Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 012008

Area Forecast Discussion
National Weather Service Louisville KY
308 PM EST Tue Dec 1 2020

.Short Term...(This evening through Wednesday)
Issued at 246 PM EST Tue Dec 1 2020

Happy first day of meteorological winter! Conditions outside
certainly feel winterlike, as observations across the region range
from low to mid 30s. A stout westerly winds has kept wind chill
readings down in the 20s for most of the day. Clouds have been slow
to clear out east of I-65, but the latest satellite trends suggest
some drier air is starting to push eastward and erode the westward
end of the stratus deck. This will continue over the next several
hours, with clearing likely reaching the I-75 corridor near sunset.

Winds will slacken some overnight, and with clear skies and very dry
air in place, temperatures tonight into early tomorrow morning will
be very cold. Currently forecasting lots of low 20s and upper teens,
with the coldest temperatures occurring where the snowpack is still

After a cold start tomorrow, temperatures should begin to quickly
warm up after sunrise. A ridge of high pressure will pass east of
the region, and winds will turn more west-southwest to southwest
during the day. Warmer temperatures will also advect in from the
west, though highs (low to mid 40s) will still be below
climatological normals.


.Long Term...(Wednesday night through Tuesday)
Issued at 305 PM EST Tue Dec 1 2020

We start the long term period with continued ridging aloft and sfc
high pressure over the Ohio Valley. High pressure will quickly slide
off to our east during the early morning hours on Thursday. Clouds
will be increasing Thursday morning as another weather system
approaches our neck of the woods. A deep closed low spinning over
the Central Plains will be approaching the Ohio Valley, and will
bring precip chances to Kentucky starting around 18z. However, model
soundings indicate very dry air in the low levels during Thursday
morning and afternoon, so we may see virga before the low
levels eventually saturate.

Models begin to quickly diverge on solutions around 00z Friday, but
general consensus is that precip chances will continue for Friday.
The GFS continues to suggest that the closed low will ride along the
southern upper level jet, which will track the closed low directly
across Kentucky. In doing so, a 45kt 850mb jet on the leading
edge could help increase rainfall rates for Friday morning (if
the GFS is correct). The GFS suggests the low will continue to
bring precip chances through Saturday and eventually dry out by
Sunday. On the other hand, the Euro solution shows the upper level
low opening and merging with the upper level flow. It splits off a
secondary 500mb low that would track across the Gulf States as it
gets picked up by the southern upper level flow. This Euro solution
also leads to precip exiting the CWA by Friday evening, and a dry
weekend. For now, due to a very wide spectrum in solutions, will
continue with NBM for the long term. NBM carries slight and chance
PoPs for the CWA from Thursday through Saturday night. It is
still worth mentioning that if the more pessimistic solution
prevails, that a light rain/snow mix could be seen early Saturday
morning, but no impacts are expected at this time.

Temperatures through this period will continue to have highs in the
mid to upper 40s and lows in the low 30s.


.Aviation...(18Z TAF Issuance)
Issued at 1200 PM EST Tue Dec 1 2020

Stratus has been slow to clear the region this morning, and
additional MVFR to VFR strato-cu has developed within the past
couple of hours. These clouds are likely to hang around for most of
the day, though should lift to VFR levels within the next couple of
hours, and then begin to dissipate toward sunset and eventually give
way to clear skies overnight. Winds will be occasionally gusty this
afternoon, with westerly +20kts likely across sites along and north
of the I-64 corridor. Winds will become lighter overnight and
generally remain out of the west or west-southwest.




Short Term...DM
Long Term...CJP
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