Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 152235
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
635 PM EDT Tue Aug 15 2017

.UPDATE...
Issued at 634 PM EDT TUE AUG 15 2017

Forecast is well on track so far this evening. A few isolated
showers are still ongoing across the southern portion of the CWA,
but should begin to wind down as we lose daytime heating.
Otherwise, the main update was just to freshen up the near term
grids to make sure they are on track with current observations.
All changes have been published and sent to NDFD/web.

&&

.SHORT TERM...(This evening through Wednesday night)
Issued at 308 PM EDT TUE AUG 15 2017

Models are in good agreement through the short term. Shortwave
ridging aloft will transit the Ohio Valley region through the
period. A shortwave trough will be approaching from the Plains at
the end of the short term window. There are some weak embedded
impulses in the flow as the ridge builds into the region late
tonight and into Thursday. At the surface, a low pressure system
will begin to take shape over the central Plains. In response, a
warm front, quite subtle in nature, will lift northward through
the area during the day Wednesday.

Sensible weather will seem more like mid summer, with warm and
muggy conditions expected through the period. Ongoing scattered to
isolated convection will gradually dissipate through the late
afternoon and early evening time frame with loss of diurnal
heating. Weak subsidence aloft will help with radiative cooling
potential through the overnight, though clouds will generally be
on the increase with the approach of dawn and through the day
Wednesday. With at least partial clearing and ample boundary layer
moisture, fog would seem to be a good bet overnight. An almost
indistinguishable surface feature, or subtle warm frontal
boundary will lift northward Wednesday. Blends and model guidance
ramp PoPs up through the afternoon in the warm sector as a result
of diurnal heating and through the overnight period Wednesday into
Thursday with the approach of the system to our west.

.LONG TERM...(Thursday through Tuesday)
Issued at 308 PM EDT TUE AUG 15 2017

A low pressure system will be crossing the Great Lakes at the
beginning of the period with a warm front lifting to our
northeast, placing eastern Kentucky in the warm sector with
somewhat warm and muggy conditions in place on Thursday. This
moisture and warmth will help to generate scattered showers and
storms during the day. The cold front associated with the system
in the great lakes will then cross the area Thursday night,
producing additional chances for showers and storms. The front
could be a slower mover with rain chance lingering ahead of the
front into Friday afternoon. By Friday evening, most models have
the front exiting to our southeast, providing a return of drier
weather.

As we head through Saturday, a shortwave trough will cross the
Ohio river valley and could bring an isolated shower into eastern
Kentucky late in the day, but instability and moisture is very
limited by this point, so confidence is not high we will see much
shower activity. Surface ridge will spread into the area from
Sunday through Monday. While the ridge will help to suppress
showers/storms, it may not be strong enough to prevent a few
isolated showers popping each afternoon. The effects the eclipse
will have on the shower chances on Monday is yet to be seen, but
thoughts are we could see a 4 to 6 degree temperatures drop during
the peak heating and if this occurs, we could see CU dissipate
after the onset of the eclipse and limit overall rain chances.
Lots of unknowns obviously, but have tossed a slight chance of a
shower back into the forecast today. Either way, shouldn`t be a
washout and any showers will be very isolated/short lived. Did
account for a slight dip in temperatures in the afternoon, with a
followup recovery following the eclipse.

Temperatures from Thursday through Tuesday will remain mild with
highs each day into the mid 80s and lows generally in the mid to
upper 60s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
ISSUED AT 150 PM EDT TUE AUG 15 2017

Scattered showers are refiring this afternoon, mainly south of
Interstate 64. There is enough surface based instability to
include the mention of thunderstorms for the first few hours of
each TAF, exception being SYM which is north of the bulk of
activity. With ample boundary layer moisture in place and at
least partial clearing through the overnight due to some
subsidence aloft, fog being advertised by model guidance seems
reasonable. Made sure to include this in the forecast for each
terminal. Winds will be light and variable through the period.

&&

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

$$

UPDATE...JMW
SHORT TERM...RAY
LONG TERM...KAS
AVIATION...RAY



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