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Area forecast discussion 
National Weather Service Jackson Kentucky
840 PM EST sun Feb 7 2016

issued at 840 PM EST sun Feb 7 2016

Eastern valleys have already reached the lower 30s and still
likely have some to fall in the next 2 to 4 hours. With this in
mind...have updated the forecast to include some freezing rain for
the colder eastern valleys that are a bit more sheltered and won't
likely recover in time before precipitation spreads in. Still
looking like primarily rain as we keep a shallow layer of warm air
just off the valley floors. Could still see some snow mix in on
the ridges...but should be inconsequential as temperatures will
remain above freezing and limit any accumulations.

Update issued at 656 PM EST sun Feb 7 2016

Valleys are dropping quickly this evening with the quicksand
mesonet station already sitting in the lower 40s. Clearly guidance
is not capturing this temperature fall this have
lowered temperatures into the valleys through the rest of the
evening...generally down to 30 to 32. We may need to go further
yet...but this will be determined by how fast clouds can move in
later this evening. Latest hi res models continuing to show most
of what moves in late tonight being in the form of rain. The
question remains how fast valleys come back up and thus if we can
avoid a freezing rain in a few of our colder valleys. Higher
terrain is still on track for snow...but initial dry air may cut
into precipitation amounts late tonight. Thus...probably looking
for under an inch in the higher terrain from anything that falls
late tonight into tomorrow morning. Updates have been sent.


Short term...(this evening through Monday night)
issued at 514 PM EST sun Feb 7 2016

A highly amplified pattern is developing as a strong upper trough
drops southeast over the eastern Continental U.S.. a very large low pressure
system will move slowly southeast over the Great Lakes during the
period. Its associated cold front will pass through the jkl
forecast area Monday morning. Models agree on precipitation developing
and moving into the area from the northwest late tonight...and
temporarily exiting to the east on Monday morning. Low level temperatures
are marginal for rain vs snow...and a mix is forecast for most
areas. However...higher elevations near the Virginia border will be
below freezing and see all snow. With accumulations expected to
start there on Monday...have issued our winter weather advisories
at this point. There is concern that decoupled valleys will fall
below freezing and not recover before precipitation begins...and that
warmer air just above the valleys will result in freezing rain at
the surface. The probability of everything coming together for
this is fairly low...and did not include it in the forecast at
this time.

Precipitation should move back in from west to east during the day
Monday. Forecast sounding show significant cooling aloft as this
round of precipitation develops...with steep lapse rates resulting in a
deep layer. Convective currents may extend beyond the -20c
level...and a few lightning strikes can not be ruled out.

Temperatures will fall below freezing in all areas Monday
evening. With snow showers continuing at times...the advisory
expands to cover the whole forecast area at that point.
Accumulations in any given period are not forecast to be all that
great..but the prolonged nature of the event will eventually lead
to advisory level snowfall.

Long term...(tuesday through sunday)
issued at 514 PM EST sun Feb 7 2016

Models remain in good agreement...with deep and broad cyclonic flow
setting up across much of the eastern Continental U.S. For a good portion of
the week. This flow will aid in bringing cold air in from to northwest down
into the Tennessee and Ohio valleys through the week. Now this broad cyclonic
flow means that we are looking at a prolonged period of snow showers
with embedded enhancements from time to time. This in lies biggest
challenge that remains this afternoon for the period will be where
and when do the pieces of energy move through the flow. These will
provide additional enhancements to the snow showers through the
start of the period. That said...the snow squall parameter would
suggest some squalls are possible Tuesday afternoon...and this seems
reasonable based on soundings with lapse rates above 6 c/km in both
the low and middle levels. Therefore will keep likely probability of precipitation in the for a
good portion of Tuesday. These snow squalls could lead to locally
higher amounts of snow depending on where they occur and if they
repeat over the same areas. Expect higher snow ratios and fluff
factor for much of the period...given the cold air in place through
the entire column and the at times convective nature of the snow.

The deeper though axis is prognosticated to finally swing east as we move
into Thursday...and will help cutoff the barrage of snow showers
seen in the first part of the week. There is potential for another
weak disturbance by Friday...however right now keeping most the
precipitation across the southeast portions of the County Warning Area based on the model blend
with fair amount of uncertainty. Models continue to struggle with
phasing of the trough that moves east with a closed low upper low
diving south out of central Canada. The GFS is much more progressive
building a ridge into the middle of the central US...which hampers a
deeper trough setting up further south in the NE US. These
differences will have greatest implications of temperatures toward
the end of the forecast period. Overall will lean toward the colder
end since GFS has continued to trend colder over the past 4 runs
based on the 850mb temperatures.


Aviation...(for the 00z tafs through 00z Monday evening)
issued at 656 PM EST sun Feb 7 2016

VFR will last well into the night. After about 06z...rain and
MVFR conditions and will begin to move in from the
northwest...reaching the Virginia border by about 11z. Conditions will
likely fall to IFR for a time as the precipitation moves through.
A break in the precipitation is likely on Monday morning...but
rain and snow showers should redevelop from west to east during
the late morning and early afternoon. There could even be a few
lightning strikes with the second round of precipitation.


Jkl watches/warnings/advisories...
Winter Weather Advisory from 6 PM Monday to 6 PM EST Tuesday for

Winter Weather Advisory from 7 am Monday to 6 am EST Wednesday
for kyz088-118-120.

Winter Weather Advisory from 6 PM Monday to 6 am EST Wednesday
for kyz104-106>110-112-113-115-117-119.

Winter Weather Advisory from 7 am Monday to 6 PM EST Tuesday for



short term...hal

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