Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 202320
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
720 PM EDT Wed Sep 20 2017

...Updated Aviation Discussion...

.Short Term (Now through Thursday Night)...
Issued at 245 PM EDT Wed Sep 20 2017

Unseasonably warm and humid air mass is taking hold over the Ohio
Valley, but the surface pattern remains quite sloppy with no
mechanisms to focus convection and the cold pool associated with the
upper low is solidly to our NE over Ohio.

Main story by day will be heat and humidity, with a few isolated pop-
ups possible each afternoon. Instability looks decent, but deep
moisture does not keep up with the low-level moisture and sources of
lift are lacking, so expect any storms to be isolated and short-
lived.

Main challenge at night will be fog potential. Weak surface
gradient, moist air mass, and increasingly long nights all weigh in
favor of fog formation. High clouds will be a limiting factor, but
still expecting temps to cross over current dewpoints to allow at
least patchy fog toward morning. Could see locally dense fog, but
will let the next shift decide on any headlines after we see whether
or not dewpoints are able to mix down at all this afternoon.

.Long Term (Friday through Wednesday)...
Issued at 245 PM EDT Wed Sep 20 2017

Strong upper ridging over the Great Lakes and Ohio Valley will
remain in control for most of the period, resulting in mainly dry
and unseasonably warm weather through the period. This pattern tends
to support subsidence, and low-level foci for precip are largely
missing, so will not mention any precip even though a very isolated
afternoon pop-up wouldn`t be out of the question. Temps through the
weekend will run roughly 10 degrees above normal both day and night.

Early next week we`ll start to see a slight breakdown in the ridge,
especially to our south, which will mainly just allow the heat to
ease slightly. Will stick with the dry forecast for now, and temps
will continue to run a few degrees above normal. Latest model runs
support slight chance POPs on Wednesday as a sharp upper trof pushes
into the northern Great Lakes, and drives a cold front SE toward the
area.

&&

.Aviation...(00Z TAF Issuance)
Issued at 722 PM EDT Wed Sep 20 2017

Main concern is fog potential again tonight across all the
terminals. Clear skies, light winds, and plenty of low-level
moisture should aid in the development of patchy to areas of fog.
The fog could become locally dense toward dawn, especially in the
favored sites HNB and BWG. It`s possible LEX and SDF could dip down
into low end MVFR or IFR visibility. Any fog that does form should
quickly burn off after sunrise. Otherwise, plan on light winds out
of the southeast during the day with a few/sct cu deck in the
afternoon.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&

$$

Short Term........RAS
Long Term.........RAS
Aviation...ZT



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