph across the east TN mountain tops. NBM not capturing this very
well so raised winds to match NAM and HREF ens values.

There is model disagreement in place on Wednesday in regards to
precip. Our precip chances during the afternoon depend on the path
that Beryl takes into the Great Lakes. If the track is more
westward, we will still have a good fetch of moisture in place
across our area. This will lead to isolated to scattered showers and
storms Wednesday afternoon. If the path is further east, then drier
air will be wrapping into the region on the backside of this low.
This means no precip for Wednesday afternoon. The NBM POPs suggest
we are still in the moisture fetch, but I lowered POPs to account
for the drier air scenario.

Otherwise, the rest of the long term looks fairly dry with
temperatures warming back into the 90s by the end of the week and
into the weekend.

&&

.AVIATION...
(18Z TAFS)
Issued at 120 PM EDT Mon Jul 8 2024

We will remain in a very moist air mass through this period as the
remnants of Beryl track into the MS Valley region tomorrow. The
uncertainty lies in how this moisture will translate to fog and/or
low clouds. Models show varying amounts of both, leading to a low
confidence forecast. The TAFs will be optimistic for now, with VFR
conditions, although there is a low chance of MVFR conditions
developing at all sites tomorrow morning.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             75  96  76  87 /  30  30  30  40
Knoxville McGhee Tyson Airport, TN  74  94  76  89 /  20  20  30  40
Oak Ridge, TN                       73  93  74  87 /  20  20  30  40
Tri Cities Airport, TN              70  92  73  90 /  20  20  30  50

&&

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

$$

SHORT TERM...DGS
AVIATION...DGS