670 
FXUS64 KMRX 052318
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
618 PM EST Mon Dec 5 2022

...New AVIATION...

.SHORT TERM...
(This evening through Tuesday)
Issued at 312 PM EST Mon Dec 5 2022

Key Messages:

1: Rain showers will continue to move across the area tonight 
through tomorrow, with a slight chance for a few rumbles of thunder.

2. Low probability of localized flooding across portions of the 
southern TN valley and southwest NC. If flooding issues arises, 
it will likely be across low lying and flood prone areas. 

Discussion:

A good slug of precipitation is currently moving across the 
southern TN valley and southwest NC this afternoon. The HRRR and 
RAP both show this first wave of moderate precip slowly sliding 
to our east later this evening. However, additional showers will 
develop and spread in from southwest to northeast through the 
night as isentropic lift persists ahead of a warm front to our 
southwest. Additional QPF overnight ranges from 0.5 to 0.75 inches
across the southern TN valley and southwest NC, around 0.5 inches
across the central and northern TN valley, and 0.25 inches across
northeast TN and southwest VA. If we see any minor flooding 
issues it will be across the southern areas as mentioned above. 
Also, low-end, elevated, instability is seen in soundings 
overnight so will include slight chance for thunder.

There is some uncertainty on how POPs play out through the day 
tomorrow. We remain in a moist environment with elevated PWATS but 
precip will be determined on where the lift is focused, which will 
be determined by where the front sets up. The NAM suggests that the 
higher POPs shift north through the day tomorrow and into KY, 
leaving much of TN valley on the drier side with only slight 
chance/chance POPs in place. This idea is currently supported by the 
NBM as well. This means that after good coverage of morning showers 
we should start to see more spotty showers during the afternoon hours 
with much less coverage. Highest POPs for tomorrow will be 
focused along the TN/KY/VA state lines, where better lift is 
expected. 

Temperatures remain well above normal through the period due to the 
southwest flow and abundant cloud cover. 

&&

.LONG TERM...
(Tuesday night through next Monday)
Issued at 312 PM EST Mon Dec 5 2022

Key Messages:

1. Periods of rain will continue through the week. Some flooding 
concerns still present for areas that see repeated rounds of 
moderate to heavy rainfall. Best chance for this is generally north 
of I-40 mid to late week. 

2. Above normal temperatures Wednesday and Thursday will gradually 
cool into the weekend.

Discussion:

Tuesday night through most of the rest of the work week will 
continue to be cloudy, rainy, and pretty warm. Quasi-stationary 
boundary will remain laid out in the southern Ohio Valley and 
sometimes dipping into the Tennessee Valley. Continuous moisture 
will be fed into the region as the low level flow generally remains 
out of the south/southwest. Models continue the trend of keeping the 
boundary and axis of heaviest precipitation Tuesday night into 
Friday to our west and north, along West/Middle TN up into southern 
KY. This is still close to the eastern Tennessee valley, and 
therefore we'll still likely see waves of rain throughout the week, 
but am still expecting QPF amounts to be the highest further west and 
north. For the middle of the week, areas north of Interstate 40, and 
the Cumberland Plateau will likely see the highest rainfall totals. 
Have continued to keep QPF amounts close to NBM/WPC guidance with a 
slight bump up in totals in areas north of Interstate 40, and a 
slight decrease in southeast TN into southwest NC. Forecasted 
amounts generally remain 2-3" for the week with mostly light rain 
expected, and periods of more moderate rain at times. 

Model discrepancies crop back up as we move into Friday with regards 
on how to handle the low moving into the Great Lakes region and 
finally forcing through the front, and drying out the area. Will 
continue with PoP chances lingering into Friday afternoon, but as we 
get closer to the end of the week, hopefully we'll be able to trim 
back the temporal extent of the PoPs when models come into better 
agreement on timing.

We'll take a break from rain heading into the weekend before another 
front that is forecasted to quickly sweep through the eastern U.S. 
during the first part of next week. This system should help to usher 
in a period of colder weather to start of next week.

&&

.AVIATION...
(00Z TAFS)
Issued at 614 PM EST Mon Dec 5 2022

Highly variable conditions are expected at the TAF sites as rain
spreads across the area tonight and tomorrow. Conditions have been
varying from VFR to IFR across the TN Valley, depending on where
the heavier rain occurs. CHA is expected to have the best chance
of IFR vis and cigs tonight as rain will be heavier there, with
TYS expected to have predominantly MVFR conditions with periods of
cigs dropping to IFR. At TRI, downslope winds off the mountains
have kept cigs VFR, but this should drop to MVFR when rain
increases there tomorrow morning. MVFR cigs will likely persist 
through tomorrow, with IFR cigs possible. 

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             48  63  59  70 /  90  70  60  60 
Knoxville McGhee Tyson Airport, TN  46  63  58  69 / 100  80  70  80 
Oak Ridge, TN                       44  62  56  67 /  90  80  80  80 
Tri Cities Airport, TN              45  61  54  66 /  90  80  70  80 

&&

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

$$

SHORT TERM...SR
LONG TERM....ABM
AVIATION...DGS