Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 142057

National Weather Service Jackson KY
357 PM EST Thu Dec 14 2017

.SHORT TERM...(This evening through Friday night)
Issued at 357 PM EST THU DEC 14 2017

Low stratus has held strong across eastern Kentucky this afternoon
in a post-frontal airmass. Temperatures have subsequently held
steady with current readings spanning the 30s. Surface ridging
building into the lower Ohio Valley and western reaches of the
Appalachians will keep light upslope flow in place through much of
the night as low-mid level moisture remains trapped beneath a
subsidence inversion. Have therefore warmed overnight low
temperatures a few degrees from the previous forecast given the
greater amount of expected cloud cover. Readings should generally
bottom out in the low-mid 20s, with perhaps a few valleys across
portions of northeast Kentucky flirting with the 20 degree mark if
any breaks in the clouds can occur nearer the core of the surface

Yet another upper trough and associated surface low will rotate
through the Great Lakes Friday, keeping below normal temperatures in
the offing. Highs look to warm into the mid 30s, resulting in a
similar overall feel to Thursday afternoon. The lack of any bonafide
moisture recovery and northward displacement of the greatest forcing
will negate the threat for precipitation throughout eastern
Kentucky. Surface ridging nosing in from the southwest later in the
day will keep winds southwesterly and preclude a significant change
in airmass.

Following what may be a quick valley dropoff in temperatures Friday
evening/early night, an increasing pressure gradient downstream
of a surface low pushing into the upper Midwest will promote warm
air advection spilling into the Bluegrass and Lake Cumberland
regions. Temperatures by daybreak Saturday should therefore bottom
out a few degrees warmer than those seen Friday morning.

.LONG TERM...(Saturday through Thursday)
Issued at 322 PM EST THU DEC 14 2017

The extended portion of the forecast begins on Saturday with the
upper level pattern transitioning to a more progressive and less
amplified flow aloft. With a brief bout of ridging quickly passing
through on Saturday. In fact, with southerly flow reengaging on
Saturday, high temps will rebound into the 50s with clear skies in
place thanks to the mentioned ridging in place. The pattern east
of the Front Range displays a northern and southern portion of the
jet stream and rather zonal. However, a strong wave over the
southern stream develops over the southwest and moves into the
lower MS Valley into Saturday night. This feature then lifts
northeast into the OH Valley for Sunday morning and into the day
on Sunday bringing a modest round of moisture. Another weaker
wave tracks across the northern stream into the Great Lakes at
this time as well. This will keep a decent round of precip over
the area for Sunday and Monday. Concerning the Sunday morning
onset, model profiles indicate the possibility of the lower
profile wet bulbing due to evaporative cooling to freezing
temperatures at the surface leading to a possibility of a sleet
and or snow mix for a very brief period of time. However, latest
trends have showed a later arrival time of precip, this combined
with the time needed for the lower levels to saturate, will
likely lead to an all rain event at this time with a few instances
of snow mixed in. Rainfall, while still entering this event with
dry conditions will accumulated roughly less than a quarter inch.

After passage, another weaker wave along the northern stream will
pass through the OH Valley on Monday with a slight chance of
precip remaining into Monday night. Even so, temps will be above
normal for this time with the lack of amplitude in the pattern and
will only expect liquid precip. By Tuesday, another wave develops
out of the southern stream and lifts northeast bringing another
chance of precip into eastern Kentucky but with warmer air in
place, this event too will be all rain. Despite some rain expected
for Sunday through Tuesday, the lack of consistency in the models
leaves more to be desired and the overall dry conditions across
the area going into these events will be good chance pops at best.
In fact, the super blend cam in dry for the last day of the
extended on Wednesday so will go with that solution.


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

Low clouds continue to hold strong in a post-frontal airmass this
afternoon. These will gradually lift and scour out later this
afternoon into this evening as high pressure builds into the Ohio
Valley, but mid clouds will persist tonight before possibly
lowering into Friday morning. VFR conditions are however expected
to persist through the period at all sites. North/northwest winds
of near 5 knots will further diminish this evening and tonight,
while backing southwesterly Friday morning and increasing back to
5-10 knots later Friday morning.




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