-- Discussion containing changed information from previous version are highlighted. --
516
FXUS64 KMRX 161846
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
246 PM EDT Thu May 16 2024

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

.SHORT TERM...
-- Changed Discussion --
(This evening through Friday)
Issued at 244 PM EDT Thu May 16 2024

Key Messages:

1. Patchy fog overnight across northeast TN and southwest VA.

2. Chances for showers increase tomorrow morning across the southern
TN Valley. Then, rain spreads from southwest to northeast into
tomorrow afternoon. A few storms are also possible, but non severe.


Discussion:

High clouds, associated with the showers and storms across the
ArkLaTex region, spread into the area overnight from southwest to
northeast. These high clouds likely prevent fog across most areas
except for northeast TN and southwest VA, where high clouds don`t
arrive until daybreak. Fog will be patchy to scattered with
visibility reduction in some areas.

For Friday, a shortwave will be moving across the Missouri River
Valley and into the Ohio River Valley. This shortwave will bring
increasing chances of rain, and a few storms, across our area.
Meanwhile, a shortwave will also be moving through the subtropical
jet across the southern Gulf States. This southern convection will
likely inhibit any meaning instability from developing across our
area. NBM and HREF probabilities show roughly a 20 to 40% chance of
SBCAPE greater than 500 j/KG during the day. Whatever instability is
able to develop will be shallow as there is a very strong mid-level
cap in place from 850 to 500mb, which would prevent any mature
updrafts. So while a few storms are possible, none are expected to
be severe and the main theme of the day will be scattered rain
showers with overcast skies and slightly below normal to near
normal temps.
-- End Changed Discussion --

&&

.LONG TERM...
-- Changed Discussion --
(Friday night through next Thursday)
Issued at 244 PM EDT Thu May 16 2024

Key Messages:

1. Wet pattern setting up Friday night and Saturday.

2. Drier and warmer Monday and Tuesday as ridging builds.

3. Cold front and storms move into the area around next Wednesday.

As the upper trough amplifies across the Lower Mississippi Valley on
Friday night, southwesterly unidirectional flow is expected across
our region. Upper-level diffluence will promote widespread synoptic
ascent with overcast sky conditions and the potential for periods of
rainfall. Upper-level heights begin to decrease late Friday night as
the trough axis shifts eastward with DPVA across the Tennessee
Valley, and at the surface, an area of low pressure will move east-
northeastward from the Lower Mississippi Valley. This will bring a
surface warm front northward near our area.

At this time, the majority of surface based instability is expected
to remain south of our area. However, there is a low chance that
this higher instability arrives in our area late Friday night after
06z with low probabilities of strong to severe thunderstorms. Any
storms that do become strong would produce frequent lightning, heavy
rain rates, and potential strong wind gusts.

Scattered rain showers continue on Saturday as the upper-level
trough axis is directly over the Tennessee Valley and Southern
Appalachians. This will promote widespread light convection with
rain showers, and perhaps a few thunderstorms, with gusty wind,
heavy rain rates, and potential small hail.

Convection will decrease with the loss of surface heating on
Saturday night, and as the trough axis moves east of our area,
subsidence on the west side of the departing trough will limit
precipitation, especially west of Interstate 75. The highest
precipitation chances on Sunday will be across the eastern counties
of our forecast area near the TN/NC state line.

Ridging bring drier weather and warmer temperatures on Monday and
Tuesday with temperatures on the high-end 90th percentile of the
distribution near 90 across our southern valley locations in the
Chattanooga vicinity on Tuesday.

A quick moving shortwave and surface cold front will approach the
region on Wednesday with a chance of scattered showers and
thunderstorms. If this front can move through the region, drier
weather would be expected late week; however, if the front stalls
near the Tennessee Valley, continued periods of wet conditions will
be possible late next week.
-- End Changed Discussion --

&&

.AVIATION...
(18Z TAFS)
Issued at 109 PM EDT Thu May 16 2024

VFR conditions through the period at TYS, and mostly VFR at CHA
other than a prob30 MVFR at the end of the period as showers move
in from the southwest. TRI will be VFR until late tonight when fog
is forecast to develop with MVFR conditions. VFR returns to TRI by
mid morning.

&&

.PRELIMINARY POINT TEMPS/POPS...
-- Changed Discussion --
Chattanooga Airport, TN             64  75  66  79 /  10  80  80  80
Knoxville McGhee Tyson Airport, TN  60  76  63  76 /  10  80  80  90
Oak Ridge, TN                       60  76  63  77 /  10  80  80  90
Tri Cities Airport, TN              57  77  60  77 /  10  60  70  90
-- End Changed Discussion --

&&

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

$$

SHORT TERM...
LONG TERM....JB
AVIATION...