611
FXUS64 KMRX 080231 AAB
AFDMRX

Area Forecast Discussion...UPDATED
National Weather Service Morristown TN
931 PM EST Fri Feb 7 2025

...New UPDATE...

.UPDATE...
Issued at 900 PM EST Fri Feb 7 2025

No significant changes to the forecast with the evening update.
Some showers still exist in the southern TN mountains, but expect
most of the area to remain dry through the overnight hours. Shower
activity should be on the uptick tomorrow morning but mainly
across the north. Freshened up the PoPs for tonight, but didn`t
make any significant adjustments. Otherwise, the going forecast
seems to be in good shape.

&&

.SHORT TERM...
(This evening through Saturday)...
Issued at 315 PM EST Fri Feb 7 2025

.Key Messages:

1. Shower chances return overnight tonight and Saturday.

2. Very warm temperatures again Saturday ahead of next front. Near
record highs. Chance of a few thunderstorms. Gusty southwest winds
also during the day.

Discussion:

The front that moved south and east of the forecast area overnight
has brought in a much cooler airmass this afternoon. Temperatures
are in the 50s at mid afternoon. A weak impulse in the fast moving
near zonal flow is moving from west to east across the southern half
of the area this afternoon. Skies are partly cloudy north to mostly
cloudy south. Some light showers are possible but with the low dew
points most of the precipitation is evaporating before reaching the
ground. Only a few sprinkles or light showers are expected to occur.

Late today and overnight A jet streak will move across the Ohio
Valley and slip south into the Tennessee Valley. A southwesterly
low level jet will strengthen from about 20 knots this evening to
35 to 45 knots by Saturday morning with the 45 knots over southwest
Virginia. This boundary layer jet will produce isentropic lift
across the mainly the northern Plateau, northeast Tennessee and
southwest Virginia tonight. Showers will increase later tonight
especially from I-40 north. Otherwise, increasing clouds this
evening with mostly cloudy skies overnight. The front to the south
will be moving back north as a warm front tonight and reach the
northeast part of the area by afternoon.

For Saturday, a weak warm front will lift north with increasing
isentropic ascent Saturday morning into the afternoon. The highest
rain chances of light rain will generally remain north of I-40
during the day. Very little to no instability will preclude to leave
thunder out of the forecast although a few strikes are possible
along the northern border areas Saturday morning. The strong low
level southwesterly flow will continue through the day Saturday
ahead of lower pressure centered over southern Illinois along the
next frontal system. This surface low will move quickly across the
northern Ohio Valley reaching eastern Ohio by early Saturday
evening. The cold front will be in central Kentucky by evening.
Winds will be gusty during the day which will help warm temperatures
to the much above normal mid to upper 60s southwest Virginia and
northern Tennessee border counties to the lower 70s elsewhere.

Daily Record High Maximum Temperatures for Saturday

Date    Chattanooga    Knoxville      Tri-Cities     Oak Ridge
02-08     76(1937)      75(1937)       70(2001)       71(2009)

&&

.LONG TERM...
(Saturday night through next Friday)...
Issued at 315 PM EST Fri Feb 7 2025

Key Messages:

1. Unsettled pattern with multiple periods of rain expected.

2. Gusty winds can be expected over the highest elevations of the
east Tennessee mountains Saturday night.

3. The heaviest rains are expected in the Monday night through
Thursday time frame, and there is a potential for significant
flooding during that time.

Discussion:

Much of the period will be dominated by fast quasi-zonal flow aloft
with multiple waves moving through, keeping the pattern unsettled.

The first of these waves will be rather weak and moisture looks
shallow, so just some mainly light rain is expected Saturday night.
QPF values with this system are currently less than a half inch with
most of the area under a quarter inch. The low level jet is forecast
to be from the southwest and west Saturday night with 850mb winds
reaching the 40 to 50kt range. Expect gusty winds especially over
the higher mountain peaks Saturday night, but while a few of the
highest mountain peaks will likely see wind gusts over 40 mph the
areal extent looks very limited given the lack of favorable
conditions for mountain wave enhancement. Since it still looks
marginal for a wind advisory in the Tennessee mountains at this
time, none will be issued as yet.

Sunday will be a mainly dry day as surface high pressure nudges in
from the north, then the next ripple in the flow will bring
additional light showers Sunday night into Monday although right now
precipitation amounts look very light with this.

The more consequential systems look to affect our area in the Monday
night into Thursday time frame. Models are still showing differences
in the details, but generally agree there will be rounds of moderate
to heavy rainfall during this period with the potential for
significant flooding.  Ensemble data indicates there is a 40% TO 60%
chance of exceeding 3 inches of rainfall across much of the area in
a 72 hour period ending Thursday night, with a 10% chance of amounts
approaching or exceeding 5 inches. This is a strong heavy rain
signal given the spread inherent in this type of data that far out.

Drier and colder air will be pushing in Thursday night and Friday
behind an exiting cold front, but a few showers may linger and the
precipitation may even end as a few snow showers over the higher
terrain.

&&

.AVIATION...
(00Z TAFS)
Issued at 704 PM EST Fri Feb 7 2025

Dry conditions should continue at all terminals through later
tonight before SHRA spread into the northern TN valley INVOF KTRI
after midnight. Flight categories will be a mix of VFR and MVFR
across the region, with MVFR persisting at KCHA through the
overnight hours and VFR elsewhere until showers push into KTRI.
Winds will be light overnight, but increasing southerly flow and
better mixing tomorrow will lead to some gusts into the 15-20kt
range at all terminals.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             56  49  74  50 /  10  10  10  90
Knoxville McGhee Tyson Airport, TN  57  46  72  46 /  20  20  40  90
Oak Ridge, TN                       58  45  70  45 /  20  20  40  90
Tri Cities Airport, TN              60  44  69  45 /   0  30  30  90

&&

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

$$

SHORT TERM...CD
AVIATION...CD