Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 061444 CCA
AFDJKL

AREA FORECAST DISCUSSION...CORRECTED
National Weather Service Jackson KY
944 AM EST Fri Dec 6 2019

.UPDATE...
Issued at 943 AM EST FRI DEC 6 2019

Mid-morning update mainly entailed an adjustment to PoPs and
hourly temperatures to account for most recent trends. In general
rain is falling across a larger portion of the area going
southward, though accumulations will be more on the light side.
Eastern valleys temperatures got down pretty low overnight and
have been slow to rise, though they are above freezing. Thus no
hazardous weather is expected. Updated both the zone package and
grids.

UPDATE Issued at 633 AM EST FRI DEC 6 2019

Radar returns continue to increase upstream across central
Kentucky, indicative of lowering ceilings and many more reports of
light rain. This expansion of precipitation appears on track with
the forecast, so no changes are warranted early this morning. The
best rain chances will continue to be along and north of the Hal
Rogers Parkway.

&&

.SHORT TERM...(Today through Saturday)
Issued at 400 AM EST FRI DEC 6 2019

A shortwave trough over the mid and lower Mississippi river valley
will remain the main focus of the short term forecast today. This
feature will push east across Kentucky/Tennessee today.
Meanwhile, at the surface, a cold front is located from Chicago,
southward across Illinois, and into central Missouri. Cloud cover
associated with the shortwave continues to spread northeast across
east Kentucky early this morning, mainly in the mid levels thus
far. As the shortwave energy continues to push east this morning,
ceilings should continue to lower as we get a nice push of better
lift in the mid to upper levels. It may take a bit to see
precipitation at the surface as we will have to fight some initial
dry air in the low levels. However, short term models show pretty
good agreement on the forcing winning out today, with some light
measureable rainfall across much of the area by late this morning.
Thus, likely to categorical pops seem justified as the shortwave
energy works east across the area. Precipitation amounts will
generally remain under a tenth of an inch for most areas since the
low levels won`t really saturate until the mid/upper level
forcing departs.

As the shortwave departs late in the day, the cold front
to our northwest will drop southward across the area this evening
through tonight. Much colder air will spread south behind this
front for the overnight period. Some lingering moisture along the
front could yield a few showers into the evening hours, but the
front is expected to weaken and eventually wash out across the
region. Thus, precipitation chances will erode through the
overnight hours as this front weakens. We do expect cloud cover to
linger along and ahead of this front through much of tonight.
Models start to dissolve this cloud cover late tonight into early
Saturday. Exactly how quickly this happens remains uncertain.
Thus, there is a chance that clouds hold a bit longer across the
south into Saturday. However, for now, will go with a clearing out
trend for Saturday morning with generally sunny skies for much of
the day as shortwave ridging builds across the region. With the
cooler start on Saturday with the cold air setting south over the
area, highs on Saturday will struggle to get back to the 50 degree
mark.

.LONG TERM...(Saturday night through Thursday)
Issued at 454 AM EST FRI DEC 6 2019

Surface high pressure nearby to our east combined with zonal flow
aloft will result in quiet weather Saturday night and Sunday. The
flow aloft will start to buckle Sunday night as a large scale
upper trough moves ESE into the central and western CONUS. At the
same time, the surface high will move further east and allow
moisture return from the south to begin. The warm air advection
regime should yield rain beginning late Sunday night or Monday.
The upper level trough will progress eastward early in the week,
supporting a cold front which is expected to move through late
Monday night or early Tuesday. After relatively mild conditions
and wet weather on Monday and Monday night, much colder air will
arrive behind the front, with temperatures likely falling on
Tuesday. An impulse rotating through the base of the trough could
cause precip to linger on Tuesday. If it holds on long enough with
the cold air arriving, a change to snow may occur. However, there
is enough uncertainty that it won`t be played up at this point.
Surface high pressure then builds in from the west Tuesday night
and Wednesday with a return of dry but cold weather. After this,
model discrepancy becomes more apparent to finish out the long
term period. Compared to the GFS, the ECMWF maintains a deeper
upper level trough over the eastern CONUS through Wednesday night.
This would allow another surge of arctic air to drop southeast
into our area and keep temperatures cold through Thursday.
Meanwhile, the GFS lifts the upper trough out to the northeast
faster and flattens our flow, resulting in moderating temperatures
on Thursday. The forecast is a compromise/blend at this point,
with the reality being a fairly wide temperature potential.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
ISSUED AT 633 AM EST FRI DEC 6 2019

Ceilings will continue to fall today with some light rain
developing this morning. Conditions will likely stay VFR through
the day as the rain should not get too heavy to bring down
ceilings or visibilities. A front will drop south Friday night,
and that could lead to the development of some MVFR cigs as the
front presses southward. Light southwest winds will eventually
switch to the north with the front tonight..

&&

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

&&

$$

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


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