Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 070807

National Weather Service Jackson KY
307 AM EST Wed Dec 7 2016

.SHORT TERM...(Today through Thursday)
Issued at 307 AM EST WED DEC 7 2016

The latest surface map features a cold front aligned from the
eastern Great Lakes down across the central and southern
Appalachians. A strong surface ridge of high pressure is nosed in
from the Continental Divide down through the central Plains and
into the Midwest, outlining the arctic air on its way in.
Aloft, a broad and deep trough is in place across the western two
thirds of the CONUS, with an upper level low churning across
southern Ontario, and a short wave trough moving east across the
central Rockies.

The models are in good agreement through the short term, with the
upper level low continuing to move east into Quebec. Meanwhile,
the Rockies short wave will also translate east and allow for an
enhanced trough axis to move through the Ohio Valley by Thursday,
resulting in mainly the onset of the arctic air moving in across
the region.

Today will feature a mostly cloudy start to the day, as low clouds
remain in place through the mid to late morning, before thinning
this afternoon. Temperatures will generally top out in the mid to
upper 40s. Tonight, clouds will be on the increase once again as
the trough axis approaches from the west, and eventually moves
through during the day on Thursday. The models have trended drier
with the available low level moisture, suggesting only a few
flurries at best for late Wednesday night into Thursday morning
across the region, before clouds thin out once again during the
afternoon hours. Lows Wednesday night will range from 25 to 30
degrees, with highs on Thursday in the mid to upper 30s for most

.LONG TERM...(Thursday night through Tuesday)
Issued at 307 AM EST WED DEC 7 2016

A very cold airmass will be settling in over the area Thursday
night. The H5 trough axis passes by during the night and models
continue to indicate an increase in low level clouds overnight
with a marginal upslope component to the low level flow. Soundings
show cloud temps in the -8C to -12C range and this should be good
for flurries to develop late Thursday night and continue into the
day on Friday. Temperatures on Friday will likely remain below
freezing for most locations giving us our coldest day since last
February. High pressure then settles in over the region Friday
night. Mid and high clouds streaming overhead may disrupt
radiational cooling some, but temperatures will still likely fall
deep into the teens.

The weekend starts dry and chilly on Saturday, and then turns
unsettled as a shortwave moves across the Upper Midwest and into
the Ohio Valley. This forces a cold front across the state Sunday
into Sunday night. Models are still having difficulty with this
system and forecaster confidence on the details is lacking. Models
are trending colder with the temperature profile and this draws
into question precip type. Models do show a 50kt H85 jet which
should draw enough warm air northward to cause the bulk of any
precip to fall as rain. However, we will continue with the idea of
a chance of rain/snow Sunday morning, then rain likely Sunday
afternoon and evening before precip transitions back to a
rain/snow mix late Sunday night into Monday morning. This system
exits leaving what should be dry and seasonably cool day behind on

Looking further out...while it appears we get a brief taste of
Arctic air late this week, longer range models bring in a true
Arctic blast later next week preceded by some accumulating snow.
Certainly something to keep an eye on with future model runs...


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)

MVFR ceilings look to hang on through the mid to late morning
hours, before scattering out. Some mid-level cloud cover will then
be on the increase towards the end of the forecast. Northwest
winds will average around 5 kts or less through the period.




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