Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 301813 AAC
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
113 PM EST Wed Nov 30 2016

.UPDATE...
Issued at 113 PM EST WED NOV 30 2016

Hourly grids have been freshened up based on recent observations
and radar trends. We still expect some additional isolated to
scattered showers to develop or linger behind the main band
gradually shifting into WV and VA as the cold front now over
Central KY nears and temperatures cool aloft.

UPDATE Issued at 1007 AM EST WED NOV 30 2016

Hourly grids have been freshened up based on upstream radar
trends as well as current observations and satellite data in
combination with near term model trends. This led to lower pops
over the next few hours in the Eastern Bluegrass counties and
higher pops along the VA border. Showers should slowly taper off
from west to east through early to mid afternoon. However, chances
will remain this afternoon and into the evening as the cold front
works into the area this afternoon and colder air moves in aloft
increasing lapse rates.

UPDATE Issued at 800 AM EST WED NOV 30 2016

Precip has tapered off in the far NW part of the forecast area a
little faster than was originally forecast, and POPs have been
lowered there. Also, lightning has diminished and shifted well
southeast of KY, so have removed it from our forecast.

&&

.SHORT TERM...(Today through Thursday)
Issued at 424 AM EST WED NOV 30 2016

Showers are ongoing across the area early this morning, but
lightning has been sparse, with most of it occurring to our
south. There are some thunderstorms again making their way to our
southern border, moving quickly northeast. The back edge of the
precip was advancing southeast across central KY. This back edge
will be about ready to move into the NW part of the JKL forecast
area around 12z. Have used likely to categorical POP as 1st
period starts, but the precip will taper off from NW to SE during
the day. Have included a slight chance of thunder during the
period of highest POP, timing its dissipation with the exiting of
elevated instability in the models.

The precip is due to an upper level impulse rotating around a
large stacked low over the north central CONUS, and an associated
surface cold front moving in from the west. Gulf of mexico
moisture was quickly drawn northward ahead of the front. Much of
the feed of warm/moist air appears to have been intercepted by
the convection which developed to our south, which limited our
thunderstorms further north. However, moisture still streamed
north, especially in the mid/upper levels. This moisture and
convection will leave today, but models show the potential for
additional shower development as the upper level impulse and
actual cold front progress through the area this afternoon. This
will exit to the east during the late afternoon and early evening,
and drier and much cooler air will begin to make its way in.

The large parent storm system will slowly move eastward, reaching
Quebec by late Thursday. Flow around it will keep cold air
advection in place locally. Deep moisture associated with the
system should stay to our north tonight and Thursday, with only
stratocumulus expected for our area.

.LONG TERM...(Thursday night through Tuesday)
Issued at 424 AM EST WED NOV 30 2016

While forecast confidence remains high through Saturday, still a
large amount of uncertainty from Sunday through the first half of
next week. High pressure will bring dry weather from Thursday night
through Saturday.  The weather will remain on the cool side into
Saturday with broad mid level troughing remaining over the region.
By Sunday night, our next storm system taking shape upstream will
start to move towards the region.  Models seem in reasonable
agreement on bringing some light precipitation into the area by
daybreak Sunday.  At this point, it doesn`t look like enough warm
air will work back north, so we may see some light snow at the onset
of the precipitation.  After it seemed models might be converging on
a solution for Sunday into early next week, they have again went
opposite directions with the 00z runs.  The ECMWF is back to a
stronger low, tracking it virtually right across eastern Kentucky
Sunday into Sunday night.  GFS remains much weaker with the system
as it has all along.  While the GFS limits precipitation to mainly
Sunday with precipitation totals under a quarter of an inch, the
ECMWF solution brings 1 to 3 inches of rain across eastern Kentucky
and has rain lingering into Monday (which the GFS is currently dry
for Monday). The GFS is then quicker to bring another system back
across the area by Tuesday, while the ECMWF is drier.  Thus, with
none of the dry and wet periods lining up in the models, going to
have to carry climatological normal values for rain chances from
Monday into the middle of next week. We certainly will be able to
squeeze out a dry period somewhere in that time frame, but right
now, difficult to discern where that will be. It does look like
that after the snow chance early Sunday, all remaining
precipitation will be rain into the middle of next week.

One last interesting note, the models have been persistent on a
surge of more arctic air for the end of next week with 850mb
temperatures plummeting to -14C. This would certainly be the
coldest air we have seen since last winter if it holds. Right
now, snow chances look low despite the surge of arctic air.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
ISSUED AT 110 PM EST WED NOV 30 2016

The main band of rain continues to shift into WV and VA with
isolated showers behind it. Initial CIGS varied widely, from IFR
to VFR, with the worst conditions generally in the southern and
southeast part of the area. Between 18Z and 0Z most locations
should experience improvement to VFR. However, cigs and or vis
may still drop to MVFR at times as additional isolated to
scattered showers are expected through 3Z behind the main band.
Low level moisture is projected to linger so some 5 KFT or lower
VFR or MVFR CIGS are expected from then through the end of the
period.

&&

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

$$

UPDATE...JP
SHORT TERM...HAL
LONG TERM...KAS
AVIATION...JP



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