-- Discussion containing changed information from previous version are highlighted. --
776
FXUS64 KMRX 221909
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
309 PM EDT Wed May 22 2024

...New SHORT TERM, LONG TERM...

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

Key Messages:

1. A few strong to maringally 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 streches along a pre-frontal
trough from central KY to West TN. Mesoanalysis of the region shows
a much les 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.
-- End Changed Discussion --

&&

.LONG TERM...
-- Changed Discussion --
(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
pattern potentially dries us out for days 8-10 (Thurs-Sat).
-- End Changed Discussion --
&&

.AVIATION...
(18Z TAFS)
Issued at 118 PM EDT Wed May 22 2024

Scattered clouds around 4-5 kft are expected at the TAF sites
through the afternoon and evening, with winds from the SW at 8-12
kt. Overnight, some showers may pass just north of TRI, so will
mention VCSH there for now. A greater chance of showers and
thunderstorm arrives late in the TAF period at TYS and TRI, and a
PROB30 for MVFR vis/cigs with thunderstorms will be mentioned.

&&

.PRELIMINARY POINT TEMPS/POPS...
-- Changed Discussion --
Chattanooga Airport, TN             88  68  86  67 /   0  10  30  40
Knoxville McGhee Tyson Airport, TN  87  67  80  64 /  10  30  60  50
Oak Ridge, TN                       86  66  80  63 /  10  40  60  50
Tri Cities Airport, TN              87  63  78  61 /  10  20  80  50
-- End Changed Discussion --

&&

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

$$

SHORT TERM...DGS
LONG TERM....GC
AVIATION...DGS