Area Forecast Discussion
Issued by NWS Jackson, KY

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566
FXUS63 KJKL 240955
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
555 AM EDT Tue Oct 24 2017

.SHORT TERM...(Today through Wednesday)
Issued at 408 AM EDT TUE OCT 24 2017

Current conditions across the area feature cloud cover moving in
from the west associated with a post frontal trough rotating
through the OH Valley. This line of showers will push through the
area as we head into the predawn hours and into the morning. So
will keep the chance of showers lingering into midday. This closed
low lingering over the Great Lakes will continue to bring a
couple disturbances southeast through the area through the next 36
hours. Lingering cloud cover associated with todays feature will
limit temperatures in the 50s for this afternoon as well with a
decent gradient, allowing 20 to 25 knot gusts today.

By tonight, a second wave will swing through bringing some cloud
cover and providing some insulation keep temps from bottoming out
into the lower 30s. So will see some mid to upper 30s for lows and
keeping frost and fog out of the forecast. By the day on Wednesday
another wave drops through the area but with depleted amount of
moisture, will only expect a slight chance of showers in the late
afternoon along with some extensive cloud cover during the day.
Lingering cloud cover will keep temps in the 50s for highs on
Wednesday.

.LONG TERM...(Wednesday night through Monday)
Issued at 555 AM EDT TUE OCT 24 2017

The models are in good agreement aloft on the large scale for the
bulk of the extended portion of the forecast. They all depict a
much different pattern for the eastern half of the nation than
what we have seen for a long time. The most noticeable feature
will be a deep tough now in place over the Great Lakes and Ohio
Valley. A reinforcing shot of energy and troughiness will pour
into the region at the start of the extended period maintaining
the lower heights into Thursday before quickly lifting out to the
northeast. This well modeled longwave pattern adjustment will
then allow the heights to rebound over Kentucky through the end of
the work week and into Saturday morning. However, mid level
heights will again crash this weekend as the next large, full-
latitude, trough digs through the middle of the country and into
the Great Lakes/Ohio Valley. This brings a renewed bout of low
heights and troughing to Kentucky with increasing support for an
upper low closing off over the Central Appalachians by the end of
the weekend. As this feature progresses off to the northeast on
Monday, heights will again rebound, but remain below normal for
this time of year. Given the general model agreement and mainly
minor timing/magnitude differences with the 00z GFS and 12z ECMWF
do not see the need for any wholesale adjustments to the blended
solution.

Sensible weather will feature a complex and active period of
seasonal cool weather across eastern Kentucky from mid week
through the weekend. Cold air in the wake of another departing
cold front will lead to frost formation in the more sheltered
valley locations Wednesday night into Thursday morning.
Temperatures will then moderate somewhat into the weekend on
return flow behind a retreating area of high pressure to our
southeast. However, a well defined cold front and low pressure
system will then work into the area on Saturday with moderate
rains possible along with more cold air pushing in on northwest
winds. As such, by Saturday night, lingering rain showers will
likely see enough cold air for a mix with snow and possible
complete transition in the higher terrain. Cannot rule out some
light accumulations on the ridgetops from this, though the still
warm ground will limit the extent of it even as the sfc air
temperature approaches freezing by Sunday morning. Should the pcpn
and cloud cover clear out quicker than expected Saturday night
frosty conditions will be possible, as well, into Sunday morning.
Lingering showers and low clouds will hinder any warm up on
Sunday but we should see better results on Monday as the core of
the cold air moves off to the east and some sunshine returns.

Did make some temperature adjustments to the gridded blended
starting point based on terrain for the first few nights of the
extended with a bit of a ridge and valley split anticipated. As
for PoPs, lingered the higher values a bit longer than the blend
on Saturday night and into Sunday with a trend suggesting a
slowing of the main front is possible. Have highlighted the frost
and freezing temperature concerns for this week/weekend in the
HWO and will continue to monitor any accumulating snow chances for
the weekend.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 120 AM EDT TUE OCT 24 2017

A break between the post frontal troughs is evident on satellite
as clear skies are being observed along I-75 this hour. Thus have
timed the break cloud cover in the TAFS. Towards dawn the second
period of cigs will arrive with MVFR being most likely. The
southern TAF sites will most likely remain VFR such as SME later
tonight. The further north sites will be most impacted as the
second trough lifts to the north. Winds will generally be
southwest to west and gusting up to 20 knots at some sites by this
afternoon. VFR conditions are expected by 15z and lasting through
the rest of the period.

&&

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

$$

SHORT TERM...SHALLENBERGER
LONG TERM...GREIF
AVIATION...SHALLENBERGER



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