Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 212018

National Weather Service Jackson KY
418 PM EDT Mon May 21 2018

.SHORT TERM...(This evening through Tuesday night)
Issued at 418 PM EDT MON MAY 21 2018

Showers and thunderstorms will continue to drift north this
afternoon into early this evening, producing brief periods of
locally heavy rainfall as they initially develop and merge with
additional cells in a summertime-type environment. Small hail will
be possible with initial updraft surges, while downburst wind gusts
to 40-50 mph may also be possible as these collapse. Have not seen
as high of coverage farther west into the Bluegrass region at this
time, farther displaced from a weak surface kink and any topographic
influence. Will see preexisting storms off to the south approach and
interact with cold pools/outflow boundaries to provide additional
lift here, with instability and storm coverage dissipating near and
after sunset.

A weakening upper trough approaching the Great Lakes and
accompanying surface low just off to its southeast will continue to
lift northeast, keeping eastern Kentucky firmly in the warm sector.
May see some shower activity linger into tonight across the
Bluegrass region nearer to a frontal boundary moving into the Ohio
Valley and associated remnant outflow boundaries from earlier
convection. Most locales should remain dry as earlier precipitation
leads to fog development even outside of valleys through the night
into Tuesday morning.

Broad/weak troughing overhead Tuesday along with a continued sultry
airmass will promote quickly developing showers/storms during the
morning. These will increase in coverage with diabatic heating
through the afternoon as a cool front makes closer approach toward
the lower Ohio Valley. While deep layer shear will be a tad stronger
compared to today, this combined with weaker instability does not
suggest much if any uptick in storm severity. Cell mergers and
initial pulses may briefly produce heavy rain and small hail
again, along with gusty downburst winds to perhaps 40 mph. Rain
chances will continue Tuesday evening and night as the front
enters Kentucky and provides greater low level forcing. Fog will
once again be in play given the recently wet ground, at least
during the early overnight prior to arrival of somewhat drier air.

.LONG TERM...(Wednesday through Monday)
Issued at 300 PM EDT MON MAY 21 2018

The extended will feature alternating periods of wet and dry
weather across eastern Kentucky. The period should begin with rain
exiting the area on Wednesday, as a trough of low pressure aloft
pushes off to the east of the area. Wednesday night through
Thursday night should be dry, as a ridge of high pressure sets up
across the region. Another area of low pressure is then forecast
to push through over the weekend, bringing more rain chances to
the area from Friday afternoon through the end of the upcoming
weekend. The best chance for thunderstorms will be during the
afternoon and evening hours. Temperatures will continue to run
above normal, with daily highs in the low to mid 80s and nightly
lows in the low to mid 60s expected for most locations. Valley fog
will also be possible each day during the late night and early
morning hours.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)

Showers and thunderstorms will continue to develop across much of
eastern Kentucky this afternoon, slowly drifting off to the north.
These will be capable of producing TEMPO MVFR or worse
conditions, prior to storms diminishing in coverage and intensity
early this evening. Fog tonight into Tuesday morning will be
largely determined by where more pronounced pockets of rain fall
this afternoon and early evening. Will very likely see some IFR or
worse conditions at times through the night into Tuesday morning,
but fine-tuning as to exactly where will need to be done with
later TAF issuances following the brunt of the rainfall. Did opt
to keep SYM in prevailing MVFR visibilities overnight given a
longer duration of better rain chances there. Showers and storms
should quickly develop Tuesday morning with borderline sub-VFR
conditions for the majority of the eastern Kentucky airspace.




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