Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 172035
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
435 PM EDT Fri Aug 17 2018

.SHORT TERM...(This evening through Saturday night)
Issued at 435 PM EDT FRI AUG 17 2018

Aloft, long wave trough is found over the upper Midwest with
eastern Kentucky under a southwest flow regime. At the surface a
series of weak low pressure waves appear along a semi-stationary
frontal boundary draped roughly from the Great Lakes southwest to
St. Louis, and further southwest to about Oklahoma City. Another
upstream cold frontal system is dropping out of the Northern Tier
and appears to make it no further south than the Great Lakes
Region. The southernmost surface front makes an honest move
eastward through the short term and may have enough support aloft
from the aforementioned trough to push through our area late
Saturday into Saturday night. Regardless our area remains in an
unsettled pattern until the frontal zone passes entirely through
the Commonwealth.

The lull in activity this afternoon is coming to an end as strong
diurnal heating is beginning to kick off some isolated activity
across our forecast area late this afternoon. The HRRR showed a
general and gradual increase in activity through the late
afternoon and evening, mainly from the southwest and across the
south. Activity continues through the overnight as it appears
more organized convection takes shape, similarly to the previous
few nights except just a bit futher east each night. This activity
appears to take shape as a result of the typical increase in the
H850 winds through the overnight period just above the boundary
layer. Synoptic setup allows for some pockets of increased
convergence in spots as weak but distinct H850 LLJ maxes help in
generating the bands of more organized convection. Our area
remains in a slight risk for heavy rain with any hydro issues
being mainly confined to areas where training cells set up,
similarly to the last few days.

Temperatures remain generally at or just below normals due to
precipitation and additional cloud cover as afternoon highs climb
into the low to mid 80s and overnight lows drop into the 60s.

.LONG TERM...(Sunday through Friday)
Issued at 352 PM EDT FRI AUG 17 2018

The models are in fairly good agreement with the overall pattern
for the extended. Weak upper level ridging, formed by an upper
level cutoff low located in the Central Plains digging to the
southeast, will help bring a brief lull in precipitation for
eastern Kentucky late Sunday into early Monday. The cutoff low
will evolve into a deep trough and progress across the eastern
CONUS through midweek before moving off to the northeast Thursday.
Southeastern Kentucky will see chances of showers and
thunderstorms Sunday afternoon into the evening as a surface
boundary passes to the south of the Commonwealth. A warm front
associated with a surface low pressure system in Missouri will set
up over Kentucky early Monday. This low pressure system will
migrate to the northeast and settle over the Great Lakes by Monday
evening, lifting the warm front to the northeast and keep chances
of showers and thunderstorms Monday into Tuesday. A cold front
will begin progressing through western Kentucky during this time
as well. This cold front will move through the Commonwealth,
bringing increased chances of showers and thunderstorms through
midweek. By Thursday, a surface high pressure will build in over
the Ohio Valley, ushering in drier conditions for the end of the
work week.

High temperatures will generally be in the mid 80s Sunday and
Monday with low temps in the upper 60s through Tuesday morning.
High temps will cool down to around 80 degrees by midweek with
lows temps in the lower 60s Thursday and Friday mornings due to
frontal passage. Temperatures will then be on the rise Friday
afternoon.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
ISSUED AT 226 PM EDT FRI AUG 17 2018

Showers and thunderstorms comprised the bulk of the early morning
hours, but have since mostly dissipated into this afternoon.
Expecting convection to redevelop during the evening into the
overnight due to some pockets of H850 convergence and with the
advancement of a cold front. Confidence is low for widespread
thunder during the overnight, so have left mention out of the TAFs
for now. Did keep thunder chances at SME and LOZ this evening
based on the HRRR showing redevelopment of convection with diurnal
heating. Visibilities will lower with showers and valley fog
through dawn. Showers will be more continuous through the end of
the TAF period as the cold front makes its way across the
Commonwealth tomorrow. Winds will generally be out of the
south/southwest around 5 to 10 knots this afternoon, but could be
higher in stronger showers and thunderstorms through this evening.
Otherwise, generally light winds are expected through the period.

&&

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

&&

$$

SHORT TERM...RAY
LONG TERM...CGAL
AVIATION...RAY/CGAL



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