Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 261928
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
328 PM EDT Mon Sep 26 2016

.SHORT TERM...(This evening through Tuesday night)
Issued at 327 PM EDT MON SEP 26 2016

A cold front is currently moving across eastern KY as of 3pm today.
While the initial line of showers and thunderstorms has sheared out
along the weakening frontal boundary during its eastward
progression, warm air and clear initial conditions across far
eastern KY helped to increase instability across this area during
the early afternoon. A gust front which pushed out well ahead of the
initial line then became the spawning ground for another line of
showers and thunderstorms across far eastern KY. For the rest of the
afternoon, expect the showers along the frontal zone to continue to
shear out and breakup. Meanwhile the secondary and more robust line
of showers and thunderstorms will continue to slowly move east of
the state. Also cannot rule out some isolated to scattered
convection between the two lines for the next few hours as well.

Since NW flow began ahead of the actual cold front, and cloud cover
is in place, expect cooler temperatures to continue to penetrate the
CWA through the rest of the afternoon. This will only work to weaken
any convection potential. The 850 mb frontal passage will
traverse the CWA later this evening and into the overnight, generally
after 0z. It is at this point that we will really start to tap into
the much cooler airmass to our NE. Strong NW to SE upper level flow
will feed Canadian air into the region throughout the remainder of
the short term thanks to a strong upper level closed low circulating
to our north. Low temperatures tonight will fall into the upper 40s
to low 50s once we begin clearing out behind the frontal passage.
Temperatures tomorrow will finally feel more seasonable, if not a
couple degrees below, topping out in the low to mid 70s with surface
high pressure in control. Clear conditions will continue Tuesday
night with temps expected to fall back into the 40s with light
southerly winds.

.LONG TERM...(Wednesday through Monday)
Issued at 302 PM EDT MON SEP 26 2016

Models continue to come into better agreement concerning a large
upper low to affect the eastern CONUS early in the period. The ECMWF
has been the most consistent in handling the system over the last
few days. A model blend will be used to account for remaining
differences. The upper low will be slowly dropping south from the
Great Lakes on Wednesday, and should bottom out over KY on Thursday.
Even with a cool surface air mass in place, cold air aloft should
result in lapse rates steep enough for showers and possibly even
some thunderstorms to occur. Precip timing and location will depend
partly on small scale features rotating around the large system,
with timing also being linked with diurnal destabilization. Model
handling of small scale features will go through changes yet, which
puts a limit on forecast confidence. Will not use any pops above
chance category at this point, but that could change in later
forecasts. Diurnal trends are more predictable and will be
incorporated.

The low should lift back north over the weekend, taking precip with
it. Low level warm air advection is expected to be slow to return,
but additional sunshine and mixing, and warming temps aloft will
allow for a slow warming trend.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
ISSUED AT 147 PM EDT MON SEP 26 2016

A cold front is currently traversing central Kentucky and will
continue to push across the eastern portion of the state through
this evening. As we went throughout the morning, most of the
precipitation associated with this system was along the actual
frontal boundary. However as we head into the afternoon, a
secondary line has developed across the far eastern portion of the
state (east of all the TAF sites), as the initial line of
convection along the front quickly sheers out to light showers.
For the remainder of the afternoon, expect generally scattered
showers and storms across eastern KY and the TAF sites. Winds will
be from the NW throughout the afternoon, potentially gusting up to
15 knots at times ahead of the frontal passage. Visibilities may
be briefly reduced in some of the heavier showers. CIGs will
remain in the MVFR range across the region until the frontal
passage, which should occur late this afternoon for the
western/northern most TAF sites (KSME and KSYM) and this evening
for the eastern most sites (KSJS). Behind the frontal passage, dry
air will quickly reduce any further chances of precip and CIGS
will improve to VFR, with clouds continuing to lift and clear out
throughout the night. High pressure will move in for tomorrow,
allowing for clear skies and light winds.

&&

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

$$

SHORT TERM...JMW
LONG TERM...HAL
AVIATION...JMW



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