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000
FXUS64 KMRX 111757
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
157 PM EDT Thu Apr 11 2024

...New AVIATION...

.UPDATE...
Issued at 1131 AM EDT Thu Apr 11 2024

Many changes to mention and an overall observation from this
morning. First, the High Wind Warning was cancelled nearly 5 hours
earlier than the original thought end time. Basically, the
strongest gusts occurred during the very late night/early morning
hours with Camp Creek recording 71 mph and Cove Mountain hitting
66 mph. Gusts have also been pretty calm or slow to get going in
the valley this morning than what was forecast. Ran a totally
different model run and blend to hopefully capture the calmer
morning winds with gradual increase in gusts this afternoon. The
higher terrain can still experience gusts up to 50 mph today,
however.

PoPs updated considerably through 00Z to match what has been
happening and future trends. Like what was talked about in the
second paragraph in the short term section below, will be
continuing to the monitor the threat for any strong to severe
storms this afternoon, especially far NE Tennessee and SW Virginia
as a "triple point" may provide just enough of a boundary to
possibly spin up a tornado. Otherwise, strong winds associated
with thunderstorms remains the main threat this afternoon and
evening.

KS

&&

.SHORT TERM...
(Today and tonight)
Issued at 319 AM EDT Thu Apr 11 2024

Key Messages:

1. Coverage of showers and storms will increase today with
decreasing coverage tonight.

2. A conditional threat of strong to severe storms this afternoon
mainly across northeast Tennessee, and southwest Virginia.

3. Windy conditions today and into tonight. Gusts up to 40 mph
possible in the valley today, with downslope wind gusts up to
75mph early this morning across the mountains and foothills of
East Tennessee.

Discussion:

An upper level trough continues to dig into the lower/mid
Mississippi Valley this morning with a healthy jet streak
approaching 80-90kts at 300mb. Upper diffluence was promoting
shower activity across much of the southeast, while a distinct
dry slot was noted from the northern Gulf Coast through the
Southern Appalachians. This dry slot is helping to provide mostly
dry conditions as of 3AM. A surface low was analyzed across the
ArkLaMiss, and this low is expected to lift NE today underneath
upper level height falls. Downslope conditions are in full swing
this morning. Camp Creek had been gusting above 60 mph for several
hours. The effects from the downslope can be seen in area
observations this morning with temperatures in the upper 60`s to
near 70 degrees.

We will see an increase in coverage of showers and storms today
associated with increasing PVA, and surface convergence. Severe
weather still looks low today but will still be something to keep
an eye on. Guidance such as the NAM/RAP depict a notable increase
in boundary layer instability today as the surface low moves into
the Tennessee Valley advecting richer theta-e air. With strong
wind shear in place any robust updrafts may become strong to
possibly severe. This may especially be true with any convection
tied to a warm front this afternoon. Model hodographs show pretty
good curvature in the lowest 3km which could support a tornado
risk if sufficient low level CAPE is present. Additionally, any
severe storms could contain damaging winds as well. Again, this
is a conditional risk and a lot may depend on coverage of morning
showers and storms and its influence on destabilization. Can`t
rule out isolated flooding given the convective nature of
precipitation today, especially with any training.

An increasing pressure gradient will produce strong southwest
winds across the valley today. Gusts approaching 40 mph will be
possible, as is typical in southwest flow events. At this time,
confidence just isn`t high that we will see wind gusts above 40
mph across enough of the area to justify a wind advisory. This
isn`t to say a site or two won`t gust above 40. Even as the
surface low moves into the Ohio valley and winds veer toward the
west, winds will still remain gusty into tonight. We will likely
need a wind advisory for the East Tennessee mountains tonight but
will let the current high wind warning continue its course before
issuing behind it.

&&

.LONG TERM...
(Friday through Wednesday)
Issued at 319 AM EDT Thu Apr 11 2024

Key Messages:

1. Showers and a few thunderstorms Friday into Friday evening,
especially north of I-40. Small hail possible with heavier showers
or any thunderstorms. Otherwise, gusty gradient winds areawide.

2. Mostly dry for the weekend into Wednesday, and it will become
quite warm.

Discussion:

We start the period with the strong low pressure system over the
Eastern Great Lakes region, and west/northwest flow over our area.
Upper level short wave energy rotating around the upper low will
bring some showers Friday into Friday evening with the best coverage
north. Model soundings generally show steep low to mid level lapse
rates and ML CAPES perhaps as high as 100-300 J/kg Friday afternoon,
so there may be some rumbles of thunder with the convection.  Also,
given that freezing levels will be quite low, small hail looks
likely with the stronger convection. In addition, the tight pressure
gradient over the area will bring gusty winds across the area with
winds gusts of 30 to 40 mph expected to be common and higher gusts
possible in the higher elevations. A wind advisory may be needed
Friday at least across the mountains, and perhaps even into the
valley although right now it still looks borderline there.

The upper low will pull away Saturday and heights will rise over the
region with surface high pressure building into our area from the
south. It looks like the weekend into mid week period will be mainly
dry across our area. We will see a quick rebound in temperatures
with temperatures near normal for highs Saturday and then to near 10
degrees above normal by Sunday with the warm temperatures continuing
through Wednesday.

&&

.AVIATION...
(18Z TAFS)
Issued at 149 PM EDT Thu Apr 11 2024

Thunderstorms have begun to build and move into the area this
afternoon. TYS and TRI are most likely to be impacted in the next
couple of hours by a quick drop in VSBY and CIGS. CHA, based on
models, may not see the next round of thunderstorms until a
couple more hours. Expect gusts at times over 20 kt at all
terminals with or without thunderstorms. Although winds have yet
to make it to TYS or TRI, LLWS is still noted in the TAF.
Activity will be moving out of the area later tonight from SW to
NE. Lingering showers, patchy fog, and MVFR CIGS possible
overnight, but confidence isn`t all that high. Winds expected to
subside some.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             49  68  46  76 /  20   0   0   0
Knoxville McGhee Tyson Airport, TN  49  63  44  72 /  60  30   0   0
Oak Ridge, TN                       49  65  44  73 /  40  30   0   0
Tri Cities Airport, TN              48  58  41  67 /  90  70  30   0

&&

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

$$

SHORT TERM...Diegan
AVIATION...KS