Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 231627 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1127 AM EST Wed Jan 23 2019

.UPDATE...
Issued at 1127 AM EST WED JAN 23 2019

The latest surface map features low pressure moving off into the
Great Lakes region, with a cold front aligned to southwest, now
east of the Mississippi River. Showers have broken out across the
area and these will likely continue to generally fill in as the
front draws closer to the area. Temperatures have also warmed up
nicely with breezy southerly winds in place. Some locations have
topped the 60 degree mark, with areas in far eastern Kentucky
likely maintaining this warmth through well into the afternoon, as
downslope flow cuts into the showers. Updates have been sent.

UPDATE Issued at 758 AM EST WED JAN 23 2019

Updated the forecast to input some latest obs and trend them into
the mid morning hours. As well, lasting downslope is drying out
the low levels and keeping precip from entering into the area. So
adjusted the pops for a later arrival. A new zfp was sent out for
this update.

&&

.SHORT TERM...(Today through Thursday)
Issued at 333 AM EST WED JAN 23 2019

Current conditions across the area feature a cold front taking
shape to the west as a dynamic low pressure system develops over
the Midwest and will be lifting to the northeast into the Great
Lakes region. Currently, southeasterly winds are creating a
downslope effect across eastern Kentucky as the rainfall to the
west is slowly inching eastward. Heading into the morning hours,
the main impact heading into the predawn hours, will be the
developing system as a low level jet pushes northeast into the OH
and TN Valley. This jet displays 50 to 60 knot winds just above
the surface. While model profiles keep a decent inversion into
the dawn hours, momentum transfer suggests some gusts into mid
morning hours will likely reach 30 mph with a few isolated gusts
up to 35 mph. Thinking is that, the inversion in place will be
stout enough to keep the strong winds aloft from mixing to the
surface. If any deeper mixing occurs, its likely a wind advisory
will be needed.

Expect the column to saturate by midday today as the surge of warm
and moist air pushes northeast into the area today. PWAT amounts
still are being advertised around the 1 inch range. With the
amount of moisture being drawn northward, there will be some
steady moderate to heavy rainfall heading into this afternoon and
continuing into the evening hours today as large scale ascent
sets up over the region. While amounts will be eaten into due to
the downslope winds heading into this event, most locations across
eastern Kentucky will still see 1.00 to 1.50 inch liquid amounts.

By tonight, as anticipated in the model runs leading up to this
event, the secondary low has developed over the lower MS River
Valley and begins to eject northeastward into the Appalachian
Range. At this time, the pattern still supports this system
quickly pushing east. Thus, the colder air moving in behind the
front tonight will be on the back edge of the exiting low. This
will mean a shorter duration of snowfall across eastern Kentucky
as much of the good moisture depth will exit the region before the
colder air enters the area. In fact, the higher elevations will
be the best locations to see an inch or more of snowfall. The
lower elevations will see the change over as the colder air enters
the region but the duration will be short leading to less than an
inch.

Heading into the day on Thursday, as the moisture becomes more
shallow, through the day with the exiting system, the snow across
the area will taper to flurries by the afternoon. In fact, the
airmass moving into the region will lack the cold air to over come
diurnal trends. Some locations will see mid 30s for highs for
Thursday afternoon. Overall, this system will be impactful but
lacking the values for a headline at this time. Will issue an SPS
to highlight the winds, the minor flooding potential, and the
wintry weather tonight. The winds will need watching through the
morning hours as upgrade is possible.

.LONG TERM...(Thursday night through Tuesday)
Issued at 349 AM EST WED JAN 23 2019

This period will feature broad upper level trough across the
eastern half of the lower 48 through the weekend. The upper levels
flatten by Sunday night into early Monday before another upper
level trough axis dives southward for Monday night into Tuesday.
This will lead to below average temperatures through Saturday and
then temperatures moderate back closer to normal Sunday into
Monday. The trough axis will also lead to several shots of light
precipitation, as upper level short waves ride through the overall
broad flow. Then a more substantial storm system is showing up by
Monday into Tuesday in the wake of the flatter upper level
pattern.

The period will begin with one of these fast moving cold fronts
and upper level shortwaves on Thursday night. This will bring some
snow showers, but more importantly this will usher in another
round of cold air. This will drive air temperatures into the teens
by Friday morning. In the wake of the front, an area of high
pressure fill into portions of the Tennessee and Ohio Valley.
While we do see clearing skies Friday, the very cold airmass will
lead to afternoon high temperatures in the 20s. There is yet
another wave that progresses east by Friday night into Saturday,
but this will probably only bring increased cloud cover to the
region. The models diverge as we move into the Saturday night and
Sunday timeframe, as the models show differing timing on the wave
and fronts for ascent. Given this did think the model blended
guidance was fine with slight to chance POPs for this portion of
the period.

The models are more in alignment with the system Monday into
Tuesday, as another upper level shortwave crashes southward out of
the Northern Plains. This system would be like the ones recently
where we begin as rain on the front end, as warm air advects
northward ahead of the approaching boundary. Then this trough and
cold front will again usher in a very cold airmass. The models
suggest this will happen quickly, with more QPF to work with
before the system exits east. This could lead to a period of
accumulating snow, but a fair amount of uncertainty remains given
this is out to next week. That said, WPC does have portions of
eastern Kentucky in a slight chance for wintry precipitation day 6
and 7. This part of the period did require a little more attention
given the non-diurnal temperature curve that is expected Monday
night into Tuesday and did max POPs out at likely for now given
the period this resides.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
ISSUED AT 700 AM EST WED JAN 23 2019

A cold front to the west will slowly move east today. Expect rain
to move into the area by mid morning. As the heavier rainfall
moves through, cigs will begin to fall and visibility will drop as
the heavier rainfall moves through the area. Expect VLIFR
conditions to set into the most of the TAF sites after 06Z. Winds
will be of impact as well with the front. Southerly winds will
gust up to 30 and 35 mph at times. With below field mins at most
of the TAF sites tonight, rain will change to snow.

&&

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

$$

UPDATE...GEOGERIAN
SHORT TERM...SHALLENBERGER
LONG TERM...DJ
AVIATION...SHALLENBERGER


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