Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 121647
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1147 AM EST Tue Dec 12 2017

.Short Term...(Today through Wednesday)
Issued at 307 AM EST Tue Dec 12 2017

...Patchy drizzle and scattered snow showers may cause slick spots
this morning...

At 08Z air temperatures were still in the lower and middle 40s
across central Kentucky and most of southern Indiana. Over the last
couple of hours patchy drizzle has been forming from central Indiana
to the Jackson Purchase. While temperatures will fall over the next
few hours, they will likely still be just above freezing in the
middle and upper 30s when the patchy drizzle arrives. Also, road
temperatures that were generally in the lower 40s at 08Z will take
some time to respond to the cooling air temperatures. So,
significant freezing precipitation before 12Z (7am EST) is beginning
to look a bit less certain.

After 12Z we will transition into more of a showery regime as
sounding progs show instability developing and short term model QPF
fields show streaks of precipitation from scattered showers. The
presence of convection suggests snow showers rather than drizzle.
There will still be the chance of some light freezing rain mixing
with the snow for the first hour or two after sunrise as surface
temperatures dip to around the freezing mark without much moisture
aloft in air cold enough to consistently produce snowflakes.

As we get into mid morning the surface and the column will cool
enough that we will just be dealing with scattered snow showers. NAM
and GFS snow squall parameter shows the best chance of snow showers
to be east of Interstate 65. Any snow shower will be capable of a
brief dusting of snow. The most likely area to see a few tenths of
accumulation from repeated snow showers will be along and east of a
Frankfort-Liberty line where showers will be the most numerous and
there will be some orographic assistance. The main streamers coming
off Lake Michigan should remain to our north and northeast.

If we do get any pre-dawn drizzle, frozen or not, wet surfaces may
cool down enough to freeze and cause patchy slick spots during the
morning hours, especially in places that get snow showers.

Winds will be another issue today as they rush in from the northwest
at speeds of 10 to 20 mph with gusts to 30-35mph. While these winds
may help to keep pavement dry and prevent light precipitation from
causing much of a problem, they will also help to reduce visibility
in snow showers and produce wind chills in the teens.

This afternoon drier air will advect into the region and the sharp
upper trof helping to spark the snow showers will be pressing off to
the east, causing our showers to quickly taper off early this
afternoon.

Tonight will be dry but chilly as we sit between weather systems.
Temperatures will drop into the teens to around 20 with wind chills
possibly dipping into the single digits especially in the Blue Grass.

Wednesday the next clipper will shoot southeastward through the
western Great Lakes. Most of the precipitation associated with this
system will stay to our north, but not by much, so southern Indiana
and the northern Blue Grass aren`t completely out of the woods yet.
High temperatures on Wednesday should be in the 40s, though the Blue
Grass may not make it out of the 30s.

.Long Term...(Wednesday night through Monday)
Issued at 313 AM EST Tue Dec 12 2017

The aforementioned clipper to our north on Wednesday will brush by
southern Indiana and the northern Blue Grass, possibly touching off
some light rain and snow showers during the evening hours.

After a dry day on Thursday yet another system will roll through on
Friday in the form of low pressure crossing the Great Lakes dragging
a cold front through the Ohio Valley. The EC and most GEFS plumes
are dry, but the operational GFS and the Canadian do show some QPF,
so will go with a low chance for rain and snow showers.

A couple days later another system will affect our region on Sunday.
Temperatures look warm enough for rain with this one, with highs on
Sunday in the 50s.

&&

.Aviation...(18Z TAF Issuance)
Issued at 1145 AM EST Tue Dec 12 2017

Ceilings have scattered out at SDF and HNB, and lifted to VFR at LEX
and BWG. Will monitor until issuance time to see if the latter two
can scatter out, and if any lingering flurries or snow showers could
still play a role.

Dry forecast across the board by mid-afternoon, with the main story
being gusty W-NW winds for the rest of the day and into this
evening. Will have frequent 25 kt gusts, with strong crosswind
component on the long runways at SDF as well as the main runway at
LEX.

Clear skies and unrestricted vis expected overnight. Winds should
diminish during the evening, and will be solidly under 10 kt by the
start of the inbound traffic peak at SDF. Overnight light NW winds
will back to SW by the pre-dawn outbound peak.

&&

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

$$

Short Term...13
Long Term....13
Aviation...RAS



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