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407
FXUS64 KMRX 240223 AAA
AFDMRX

Area Forecast Discussion...UPDATED
National Weather Service Morristown TN
1023 PM EDT Thu May 23 2024

...New UPDATE...

.UPDATE...
-- Changed Discussion --
Issued at 1006 PM EDT Thu May 23 2024

Active evening across the region due a strong upper jet moving
across the Tennessee valley. Satelittle and radar shows a MCV
moving across east Kentucky. The upper forcing has produced
widespread thunderstorms with a good deal of organization with the
convection. Effective shear up to 35 knots and 0-1km shear near 15
knots were favorable to produce supercells especially over
southeast Tennessee and southwest North Carolina. Reports of
possible funnel clouds also reported as well as PingPong hail.

Continued upper forcing continues to produce strong convection
over southeast/central east Tennessee, generally south of
interstate 40. This activity will move east out of the area soon
after midnight.

Latest HRRR shows widely scattered to scattered showers continuing
through the early morning so will continue with low chance PoPs.
Some fog development is possible.
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&&

.SHORT TERM...
(This evening through Friday)
Issued at 307 PM EDT Thu May 23 2024

Key Messages:

1. Strong to severe storms this evening with the main threats being
wind gusts and hail, mainly affecting locations along and west of I-
75.

2. Another round of showers/storms is expected Friday afternoon, but
mainly in southern sections as an upper level disturbance moves
through that area. A few strong to marginally severe storms are
possible.

Discussion:

Convection is starting to blossom in the Plateau and southern
portions of the TN Valley. Over the next few hours, this activity
will expand and intensify as clouds clear out and surface heating
builds. Mesoanalysis shows the best instability to our west, so the
storms that are developing in Middle TN will have the best chance of
becoming severe, and with a an effective shear max located over the
northern Plateau/eastern KY, that area will have the highest severe
chance as those storms track NE. Damaging wind gusts and large hail
will be the primary threats, and locations that have repeated storms
may experience localized flooding. Most of this activity should
weaken or exit the area by midnight.

Overnight, a moist low level air mass will be in place that will
favor fog and low cloud development. The models show that this
will be slow to lift in the morning, but by noon we should have
some good surface heating to aid in destabilization. In the
midlevels, a weak shortwave trough/500 mb vort max will be
crossing northern AL and GA in the late morning and early
afternoon, which may bring showers to the southern sections as
early as 10 AM. CAMS are not in good agreement with the
development of convection tomorrow, so confidence is low. But it
does appear that areas south of I-40 will have the best chance of
showers/storms, and that a few of these could be strong to
marginally severe, with wind/hail being the main threats.

&&

.LONG TERM...
(Friday night through next Thursday)
Issued at 307 PM EDT Thu May 23 2024

Key Messages:

1. An unsettled period with multiple rounds of showers and
thunderstorms for much of the period.

2. Some of the storms may be strong to severe at times, with the
higher chances for severe storms looking like Sunday and/or Monday.
Localized flooding will also be possible.

3. Drier and cooler air moving in toward the end of the period, but
a few additional showers and/or storms still cannot be ruled out.

Discussion:

Unsettled weather pattern will continue, as 500 MB flow remains
somewhat flat through the weekend, with a series of disturbances
touching off rounds of convection. By Sunday, deepening of a
trough near the Great Lakes will usher through a cold front
accompanied by organized convection around Monday morning that has
caused SPC to put us in a 15+% area in the severe weather outlook.

However, as the present Watch attests, chances of severe weather
will not be limited to Sunday night/Monday. Furthermore, repeated
rounds of rainfall will increase proneness to localized flash
flooding from today through Monday.

Post frontal precip chances on Tues and Wed will likely be
scattered in nature and not likely to be heavy. Models are
diverging that far out now anyway, with the ECMWF maintaining
something of a blocking pattern, while the GFS has backed off of
that solution and instead wants to continue with more of a
northwesterly flow across the nation that keeps us impacted by
another shortwave or two. We will cheer for the ECMWF`s quieter
solution, but will have to wait and see what pans out.

&&

.AVIATION...
(18Z TAFS)
Issued at 250 PM EDT Thu May 23 2024

Showers and thunderstorms are developing in Middle TN and the
Cumberland Plateau. They are expected to increase and spread into
the northern half of East TN through the evening, impacting TYS
and TRI. MVFR conditions with gusty winds of 30-40 kt are
possible, possibly IFR if a storm moves directly over the
terminal. Tonight, a moist air mass will result in fog and low
clouds, likely MVFR at CHA and TYS but TRI may drop to IFR.
Another round of showers and storms is expected late in this TAF
period, mainly affecting CHA and TYS.

&&

.PRELIMINARY POINT TEMPS/POPS...
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Chattanooga Airport, TN             67  83  67  88 /  30  60  40  50
Knoxville McGhee Tyson Airport, TN  64  79  64  85 /  70  60  50  50
Oak Ridge, TN                       64  79  63  85 /  70  50  50  50
Tri Cities Airport, TN              61  79  61  81 /  60  50  40  60
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&&

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

$$

SHORT TERM...DH
LONG TERM....GC
AVIATION...DH