Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 200906
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
506 AM EDT Fri Apr 20 2018

.SHORT TERM...(Today through Saturday)
Issued at 348 AM EDT FRI APR 20 2018

The center of a surface high pressure system near the Corn Belt
will migrate across the Great Lakes and upper Ohio Valley today.
This has led to temperatures falling to near or below freezing for
much of eastern Kentucky this morning, resulting in widespread
frost. Shortwave ridging building east of the Great Plains will
bring rising heights aloft and subsequent warmer temperatures,
with highs warming into the low-mid 60s this afternoon.

Light north/northeast winds will be in store tonight as ridging
slides eastward and promotes favorable conditions for radiational
cooling once again. Areas of mainly valley frost will be in store
as temperatures fall into the upper 20s to near 30 degrees. Ridges
look to remain in the mid-upper 30s and mostly void of frost given
fairly low dewpoints this afternoon. Have elected to hold off on
a Frost Advisory for tonight/Saturday morning at this point, but
will monitor temperatures/dewpoints through the day to assess the
potential for more widespread frost development.

Upper ridging cresting overhead Saturday will further warm
temperatures into the mid 60s to low 70s. Will see an increase in
cirrus cloud cover through the day downstream of a central Great
Plains disturbance aloft, but a persistent subsidence inversion
and lack of deep layer moisture will keep the first half of the
weekend dry.

.LONG TERM...(Saturday night through Thursday)
Issued at 440 AM EDT FRI APR 20 2018

The extended period is expected to begin with a split flow pattern
over the Plains with ridging over the southeast Conus at mid
levels and a mid level low/trough moving from the Plains toward
the MS valley with mid level ridging extending into the southwest
Conus. The northern stream initially will be near the US/Canadian
border. At the surface a ridge of high pressure is expected to
initially extend from the Great Lakes to the eastern seaboard. The
airmass will initially be dry with PW areawide expected to be
under a half of an inch.

From Saturday night into Sunday, the mid level low will move east
southeast and should be centered southwest of Memphis by sunset on
Sunday. At the same time surface high pressure should shift
northeast of the area while southeast Conus ridging weakens and
shifts to the east. Surface low pressure should track from the
Southern Plains to MS during that time. Moisture should begin to
increase from the top down in this scenario with mainly just some
mid level clouds at times by Sunday afternoon, especially across
the southwest part of the area. A dry end to the weekend is
expected with near normal highs on Sunday after a chilly start
especially eastern valleys which should bottom out in the upper
30s on Sunday morning. PW should increase to the two thirds of an
inch range in the northeast part of the area by 0Z Monday with PW
nearing 0.9 inches near Lake Cumberland by that point. Further
increase through Sunday evening will eventually support shower
chances first in the far south.

Clouds should thicken and lower Sunday night into Monday with a
period of unsettled weather to follow. The unsettled weather
should continue for the rest of the extended period as the mid
and upper level low meanders over the southeast and then moves
into the TN and OH Valleys around Monday night and Tuesday. As
the system gets closer moisture and lift will increase with the
potential for diurnally enhanced chances for showers for spreading
north across East Ky by late Sunday night into Monday. This mid
and upper level system should then open up and begin to merge or
phase with a northern stream system working across Canada and the
Great Lakes around midweek. From Tuesday night on, model agreement
increases with timing uncertainties along with uncertainties in
the details of the upper level pattern. The general consensus is
for a trough over the eastern Conus from midweek through the end
of the period with at least some weaker embedded disturbances
moving through the OH Valley and Appalachians. This pattern would
support continued unsettled weather with chances for showers from
time to time. Limited diurnal temperature ranges with highs
averaging below normal are anticipated from Sunday night on due to
the cloud cover and shower chances.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
ISSUED AT 140 AM EDT FRI APR 20 2018

VFR conditions will prevail with winds of less than 10 knots.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
Freeze Warning until 10 AM EDT this morning for KYZ044-050>052-
058>060-068-069-080-086>088-104-106>120.

Frost Advisory until 10 AM EDT this morning for KYZ079-083>085.

&&

$$

SHORT TERM...GUSEMAN
LONG TERM...JP
AVIATION...GUSEMAN



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