Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 230036 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
736 PM EST Wed Nov 22 2017

.UPDATE...
Issued at 725 PM EST WED NOV 22 2017

Hourly temperatures in the eastern valleys were dropping quicker
than the previous forecast as the nocturnal inversion is
deepening. These locations have decoupled while the ridgetops and
more open terrain locations have remained more mixy with north to
northeast flow around high pressure currently centered over the OH
Valley. With the high remaining in place, net radiational cooling
should continue unimpeded for nearly the entire night as thicker
high clouds associated with an upstream shortwave should not
arrive until closer to dawn. The previous overnight lows still
look reachable so no changes were were made at this time as the
inversion should eventually lift to near the ridgetops in the
coalfields and winds slacken in the southwest as the night
progresses.

&&

.SHORT TERM...(This evening through Thursday night)
Issued at 300 PM EST WED NOV 22 2017

Nothing but cool and dry weather in the forecast in the short
term. A strong ridge of high pressure will remain in place across
the region through the end of the week and beyond. Mostly clear
skies, light winds, and dry conditions will be on tap across
eastern Kentucky. The weather feature of note in the short term
will be ridge/valley temperature differences tonight and tomorrow
night. The more well defined split should occur tonight, with
valleys bottoming out in the lower 20s, with the surrounding
ridges coming it in the mid 20s. A split will occur to some degree
Thursday night, but should not be quite as well defined as
tonight`s as some warming will occur during the day on Thursday.

.LONG TERM...(Friday through Wednesday)
Issued at 357 PM EST WED NOV 22 2017

The significant features during the period consist of two cold
fronts. The models are in good agreement for the passage of the
first front, but are showing terrible disagreement for the second
one.

The first one should pass during the day Saturday. Forecast
soundings suggest moistening will occur from the top down along
the front, but will not be able to completely overcome dry mid
levels before the upper level support passes/wanes. A notable
increase in cloud cover will be carried, but a dry forecast will
be maintained. High pressure and a cooler air mass will build
into the region behind the front and bring clear skies and a brief
downturn in temperatures to start the new week.

Another cold front is expected to reach the area around the middle
of next week. Unfortunately, the models have become even more
disparate in the 12z runs than they were before. The 12z GFS and
Canadian bring the front through on Tuesday night, the GFS
ensemble mean brings it through on Wednesday, and the ECMWF
brings it through on Thursday. All models show at least light
precip with the front. However, due to very low confidence in
timing, nothing more than 30% POP will be carried in any given 12
hour period at this point. Timing of the front will also impact
temperatures. Have followed a blend for the time being. That being
the case, will expect the temperature forecast for Tuesday night
and Wednesday to change (possibly a considerable amount) as
confidence in timing increases.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
ISSUED AT 736 PM EST WED NOV 22 2017

High pressure dominating at the surface with only a moisture
starved shortwave trough to move through the Great Lakes and OH
Valley later tonight and on Thursday. This should result in
nearly cloud free skies until 6Z to 9Z with some bands of mid and
possibly some high clouds moving through the region through end
of the period with VFR persisting. With a weak pressure gradient
in place, winds should be light through the period.

&&

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

$$

UPDATE...JP
SHORT TERM...AR
LONG TERM...HAL
AVIATION...JP



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