Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 110654 AAC
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
154 AM EST Tue Dec 11 2018

.UPDATE...
Issued at 145 AM EST TUE DEC 11 2018

Adjustments have been made to weather grids based on the fog
trends noted on regional AWOS and ASOS observations and GOES East
nighttime cloud microphysics that show the area extent of fog.
This fog is dense in some spots and with temperatures below
freezing and in the upper teens to low 20s, there is some freezing
fog being reported. An SPS was issued for the southeast counties.
Observations will continue to be monitored overnight for the areal
extent of the fog and if any additional counties need to be added
into the SPS. Other than the fog that is generally in the valleys,
but is more widespread in the far southeast, temperatures will be
cold with the coldest overnight lows in the deeper valleys and
typical cold spots. The coldest min T should occur in the deeper
valleys where snow remains on the ground.

UPDATE Issued at 1000 PM EST MON DEC 10 2018

Some river valley fog has developed with the good radiational
cooling underway and lingering boundary layer moisture around.
Have updated the grids for this extending the fog through through
dawn. Cannot rule out some patchy dense fog in those river valleys
for a time overnight, but believe it will be fleeting so have
capped low visibility to 1sm with this update. Also, added in the
latest obs and trends for the T and Td grids. An updated set of
zones is on the way along with grids sent to the NDFD and web
servers.

UPDATE Issued at 640 PM EST MON DEC 10 2018

23z sfc analysis shows high pressure building into the area. This
has cleared the sky and brought in drier air to the north while a
bit more moisture is found in the southeast where a dwindling snow
pack is found. With light northwest winds temperatures vary across
the area from the low to mid 30s on the ridges and in the upper
20s in the valleys. Dewpoints meanwhile range from the upper teens
and low 20s across the northern half of the area to the upper 20s
and lower 30s in the south. For tonight, clear skies with good
radiational cooling conditions will mean temperatures falling
into the teens for most - coldest in sheltered valleys with some
snow still on the ground and mildest on the snow free ridgetops.
Have fine tuned the lows and dewpoints this night to try and
capture the chill. These updated grids have been sent to the NDFD
and web servers with a freshened set of zones on the way.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 356 PM EST MON DEC 10 2018

Surface high pressure is currently centered across Texas, with
ridging spread to the northeast into the Ohio Valley. Aloft, a
very positively tilted trough is aligned from near the southern
Appalachians down towards the Arklatex region. Eastern Kentucky
has enjoyed a mostly sunny day across the majority of the area,
besides some slowly eroding low clouds in the far southeast
portion of the state. Temperatures have recovered to the upper 30s
to lower 40s for most locations today.

The models are in good agreement through the short term, with
heights gradually flattening out and generally increasing across
the Ohio and Tennessee valleys through the period, bringing dry
weather and mostly clear skies. At the surface, the high pressure
ridge will shift southeast with time, with return flow ensuing.

Tonight will feature mostly clear skies and cold temperatures, as
readings drop down into the teens for many of the valleys. Highs
on Tuesday look to be a bit warmer than today, generally low to
mid 40s. Tuesday night lows will range from the mid 20s for the
cooler eastern valleys, to around 30 degrees on the ridges. High
clouds will be on the increase after midnight.

.LONG TERM...(Wednesday through Monday)
Issued at 404 PM EST MON DEC 10 2018

The long term will begin with upper level ridging over Kentucky
along with surface high pressure over the southeastern CONUS. This
will bring mostly dry conditions for Wednesday afternoon.
However, the far north will have a slight chance for some showers
late Wednesday into early Thursday as a northern stream shortwave
moves across the upper Ohio Valley. As the surface high pressure
in the southeast moves up along the east coast, return flow will
help usher in warmer temperatures for the Commonwealth through the
end of the work week. The main story in terms of precipitation
for the extended period will be the progression of a southern
stream system Thursday evening through the first part of the
weekend. Models have come into better agreement with recent runs,
but are still a bit out of sync with timing. Therefore, have
lowered PoPs given by the SuperBlend slightly with the onset of
the system for Friday as well as Saturday into Sunday as the
system moves on to the northeast. Rain will be the dominant
precipitation type due to warmer temperatures, but as the system
exits to the northeast there is a possibility for a light
rain/snow mix and/or changeover to snow into Sunday morning with
temperatures approaching the freezing mark. However, with
uncertainty in the timing of the system, will continue to monitor
its development with future model runs. There is another chance
for showers Monday, but as this system is at the tail end of the
forecast period, confidence is very low at this time.

High temperatures will increase from the upper 40s Wednesday to
generally be in the mid 50s on Friday. Highs will then return to
the upper 40s for the weekend and into next week. Lows will also
increase to be around 40 degrees for Friday and Saturday morning.
Lows will then decrease to be in the low to mid 30s by Monday
morning.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 135 AM EST TUE DEC 11 2018

The near term concern through about 14Z, is the threat of valley
fog that per trends and GOES imagery should affect all the TAF
sites except KSYM during that time. Some of this could be dense
for at least KLOZ and KJKL and possibly at KSME and KSJS. With
temperatures below freezing, FZFG will be possible. Once the fog
dissipates, VFR conditions will prevail as a ridge of high
pressure gradually slides southeast across eastern Kentucky. Winds
will average around 5 kts or less through around 15Z, before
picking up from the southwest at 5 to 10 kt. Winds should again
become light late in the period.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...JP
SHORT TERM...GEOGERIAN
LONG TERM...CGAL
AVIATION...JP



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