Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 161112

Area Forecast Discussion
National Weather Service Louisville KY
612 AM EST Fri Nov 16 2018

...Updated Aviation Discussion...

.Short Term...(Today and tonight)
Issued at 315 AM EST Fri Nov 16 2018

Seeing a dry and subsident airmass in the wake of the departing
storm system. Low level moisture is trapped beneath a strong and
shallow inversion, so we are seeing lingering stratus. The clearing
line is slowly moving to the east, however it is also filling back
in as it clears which will slow the overall process through the
remainder of the overnight. Still, expect mostly clear skies by

We`ll start out the day with chilly temps on either side of 30
degrees, and the hope that we`ll see some sunshine at least
initially. A secondary shortwave will rotate through the Great Lakes
region and will likely bring more stratocu to at least the northern
third/half of the CWA. This should limit heating, and only expect
southern IN and northern KY temps to get into the low to mid 40s for
highs. Across southern KY under clearer skies, we should see upper
40s to around 50.

An interesting setup may occur later tonight as the low level
moisture remains trapped under the shallow/strong inversion. With
good radiational cooling conditions expected, fog and/or low stratus
should take hold. Leaning toward more fog given the light 925mb
winds and a strong crossover T signal. In addition, plenty of hi-res
data to also support fog. Won`t get too aggressive with the wording
yet, but will mention patchy fog, mainly across central and southern
KY. Will also have to take note of the potential for freezing fog as
temps drop down around 30. Given that ground/road temps should be
warm, don`t expect any major impacts if that scenario plays out, but
could see some elevated effects of freezing fog. Day shift can take
another look at this potential as we move through the day.

.Long Term...(Saturday through Thursday)
Issued at 310 AM EST Fri Nov 16 2018

Period begins with zonal flow aloft and one high pressure system
heading off to our east. A weakening frontal boundary will drop into
the region Saturday late afternoon and evening. Guidance shows some
real light QPF totals with showers ahead of this front, but there
will be quite a bit of dry air to work against. Consequently, this
forecast will have no mentionable precipitation until the slow-
moving boundary gets a little extra push from an upper level system
dropping into the region Sunday afternoon/evening.

QPF still looks to be pretty light even then, and for now just
looking at a hundredth or two. We may see a brief transition to snow
later Sunday night before the precip ends, but again with such light
precip, not concerned at this time. Cloud cover lingers into
Tuesday, and some flurries are possible in our far eastern zones,
because of upslope flow. Will leave out of the forecast for now, and
see how the forecast evolves.

We then should dry out for the rest of the mid week period, with a
return to "normal" temperatures possible by Thursday.


.Aviation...(12Z TAF Issuance)
Updated at 611 AM EST Fri Nov 16 2018

Back edge of cloud cover will be clearing the SDF/LEX terminals over
the next 1 to 2 hours. Included a TEMPO Sct layer at LEX for the
first couple of valid hours. Also will continue mention of brief
LLWS at BWG/SDF this morning as notable directional shear occurs in
coincidence with a strong inversion in the lowest 1500 ft. agl.

Otherwise, expect VFR this morning until a secondary stratocu deck
drops down along the Ohio River later today. Confidence is low in
Sct vs Bkn coverage, but think HNB/SDF/LEX could see some low MVFR
for periods this afternoon. In addition, SW winds will become a
little gusty late morning to early afternoon.

The last concern will be for fog and/or low stratus formation later
tonight. Could see IFR or worse visibilities/ceilings as low level
moisture remains trapped under a strong and shallow inversion.




Short Term...BJS
Long Term...RJS
Aviation...BJS is the U.S. government's official web portal to all federal, state and local government web resources and services.