969
FXUS64 KMRX 301259
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
859 AM EDT Sun Jun 30 2024

...New UPDATE...

.UPDATE...
Issued at 841 AM EDT Sun Jun 30 2024

Showers and storms continue to weaken as they move toward the
northern Cumberland Plateau from out of northern middle TN. The
HRRR has been depicting this as well over the last few runs. The
showers and storms to our northwest have provided quite a bit of
downstream debris clouds across our area. This will delay heating
and possibly initiation of afternoon convection. Previous
initiation time looked like it would occur around 17 to 18Z. The
latest HRRR suggest it could be as late as 20 to 21Z before
coverage begins to substantially increase. This makes sense based
on the amount of high clouds currently in place. As far as updates
go, no big changes to the grids. Mainly just tweaking hourly
temps to slow heating and bumping up sky cover a little bit.

&&

.SHORT TERM...
(Today and tonight)
Issued at 256 AM EDT Sun Jun 30 2024

Key Messages:

1. Scattered to numerous showers and storms today. A few may become
strong to severe.

2. Hot and humid today.

3. Cooler and drier air moving in tonight.

Discussion:

A cold front currently over the Great Lakes and Ohio Valley will
drop southeast and move across our area later today before exiting
to our southeast this evening.  The atmosphere ahead of this frontal
boundary will be quite moist, with models generally showing PWAT
values near or above 2 inches. In addition, HREF ensemble
probabilities show a 60 to 80% chance for SBCAPE to reach or exceed
2000 J/kg across much of the area. Shear will be weak, with models
generally indicating 0-6km shear will remain below 20kts.  While
most storms are expected to remain below severe limits, a few may
become strong to severe with the main threat being damaging wind
gusts.

It will be hot again today, although the details of exactly how hot
it becomes will be tied to how any convection and associated cloud
cover evolve during the day which leads to some uncertainty.  Dew
points are expected to be a bit higher than yesterday, and high
temperatures are expected to be near or slightly lower given the
expected convection. Heat index values will likely climb to near or
a bit above 100 in many locations again mainly across central and
especially southern valley areas. A few locations may reach a heat
index value of around 105 if convection and clouds hold off long
enough, but right now the probability of 105+ heat index values
looks low and nearly all of the area is expected to stay below heat
advisory criteria, so none will be issued at this time.

Any lingering showers/storms will be moving out this evening, with
drier and cooler air moving in behind the front.

&&

.LONG TERM...
(Monday through Saturday)
Issued at 256 AM EDT Sun Jun 30 2024

Key Messages:

1. Brief below normal temperatures Monday followed by a return of
the hot weather the remainder of the week.

2. Dry or mostly dry through Wednesday, better chances of showers
and thunderstorms Thursday into the weekend.

Discussion:

Monday kicks off the work week with a post-frontal dry airmass, and
expected afternoon temperatures near or maybe even a couple degrees
below normal. With relative humidities dipping into the 35 to 40%
range in the afternoon, this is by far the best day to get outdoor
work done at any hour of the day. However upper heights never really
drastically weaken, and as soon as the flow in the atmosphere pivots
back around for Tuesday, in returns the heat and humidity.

Upper ridge then parks itself through the midweek over the wider
Tennessee and southeast region, peaking near 596 dm. Ensembles
aren`t gung-ho on even having 500J of CAPE Wednesday afternoon, so
bumped the PoPs down for then in accordance. Afternoon convection in
this June heat has struggled to overcome the warm air aloft
associated with the persistent upper ridge, With the return of the
strong ridge, that will be a consideration in any storm chances. By
late week, guidance has better moisture profiles that should allow
for better convective chances. At the very tail end of the week into
Saturday, guidance indicates the potential arrival of another front,
which would bring about more widespread rain chances.

&&

.AVIATION...
(12Z TAFS)
Issued at 640 AM EDT Sun Jun 30 2024

Will see scattered to numerous showers and thunderstorms around at
times, with chances quickly decreasing this evening. Expect mainly
VFR conditions outside of any showers or storms. Will try to time
the highest probability period for thunderstorms with prob30
groups all sites. Will also include a tempo shower group (with
MVFR cigs) at TRI this morning. Winds will generally be light,
then will become more north and northwest later today into tonight
but will generally be less than 10kts.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             94  69  88  68 /  60  20   0   0
Knoxville McGhee Tyson Airport, TN  91  66  84  64 /  70  20   0   0
Oak Ridge, TN                       91  64  83  63 /  60  20   0   0
Tri Cities Airport, TN              88  60  81  59 /  70  30   0   0

&&

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

$$

SHORT TERM...
LONG TERM....Wellington
AVIATION...