Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 160605 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
105 AM EST Sat Dec 16 2017

.UPDATE...
Issued at 105 AM EST SAT DEC 16 2017

Clouds are finally relenting across the area. Have freshened up
the sky cover through the overnight based on satellite trends,
otherwise the forecast remains on track.

UPDATE Issued at 714 PM EST FRI DEC 15 2017

An expansive area of stratus near 4k feet has slid into eastern
Kentucky this evening, with a thin line of clearing ahead of
another area of low clouds approaching southeast Indiana. This
second batch of stratus may only skirt northeast Kentucky as
surface ridging builds in from the Tennessee Valley.

Altered hourly temperatures a bit this evening, keeping everyone
fairly uniform, before showing a developing ridge/valley split
after midnight when clearing ensues.

&&

.SHORT TERM...(This evening through Saturday night)
Issued at 252 PM EST FRI DEC 15 2017

Current conditions across the area features a lingering low level
stratocumulus layer slowly pushing to the east. In fact, the
western edge is now beginning to cross in the Somerset and Fleming
County area. With drier air working in and westerly winds pushing
the layer out, will begin to see clearing and lifting skies
heading into tonight. In fact, the lingering cloud cover stunted
the high temps for today leaving a rather cold night on tap with
low temperatures dropping into the lower 20s. The clearing skies
will continue into the day for tomorrow with stout southwest
winds engaging during the day. This will bring warm air advection
into eastern Kentucky with high temperatures during the day
rebounding into the upper 40s to around 50. The slightly moist air
will be slow to enter the area for Saturday leaving dew points in
the mid 20s.

Concerning Sunday night, models have significantly slow the
approach of the system from the southwest and thus, the chance of
the lower layer saturating in time for surface temps to be below
freezing is very unlikely at this point. Warm air advection into
the area will warm temperatures in time for an all rain event. Mid
and upper level cloud cover quickly moving into the area will also
lessen the ridge to valley differences in temperature. Thus, the
short term forecast remains a temperature and cloud cover
forecast.

.LONG TERM...(Sunday through Friday)
Issued at 230 PM EST FRI DEC 15 2017

Morning runs are in reasonable agreement with the mid/upper level
pattern through the period. As usual more significant differences
show up in the lower level details. The pattern remains amplified
and generally progressive. However, southern stream energy is
distinctively slower with an occasional pause in the movement of
disturbances across the deep south. The end result is a type of
split flow regime. Weather with this type of pattern is typically
uneventful for those caught in the middle. But longer term solutions
suggest the potential for some interesting weather, hinting that a
mean split flow could persist but narrow a bit allowing both the
northern and southern streams to become more interactive across our
region before the end of December.

At present there are three main features of interest. The first is a
short wave trough passing through the mid Mississippi Valley and
into the Great Lakes Sunday. This disturbance is weak and fills as
it progresses northeast with time. The second is a similar type
disturbance that fills as it pushes through the southern Plains and
into the Tennessee Valley by Tuesday night. Of particular interest
is the 12Z ECMWF, which has suddenly trended much slower with the
second disturbance, bringing it through the region about 24 hours
later than the GFS and Canadian. Thereafter not seeing any well
defined systems or disturbances through our area until just beyond
the end of the period as a deep northern stream trough approaches
the Ohio Valley from the west. By Sunday we are well entrenched in
the warm sector of the core track of storm systems and generally
remain there through the end of the extended window.

Sensible weather is best described as warmer than normal with the
occasional chance of some rain. The first disturbance will bring a
chance of rain to our entire area by late in the day Sunday as the
system passes to our northwest. The second disturbance passing
through the Tennessee Valley could provide another opportunity for
some rain across the area. But confidence is low on timing with the
most recent run of the European. At present will stay with the
blends, which shows overrunning light rain developing mainly over
the southern half of our forecast area Monday night into Tuesday,
but more likely Tuesday. But keep in mind the ECMWF brings that
precipitation into the area as late as Wednesday afternoon or night.
The threat of precipitation returns once again by Friday as the
aforementioned northern stream trough approaches from the west. On
average our temperatures will run above normal, but especially with
respect to daily highs running generally in the 50s, possibly
approaching 60 by Monday. Sunday and Wednesday will be cooler, with
highs in 40s on Sunday and around 50 Wednesday. Overnight lows will
run a bit closer to normal each night, but appear to remain above
freezing for many locations.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
ISSUED AT 105 AM EST SAT DEC 16 2017

VFR conditions will prevail through the period. A broken stratocu
deck ranging from 4-6k feet agl will break up and exit off to the
east through the overnight hours, with mainly just a few passing
mid and high level clouds expected thereafter. Southwest winds
will average between 5 and 10 kts through the period, with the
strongest winds occurring during the afternoon hours.

&&

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

$$

UPDATE...GEOGERIAN
SHORT TERM...SHALLENBERGER
LONG TERM...RAY
AVIATION...GEOGERIAN



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