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FXUS63 KJKL 180930
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
430 AM EST Mon Dec 18 2017

.SHORT TERM...(Today through Tuesday)
Issued at 405 AM EST MON DEC 18 2017

The latest surface analysis shows an area of high pressure posted
up across the southeast US including much of the Ohio Valley. The
biggest issue that remains for the near term is the large area of
stratus across the Ohio and Tennessee Valleys. This is brought to
us by a 850mb inversion that continues to trap moisture within
boundary layer. The latest model soundings and time heights
suggest this will remain the story today into tonight. Also given
the increasing jet energy aloft and slight hints of lower level
omega we have seen some patchy drizzle develop across the area
overnight and will likely continue for most through the afternoon.
This is especially prevalent in the high terrain locations where
more significant drops in visibility have remained the trend
overnight. The aforementioned clouds and drizzle lead to under
cutting the temperatures given the lack of diurnal heating. Also
developing jet streak at the 300mb this afternoon could enhance
the potential for patchy drizzle closer to the Bluegrass region
nearer the favored right entrance region, and we did increase POPs
slightly in those locations this afternoon but keep it patchy
drizzle.

Tonight think the clouds will be most robust in the evening and
decrease some thereafter, as the time heights do indicate slow
erosion of the low level moisture layer from the top down. Overall
we will remain mostly cloudy and this will lead to another night
of uniform low temperature readings across eastern Kentucky. Then
Tuesday we watch an 500mb shortwave progress into Texas and some
overrunning like moisture begins to stream northward ahead of this
developing system through the day Tuesday. This could lead to a
few rain showers in the south toward the end of the short term
period. The biggest question will be how much we recover
temperature wise and for now will keep mid to upper 50s that the
model blend provided.

.LONG TERM...(Tuesday night through Sunday)
Issued at 430 AM EST MON DEC 18 2017

A split-flow long wave pattern will initially be ruling across the
CONUS for the middle of the upcoming week, with the Ohio and
Tennessee valleys seeing more influence from the southern stream.
The long wave pattern will then amplify significantly towards the
weekend, with phasing taking place and a deep trough evolving
across the central and western CONUS, bringing high confidence
that colder air will eventually affect much of the lower 48 by
early next week. Details on the evolution of this trough and the
outcome of a stout baroclinic zone set up across the region
continue to be low confidence at this point, with models showing
discontinuity from previous runs. The ECMWF is now showing a much
more positively tilted trough, keeping the baroclinic zone closer
to our area, with mainly periods of rain to contend with through
the holiday weekend. The GFS is now looking closer to the ECMWF
did yesterday, showing much colder, but mainly drier weather after
Saturday morning. Given the uncertainty, did not deviate much
from the blended guidance.

An active weather pattern will be in store for eastern Kentucky
through the period, with rain affecting most locations south of
the Mountain Parkway Tuesday night into Wednesday, as a short
wave trough moves from the northern Texas to the Tennessee Valley
through Wednesday. Locations along and south of the Hal Rogers
Parkway and Highway 80 corridors will see the heaviest rainfall
amounts, where between a half inch and an inch could fall. Amounts
will lower quickly to the north, as there will be a sharp cutoff
to the measurable precipitation. Showers will taper off into
Wednesday night, as the short wave exits off to the east.

Thursday looks to be the one pleasant day next week, with a
mostly sunny and mild day across the area. A more significant
cold front will then take aim at the area Friday into Saturday.
POPs continue to trend upward for this time frame, with the
highest chances peaking late Friday night into early Saturday
morning. Mild temperatures through the time range keep all of the
precipitation as rain. Confidence then breaks down significantly
into Sunday, as the GFS shows a more progressive outcome of the
colder air, more similar to what the ECMWF was showing yesterday.
The latest ECMWF, as mentioned earlier, is now holding back
another slug of mid and upper level energy, which would keep the
baroclinic zone more entrenched across the area, bringing another
more prolonged period of precipitation across our area beginning
Sunday. Have allowed for an increase in POPs into Sunday;
however, will hold out hope for better model continuity before
assessing eventual impacts at this point.

Temperatures will be well above normal through the majority of
the period. Highs will average between 55 and 60 degrees from
Thursday through Saturday, with the colder air looking to be
delayed a bit more compared to yesterday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
ISSUED AT 1246 AM EST MON DEC 18 2017

This period is met with a mix of MVFR and IFR conditions mainly
because of lower CIGS. This low level moisture in combo with
upper level jets will keep the potential for drizzle overnight
into Monday. That said, several sites are showing signs of this
with lowering VIS over the past few hours and here at JKL we are
seeing drizzle this hour. This low level moisture will continue
to promote IFR or lower CIGs through much of the TAF cycle and
then some improvements are possible to round out the period to
lower MVFR. The winds through the TAF cycle will remain light out
of the south.

&&

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

$$

SHORT TERM...DJ
LONG TERM...GEOGERIAN
AVIATION...DJ
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