-- Discussion containing changed information from previous version are highlighted. --
863
FXUS64 KMRX 141149
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
749 AM EDT Tue May 14 2024

...New AVIATION...

.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...
-- Changed Discussion --
(12Z TAFS)
Issued at 740 AM EDT Tue May 14 2024

Expecting a couple rounds of showers and thunderstorms today,
with the first approaching the area later morning and the second
and probably much stronger activity, arriving from the west
sometime in the late afternoon and evening. CHA appears will
remain mostly MVFR for the day. TYS and TRI appear will remain VFR
to low VFR with CIGS dropping from a shower or thunderstorm
through the period. Winds no more than 10 KT, but could very well
gust with a thunderstorm. Depending how much clearing occurs
overnight, if at all, there may be a chance for fog.
-- End Changed Discussion --

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             77  62  78  61 /  70  70  60   0
Knoxville McGhee Tyson Airport, TN  77  61  74  61 /  70  80  80  20
Oak Ridge, TN                       76  60  75  60 /  70  80  80  20
Tri Cities Airport, TN              76  58  72  59 /  70  80  80  40

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
NC...NONE.
TN...NONE.
VA...NONE.
-- End Changed Discussion --
&&

$$

SHORT TERM...KS
LONG TERM....CD
AVIATION...KS