343
FXUS64 KMRX 091840
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
240 PM EDT Sun Mar 9 2025

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

.SHORT TERM...
(This evening through Monday)
Issued at 239 PM EDT Sun Mar 9 2025

Key Message:

Drizzle/virga possible near the TN/GA state line.

Discussion:

Currently a weak shortwave is continuing to move across the
Tennessee Valley bringing with it rain to parts of the southeast
United States. Closer to our region we`re seeing some radar
returns as far as north Georgia and Alabama... However the lower
levels of the atmosphere are very dry with many weather stations
reporting a 30+ degree dew point depression, with measurable rain
not reaching the ground for most places until you get to
Interstate 20 or south further south. Expect that much of the
radar returns north of Interstate 40 are producing virga, or
possibly a very light drizzle.

This system will continue to meander it`s way across the southeast
and eventually take away all chances of precipitation by Monday.
Expect skies to clear out throughout the day on Monday leading to
temperatures about 5 degrees warmer than today.


&&

.LONG TERM...
(Monday night through next Sunday)
Issued at 239 PM EDT Sun Mar 9 2025

Key Messages:

1. Above normal temperatures through the long term with temps mostly
in the 70s.

2. Elevated fire weather concerns Tuesday and Wednesday due to low
RH values and slightly breezy conditions.

2. Weak system to moves through Thursday into Friday morning, a low
probability for light rain.

3. Strong weather system brewing for next weekend. Increasing risks
for heavy rainfall and a possible strong mountain wave wind event.

Discussion:

Weak ridging/zonal flow will be across the area on Tuesday and
Wednesday. Dry air will be in place and afternoon min RH values will
generally range from the mid 20s to mid 30s. Afteroon wind gusts
from 15 to 20 mph are also expected. These conditions will allow for
elevated fire weather concerns for both days.

On Thursday a weak shortwave will move across the region. Clouds
along with low probabilities of light precipitation are currently
forecast. NBM probabilities for QPF of 0.1 inches or greater only
range from 15 to 25 % for most of the area.

Friday into Saturday an anonymously deep area of low pressure will
develop across the plains and midwest. With strong high pressure
across Bermuda, this sets the stage for a very tight pressure
gradient and resultant strong atmospheric winds aloft across the
southeast U.S.

Wind:

Breezy winds will begin to develop across the area on Friday but
will really ramp up between Friday night and Saturday afternoon. If
the timing holds, the period of strongest winds looks like they will
occur on Saturday evening due to a 60 to 70 kt 850mb jet moving
across as shown in the deterministic GFS and ECMWF. This will allow
for a possible strong mountain wave event. The 60 to 70 kt 850mb
winds are around 2 to 3 STD above normal as shown by the NAEFS
table. EFI values of 0.8 to 0.9 show up during this timeframe which
also suggest an anomalous event setting up. If the model trends
hold, a Wind Advisory across our higher elevations will almost be
certain with a High Wind Warning probable. Additionally, RH values
during this time will be elevated but if there are any ongoing
wildfires there will be concerns due to the strong winds.


Heavy Rain:

This system will bring a round of heavy rain across the area. Latest
WPC guidance shows storm total precip of 1.5 to 2.5 inches for most
of the east TN valley and southwest NC, with some isolated 3 inch
amounts across the southern Cumberland Plateau. Lesser amounts of 1
to 1.5 inches are expected along the favored downsloping area of the
east TN mountains and into southwest VA. Widespread flooding is not
anticipated due to our recent dry conditions but 2 to 3 inches of
rain could cause some isolated issues.

We clear out on Sunday with cooler temps in the 60s behind the cold
front. Breezy remain across the area.

&&

.AVIATION...
(18Z TAFS)
Issued at 116 PM EDT Sun Mar 9 2025

Light radar returns present just south of the TN state line could
briefly impact KCHA, but the lower levels are so dry that it
would likely fall as VIRGA. Expect VFR conditions for the next 24
hours.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             45  67  38  74 /  50  20   0   0
Knoxville McGhee Tyson Airport, TN  40  63  36  71 /  20  20   0   0
Oak Ridge, TN                       40  66  36  72 /  10   0   0   0
Tri Cities Airport, TN              35  61  33  68 /  10  10   0   0

&&

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

$$

SHORT TERM...
AVIATION...