757
FXUS63 KJKL 091138
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
638 AM EST Tue Dec 9 2025

.KEY MESSAGES...

- Mainly dry weather is expected through Tuesday night.

- Gusty southwesterly winds between 30 and 40 mph are likely on
  Wednesday.

- The pattern remains active through the end of the work week,
  although confidence remains low in each passing system`s
  precipitation type forecast.

- A much colder airmass is forecast to move into the region late
  next weekend.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 530 AM EST TUE DEC 9 2025

Temperatures vary widely across the forecast area this morning, ranging
from the mid teens to near 20 in the far north where skies have
remained clear to the mid 20s to lower 30s farther south where a
low stratus deck has been persistent. A glance at the surface map
reveals high pressure extending from Southern Quebec tracing
southward to over the Southern Appalachians and then westward
across the Lower Mississippi Valley. A weak ~1007 mb surface low
is noted near Duluth, MN with a warm front extending southward
along the Mississippi River. A much stronger ~990 mb surface
clipper low is noted over Alberta. The latest 500 hPa weather map
shows much of the CONUS east of the Rockies under a broad trough.
An embedded vorticity max is noted near Duluth, MN, while another
vorticity max is noted over Western Canada (near the clipper low).

The warm front and its associated upper level disturbance will
sweep eastward today, crossing eastern Kentucky with little more
than a period of increased cloud cover. Meanwhile, the surface
high pressure slowly departs off the Atlantic Seaboard. A robust
~30 kt 925 mb southwesterly jet will develop behind the front.
With the diurnal heating, the mixing layer should deepen
sufficiently for mixed layer momentum transfer values of 15 to 25
kts across the area, a good proxy for peak surface wind gusts. The
pressure gradient will only tighten more tonight as the aforementioned
clipper initially over Alberta races southeast to over Lake
Michigan late tonight while deepening to ~980 mb or lower. This
will almost certainly keep mixing going overnight (or reengage
mixing shortly after sunset if boundary layer decoupling is able
to occur in some of the more sheltered valley locales). Anticipate
that winds will further increase on Wednesday as the GFS BUFKIT
soundings show mixed-layer momentum transfer increasing to 25-35+
kts with heating. Multiple rounds of light precipitation appear
probable on Wednesday; the first is a round of showery
precipitation in the morning to midday associated with a strong
vorticity lobe within the 500 hPa trough axis. The second round,
more likely to mix with snow, comes during the evening with a
strong cold front trailing behind the clipper. Soundings suggest
brief graupel is possible with any embedded convective elements,
although a switch to all snow cannot be entirely ruled out,
especially on the back edge of the quickly moving cold front.
Strong CAA follows heading into the beginning of the long-term.

In sensible weather terms, look for a cool start of the day
yielding to increasing sunshine and high temperatures rebounding
into the lower to middle 40s while the southwest breeze picks up
and becomes gusty (15 to 25 mph gusts from the southwest). For
tonight, the breeze remains gusty and may actually strengthen in
more exposed locales. Temperatures may dip back into the 30s for a
time this evening but will almost certainly rise back to near or
even well into the 40s. On Wednesday, it will become windy with
multiple rounds of showers, possibly mixed with graupel and even
some flakes. Southwest wind gusts in excess of 30 mph are probable
for most locations outside of the sheltered valley locales, most
widespread during the afternoon and evening. Temperatures peak in
the mid 40s north to near 50 south before dropping.

.LONG TERM...(After midnight Wednesday night through Monday)
Issued at 636 AM EST Tue Dec 9 2025

An active synoptic weather pattern will bring periodic precipitation
chances and shots of colder air to the forecast area over the next
seven days. The period is defined by broad troughing over much of
the eastern CONUS, with embedded shortwave disturbances rotating
through the resultant mean northwesterly flow aloft. At the surface,
this translates to a series of quick-moving, clipper-type systems
approaching the Greater Ohio River Valley. The 00z deterministic
forecast guidance suite appears to be coming closer to a consensus
regarding the timing and evolution of these systems relative to what
was observed at this time yesterday, but there remains a significant
deal of model spread later on in the forecast period.

When the period opens on Wednesday night, mid/upper-level troughing
will have dug deep into the Eastern CONUS. That trough`s axis will
be positioned in the vicinity of the forecast area, marking the
passage of a cold front at the surface. Thus, a cold air advection
regime is likely to set up overnight into Thursday. Models
collectively depict the 540 decameter critical thickness line over
the Cumberland River Basin on Thursday morning as 850mb temperatures
drop to between -5 and -10 degrees Celsius. These values favor a
transition over to snow showers overnight, and surface temperatures
are forecast to drop below freezing area-wide after midnight.
Ensemble probabilities for measurable snowfall (>= 0.01 inches) are
above 70% for locations east of the I-75 corridor, and locally
higher-accumulations appear possible wherever mesoscale-type
precipitation enhancements materialize. The post-frontal west-
northwesterly low-level flow regime should lead to some orographic
enhancements in the higher terrain locales of Southeastern Kentucky.
Likewise, some of the currently-available higher-resolution guidance
(the NAM) suggests that a fetch off Lake Michigan could overlap with
favorable snow squall parameters to yield locally higher
accumulations in narrower precipitation bands. The other CAMs will
need to be watched closely as this system enters their temporal
range, as these smaller-scale details are smoothed over in the
baseline NBM grids used to populate the long-term forecast grids.
The showery nature of Thursday night`s precipitation will make
accumulations more spotty, and it is plausible that there will be
high spatial variability in this system`s storm totals. If the
smaller-scale accumulation enhancements come to fruition, isolated
travel issues, including potential visibility reductions, could
materialize on Thursday morning. Highs will likely struggle to get
much warmer than the mid-30s on Thursday afternoon due to the cold
air advection regime and residual cloud cover lingering over the
area. Additional light snow showers or flurries cannot be ruled out,
but more widespread precipitation chances return on Thursday night
as another clipper system approaches.

By Thursday night, the deeper upper level troughing will have lifted
northeast, although there is generally good model agreement that
another shortwave disturbance will rotate around its backside and
into the Ohio River Valley by Friday morning. The cold air in place
out ahead of this particular system should allow precipitation to
begin as snow, although as its surface low reflection approaches,
low level winds will back towards the southwest. This could
introduce warm air in the bottom portions of the atmospheric column,
which could result in a transition to liquid precipitation types.
Once this system enters the temporal range of higher-resolution
forecast guidance, soundings and temperature profiles will need to
be monitored closely, as these will provide greater insight into the
p-type forecast and the timing of any transitions. The cold air
should stick around for longer the further north and east one goes
into the forecast area, and locations northeast of the Cumberland
River basin have the highest ensemble probabilties (>50% chance) of
measurable snow with this second system. These probabilities
increase towards the I-64 corridor, where there is a >80% chance of
measurable snow and a 40-50% chance of seeing an inch. Due to
greater precipitation coverage and colder antecedent temperatures,
more widespread travel impacts cannot be ruled out on Friday
morning, and interests with AM travel plans should monitor future
forecast updates closely.

Compared to what was forecast a few days ago, guidance has trended
warmer for the Friday afternoon to Saturday morning time frame.
Shortwave ridging is expected to build into the Upper Midwest and
interrupt the train of clipper systems around then, leading to a
brief period of midlevel height rises and quasi-zonal flow aloft.
Coupled with the previously-discussed southwesterly return flow,
this indicates that low-level temperatures will moderate to above
freezing values on Friday afternoon. Saturday`s MinT and MaxT grids
will likely trend upwards in future NBM runs, but spread begins to
increase in the temperature guidance beyond then. This makes the
precipitation forecast for a third system on Saturday night more
ambiguous, although guidance collectively points towards a much
colder than average airmass advecting into the region on Sunday. For
now, the precipitation type forecast reflects a changeover from rain
to snow as the cold air arrives. The magnitude of this cold is
highly uncertain, as demonstrated by the 11 to 12 degrees of
standard deviation in the European Ensemble`s MOS guidance. It is
very difficult to provide specific sensible weather details for
Sunday and beyond given the compounding uncertainty, but WPC has
maintained a 40-60% chance of below-normal temperatures in Kentucky
early next week. Average low temperatures for mid-December in
Eastern Kentucky are highs in the mid 40s and lows near 32 degrees.
The current 25th and 75th NBM temperature percentile data for Monday
are 11-22 degrees for AM lows and 27-44 degrees for PM highs.
Therefore, it is likely to be noticeably colder than usual at the
end of the long term forecast period, regardless of specific
values.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 1257 AM EST TUE DEC 9 2025

A low MVFR to high IFR ceiling is drifting back north of the
Mountain Parkway early this morning. This cloud deck will likely
overspread the remainder of the forecast area including SYM
over the next few hours. The ceiling is expected to begin breaking
up toward/after sunrise allowing for the return of VFR conditions
area wide. Winds will be light and variable through 12Z and then
become southwest and increase to the 5 to 12KT range on average
for the afternoon hours, remaining gusty or even increasing
Tuesday night. Winds aloft will increase late in the period. Thus
LLWS wind shear may become a threat during the last ~6 hours of
the period.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SHORT TERM...GEERTSON
LONG TERM...MARCUS
AVIATION...GEERTSON