Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 030257
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
957 PM EST Fri Dec 2 2016

.UPDATE...
Issued at 957 PM EST FRI DEC 2 2016

IR SAT does show the Stratocu deck has been sinking south over
the past few hours and therefore tried to match up the grids with
this idea. This has made the hourly temps quite tricky, as you
have lower deck north and east and high deck creeping into the SW.
Tried to trend somewhat away from the typical diurnal curve given
this more unorthodox temp progression. In terms of the SKY did
opt to also increase coverage in the east through Sat morning just
given the overall trends and model sounding data. Other edits were
more minor and related to overall trends.

UPDATE Issued at 632 PM EST FRI DEC 2 2016

The stratocu challenge remains this hour with models continuing
to struggling with timing. Opted to back off the clouds given the
struggle and move these in slowly through the evening. Overall the
confidence remains low at this point on how this will evolve.
Also opted to lower valley temps where clear skies and decoupling
has already brought Quicksand Mesonet site to 36 degrees this
hour. Otherwise most the changes to the grids were minor, and will
continue to update/monitor trends with the previously mentioned
elements through the night.

&&

.SHORT TERM...(This evening through Saturday night)
Issued at 309 PM EST FRI DEC 2 2016

The challenge in the near term portion of the forecast is how to
best handle the low cloud deck that covers the northern part of
the forecast area. Earlier today the cloud deck had been making
good southward progress, but this has temporarily halted. However,
winds at 925 mb to 850 mb are still forecast to continue to veer
and become more northwest as the evening progresses. Based on
this and with support from short term model sounding forecasts we
are still expecting the cloud deck to make southward progress
tonight. There is some question about how far southwest the cloud
deck will eventually extend. The clouds will impact overnight
minimum temperatures, and with more clouds in the northeast will
have warmer overnight lows there and colder temperatures in the
southwest part of the forecast area. The uncertainty of the extent
of the cloud cover later tonight into Saturday results in a lower
confidence forecast than normal for temperatures for the near term
portion of the forecast.

On Saturday night the focus of the forecast shifts to developing
precipitation in advance of a mid level short wave trough. Current
model trends, especially with a view to soundings and cross
sections point towards less chance of any snowflakes mixing in
late Saturday night and early Sunday morning. The new forecast
will decrease the duration and coverage area for any light rain
snow mix possibilities, but will still include it for now in the
north. However if current trends continue complete removal of any
mention of snow mixing with the rain could occur in future
forecasts.

.LONG TERM...(Sunday through Friday)
Issued at 309 PM EST FRI DEC 2 2016

Active weather is store during the extended period, as a series of
weather systems are poised to bring multiple rounds of precipitation
to eastern Kentucky. The first round of precip is expected Sunday
and Sunday night, as two phased areas of low pressure aloft move
across the region. One system is expected to move across the
northern CONUS, while a second area of low pressure is still
forecast to traverse the Gulf Coast. The area between these two
weather systems is where our precipitation will come from to end the
weekend and kick off the upcoming work week. Some locations north of
the Hal Rogers Parkway may see a few snow flakes mixing with the
rain early Sunday morning, but the latest model data is suggesting
that most precipitation will be in the form of rain Sunday. The best
chance for precipitation looks to be Sunday afternoon and evening,
as the southern stream system moves by to our south, bringing Gulf
of Mexico moisture into the area. This initial round of
precipitation should be coming to and end early Monday morning, as
the causative weather systems move off to our east. After a brief
respite, a second more potent area of low pressure is expected to
move toward the area out of the southern Plains Monday afternoon and
night. This system will be more intense and have more moisture with
it than the first one. In fact, widespread soaking rainfall is
expected across all of eastern Kentucky Monday night and Tuesday.
Energy and moisture from this system will allow for isolated to
scattered rain showers to linger across the area through Wednesday
afternoon.

There will be another lull in the weather Wednesday afternoon and
evening, as a weak ridge of high pressure briefly settles over the
region. A third and final weather system is then expected to move
quickly out of the northern Plains and across the Great Lakes and
Ohio River Valley regions Wednesday night through Thursday night.
Based on the latest model temperature profiles, it appears that this
mid to late week system will have a bit more warm air with it, so
the precipitation forecast will feature less snow and much smaller
snow accumulations for Wednesday night and early Thursday then
previously forecast. There should be periods of rain/snow mix and
snow late Wednesday night into Thursday morning. Most of the day on
Thursday should feature all rain, as warmer air filters into the
area. Another push of cold air may bring another round of rain snow
mix and some isolated light snow showers to eastern Kentucky late
Thursday night into Friday, as the upper level low departs to our
east. Little if any snow accumulation is expected.

Temperatures through the period will vary from below normal to above
normal depending on the day. Sunday and Thursday should see highs in
the 40s across the area, while Tuesday and Wednesday will most
likely see highs in the 50s. The coldest day of the week could be
Friday, when the mercury may only climb into the 30s area wide.
Nightly lows will generally be in the 30s and 40s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
ISSUED AT 621 PM EST FRI DEC 2 2016

Models have struggled with this stratocu deck and continue to
struggle this evening. Overall have slowed this deck down and
attempted to trend this with the actually VIS SAT data. Low
confidence in this deck making into the SW sites and actually
opted to only bring a SCT 5kft deck into SME. The challenge will
also be how much does this deck in fact remain in the area for
Saturday. Right now will lift this deck to VFR by 15Z and then
more clouds will move in from the south by late in the day. This
however will be more of a build down of moisture beyond the TAF
period based on time heights and forecast soundings. Winds will
remain light through the period.

&&

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

$$

UPDATE...DJ
SHORT TERM...SBH
LONG TERM...AR
AVIATION...DJ


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