-- Discussion containing changed information from previous version are highlighted. --
740
FXUS64 KMRX 041845
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
245 PM EDT Sat May 4 2024

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

.SHORT TERM...
-- Changed Discussion --
(This evening through Sunday)
Issued at 241 PM EDT Sat May 4 2024

Key Messages:

Drying trend tonight, then less coverage of showers and storms on
Sunday than is occurring today.

Discussion:


The short wave trough that is over the region will exit tonight,
followed by rising heights/short wave ridging on Sunday. Scattered
to numerous showers and thunderstorms this afternoon will gradually
diminish overnight, but some at least isolated weaker convection
will be possible through much of the night.

On Sunday the overall environment will consist of minimal shear and
modest instability, with MLCAPEs likely to top out between 500 and
1000 J/kg most locations. Given the weak subsidence over our area as
the short wave ridging builds in, expect less convective coverage
with mostly isolated to scattered showers and storms especially in
the afternoon.
-- End Changed Discussion --

&&

.LONG TERM...
-- Changed Discussion --
(Sunday night through next Saturday)
Issued at 241 PM EDT Sat May 4 2024

Key Messages:

Shower and thunderstorm chances are possible almost every day for
the next week. With the strongest and most organized storms likely
to occur Wednesday/Thursday.

Discussion:

By Sunday night yet another shortwave will be moving into the
southern Appalachian region, but will lose some of it`s power as it
flattens out and runs into the more stable atmosphere. This will
however be enough to spark off even more showers and thunderstorms,
with the greatest coverage and intensity of storms expected during
the daytime on Monday as the vortmax moves right over head. Luckily
with the almost continuous cloudy conditions we should struggle to
destabilize on Monday which will hopefully lead to weaker
thunderstorms. However if some sun is able to make it through to the
surface we could see pockets of stronger storms.

On Tuesday the shortwave should be out of our area, but the rain
chances don`t completely go away as LLJ begins to increase in
strength and move eastward through the Tennessee/Ohio Valleys.
Storms that are able to form on Tuesday will have an atmosphere more
conducive to organized convection, but again the CAPE looks to
remain limited with cloudy conditions.

Wednesday and Thursday look to have an interesting set up as the LLJ
continues to strengthen and a low moves through the Great Lakes
region bringing with it a frontal boundary to the southeast, which
will aid in synoptic level forcing across the southern Appalachian
region. Wednesday into Thursday still looks to be the day with the
best chances to see strong to severe convection with this synoptic
set up, and we cannot rule out an MCS moving through somewhere in
our area. With that being said we are still 4-5 days out from this
event with LOTS of convection and turnover in the atmosphere between
now and late next week, so still expect models to change the
location and timing of the front/low/jet into next week.

Also of note will be the increasing chances to see flooding with all
this shower and thunderstorm activity. There will likely be large
differences in rainfall totals from county to county by this time
next week due to the convective nature of the storms, but we could
see several counties get widespread 2-3 inches of rain before
Friday. Cannot pinpoint exactly where the heaviest rain will be over
the next week, but expect we could see several flood advisories or
warnings issued before next weekend.
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&&

.AVIATION...
(18Z TAFS)
Issued at 115 PM EDT Sat May 4 2024

There will be showers and a few thunderstorms around mainly this
afternoon/early evening, but timing/location uncertainties abound
so for now will carry vicinity and tempo groups to try to capture
highest probability times for convection. Will likely see MVFR or
lower conditions with any thunderstorms or heavier showers this
afternoon, then more widespread MVFR or lower conditions look
likely later tonight as lower cigs and fog develop. Should see
improving conditions late in the period.

&&

.PRELIMINARY POINT TEMPS/POPS...
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Chattanooga Airport, TN             64  85  66  82 /  30  20  40  80
Knoxville McGhee Tyson Airport, TN  61  82  63  79 /  30  20  30  90
Oak Ridge, TN                       61  83  63  79 /  30  30  30  90
Tri Cities Airport, TN              59  79  60  77 /  60  50  20  90
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&&

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

$$

SHORT TERM...
LONG TERM....
AVIATION.....