Area Forecast Discussion
Issued by NWS Jackson, KY

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085
FXUS63 KJKL 132111
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
411 PM EST Wed Dec 13 2017

.SHORT TERM...(This evening through Thursday night)
Issued at 404 PM EST WED DEC 13 2017

A potent clipper type system was moving southeast across the
Midwest today, headed for the upper Ohio Valley by late tonight.
It is bringing an increasing pressure gradient and warm air
advection to Kentucky this afternoon. An increase in mid level
moisture was resulting in radar returns moving over the area, but
very dry low levels were resulting in virga. Despite the
combination of wind and dry air, verification for the RFW has been
hard to find. Much of the area has seen RH below 25%, but the 20
ft winds above 15 mph have been much more limited so far, and not
coincident with the lowest RH. There is still time for winds to
pick up more by early evening, and the RFW will be left to ride.
If conditions do not materialize, it`s possible it could be lifted
early.

During the night, the clipper system`s cold front will pass
through. With a return to cold air advection, the low levels will
moisten in the upslope flow once again, and low clouds should
develop. If the top of the convective moist layer can reach cold
enough levels, we could see some flurries, but forecast soundings
look marginal for this. Have included a chance in all but our far
southwest counties for late tonight into Thursday morning.

The system quickly departs to the east on Thursday and a weak
surface ridge will build in from the west. Cold air advection will
ease and become more neutral, and the moisture in forecast
soundings become very shallow. We should see low clouds start to
break up, but whether or not the whole area sees it by the end of
the day is uncertain. High clouds will start to thicken during the
day, which would limit sunshine even where low clouds do scatter
out.

.LONG TERM...(Friday through Wednesday)
Issued at 411 PM EST WED DEC 13 2017

The extended portion of the forecast begins on Friday with an
amplified upper level pattern in place with a stout ridge in the
western CONUS transitioning to a trough in the east. On Friday, a
decent short wave passes through the OH Valley but current model
trends keep the majority of the lift and moisture to the north of
the CWA so Friday will remain dry in addition to Saturday as a
weak ridge quickly passes through the area. The upper level
pattern transitions to a more progressive through the weekend
before the next system develops with a stronger shortwave diving
to the south and developing over the lower MS Valley area. This
combined with another wave passing to the north. This set up will
bring a much needed surge of moisture northward with precip
developing into eastern Kentucky by Sunday morning and lasting
into Monday evening.

Concerning the top down of Sunday morning. At this point, surface
temps will be border line for any sleet or freezing rain
development. It appears with surface temps warming up ahead for
this event, will keep a snow and rain mix in the morning hours and
warming quickly into the late morning hours. Thus, will not expect
any accumulation as well. With the drier pattern taking over again
and the main storm track remaining to the north, the last two days
of the extended will likely be dry at this point. This is
especially the case with the outlooks and climatology. The last
half of the extended looks to be at or just above normal as well.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
ISSUED AT 200 PM EST WED DEC 13 2017

Breezy VFR conditions will prevail into this evening. Southwest
winds gusting 20-25 kts should be common by late today. A cold
front will pass through tonight and winds will veer toward the
northwest. Winds will gradually ease later tonight. An MVFR
ceiling is expected to develop from northwest to southeast behind
the front between about 04z and 07z and persist through the rest
of the period.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 9 PM EST this evening for KYZ044-050>052-
058>060-068-069-079-080-083>088-104-106>120.

Lake Wind Advisory until midnight EST tonight for KYZ051-052-060-
079-080-083>085-106.

&&

$$

SHORT TERM...HAL
LONG TERM...SHALLENBERGER
AVIATION...HAL



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