Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 101642 AAB
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1142 AM EST Sun Dec 10 2017

.UPDATE...
Issued at 1139 AM EST SUN DEC 10 2017

Hourly grids have been updated based on observation and satellite
trends. The northern third to half of the area should experience
a band of mid level clouds working through during the afternoon
and sky cover has been adjusted accordingly. Even with the
increased cloud cover, forecast max T still appears to be
reachable.

UPDATE Issued at 637 AM EST SUN DEC 10 2017

The forecast is still on track this morning. Partly cloudy skies
and southwest winds at 5 to 10 mph are expected to persist through
out the day today. The latest obs were ingested into the forecast
grids to establish new trends. No forecast update at this time.

&&

.SHORT TERM...(Today through Monday)
Issued at 300 AM EST SUN DEC 10 2017

Low and middle level cloud cover will linger across portions of
eastern Kentucky this morning, as an area of low pressure aloft
continue to pull off to the east of the area. Partly cloudy skies
will be on tap all day today. Temperatures will remain quite cold,
with highs forecast to reach the mid to upper 30s for most
locations today. A modest warm up is then on tap for tonight and
Monday, with tonights lows expected to only fall into the mid to
upper 20s for most locations, and highs on Monday ranging from
the lower 40s in the far north, to the mid to upper 40s most
everywhere else. A ridge of high pressure will keep skies partly
cloudy to mostly clear through the first of the week. Winds will
start off fairly light this morning, and should increase to 5 to
10 mph out of the southwest by this afternoon.

.LONG TERM...(Monday night through Saturday)
Issued at 440 AM EST SUN DEC 10 2017

The models continue to be in good agreement with the overall
pattern aloft through North America in the extended portion of
the forecast. However, the smaller features moving through the
longwave pattern are still exhibiting fairly large model spreads -
particularly heading into the next weekend. Early on, a compact
shortwave will run through the base of the larger Great Lakes
trough. This will move through the lower Ohio Valley by Tuesday
morning - stronger in the NAM12 and ECMWF than the GFS.
Additional energy follows by evening as the core of the main upper
low descends into the northern Ohio Valley with decent model
consensus. Sharp height fall accompany this energy through
Kentucky on Tuesday before relaxing that night and Wednesday as
the parent 5h low pivots east into northern New England. The ECMWF
takes a trailing shortwave through the region, but dampening it
as it moves into Kentucky Thursday morning. Meanwhile the CMC and
GFS do not have much reflection of this feature lowering
confidence in its potential impact. There is better model support,
at least from the GFS and ECMWF, for a resurgence in troughing
coming out of the Plains later that day and into Friday. This
trough becomes full latitude with ample energy swinging toward the
area on Friday, though the ECMWF maintains the core of the trough
better than the GFS and more to the south of the area later that
day and into Saturday morning. The pattern again relaxes in the
wake of this trough for Saturday with heights rebounding
throughout the Ohio Valley - though another fast moving wave will
be inbound later that night - this time targeting more the
northern half of the region. Given the continued model
discrepancies and limited support for key features will again
favor a general model blend, but with added enhancement for our
terrain toward more climatological norms for this type of cold and
generally northwest flow pattern.

Sensible weather will feature another couple of clipper systems
affecting the area during the bulk of the extended with bouts of
very cold air moving through, as well. The next one of these
passes through the Ohio Valley Monday night into Tuesday morning.
Upslope flow will again kick in by midday Tuesday in this
clipper`s wake with enough moisture around to generate scattered
snow showers of varying strength similar to the system that
brought snow to the area yesterday evening. The difference will be
likely more wind but also more insolation to help limit the
refreeze potential on the roads, though with sunset icy spots will
again be possible but the bulk of the snow showers should have
moved on to the east by then. Very cold air and still some
northwest breezes around that night will make for rather low wind
chill values into Wednesday morning. Drier weather does return
for Wednesday but another clipper will be approaching by that
evening. This one looks to be weaker with less wind and upslope as
it passes through the region on Thursday but with more in the way
of moisture it could actually yield better chances for snow/rain
into that night. Some upslope does eventually develop for Friday
with snow showers potentially lingering through the day. A WAA
pattern then sets up through the area Friday night into Saturday
on the backside of a southeast High.

Did make some minor, terrain based, changes to the low
temperatures Wednesday and Friday night between clippers with a
potential for ridge to valley temperature splits. Again refined
the SuperBlend PoPs to reflect the more typical pattern with these
northwest flow clipper systems in holding PoPs back over the
higher terrain in the east longer and more detailed than provided
by the blends.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
ISSUED AT 637 AM EST SUN DEC 10 2017

SCT to BKN low level clouds will persist at JKL, SJS, and SYM
through 13 or 14Z this morning before scattering out. In general,
the cloud should remain scattered from late this morning through
the end of the period. Winds should remain out of the southwest
today, and will increase to 5 to 10KT by this afternoon across the
area. VFR conditions will prevail at the TAF sites through the end
of the period.

&&

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

$$

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


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