Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 150540

Area Forecast Discussion
National Weather Service Louisville KY
140 AM EDT Thu Apr 15 2021

...Updated Aviation Discussion...

.Forecast Update...
Issued at 853 PM EDT Wed Apr 14 2021

Rain has pushed east of the region and we will remain dry for the
remaining overnight hours. Skies have been slowly clearing from NW
to SE, but we are seeing additional (albeit thin) mid to high level
clouds stream in from the west. Latest satellite trends suggest
these clouds will remain over the region through early tomorrow
morning. This, combined with light sustained winds, should keep any
frost threat patchy in nature and mainly confined to sheltered
valley locations.


.Short Term...(This evening through Thursday)
Issued at 243 PM EDT Wed Apr 14 2021

The focus for light rain has now shifted to areas east of I-65, and
will exit our eastern CWA fairly quickly over the next few hours as
a cold front drops SE through the region. Still have pretty high
pops in the likely range across our far east for another hour or
two, but these diminish quickly. Any additional rainfall should be a
tenth of an inch or less. Temps will continue to struggle in the 50s
under the heavy cloud cover across the area, however some late
afternoon clearing across our northern CWA could still allow for
some brief low 60s to come into play.

Otherwise, skies do gradually clear out from NW to SE through this
evening into the overnight with steady NW surface winds behind the
weak cold front. Given the clearing skies and a light cool advection
component behind the departing cold front, temps are expected to
drop into the upper 30s and low 40s in most spots. Can`t rule out a
few isolated locations along and north of I-64 where patchy frost
could come into play, however light winds staying up a bit and some
variable upper cloudiness will limit the radiational cooling
potential just enough for more widespread frost concerns.

The eastern closed low of the two dominating the CONUS upper pattern
will continue to wobble over the eastern Great Lakes by Thursday.
However, with the trailing surface front to our south and east and
surface high pressure building in from the west we will stay dry. In
addition, we should see a decent amount of sun. Some steady cool
advection will offset heating a bit, but still expecting highs
a few degrees on either side of 60.

.Long Term...(Thursday night through Wednesday)
Issued at 245 PM EDT Wed Apr 14 2021

At the start of the extended period, upper-level low will be pushing
across the Northeast towards the Atlantic as a dampening ridge moves
east towards the OH Valley. Dry weather will prevail Thursday night
and Friday with temperatures remaining below seasonal normals.
Patchy frost will be possible early Friday morning as low
temperatures dip into the mid 30s to lower 40s under mostly clear
skies and light winds. Best chances to see patchy frost look to be
across the Bluegrass region and down towards Lake Cumberland region
where probabilities of temperatures near 35 degrees are the highest.
High temperatures for the day then look to top out in the upper 50s
to mid 60s.

As we move through the weekend, starting to see better agreement
amongst model guidance that a couple of shortwave troughs will swing
out of the Plains region and across the OH Valley, bringing
increased rain chances. The first wave looks to move through on
Saturday with the second wave following close behind and pushing
through later Sunday. With both waves, not expecting much in the way
of QPF as moisture availability remains a bit of a question mark.
Integrated water vapor transport is progged to be rather weak with
the better moisture staying to our south. High temperatures for the
weekend will remain in the upper 50s to lower 60s with low
temperatures generally in the lower to mid 40s.

Next rain chances then come Tuesday as a cold front approaches the
region. Highs will warm slightly into the lower to mid 60s with lows
in the mid 30s to mid 40s.


.Aviation...(06Z TAF Issuance)
Issued at 136 AM EDT Thu Apr 15 2021

impacts: VFR conditions expected.

Discussion: Latest surface analysis reveals a weak cold front draped
roughly along the Ohio River, which will continue to push eastward
reaching LEX by 15/08Z. Observations out of SDF show that the
front has passed through as winds have veered to NW. Satellite
shows mid and high cloud streaming eastward across portions of the
region and expect this to continue overnight. Later this morning
winds will pick up out of the NW with gusts in the 15-20mph
possible at times. Also expect a BKN CIG around 4-5kft to form in
the afternoon, mostly affecting SDF, LEX, and HNB.

Confidence: High in all forecast elements.




Short Term...BJS
Long Term...JML
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