Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 180907
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
507 AM EDT Sun Jun 18 2017

.SHORT TERM...(Today through Monday)
Issued at 407 AM EDT SUN JUN 18 2017

A mesoscale convective system continues to track east toward the
Ohio River this morning ahead of a cold front extending from
Chicago to near St. Louis. Will continue to monitor this complex
of storms as it moves into southwest Ohio and northern portions of
Kentucky this morning, but a less favorable environment in place
locally continues to point at this feature decaying for the most
part before entering the Bluegrass region. A few showers could
threaten Fleming County near dawn, but less instability and much
weaker mid level lapse rates should bring an abrupt halt to its
eastward progression.

Focus will then turn to increasing shower and thunderstorm chances
this afternoon through tonight, complete with the potential for
damaging wind gusts this afternoon/evening, followed by a
localized flooding potential. An upper impulse will phase with a
broader low across lower Canada and the Great Lakes, digging a
fairly broad trough through the Missouri and Tennessee Valleys.
Falling heights will take place by mid-late afternoon, helping to
increase lapse rates and deep layer instability as surface
temperatures warm into the mid-upper 80s. A few storms will be
possible prior to these height falls arriving, both along the
higher terrain, including propagating northeast from the
Cumberland Plateau, and along outflow boundaries stemming from
this morning`s convective complex.

The potential for damaging wind gusts will exist for a period late
this afternoon and this evening as 0-6 km shear increases to 30-35
knots coupled with surface-based CAPE of 1500-2000 J/kg.
Precipitation loading above a briefly drier sub-cloud layer, as
evidenced by inverted-V sounding profiles, will support this
potential for wet downbursts where updrafts can become at least
briefly sustained. This threat will diminish by mid-late evening
as southwest flow continues to pump in impressive moisture with
precipitable water values approaching the 2 inch range. This will
subsequently further moisten the boundary layer and lessen the
threat for rapid evaporative cooling/downbursts as storms become
increasingly elevated overnight.

However, the threat for flash flooding will likely pickup
overnight the frontal boundary approaches eastern Kentucky in a
parallel fashion with the upper level southwest to northeast flow
in place. Deep warm cloud processes in tandem with this abundant
moisture will promote heavy rain, with training storms and
repeated rounds of rainfall leading to localized flash flooding.
Will continue to assess how activity plays out through the
afternoon in relation to making any decisions as to whether to
hoist a Flood Watch.

The threat for heavy rain will likely continue across portions of
far eastern Kentucky Monday, prior the cool frontal boundary
finally pushing through the Commonwealth. Thunderstorms should
remain sub-severe given a worked over atmosphere. Better shear
will exist east of the front Monday afternoon compared to this
afternoon, but less than stellar thermodynamic parameters should
preclude much if any in the way of robust storms. A reprieve in
the hot weather will accompany the rainfall and front`s arrival,
with highs topping out in the mid-upper 70s.

.LONG TERM...(Monday night through Saturday)
Issued at 253 AM EDT SUN JUN 18 2017

The extended period will feature a mostly dry first half and an
increasingly active and wet second half. Scattered showers will be
departing the area Monday night, as a trough of low pressure aloft
moves off to our east. The weather should again become warm and dry,
as a ridge of high pressure settles over the region from late Monday
night through Thursday morning. The ridge will finally begin to
break down Thursday afternoon, as an area of low pressure that will
be taking shape over the eastern Gulf of Mexico begins to move
slowly northward. Isolated to scattered showers and storms are
expected across eastern Kentucky by Thursday afternoon. This
activity should slowly increase in coverage Thursday night and
Friday, as low pressure moves closer to the area. The best chance
for rain during the week should be on Friday, when a 40 to 50
percent chance of precipitation is forecast. The highest likelihood
of rain should be Saturday and Saturday night, as a frontal boundary
moving in from the north begins interacting with area of low
pressure that moves in from the south. In fact, scattered to
numerous showers and storms may occur Saturday and Saturday night
across eastern Kentucky, should the latest model data hold true that
is. Temperatures during the period are expected to max out in the
70s and 80s each day, with nightly lows forecast to range from
around 60 Tuesday and Wednesday nights, to the mid to upper 60s the
remainder of the period.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
ISSUED AT 155 AM EDT SUN JUN 18 2017

VFR conditions will remain in play this morning and likely through
much of this afternoon, before showers and thunderstorms develop
late this afternoon and this evening into tonight. Still some
uncertainty as to when sub-VFR ceilings will really begin to set
in, but should certainly see these deteriorate to MVFR/IFR or
possibly lower into Monday morning. Visibility degradations will
be determined by where heavy rain occurs underneath storms, with
further issues later tonight and Monday morning away from storms
and associated mixing. Southwest winds will increase to near 10
knots later this morning, with gusts approaching 15-20 knots
through this afternoon. Erratic winds and much higher gusts will
occur underneath thunderstorms late this afternoon and evening.

&&

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

$$

SHORT TERM...GUSEMAN
LONG TERM...AR
AVIATION...GUSEMAN



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