Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 172045

National Weather Service Jackson KY
345 PM EST Sun Dec 17 2017

.SHORT TERM...(This evening through Monday night)
Issued at 345 PM EST SUN DEC 17 2017

20z sfc analysis shows low pressure working into Kentucky with a
weakening cold front spreading into our area. This is continuing
to support light pcpn and a lowering cloud deck late this
afternoon. Under the thick clouds temperatures are holding in the
upper 30s to lower 40s most places while dewpoints are in the low
to mid 30s. Winds are predominantly light and variable with the
higher elevations and locations closer to the Bluegrass seeing
southwest ones. They are light to the northwest with stronger ones
at 10 to 20 kts above 2000 feet along with some gusts in the 30s.

The models are in good agreement aloft through the majority of
the short term portion of the forecast, though they diverge a bit
late. They all depict fast and nearly zonal flow over the Ohio
Valley tonight through Monday night. A dampening wave is currently
departing the area with additional energy more concentrated well
to the north of Kentucky on Monday. Meanwhile, a fairly deep and
closed trough will be swinging through the Four Corners region
tomorrow afternoon elongating as it heads into western Texas by
Tuesday morning. At this point the models start to stray from each
other with the NAM taking the core of the trough further north
than the GFS and ECMWF. This difference continues through the day,
Tuesday as the ECMWF digs its trough deepest and a bit quicker
east than the others. Downstream, this will affect the amount of
height rises over Kentucky with additional bits of energy slipping
over the JKL CWA. Given the increasing model spread a general
blend is preferred, though the higher resolution HRRR and NAM12
were leaned upon for wx details.

Sensible weather will feature plenty of clouds through the short
term as low level moisture will be tough to clear out. With
lowering cigs tonight into Monday drizzle and pockets of light
rain can be expected but very little in the way of QPF resulting.
In addition the cloud cover will really tamp down the diurnal
curve through the entire short term period of the forecast. With
the falling cigs some may get low enough tonight for areas of
ridgetop fog. Have included this in the grids, as well.

Given the limited diurnal range did not deviate too far from the
ShortBlend temperatures through the period. Did raise PoPs a notch
during most of the short term to help define the drizzle threat.

.LONG TERM...(Tuesday through Sunday)
Issued at 250 PM EST SUN DEC 17 2017

The latest model data is suggesting that there will be two periods
of active weather in the extended. The first will be from Tuesday
afternoon through Wednesday evening, as an area of low pressure
moves slowly across the Tennessee Valley. Scattered to numerous rain
showers are expected for most of the area, as the weather system
makes its way off to the east. The second period of active weather
looks to be from Friday through early Saturday evening. It appears
once again that temperatures will be warm enough to keep any
precipitation in liquid form across the area. Both precipitation
episodes should provide nothing more than a good soaking rain to
eastern Kentucky.

Temperatures through out the period are expected to be well above
normal, with daily readings topping out in the 50s for most
locations. There will be a few days where some spots will only make
into the upper 40s, and other days where highs will be in the upper
50s. Nightly lows are forecast fall into the 30s and 40s, which
would also be well above normal for this time of year.


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)

Mid level clouds and VFR conditions remain across eastern
Kentucky early this afternoon even as the light rain moves on
through. Look for lowering CIGS to MVFR by evening. After this,
lingering low level moisture in the form of stratus deck will
remain in place and descend through the night. This will also lead
to the potential for drizzle and IFR or lower CIGs late tonight
and into the first part of Monday. Winds will remain light out of
the south and southwest.




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