Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 200637

Area Forecast Discussion
National Weather Service Louisville KY
237 AM EDT Fri Oct 20 2017

.Short Term...(Today through Saturday)
Issued at 230 AM EDT Fri Oct 20 2017

Warm and dry weather will continue through Saturday with surface
high pressure over the Appalachians slowly retreating toward the mid-
Atlantic coast and an amplifying upper ridge over the southeastern
CONUS. Based on low-level thickness progs, expect max temperatures
to trend up from Thursday`s readings by a degree or two each day.

Only fly in the ointment will be fog, as we expect at least patchy
fog to start off this morning. There is a decent signal for fog
given light boundary layer winds and temps just barely crossing over
Thu afternoon dewpoints, but expect any dense fog to be quite
localized, mainly in river valleys.

Limited potential for a repeat performance of fog on Saturday
morning, as the winds just above the boundary layer will be 15-20
kt. Believe this will keep it just mixy enough to hold off any
substantial fog, but it still bears watching for stronger winds that
could just skate across the top of the inversion.


.Long Term...(Saturday night through Thursday)
Issued at 230 AM EDT Fri Oct 20 2017

Weather pattern turns unsettled the latter half of the weekend as a
sharp upper trof makes its way across the Plains, with increasingly
moist southerly flow ahead of it in the Ohio Valley. Clouds will
increase on Sunday and by late in the day we`ll see solid chance
POPs along and west of I-65.

By Sunday night, the southern stream portion of the upper trof is
left behind and develops a closed low over the Lower Mississippi
Valley. Will carry categorical POPs Sun night and Mon as medium-
range models remain fairly consistent in developing a deformation
feature across the Ohio Valley. Expect mainly a soaking rain from
this system, with QPF anywhere from 0.75 inches over southern
Indiana to 1.5 inches across south-central Kentucky. No instability
to support severe wx. Unseasonably warm temps are expected Sunday
into Sun night, with Monday as a transition day.

By Tuesday we`ll see a deep longwave trof carved out over the
eastern CONUS, with lingering precip chances into Tuesday under the
influence of the cold pool. Temps will run solidly below normal from
Tuesday onward, with lows around 40 Wed/Thu mornings. If we see more
clearing, frost potential would enter the picture, but confidence is
too low at this time.


.Aviation...(06Z TAF Issuance)
Issued at 122 AM EDT Fri Oct 20 2017

Decent setup for fog at all four TAF sites this morning, but some
variation is likely in how low everyone goes in terms of vsby.
Compared to previous nights, a bit more low-level moisture exists
in addition to very light winds at the surface and aloft. LIFR
conditions are most likely at BWG, possibly impacting LEX as well.
A period of MVFR fog is forecast for SDF/HNB, with some IFR mixed
in after 09z.

Once fog burns off shortly after sunrise, the rest of the day will
be VFR with mostly sunny skies. Scattered cirrus will begin
spreading in from the west this afternoon and evening. Winds will
remain light or calm early this morning, increasing to 5-7 kts out
of the SE during the day.




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