Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 150346 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1046 PM EST Tue Nov 14 2017

.UPDATE...
Issued at 1046 PM EST TUE NOV 14 2017

Temperatures continue to drop off this evening under mostly clear
skies. The coldest readings are around 30 degrees, with most other
locations ranging from the lower to upper 30s. Have lowered many
of the valleys a few more degrees across the area, as several more
hours of good radiational cooling will be on tap into the overnight
hours. This will result in temperatures as cold as the mid to
upper 20s in the eastern valleys. Updates have been sent.

UPDATE Issued at 723 PM EST TUE NOV 14 2017

Mostly clear skies currently reign across eastern Kentucky, as a
short wave ridge moves in aloft from our west. Some higher cirrus
is noted upstream, but this should remain fairly thin through most
of the overnight period. The eastern valleys have already taken
advantage of the mostly clear skies and relatively calm winds in
place at the surface, as some temperatures in the mid 30s are
currently being reported. As such, did drop the lows a bit,
allowing for a few spots to dip into the upper 20s tonight.

&&

.SHORT TERM...(This evening through Wednesday night)
Issued at 352 PM EST TUE NOV 14 2017

After a shortwave exited to our east through the morning, cloud
cover ongoing across eastern Kentucky began to dissipate from west
to east. Mostly clear skies are now in place, with the exception
of portions of Pike county which should continue to clear over the
next hour or two. High pressure and a brief period of upper level
ridging will take hold for the overnight and into the first part
of the day Wednesday. Given the clear skies and light winds from
the east, can`t rule out some patchy fog in some of the sheltered
valleys and near bodies of water. Temperatures could also drop off
a bit in the sheltered valleys, with some low 30s possible. Winds
will slowly shift to a more southerly direction by daybreak
tomorrow, as surface high pressure continues to drift east of the
region. This southerly flow will continue through the day
Wednesday, helping boost temps into the mid and upper 50s for the
day.

Also during the day Wednesday, another shortwave will shift across
the mid and upper Mississippi Valley and into the Ohio Valley. At
the surface, a cold front will slowly drag southeastward towards
the Ohio Valley, becoming elongated just north of the Ohio River
into Wednesday evening. It will finally make a quick shift
southeastward across the CWA through the overnight, exiting by or
just before 12Z Thursday. The increase in moisture/southerly flow
will prompt showers along and just ahead of the front. Models
(including the GFS/NAM/and ECMWF) are all in fairly good
agreement about the timing of the rain as it moves into the CWA,
with best intensity expected late Wednesday afternoon into the
evening, and lessoning up as it continues to spread across eastern
Kentucky through the first part of Wednesday night, then quickly
tapering off during the last half of the night once the front
exits.

.LONG TERM...(Thursday through Tuesday)
Issued at 318 PM EST TUE NOV 14 2017

Model agreement appears to be improving just a bit with the morning
runs, but differences in timing and strength of a storm system
through the region next weekend (our main weather feature of
interest for the extended) remains significant resulting in a lower
than normal confidence in the forecast overall. However, there has
been a consistent run-to-run trend in a generally slower timing.
There has also been a more subtle trend towards a slightly weaker
system, though the GFS continues to come in much stronger than
previous runs of the ECMWF. National guidance suggests the weaker
trends, and thus the ECMWF solution is favored as a result of
upstream teleconnections. Leaning towards the ECMWF solutions would
also suggest a bit warmer temperatures behind next weekend`s system.

Progressive pattern has a trough lifting out of the mid and upper
Ohio Valley at the start of the period. Brief transiting ridge
Friday is quickly followed by next weekend`s storm system.
Thereafter model consensus becomes even more muddled but in general
models hint at some shortwave energy approaching at or just beyond
the end of the forecast window. For now will keep that portion of
the forecast dry until a better consensus appears.

Sensible weather will see lingering shower activity coming to an end
early Thursday morning, restricted to mainly far southeast Kentucky.
Only slightly cooler air will filter in behind an exiting cold
frontal boundary Thursday. The threat of rain increases again Friday
night into Saturday with the approach of the next storm system.
Forecast soundings and guidance indicate little if any instability
associated with this system. Consequently not expecting any thunder.
A surface cold front will move through the area very late Saturday,
or more likely Saturday night. Colder air will once again settle
down into our area. ECMWF H850 temperatures drop to around -6 C by
Sunday. The GFS is about 7 degrees colder. Will stick with the
blended guidance for temps through the period but will attempt to
tweak temps up slightly for the latter half of the weekend and early
next week, closer to the warmer ECMWF. For PoPs, window of most
likely PoPs will probably occur late Saturday into Saturday night.
With significant differences in the timing of the cold frontal
boundary through the area blended PoPs are being averaged down to
lower values. Made some minor adjustments to the PoPs in an effort
to correct this.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
ISSUED AT 723 PM EST TUE NOV 14 2017

VFR conditions will prevail through the majority of the period;
however, ceilings will be lowering on Wednesday, as a cold front
approaches from the northwest. For tonight, just some high clouds
will be moving in. Some patchy fog will also be seen along the
deeper river valleys between 06 and 13z, but this is not expected
to occur at the TAF sites. On Wednesday, clouds will increase and
lower, with some showers threatening from northwest to southeast
Wednesday afternoon. Winds will remain light and gradually veer to
the southeast through early Wednesday morning. Winds will then
turn more south to southwest by Wednesday afternoon at 5 to 10
kts, with some gusts of around 15 kts at times.

&&

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

$$

UPDATE...GEOGERIAN
SHORT TERM...JMW
LONG TERM...RAY
AVIATION...GEOGERIAN



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