730
FXUS64 KMRX 201424 AAB
AFDMRX

Area Forecast Discussion...UPDATED
National Weather Service Morristown TN
1024 AM EDT Sat Jul 20 2024

...New UPDATE...

.UPDATE...
Issued at 1004 AM EDT Sat Jul 20 2024

Regional radar imagery shows scattered to numerous showers along
and north of the I-40 corridor this morning in east Tennessee and
stretching up into our Virginia counties. South of the I-40
corridor, precip is much more difficult to come by at the moment.
The NAMNest seems to be handling precip coverage quite well,
matching up nicely with the break from I-40 southward into
northeast AL that is currently shown on radar mosaic imagery.
Guidance shows that we`re beneath the entrance region to an H3
jet streak which, when coupled with some meager elevated
instability, seems to be driving the fairly uniform coverage of
showers across that portion of the CWA this morning. Haven`t seen
any evidence of lightning so far, and radar doesn`t show these
cells to be very tall, which suggests the GFS BUFR soundings are
probably assessing the environment fairly well at this time and
they show only a few hundred J/kg of elevated MUCAPE. As such,
expect the trend of weak convection to continue until we get into
the afternoon hours and surface based instability becomes more
prevalent. Made some adjustments to the PoP grids through midday
or so, blending in the NAMNest with current hourly NBM PoPs.
Forecast for the afternoon seems to be on track, including
temperature wise, so no changes necessary there.


&&

.SHORT TERM...
(Today and tonight)
Issued at 246 AM EDT Sat Jul 20 2024

Key Messages:

1. Scattered to numerous showers and a few thunderstorms are
expected today.

2. Below normal temperatures will continue.

Discussion:

A shortwave trough remains west of the area this morning, over
West TN. A plume of moisture from the Gulf extends across the TN
Valley and Appalachians. PW values in the range of 1.75-2 inches
will be over the area today, and soundings show a deep, skinny
CAPE profile. The question is when/where forcing will enhance
convetive development. The NAM shows a jet streak developing this
morning over the Plateau, whcih produces some upper divergence in
the area this afternoon. Expect scattered to numerous shower
coverage, with mainly isolated thunderstorms. A few slow-moving or
training showers may produce locally heavy rainfall, and possibly
some minor flooding issues. This evening, the jet streak and
trough axis lift NE of our area, which should result in decreasing
rain chances. With cloud cover expected to be broken to overcast
today, highs will continue to be below normal, with highs in the
lower to mid 80s.

&&

.LONG TERM...
(Sunday through Friday)
Issued at 246 AM EDT Sat Jul 20 2024

Key Messages:

1. An unsettled weather pattern will persist through the long term
with daily mostly diurnal chances for showers and thunderstorms.
Although there will still be some showers and a few storm in the
overnight hours.

2. Slightly below normal temperatures expected through the extended
forecast and considerable cloud cover.

Discussion:

A significantly strong upper level closed low will be over northeast
Canada at the start of the extended forecast Sunday morning. This
low moves east through Monday but new troughing develops Monday
night and onward over the northeast states and the Great Lakes. A
weak upper low to the southwest of the Canadian low will enhance a
southwest flow over the Tennessee Valley as an upper ridge lies over
Florida and the Carolina coasts Sunday into Sunday night. This low
opens up and upper troughing digs southwest through the Mississippi
Valley to the west of the forecast area. At the same time a
stationary front over the eastern sections of TN this morning will
be lifting northward towards KY Sunday morning.

Rain chances will increase in the afternoons and evenings Sunday and
Monday. Rainfall amounts are not expected to be that high for these
2 days. From Tuesday through Thursday a better southwest flow as the
southeast US high pressure ridge strengthens will increase moisture
for more significant rainfall amounts with the potential late in the
week for some isolated flooding as total rainfall amounts reach 2 to
4 inches by this time. The frontal boundary will still be north and
west of the region through the rest of the extended and will help to
enhance rainfall amounts as well. Instability will be high each day
which will help the initiation of showers and thunderstorms. Cloud
cover and rain will keep temperatures in the lower to mid 80s each
day across lower elevations. Lows will be in the upper 60s and lower
70s and dewpoints will stay high too making it feel sticky.

With the current drought D! and D2 categories this significant
rainfall will help drought conditions improve slowly. Highest
rainfall amounts will be in the Appalachians along the TN border and
across southwest North Carolina. High PWATS from 1.5 to possibly
over 2.0 inches will enhance rainfall amounts.

&&

.AVIATION...
(12Z TAFS)
Issued at 646 AM EDT Sat Jul 20 2024

Light showers will be around the area this morning. MVFR cigs are
expected all sites at times. Most showers should exit by late
morning, with cigs rising to VFR in the noon to 18Z time frame.
Can`t rule out additional showers/storms in the afternoon, so
VCTS will be mentioned with VFR conditions. Winds will be light
through the period.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             84  71  86  71 /  50  30  70  50
Knoxville McGhee Tyson Airport, TN  83  70  86  69 /  70  30  70  50
Oak Ridge, TN                       84  69  86  69 /  70  20  70  40
Tri Cities Airport, TN              80  66  86  67 /  70  30  60  40

&&

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

$$

SHORT TERM...CD
LONG TERM....TD
AVIATION...DGS