-- Discussion containing changed information from previous version are highlighted. --
360
FXUS64 KMRX 230551
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
151 AM EDT Thu May 23 2024

...New AVIATION...

.UPDATE...
-- Changed Discussion --
Issued at 1058 PM EDT Wed May 22 2024

MCV is quickly dissipated with only some light rain/sprinkles
across the central valley and scattered showers and thunderstorms
over far northeast Tennessee and southwest Virginia. Latest HRRR
suggests chance of rain will continue to end as the MCV moves
east. Potential of convection developing over southern Kentucky
toward daybreak that may move into the northern Plateau but
overall dry the rest of the night.
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&&

.SHORT TERM...
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(This evening through Thursday)
Issued at 308 PM EDT Wed May 22 2024

Key Messages:

1. A few strong to marginally severe storms possible in the
northern Plateau this evening.

2. Another round of potentially strong to severe storms is expected
Thursday from late morning through early afternoon, mainly north of
I-40. Potential for training storms will pose a flooding threat.

Discussion:

A line of strong to severe storms stretches along a pre-frontal
trough from central KY to West TN. Mesoanalysis of the region shows
a much less favorable environment for severe over our area, with
CIN keeping convection capped and weak deep layer shear. The HRRR
and ARW are in good agreement with the progression of storms
across Middle TN through the afternoon, and show them reaching our
Plateau counties around 00-01Z. By the time they reach I-75, the
storms weaken quickly and have virtually dissipated before
reaching Tri- Cities. The forecast for the evening will have
likely PoPs only in Morgan/Scott counties, dropping to a chance in
SW VA and NE TN by midnight. This activity should end around
06-08Z once the shortwave trough exits, but another stronger
trough will be approaching from the west.

Convection is expected to develop tomorrow morning to our west in
association with this trough and upper jet streak. The CAMS are not
in good agreement on the details of the evolution of this
convection, but the general trend appears to be showers and
thunderstorms moving into the Plateau area during the mid to late
morning hours, about 12-16Z, and crossing the TN Valley through the
early afternoon. Some additional development may occur behind this
initial activity during the mid to late afternoon. Given the model
disagreements, PoPs have been cut back from categorical, except in
SW VA where confidence is highest. CAPE values of will support some
strong to severe storms, but deep shear is rather weak. A marginal
wind threat is possible, and given the unidirectional winds and
expected storms in the same area this evening, training of storms
may pose a threat of flooding in some isolated locations.
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&&

.LONG TERM...
(Thursday night through next Wednesday)
Issued at 308 PM EDT Wed May 22 2024

Key Messages:

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

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

Discussion:

The period begins with flat ridging over the Gulf and a series of
upper lows over the northern plains. These conflicting sets of
features will meet overhead, contributing to disturbances that will
move in the zonal flow over us to bring convection-triggering
convective rounds for the rest of this week.

By Sunday, that northern parade of troughs will orient somewhat
further south, and begin the process of what will become a deepening
Great Lakes upper low which will usher a cold-frontal line of
convection through the area around Monday morning. This frontal
convection might be the primary risk for organized severe convection
for the period...otherwise a little something here or there is
possible on other days.

No day in particular has impressive QPF, but the repeated rainfall
will tilt the risk of excessive rainfall and localized flooding
upward by week`s end, and that will probably carry over through the
frontal passage event Monday morning.

Afterward, that 500MB low over the Great Lakes will deepen as it
slowly rolls eastward, and we look to end up on the northwest-flow
side of an omega-pattern central U.S. ridge. This will create
potential for additional disturbance-driven rounds of scattered
precip Tuesday and Wednesday, moreso around VA, before the blocking

&&

.AVIATION...
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(06Z TAFS)
Issued at 142 AM EDT Thu May 23 2024

Cloud ceilings should remain VFR at CHA and TYS overnight. Depending
on how cloud cover evolves overnight at TRI, added a TEMPO to
account for fog related VIS restrictions. Terminals should remain
VFR during the day tomorrow, except during any TS occurrences.
Expecting scattered SHRA and TS across the region primarily
between 16z and 00z. Storms could contain brief VIS and CIG
restrictions and strong gusty downdraft winds.
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&&

.PRELIMINARY POINT TEMPS/POPS...
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Chattanooga Airport, TN             86  67  83  68 /  50  40  60  40
Knoxville McGhee Tyson Airport, TN  80  64  79  65 /  80  50  70  50
Oak Ridge, TN                       80  63  79  64 /  80  50  70  50
Tri Cities Airport, TN              78  61  79  62 /  80  50  70  50
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&&

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

$$

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