Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 161056
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
556 AM EST Sat Dec 16 2017

...Updated Aviation Discussion...

.Short Term...(Today through Sunday Night)
Issued at 245 AM EST Sat Dec 16 2017

Current surface analysis reveals a 1026mb high over central Alabama
influencing the weather over the lower Ohio River valley. Winds were
generally light out of the south or southwest at this hour, and
skies were mostly clear except across portions of the Kentucky
Bluegrass where some mid level clouds remained.

Today should be a pleasant mid-December day. High pressure over
Alabama will move over the southeastern US this afternoon. Surface
to 850mb flow will pick up out of the southwest and advect warmer
air to the region. Highs will top out in the low to mid 50s for many
locations this afternoon, and with strong subsidence, skies will
remain mostly clear with only a few passing cirrus.

A 500mb cutoff low over Mexico/Texas will begin moving toward the
lower Ohio River Valley Saturday evening. Clouds will begin
increasing, but with dry mid/low levels of the atmosphere, should
remain dry overnight Saturday. By Sunday morning, we should begin
seeing rain developing over southwestern portions of the CWA first,
before spreading northeastward into northern KY and southern Indiana
by late Sunday morning into early Sunday afternoon. With the cut-off
low weakening and being absorbed into the main flow Sunday, overall
rainfall amounts will be on the marginal side, generally under a
quarter inch. The rainfall will have an impact on temperatures, and
we may not see much of a diurnal range in temperatures if rain moves
in during the mid to late morning hours.

Most guidance, with the exception of the Canadian, has the rain out
of the region by early evening Sunday. Clouds will hang around for
most of the evening, and as a result, temperatures will not fall
much and hover near the 40 degree mark for overnight lows.

.Long Term...(Monday through Friday)
Issued at 255 AM EST Sat Dec 16 2017

500mb cut-off low in the desert SW will set up a split-flow regime
over the lower Ohio River Valley Monday and Tuesday. During this
timeframe, flow will remain generally out of the southwest, and
temperatures will be quite mild. We may even see some 60 degree high
temperature readings Tuesday afternoon across portions of the
southwest CWA.

A cold front associated with an upper level trough will come
sweeping through the region Tuesday evening. Around this same time,
the 500mb cut-off low over the desert SW will get swept up and
carried toward the lower Ohio Valley by Wednesday. Models still vary
on the placement and timing of precipitation, with the GFS/Canadian
keeping us mostly dry, while the Euro has the whole region receiving
some precipitation at some point Wednesday. Will stick with a
blended model solution for now, but if the Euro comes more in line
with the GFS/Canadian, PoPs may be dropped from subsequent forecast
updates.

We`ll have a brief warm-up Thursday before another, stronger cold
front moves through the region on Friday before stalling out over
the southeast into the weekend. Should any systems develop and track
over the region, they would need to be watched closely for any
potential p-type concerns. Up to this point, models have been all
over the place with solutions, resulting in low forecaster
confidence. It is important to not lock into any one model
solution over the next 7 to 10 days. Our advice is that if you
have travel plans for late next week and into Christmas, that you
keep a close eye on the latest forecasts since model solutions
will change.

&&

.Aviation...(12Z TAF Issuance)
Issued at 555 AM EST Sat Dec 16 2017

VFR TAFs are forecast.  A strong return flow today will result in
breezy SSW winds with gusts of 20-23 kts.  Wind gusts will diminish
this evening.  An upper level shortwave will bring rain tomorrow
after 12Z.

&&

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

$$

Short Term...DM
Long Term...DM
Aviation...AMS



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