Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 151731
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1231 PM EST Fri Dec 15 2017

.UPDATE...
Issued at 1039 AM EST FRI DEC 15 2017

Updated the forecast to input the latest observations through the
the morning hours and trend them into the afternoon. It appears
the forecast challenge for the day will be forecasting the
departure of the cloud cover today and its impact on the high
temperatures.

UPDATE Issued at 737 AM EST FRI DEC 15 2017

Fine-tuned the hourly temperatures and dew points through the
morning, otherwise the forecast remains on track.

&&

.SHORT TERM...(Today through Saturday)
Issued at 353 AM EST FRI DEC 15 2017

Surface high pressure is currently nosed in across the Ohio
Valley, with weaker low pressure centered across Lake Superior.
Aloft, a trough axis is aligned from the western Great Lakes down
to the Desert Southwest. Low level clouds have been persistent
across eastern Kentucky overnight, as moisture continues to be
trapped at the 925-850mb layer.

The trough axis will move southeast across the Ohio and Tennessee
valleys today. Heights will then recover aloft tonight into
Saturday, as a ridge axis sharpens up across the Mississippi
Valley.

Low clouds will be hanging around through the morning across most
of the area, before some thinning occurs in the afternoon. This
will limit the diurnal rise once again, with highs generally in
the mid to upper 30s, with perhaps a few 40 degree readings, where
places start out milder.

Clouds will be on the decrease tonight into Saturday, as the ridge
builds in from our west. Lows tonight will range from the low to
mid 20s in valley locations, to the upper 20s on the ridges under
partly cloudy to mostly clear skies. Saturday will feature a
mostly sunny day, with temperatures rebounding to around the 50
degree mark.

.LONG TERM...(Saturday night through Thursday)
Issued at 328 AM EST FRI DEC 15 2017

The period begins Saturday night with high pressure to our
southeast and ridging aloft. Despite the gradient from approaching
system to the southeast think the eastern valleys will decouple
early and lead to at least a 5 degree ridge/valley split Saturday
night. Then we see a southern stream shortwave ride northeast out
of Texas and this will bring overrunning precipitation toward the
area by Sunday. We continue to see models slowing the progression
of this system and therefore have slowed this down further from
previous forecast. There was talk of mix precipitation in previous
forecast, but given the slower progression this has been removed.
The models have also trended drier, as the upper level wave
dampens overtime and 850mb jet is fairly weak overall. The better
low level jet will be strongest in the afternoon on Sunday leading
to more confidence for later onset. We remain in the southwest
flow regime through early next week and therefore keep small
chances of precipitation each day with lowest POP day being
Monday. The next best chance of rain showers will be Tuesday, with
the help of a jet streak and shortwave aloft. The flow aloft does
flatten out and a surface high progresses east out of the Central
Plains to round out the period. This will lead to cooler nights
and better shots of seeing ridge/valley splits. Overall afternoon
high temperatures will be near to above normal and low
temperatures near to above normal.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
ISSUED AT 1231 PM EST FRI DEC 15 2017

Current conditions across eastern Kentucky feature a lingering low
level stratocumulus deck that is slowly progressing east across
the area. This deck will slowly lift and dissipate by the evening
hours as southwest flow engages behind it. Timing this will be the
key so will keep MVFR conditions through 22z to 00z at the TAF
sites to time this. After this, skies will give away to a cirrus
layer and clearing skies heading into tomorrow as high pressure
passes through. Expect the winds to remain west and gusting to 20
knots at some place before becoming light and variable by 00z.

&&

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

$$

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



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