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 181728
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
128 PM EDT Mon Mar 18 2024

...New AVIATION...

.UPDATE...
Issued at 1144 AM EDT Mon Mar 18 2024

Observations this morning were running a little warm against the
forecast, but did not want to make much changes to the max
temperature since expect temperatures today will struggle with
the cold airmass moving across. Dewpoints are running pretty close
to the forecast, so just blended in observations and smoothed the
hourly forecast out. A special weather statement was issued area
wide earlier this morning for fire danger today, breezy winds
especially this afternoon combined with the low relative
humidities means outdoor burning is strongly discouraged.

&&

.SHORT TERM...
(Today and tonight)
Issued at 340 AM EDT Mon Mar 18 2024

Key Messages:

1. Cold weather arrives today and with cold air advection.
Temperatures will be 10 to 15 degrees below normal. Winds from the
northwest 15 to 25 mph with higher gusts to 35 mph at times this
afternoon and evening.

2. Wind chills will be significant tonight and Tuesday morning. The
wind chill values will be from 15 to 25 lower elevations and from
zero to 10 degrees across the higher elevations of the eastern
Tennessee mountains.

Discussion:

The stronger cold air advection has lagged behind the cold front
that is now made it well into the Carolinas to around Raleigh to
Charlotte NC and south of Atlanta early this morning. Temperatures
have dropped into the 40s lower elevations and 30s higher elevations
at this time. The airmass behind the front is very dry and skies are
partly cloudy to clear. Some locations will be near freezing tonight
where winds decrease but frost formation is expected to be limited.
Right now dewpoint depressions are still 10 to 20 degrees.

Northwest flow looks to strengthen this afternoon, bringing stronger
winds to east Tennessee and southwest Virginia. This will happen as
the deepening upper trough moves into the region. Precipitable water
values are forecast to be around 0.20" across all of East Tennessee
and southwest Virginia which is near a daily minimum for this time
of year. So with this happening afternoon relative humidities will
dip to around 25 to 35 percent area wide. This will give fire
weather concerns with the strong wind gusts. Some cloud cover is
expected across the northern sections of the area late today with
the deepening trough which may keep relative humidity values higher
there. Will be deciding on a Special Weather Statement for Fire
Weather for TN and NC this morning.

Monday night and early Tuesday morning the coldest air settles
southward into the Tennessee valley and southern Appalachians with
a hard freeze across much of the area. With the continued cold
air advection although winds will be decreasing, the dry airmass
will limit frost development. The main impacts will be low wind
chills below 20 degrees lower elevations and below 10 degrees in
the higher elevations above 3000 feet across the higher mountains.

&&

.LONG TERM...
(Tuesday through Sunday)...
Issued at 248 AM EDT Mon Mar 18 2024

Key Messages:

1. Low RH values with gusty winds will pose fire weather concerns
on Tuesday afternoon.

2. Dry conditions continue but with warmer temperatures Wednesday
and Thursday.

3. Rain chances return Friday.

Discussion:

On Tuesday a low pressure system will be over the Great Lakes, with
high pressure over LA. Aloft, a dry NW flow pattern will continue
with a trough off the East Coast. The surface pressure gradient will
likely create a SW wind of 10-20 mph with gusts of 25-30 mph. The
dry air mass in place and afternoon mixing will lower min RH values
to 20-30%. For now, these conditions will be headlined in the FWF,
although a Red Flag Warning may be needed with later forecast
issuances.

On Wednesday a dry frontal passage will occur, shifting winds to a
more westerly direction. Breezy conditions with RH values in the 25-
35% range will likely continue. As high pressure builds in from the
northwest Wednesday night, colder air will advect in behind the
front. Lows in the 30s to upper 20s north are expected Thursday
morning. Low RH values continue Thursday afternoon, although winds
should be lighter.

A southern stream shortwave trough will approach the area Thursday
night, and cross the area Friday. Chance PoPs will be forecast for
this period, with light QPF. Beyond this period, forecast confidence
is low as the models diverge in their solutions for the weekend.
Will have dry conditions Saturday and Sunday with temperatures near
to slightly above normal.

&&

.AVIATION...
(18Z TAFS)
Issued at 117 PM EDT Mon Mar 18 2024

VFR conditions are expected to continue through the TAF period.
Scattered midlevel cumulus field will continue to build this
afternoon before clearing out overnight. Breezy winds with gusts
to 20 knots expected periodically this afternoon, winds will
weaken tonight before pivoting to more westerly or west-
southwesterly flow tomorrow.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             29  57  39  69 /   0   0   0   0
Knoxville McGhee Tyson Airport, TN  27  55  38  66 /   0   0   0   0
Oak Ridge, TN                       27  56  36  67 /   0   0   0   0
Tri Cities Airport, TN              25  53  36  63 /   0   0   0   0

&&

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

$$

SHORT TERM...Wellington
LONG TERM....DGS
AVIATION...Wellington


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