Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 301719

Area Forecast Discussion
National Weather Service Louisville KY
119 PM EDT FRI SEP 30 2016

...Updated Aviation Discussion...

...Forecast Update...
Issued at 845 AM EDT Fri Sep 30 2016

Upper low continues to rotate right over Louisville this hour. Sent
out a quick update to match up radar trends and to try to match up
areas with fog. Will issue one more update at 10 AM to expire the
dense fog advisory.

Issued at 630 AM EDT Fri Sep 30 2016

Visibilities have decreased substantially in the last hour, and
dense fog is affecting enough of the area to warrant a short lead
time advisory. However, will restrict it to areas east of Interstate
65, because visibility will improve along and west of I-65 as rain
moves in.

Issued at 535 AM EDT Fri Sep 30 2016

Fog has become extensive enough across south central Kentucky to
warrant at least a mention in the 1st period of the forecast. While
there are pockets of dense fog, webcams and observations show they
are localized enough that a Special Weather Statement should cover
it. Expect visibility to actually improve around daybreak in some
places as a band of showers pinwheels into the area from the north.

.SHORT TERM (Now through Saturday)...
Issued at 320 AM EDT Fri Sep 30 2016

Deep upper low currently lifting slowly through central Kentucky,
slinging just enough moisture around onto its north and west side to
bring a decent batch of showers into the I-65 corridor in north
central Kentucky and southern Indiana.

This upper low will keep our weather chilly and unsettled well into
the weekend as it takes its sweet time lifting through Kentucky
today, and then through Indiana tonight and Saturday. Expect rounds
of mainly scattered showers as different impulses pinwheel around
this upper low through the period. Fairly steep lapse rates in the
afternoon will support isolated thunder chances, and with low
wetbulb zero heights, can`t rule out some small hail with any
stronger cells. Overall, clouds and precip will keep temperatures
well below climo.

POPs will be in the chance range on Saturday, with a more pronounced
taper from 50% near the Ohio River to 30% along the Tennessee
border, as the upper low continues its trek north of the area. Hail
is not a concern for Sat with the diminishing influence of the cold
pool aloft, but still worth isolated thunder mention.

.LONG TERM (Saturday Night through Thursday)...
Issued at 255 AM EDT Fri Sep 30 2016

Upper low somewhere near the NW corner of Ohio to start the period,
but will continue to lift NE toward Lake Ontario by Sunday night.
Flow aloft over the Ohio Valley remains cyclonically curved on
Sunday, so will hang onto a decent amount of cloud cover and even
some slight chance POPs. Should be enough breaks to allow temps to
recover to near climo. Still expecting a dry day on Monday, but
confidence is limited by the GFS still holding some trofiness in the
Ohio Valley while pumping up the ridge more to our west and north.

Better confidence in the ridging for Tue/Wed, so look for quiet
weather and above normal temps, with most of the area punching into
the lower 80s on Wednesday.  Upper trof will approach the area on
Thursday, and this forecast will include a very low-confidence 20
POP. This precip chance will hinge on how far east the moisture feed
can set up, as the upper low closes over the Upper Midwest. If
anything this pattern could slow down further, given the blocky
nature of upper ridging over the mid-Atlantic/New England while
Matthew spins off the southeast coast.


.AVIATION (18Z TAF Update)...
Issued at 115 PM EDT Fri Sep 30 2016

Low clouds, fog and chances for showers will dominate this TAF
period. Center of upper low near SDF this afternoon will slowly
drift west/northwestward over the next 24 hours. Ceilings have risen
to MVFR or VFR this afternoon, but with the setting sun, expect
conditions to worsen this evening, tanking after midnight. Good
consensus in the data that IFR to LIFR conditions will be seen
either in low stratus or fog, with the worst conditions possible
from BWG to LEX. These poor flying conditions could linger through
the mid to late morning hours Saturday. Winds will be light/variable
for most of the period, becoming southerly toward 18z Saturday.


.LMK Watches/Warnings/Advisories...


Short Term.....RAS
Long Term......RAS
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