Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 031732

National Weather Service Jackson KY
1232 PM EST Sat Dec 3 2016

Issued at 945 AM EST SAT DEC 3 2016

Updated the forecast to better reflect the current cloud cover
across the area. Based on the latest satellite obs, most of
eastern Kentucky has been under overcast skies for the past few
hours, and it appears this trend will not change anytime soon.
Therefore, the sky cover grids were updated to reflect cloud skies
for most locations for the rest of the day. The updated zones have
already been sent.

UPDATE Issued at 656 AM EST SAT DEC 3 2016

Low stratocu continues to encompass much of eastern KY. This has
allowed for more regulated temperatures through the early morning
hours, and reduced any ridge valley split from earlier in the
evening. Expect temperatures to begin rising over the next hour as
the sun rises. These clouds will likely hold on through much of
the morning, and will finally start breaking apart this afternoon
in the south, eventually making its way to the northern CWA by
late this evening. The remainder of the near-term forecast seems
to be well on track with current conditions. All changes have been
published and sent to NDFD/web.


.SHORT TERM...(Today through Sunday)
Issued at 356 AM EST SAT DEC 3 2016

Surface high pressure will continue to overspread the state
throughout the day today, passing just to our east by 6Z tonight.
Overall this will result in light winds at the surface with llvl
stratus clouds continuing to pull into the region from the NE
through at least mid day in many locations. Llvl winds will begin to
lighten and become more variable as the center of the high passes to
our north and then heads east, allowing the llvl clouds to begin
breaking up throughout the afternoon. Meanwhile, aloft, a shortwave
will begin digging across the northern plains throughout the day,
shifting eastward. This shortwave is expected to reach the
Mississippi River Valley by Sunday, then move across the Ohio River
Valley and points to the north by 0Z Monday.

The upper level wind pattern will feature a jet streak across the
Ohio River Valley ahead of the shortwave, increasing in strength as
the shortwave nears. Mid/upper level winds will be westerly across
KY and then SW just to our east. This will effectively pull moisture
from the Gulf of Mexico northward and then eastward into the state.
As such, this will result in high clouds expected to push northward
into the CWA by later this afternoon. Moisture and clouds will
continue to build this evening with the nearing mid/upper level
wave, however it will have a hard time overcoming the bubble of dry
air at the surface with the surface high pressure center still in
place just to our east. Latest forecast soundings show moisture
finally overcoming the drier air between 6 and 9Z at KSME and KLOZ
in our southern CWA, between 6 and 12Z in the mid sections, and a
few hours later in the northern CWA.

Despite W to SW flow aloft, temperatures in the mid and upper levels
will still be on the cooler side as precip moves into the region
overnight Saturday, below freezing through much of the column. As
such, even as temperatures at the surface may be at or above
freezing at precip onset, rain may still mix with snow for the first
couple of hours. However, temperatures will quickly warm as we head
into the daytime hours, with the surface high continuing eastward
and allowing warmer return flow at the surface.  All precip will
change over to rain during this time, with generally no snow
accumulation or impacts expected. Rain is expected to continue
through the day Sunday as the mid/upper level shortwave closes in on
the region. This will produce generally between 0.10 and 0.20 inches
or rain across the CWA, an overall light system but much needed none
the less.

.LONG TERM...(Sunday night through Friday)
Issued at 503 AM EST SAT DEC 3 2016

Challenging extended package this morning. Models are in
good agreement for DYS 3-4 but diverge significantly beyond that
both with the details of the mid/upper level pattern as well as
with sensible weather. Mid/Upper level cut off low moving out of
Texas Monday opens up into a wave by Tuesday as it transits the
MS/TN/OH valleys. This feature will provide another soaking rain
to the area with models spitting out around an inch of rainfall
on average, mainly from Monday night through Tuesday.

Forecast gets complicated thereafter as a series of disturbances
rotate around a low pressure system residing along the Northern
Tier and southern Canada. Models appear to have difficulty with
the strength and timing of several lobes of energy rounding this
parent low. The GFS presents a quicker solution with weaker
disturbances. The ECMWF advertises stronger disturbances which
dig a bit further south resulting in an overall slower solution
and correspondingly stronger surface features. The Canadian
generally provides partial support for both solutions.

For sensible weather we can expect a seasonably warm start to
the extended but cool significantly through the period after
Tuesday. Rain will be tapering off Sunday night before
redeveloping across the region Monday night into Tuesday. There
is very low confidence with respect to precipitation types and
amounts beyond that. Depending on your model of choice we could
see anything from rain to snow from Wednesday night through
Friday. At this time felt the best approach was to stay close to
the blend of model solutions and guidance which suggest that a
wintry mix of precipitation will be possible through that time
frame depending on the time of day/night.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)

Low and middle level cloud cover will continue to plague the
airports of eastern Kentucky through early this evening. The
result will be a fluctuation between MVFR and VFR CIGS through
between 5 and 8Z tonight. Conditions will likely worsen by between
12 and 13Z Sunday, as an area low pressure moves by just to our
south, with MVFR to IFR conditions possible at the TAF sites due
to low cloud cover and incoming rain showers. The first rain
should begin moving into eastern Kentucky between 1 and 2Z this
evening. The precipitation will gradually further and further
north overnight, with some snow perhaps even mixing with the rain
by 6Z. The northern edge of the precipitation shield is expected
to push through our northernmost counties by 13Z Sunday.




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