-- Discussion containing changed information from previous version are highlighted. --
105
FXUS64 KMRX 161739
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
139 PM EDT Sun Jun 16 2024

...New AVIATION...

.UPDATE...
Issued at 1101 AM EDT Sun Jun 16 2024

Return flow has started, but the surface dewpoints are kind of
sluggish to moisten up. The heatwave is underway, but not quite
as blistering as it seemed like it might be a few days ago, albeit
hot summer-type weather in store for this afternoon. Heat Index
values are expected to be in the 95-100 degree range from
Knoxville to Chattanooga at max heating this afternoon.

The other issue today is how much and how intense convection will
be. Modified sounding has about 2500 J/kg MLCAPE, but with very
little shear. Looks like convection will be very likely in the
mountains with terrain contributions, with a second favorable area
on the plateau with some terrain influence and also being a
little farther away from the upper ridge (now that it is getting
away to our east). We have a weak upper level flow from the
southwest, that would generally tend to keep convection moving
along the terrain, but with the instability and dry air aloft, it
looks like localized cold pools and subsequent convection on the
flanks of previous convective cells would affect areas out into
the valley as well. So there will probably be some corridors with
good coverage of storms while other corridors largely miss out. At
any rate will keep the current PoPs running with "chance" PoPs in
the valley and "likely" PoPs in the mountains.

&&

.SHORT TERM...
(Today and tonight)
Issued at 340 AM EDT Sun Jun 16 2024

Key Messages:

1. High pressure begins to shift east today with southerly return
flow. Continued hot weather.

2. Higher precipitation coverage expected this afternoon compared
to the past couple days--mainly across southern areas and higher
elevations.

Discussion:

The 592 dam 500mb upper ridge axis remains across the
Appalachians and the Carolinas this afternoon with surface high
pressure shifting eastward with weak southerly flow returning to
the region. This will result in continued above normal
temperatures across the region. Moisture will be highest across
southern counties, and precip chances will be maximized across
southern higher elevation areas near the Southern Zone Cherokee
National Forest and southern Cumberland Plateau. Thunderstorms
will be possible, but severe weather is unlikely.

Afternoon convection will decrease in coverage tonight with
clearing sky conditions. Patchy fog will be possible for areas
that receive rainfall this afternoon.

&&

.LONG TERM...
(Monday through Sunday)
Issued at 340 AM EDT Sun Jun 16 2024

Key Messages:

1. Isolated to scattered thunderstorms are expected on Monday with
hot and dry conditions through most of the week.

2. Low-end chances for storms return by next weekend with continued
hot temperatures well into the 90s.

Monday through Wednesday

At the start of the period, ridging will be in place with a 5,920m
500mb high centered just to our east. A strong surface high will be
centered just off the New England coast. This initial setup will
continue hot and humid conditions into Monday to start the period.
Around the 250mb level, a weak jet streak of near 40 kts will
approach from the southwest and help to provide at least some upper
divergence. With decent moisture remaining in place, diurnal
convection is anticipated again, especially along the higher
terrain. The environment will be modestly unstable (MLCAPE near
1,000 J/kg) with very weak shear. This will keep the severe
potential very limited with strong winds possible in any storms that
become tall enough.

By Tuesday, the 500mb high will strengthen further to our northeast,
reaching near 5,960m. The Atlantic surface high will expand westward
and will advect drier air into the area. This trend will diminish
chances for convection and will continue anomalously hot conditions.
With the advection of drier air, lower humidity will keep heat index
values close to the actual air temperature. By Wednesday, the 500mb
high will strengthen even more to a near record 6,000m over New
England with surface high pressure expanding even more into the
area. Similarly hot and dry conditions can be expected again.

Thursday through Saturday

Late in the week into the weekend, the overall pattern will remain
fairly similar to Wednesday, continuing hot conditions through the
end of the period. One feature to watch is the potential development
of a weak tropical cyclone east of Florida. Based on the latest
National Hurricane Center (NHC) forecast, this probability is near
30 percent. If it develops, the progression would be towards the WNW
into the southeastern U.S. However, the very strong high would
likely keep this system to our south. The result is a reintroduction
of low-end PoPs by the end of the period with no other impacts
currently anticipated.

&&

.AVIATION...
-- Changed Discussion --
(18Z TAFS)
Issued at 135 PM EDT Sun Jun 16 2024

Isolated convection has started, mainly in the mountains but will
likely spread out of the mountains as well. The storms should
dissipate by around sunset. With the moisture expected to increase
up the valley, think it is possible for some fog tonight at KTRI.
Storms will likely fire again Monday, with better coverage after
18z.
-- End Changed Discussion --

&&

.PRELIMINARY POINT TEMPS/POPS...
-- Changed Discussion --
Chattanooga Airport, TN             95  74  94  74 /  30  20  20  10
Knoxville McGhee Tyson Airport, TN  93  71  92  71 /  40  20  40  10
Oak Ridge, TN                       93  70  93  70 /  30  20  40  10
Tri Cities Airport, TN              90  69  88  68 /  30  20  60  10
-- End Changed Discussion --

&&

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

$$

SHORT TERM...
AVIATION...