Area Forecast Discussion
Issued by NWS Jackson, KY

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646
FXUS63 KJKL 181804
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
104 PM EST Wed Jan 18 2017

.UPDATE...
Issued at 1259 PM EST WED JAN 18 2017

Clearing has occurred over parts of Eastern TN and Southwest VA
and some of this has spread into some of the higher terrain near
the VA and TN borders over much of Harlan County and the Log Mtns
in Bell Co. Meanwhile breaks in the low clouds are occurring
across other portions of the Cumberland Valley Region and the Lake
Cumberland Region as sfc and upper ridging continue to build in.
However, deep enough moisture and an uslope low level component is
still leading to a few patches of drizzle east of JKL that are
diminishing. A gradual mixing out of low clouds should continue
throughout the afternoon and into the evening. The clouds should
linger longest in the central and norther part of the area where
temperatures may average near normal for highs, but locations in
the central to south that receive sun should climb above average.

UPDATE Issued at 1005 AM EST WED JAN 18 2017

Low level moisture remains across the region with weak upslope
flow. Radar indicates drizzle still lingering across the northern
and eastern counties. This moisture should become more shallow by
midday into early afternoon as sfc and upper level ridging build
into the area. However, the it appears that the drizzle should
linger a bit longer than the previous forecast and has been
extended in the weather grids by about 2 hours. Otherwise, no
changes were needed at this time.

UPDATE Issued at 620 AM EST WED JAN 18 2017

Did a quick update to the grids to account for the latest obs and
trends - keeping the patchy drizzle and sprinkles in there for a
couple of more hours. These have been sent to the NDFD and web
servers.

&&

.SHORT TERM...(Today through Thursday)
Issued at 355 AM EST WED JAN 18 2017

08z sfc analysis shows a cold front departing to the east while
high pressure builds in from the west. However, plenty of low
level moisture remains in place and, along with the passage of a
compact upper trough to the northeast early this morning, this is
keeping the cigs low and a potential for drizzle or sprinkles in
the forecast through dawn. Temperatures remain mild overnight for
this time of year with readings varying from the low 40s northwest
to the lower 50s in the southeast. Dewpoints are not far off from
the dry bulb temperatures - just a few degrees lower in most
places. Meanwhile, winds are from the northwest to west at 5 to
10 mph with occasional gusts to 15 mph. Patchy fog also is found
through the area early this morning.

The models are in better agreement aloft than last night as they
all depict a sharp trough - with minimal spread - diving into the
Central Appalachians from the northwest early this morning. This
is followed by a quick shot of ridging today and renewed deep
layer southwest flow later tonight and Thursday in the face of a
deep and broad closed low over the High Plains. In this flow, a
lead batch of energy will lift into the Tennessee Valley early
Thursday with more support and height falls arriving by evening.
Given the better model agreement will favor a blend, though with a
strong lean toward the HRRR in the near term.

Sensible weather will feature patches of sprinkles and drizzle
around this morning before a lull for drying sets up later today
and tonight as high pressure passes quickly over the area. The
next system then approaches from the southwest late tonight
pressing into the Cumberland Valley on Thursday. All the while
warm weather continues so that all pcpn will continue to be only
in the form of rain across eastern Kentucky through the short
term and well beyond.

Again started with the CONSShort and ShortBlend for most elements
through the short term portion of the forecast - making only minor
adjustments to the low temps tonight. Also, adjusted PoPs to
spread the next round of pcpn in a bit quicker and slightly more
extensively on Thursday than suggested by the CONSShort.

.LONG TERM...(Thursday night through Tuesday)
Issued at 245 AM EST WED JAN 18 2017

The models overall were in good agreement once again in the
extended, with a few timing differences here and there and the ECWMF
being a bit slower than the GFS. That said, the general consensus is
for a series of low pressure systems aloft to move across the Ohio
and Tennessee valley regions this weekend into the first of next
week. Each of these systems will bring a good chance of rain to
eastern Kentucky, with the potential for moderate rainfall from time
to time. We should see a break in the action Friday night and
Saturday, before things ramp up again Saturday night and Sunday. The
first round of rain is slated for Thursday night and Friday, as a
well developed area of low pressure moves out of the southern
Mississippi valley and across the Tennessee and Ohio Valleys. The
second round of rain is expected Saturday night and Sunday, as a
warm front, associated with an area of southern Plains low pressure,
makes its way northward across our area. This boundary will likely
bring only scattered showers to the area initially, with the
activity forming well ahead of the boundary. Once the front moves
closer to and across our area early Sunday morning, we should see
numerous rain showers through out the morning. The activity should
taper off again by Sunday afternoon, after the front moves to our
north.

The main shot of rain is expected from late Sunday afternoon
through late Monday, as a strengthening, and therefore slow
moving, area of low pressure ejects out of the southern Plains and
across the lower Tennessee valley region. The models begin to
diverge here slightly, with the GFS depicting a split of energy,
with an area of low pressure breaking off from the main low Monday
and Monday night and slowly moving toward the eastern Great Lakes.
The ECWMF, no the other hand, tries to keep the southern Plains
low more consolidated as it moves across the region. The end
result is still going to be widespread rainfall across the area
from this weekend through the beginning of next week. A third
weather system may bring some scattered showers back to eastern
Kentucky by Wednesday.

Temperatures during the period will be well above normal, with daily
highs in the 60s expected over the weekend, and daytime maximums in
the 50s the first couple of days of the new work week. Nightly lows
will generally be in the 40s, with a few locations perhaps seeing
lows around 50 Friday and Sunday mornings.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
ISSUED AT 105 PM EST WED JAN 18 2017

Low clouds leading to MVFR should gradually decrease through the
first 9 to 11 hours of the period as surface and upper ridging
build in. Meanwhile, clouds will begin to increase and lower ahead
of a warm front beginning first in the southwest between 6Z and 9Z
and then shifting to the northeast through the end of the period.
However, VFR is expected with this through the end of the period.
Light winds are expected through the period.

&&

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

$$

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



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