Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS64 KMRX 270728
AFDMRX

AREA FORECAST DISCUSSION
National Weather Service Morristown TN
328 AM EDT Tue Jul 27 2021

.SHORT TERM...(Today and Tonight)...

Key Messages:

1. More showers and thunderstorms today - greatest coverage south of
the I-40 corridor. Outside chance of some damaging winds.

Discussion:

An amplifying ridge out west and a shortwave diving southeast from
Iowa towards Kentucky today, will help push a front south through
the CWA as the day wears on. Influx of relatively drier air behind
the front should limit convective activity in the far north but
expect some shower and thunderstorm activity once again today for
the central and southern areas. Don`t expect storms to be as
widespread as yesterday afternoon, but relatively speaking
coverage will be the greatest in the southern valley, mountains,
and plateau areas. With PWAT values decreasing as a general rule
today, what isolated flash flood threat was present yesterday will
be negligible today. However it is worth noting that BUFR
soundings indicate that we will still have a fairly unstable air
mass and with this influx of slightly drier air today DCAPE values
increase accordingly. So while the pattern and expected coverage
don`t point to any significant severe weather threat, it wouldn`t
be surprising to see a few storms get close to severe territory.
Strong winds would be the biggest threat in such a scenario. The
limiting factor is where the drier air and increased downburst
potential will overlap with stronger convection. Suspect that will
be in the central parts of the CWA nearer the I-40 corridor.

For tonight, expect rain chances to tail off quickly after sunset,
for dry conditions overnight. Patchy fog will be present once again
as well, with lows in the upper 60s to low 70s.

CD

.LONG TERM...(Tomorrow through Monday)...

Key Messages:

1. Hot weather second half of the work week with temperatures in the
mid 90s and heat indices 100 to 105.

2. Frontal boundary will bring isolated to scattered convection
Friday through the weekend.

3. Temperatures expected to be cooler and near normal by early next
week.

Discussion:

Main weather story will be the extremely hot temperatures on
Wednesday through Friday across the southeast U.S. Through the
second half of the week we`ll be sitting on the eastern side of a
mega-ridge centered over the plains states. Mid level heights
increase leading to strong subsidence and very hot temperatures.
We`ll be very close to advisory criteria in the southern and maybe
central Valley on Wednesday. Unfortunately temperatures will remain
warm, and probably a few degrees hotter on Thursday and Friday. Heat
Advisories look like they`ll be necessary for portions of the
southern and central valley Thursday/Friday, but don`t get too hung
up on where the borders of the advisory are, just know that it will
be HOT EVERYWHERE. Heat safety should be practiced, and time spent
outside (especially in the afternoon) should be limited. Dew points
will be generally in the mid to upper 60`s, so it`s going to feel
muggy and your bodies natural cooling abilities will be limited.

We`ll finally get a bit of a break towards the weekend as a front
dives southward towards the Tennessee Valley. Depending on the
timing of the arrival of the front we could see very hot
temperatures on Friday, but hopefully we`ll have a bit more of a
northwesterly breeze on Friday which will help it feel a bit better
outdoors. With this front precipitation chances will return, but
mainly be confined to some diurnal storms focused across northeast
TN and southwest VA. Still looks like a shortwave will develop over
the weekend and move through the area which will help increase the
coverage of storms in the afternoons/evenings. GFS continues to hold
up the front over the Tennessee Valley while the ECMWF wants to push
it further south, closer to the Gulf. So unfortunately confidence
hasn`t increased much on precipitation chances over the weekend. But
even if the wetter GFS solution comes to pass some places will
likely miss out on the isolated to scattered convection, so there
will be some angry lawn owners after this weekend. Good news is that
the more troughy pattern early next week will help bring
temperatures back into the 80`s and back to near normals for this
time of year.

ABM

&&

.AVIATION...
06Z TAF DISCUSSION.

Fog will be an issue at most sites through daybreak, but think
KTRI has the best chances for seeing significant VSBY reductions.
Dewpoint spreads are still a couple of degrees so pushed back the
onset of IFR categories there. Elsewhere, 3-5SM vsby is expected
before daybreak. Later today, convection should be tied mostly to
the mountains and south of the I-40 corridor. Kept SHRA/TSRA out
of KTRI but included PROB30 for TSRA at both KTYS and KCHA this
afternoon.

CD


&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             92  73  95  73  97 /  40  10  10   0   0
Knoxville McGhee Tyson Airport, TN  92  72  95  71  97 /  30  10  10   0   0
Oak Ridge, TN                       92  71  95  70  96 /  30  10   0   0   0
Tri Cities Airport, TN              91  67  93  66  94 /  20  10   0   0  10

&&

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

$$


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.