790
FXUS64 KMRX 141750
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
150 PM EDT Tue May 14 2024

...New AVIATION...

.UPDATE...
Issued at 1110 AM EDT Tue May 14 2024

An upper low was located over Missouri late this morning with a
surface low over the lower Ohio Valley. Showers were beginning to
develop to the south of the area late this morning. Temperatures
were in the mid to upper 60s. This convection should increase
rapidly by early afternoon as temperatures warm to the lower 70s with
some heating with a risk for some strong winds and marginally
severe hail with instability increasing. This afternoon convection
should decrease early this evening. Farther west over middle
Tennessee ahead of the upper low where instability will be higher
an area of showers and thunderstorms will approach the plateau
around 00Z with a better risk for strong to severe thunderstorms
across the central and southern areas through the evening along
and south of I-40. Marginally severe hail around 1 inch diameter
and wind gusts over 50 mph are possible and a very low risk for
tornadoes. The upper low will move into northern KY and southern
IN by around 06Z tonight. Updated zones to increase rain chances
some this afternoon. Skies should stay mostly cloudy all areas
with highs in the 70s. Updated forecast sent.

&&

.SHORT TERM...
(Today and tonight)
Issued at 316 AM EDT Tue May 14 2024

Key Messages:

1. First round of showers and possibly embedded thunderstorms,
will arrive later this morning with best chances along the
Appalachians. Late morning and early afternoon clearing in some
areas may allow the atmosphere to destabilize.

1. Strong to possibly severe storms from the next round arrive
late this afternoon and evening for the Plateau and southeast
Tennessee. Marginal severe hail up to 1 inch and strong gusty
winds to 50 mph are possible. Low-end threat of tornadoes across
southeast Tennessee late in the day.

Discussion:

A nearly vertically stacked upper low and sfc low pressure center
will slowly edge eastward from west of the Mississippi to the
Tennessee Valley by late tonight. A warm front is expected to lift
north and then the occluded front will lift northeast later
tonight.

Generally, two rounds will occur today with a very short window
between them. The early day showers and thunderstorms are not
expected to be anywhere near severe thresholds as CAPE values will
generally be under 500 J/kg with this first round. The best
chances for this activity will be along the Appalachians.

Breaks in the clouds and daytime heating will allow the
atmosphere to destabilize in time for the next round late this
afternoon and early evening. CAPE values will generally exceed
1000 J/kg. Shear will be strong enough to support organized multi-
cluster storms with effective shear of 35 m2/s2 and up. Mid-level
lapse rates near 6.5 deg C supports at least severe sized hail.
Overall, marginal severe hail and damaging winds are the main
threat. Which the SPC has placed us under for today. Also cannot
rule out a low-end threat for tornadoes as well.

The Wind Advisory for the mountains will also expire a 4 AM EDT
this morning as winds have decreased. Winds elsewhere will
generally be pretty light today, but of course can be gusty with
any thunderstorms.

&&

.LONG TERM...
(Wednesday through Monday)
Issued at 316 AM EDT Tue May 14 2024

Key Messages:

1. Showers and thunderstorms continue on Wednesday, though likely
not severe in nature.

2. A short break is expected on Thursday before another round of
storms begins heading into the weekend.

Discussion:

A slow moving upper low will traverse the southern Appalachian
region on Wednesday, with center passing over general vicinity of
the Kentucky, Virginia, and West Virginia border during the early to
mid afternoon time frame. Models currently depict another vort lobe
associated with this feature swinging through our CWA during the
same general time of day. Model soundings show, understandably, weak
shear in place, but the increased lapse rates aloft associated with
the passing upper low will promote surface based instability of
around 1,000 J/kg over the central and northern parts of the CWA Wed
afternoon. Perhaps there`s an outside chance for a stray damaging
wind gust, but overall I would expect just some stronger cellular
convection.

Much of Wednesday night and Thursday should be dry as the upper low
pushes and we sit between systems. Expect temperatures to climb back
up to near or above normal to end the week.

The next system approaches on Friday, ejecting out of the plains
towards the Ohio valley as we head into the weekend. Have pretty
high confidence in increasing rain chances during the day Friday,
and into Saturday, but less so about whether there will be any
severe storms in our area. Some models are showing more vigorous
thunderstorm activity to our south near the Gulf Coast which
typically inhibits convection in the southern Appalachian. But if
the boundary and storms develop further to the north we`ll likely
see more widespread thunderstorms in our region.

&&

.AVIATION...
(18Z TAFS)
Issued at 139 PM EDT Tue May 14 2024

First round of showers and storms moving through now with no
storms currently. More storm development likely this afternoon and
becoming stronger late afternoon and evening. CHA should stay
mostly MVFR today. TYS and TRI are VFR with CIGS around 5000 feet
could lower to MVFR briefly with a shower or storm. Winds will be
light except gusty in thunderstorms. Fog looks most likely at TRI
late tonight so MVFR visibility there late.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             62  78  61  85 /  70  60   0   0
Knoxville McGhee Tyson Airport, TN  61  74  61  80 /  90  80  20  10
Oak Ridge, TN                       60  75  60  82 / 100  80  20   0
Tri Cities Airport, TN              58  72  59  77 /  70  80  40  20

&&

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

$$

SHORT TERM...TD
LONG TERM....CD
AVIATION...TD