Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 010247
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1047 PM EDT FRI SEP 30 2016

...Forecast Update...
Issued at 1047 PM EDT Fri Sep 30 2016

After much deliberation, have decided to expand the Dense Fog
Advisory to the northwest. For several hours local models have
really been pinpointing areas west of Louisville for the development
of fog tonight. The area has very little low level flow given its
proximity to the surface low over the Wabash Valley. Though not much
rain fell there today, dew point depressions are narrowing and Fort
Knox has already dropped to 1/4SM. Earlier we received a report of
dense fog in northwest Hart County. So, with support from both the
mesoscale models and current conditions, went ahead and expanded the
advisory.

Thanks to IND and PAH for coord.

.SHORT TERM (Now through Saturday Night)...
Issued at 230 PM EDT Fri Sep 30 2016

...Persistence forecast may get a change!...

Pesky upper low that has been slowly wobbling around central
Kentucky will drift northward tonight to a position somewhere along
the IN/OH border by daybreak Saturday. This shift is in response to
a nudge from upper flow over the Central and Northern Plains states.
Water vapor imagery agrees with the model thinking, showing that
flow edging closer to us this hour. That nudging could stop though
during the day. Models show the upper low continuing on its
northward trend, though would not be surprised at it slowing down
before making it to Lake Erie, as several models suggest.

What that means for our forecast is continued good chances for light
to occasionally moderate rain tonight and Saturday. Those chances
should start waning with loss of heating and with our distance from
the low Saturday night. For temperatures, we should be close to
normal for lows, but with cloud cover during the day we stay below
normal for highs.

The other thing to deal with overnight is fog potential. The
consensus of short term models indicates less than a mile vsby
across roughly the southern half of the forecast area. Given the
dense fog we had this morning, would not be surprised to have some
dense fog again.

.LONG TERM (Sunday through Friday)...
Issued at 220 PM EDT Fri Sep 30 2016

The main highlight in the long term period is the expected exit of
the upper low across the region, giving way to a warmer, drier
period for the lower Ohio Valley.

On Sunday, the synoptic pattern is expected to feature the closed
upper low center near southern Michigan, moving to the northeast
throughout the day. This should allow the low clouds, fog and
showers to be mainly confined to our north and east, so plan on
highs in the low 70s. There`s still a chance of an afternoon shower,
but the trend will be for drier conditions.

By Sunday night through the middle of the next work week, the
pattern will transition to zonal to ridging as a deeper system moves
in the central Plains and Hurricane Matthew moves through the
western Atlantic. Expect more seasonable temperatures early next
week, trending above normal into the low 80s by late in the week.
Dry weather is expected to prevail until a frontal system
approaches the region late in the work week.

&&

.AVIATION (00Z TAF Update)...
Issued at 735 PM EDT Fri Sep 30 2016

The upper low that has been overhead will continue to supply the
region with low clouds and spotty showers through tonight into
Saturday as it wanders from Kentucky to Indiana. Shower coverage is
expected to diminish overnight tonight as we lose insolation. As
they do so, ceilings should lower dramatically and visibilities will
lower as temperatures drop tonight.

Visibilities will improve first Saturday morning as a SSW surface
breeze kicks in around 5-7 knots. Ceilings will lift slowly though
will probably stay MVFR into the afternoon.

&&

.LMK Watches/Warnings/Advisories...
KY...Dense Fog Advisory from 3 AM EDT /2 AM CDT/ to 10 AM EDT /9 AM
     CDT/ Saturday for KYZ023>028-053-054-061>066-071>078-081-
     082.

IN...Dense Fog Advisory from 3 AM EDT /2 AM CDT/ to 10 AM EDT /9 AM
     CDT/ Saturday for INZ076-083-084-089-090.

&&

$$

Update.........13
Short Term.....RJS
Long Term......ZT
Aviation.......13



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