685
FXUS64 KMRX 180008
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
808 PM EDT Mon Jun 17 2024

...New UPDATE, AVIATION...

.UPDATE...
Issued at 805 PM EDT Mon Jun 17 2024

Convection has generally ended as expected by 00Z, so updating
zones to remove the pre-first period afternoon wording.

&&

.SHORT TERM...
(This evening through Tuesday)
Issued at 325 PM EDT Mon Jun 17 2024

A warm and muggy afternoon across the forecast area with scattered
showers and thunderstorms over east Tennessee and parts of
southwest Virginia. The storms are moving slowly north to
northwest near the edge of upper Ridge centered over NC. Visible
satellite imagery showing increasing shower/thunderstorm activity
this afternoon. Shear is minimal and there is very weak mean flow
of just 5-10 kts. Storms should be moving very slowly and could
be tied to the terrain. PWs of around 1.5-1.7 inches, are at or
above the 90th percentile, which when combined with the 1500-2000
J/kg of MLCAPE will support potentially widespread coverage
through early evening. Storms should decrease with sunset.
Rainfall rates within any slow moving storm may exceed 1"/hr, with
one inch already this afternoon with a storm near Cosby in Cocke
County. The storms may not last that long in any one place.
However, a few spots of 2-3" of rain are possible according to
WPC. If a cell sits over a more sensitive terrain feature or urban
area there is a chance of flooding. Later tonight fog will form
where rainfall occurs. Upper ridge strengthens Tuesday north
through the mid Atlantic and west into the eastern TN Valley with
little chance of convection over much of the area. There will
still be a slight chance of showers and storms near the KY/VA
border and in the Big South Fork area on the edge of the building
Ridge. Highs Tuesday will be near todays in the upper 80s to lower
90s. Heat Index values were in the lower to mid 90s today and
should be in the same range Tuesday.

&&

.LONG TERM...
(Tuesday night through next Monday)
Issued at 250 PM EDT Mon Jun 17 2024

Key Messages:

1. Average temperatures Wednesday, then hot weather to continue.

2. Next low chance of showers and thunderstorms (20 to 30%) to
arrive during the weekend.

Discussion:

Another day, another discussion about the upper ridge and the warm
summer temperatures. The period begins with the trend of a 500mb
high continuing until Friday, with light flow aloft. A surface high
remains off the coast of Virginia/North Carolina, fading away by
Sunday. While the intense part of the ridge will remain displaced
from our local area, the broad higher heights coupled with
seasonable humidity will maintain high heat indices in the Tennessee
valley. Ensemble probabilities of CAPE > 500 are at 0 for the
remainder of the workweek, and NBM maintains 0 PoPs thanks to the
suppressive ridge.

With the arrival of the weekend, a pattern change shall arrive. The
upper level ridge is forecast to weaken, and an upper trough pushes
into the Great Lakes on Sunday, bringing weak southerly flow into
the area. Ensembles have been consistent the last several runs in
agreement with the deterministic global models in depicting the
weekend evolution of the upper trough, so rising confidence the
trough will be moving into the eastern US at the end of the period.
Sunday might be the last truly hot day then shall see if
temperatures can edge cooler Monday at the very end of the period
when more widespread rain chances arrive.

&&

.AVIATION...
(00Z TAFS)
Issued at 805 PM EDT Mon Jun 17 2024

Mostly VFR expected at the TAF sites, except for some MVFR with BR
overnight 08Z-12Z at TRI.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             94  75  91  72 /  10  10   0   0
Knoxville McGhee Tyson Airport, TN  89  72  90  69 /  40  10  10   0
Oak Ridge, TN                       91  71  91  69 /  30  10  10   0
Tri Cities Airport, TN              90  68  89  65 /  50  10  10   0

&&

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

&&

$$

SHORT TERM...TD
LONG TERM....Wellington
AVIATION...GC