Area Forecast Discussion
Issued by NWS Louisville, KY

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644
FXUS63 KLMK 182233
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
633 PM EDT Wed Apr 18 2018

...Forecast Update...

.Forecast Update...
Issued at 630 PM EDT Wed Apr 18 2018

Line of low-topped showers has developed across southern Indiana and
and extreme north central Kentucky. It formed in an area of higher
dewpoints where the recent SPC mesoanalysis shows a bubble of 500
J/kg SB CAPE. It`s racing across the area in a higher shear
environment so the main concern is gusty winds mixing down over the
next few hours. So far however wind gusts have remained at or below
40 mph. Recent HRRR and other hi-res models handling this line
fairly well. Adjusted hourly PoPs to match reality and to
extrapolate the line through the evening hours. Minor other
adjustments were made.

&&

.Short Term...(This evening through Thursday night)
Issued at 315 PM EDT Wed Apr 18 2018

...Strong Winds and Gusty Showers Through This Evening...

Strong and fast-moving sfc low has filled in a little bit, now
1004mb over west-central Indiana. Main challenge through about
midnight tonight will be precip chances and wind potential. Very
high-momentum air is available aloft as the closed upper low makes
its way across Iowa and into northern Illinois. Starting to see wind
gusts around 30 mph already, and these winds will continue to ramp
up as the low passes to our north and its trailing cold front drops
in.

Deep moisture has so far been unavailable to generate precip, but
dewpoints over Kentucky have risen solidly into the 50s. Expect to
have some shallow scattered showers develop later this afternoon
through about mid-evening as the front pushes in. QPF is very light
and convection will be too shallow for any thunder, but these could
get quite gusty. Wind Advisory is already in effect for widespread
recurring 40 mph gusts, and any showers could mix down localized 50
mph gusts.

Steep low-level lapse rates in the post-frontal cold advection will
keep the gusts up around 40 mph through about midnight. Valid time
of the wind advisory looks good.

Precip ends and winds slowly diminish after midnight, and Thursday
will be as much below climo as today is above. Leaned on raw model
consensus in the chilly NW flow and substantial cloud cover, which
will limit max temps to lower/mid 50s.

Another frost/freeze on tap for Thursday night into Friday morning,
as the Bluegrass region looks to bottom out around 29-30 degrees.
Recent cold nights have not seen quite the temp crash advertised in
the models, and we don`t have to miss by much to avoid a freeze, so
will hold off on any Freeze Watch for now. However, widespread frost
is possible throughout the area.

.Long Term...(Friday through Wednesday)
Issued at 325 PM EDT Wed Apr 18 2018

Sfc and upper ridging will dominate through the weekend, with the
upper low trying to come out of the Plains remaining well suppressed
to the south. Temps will run on the low side of climo with no
sensible weather impacts beyond increasing mid/high clouds on
Saturday.

Early next week, the upper low tries to lift into the Tennessee
Valley, so precip chances will be on the increase as lobes of
vorticity pinwheel around the closed low. Expect plenty of cloud
cover and off and on precip chances, with temps close to normal for
late April.

&&

.Aviation...(18Z TAF Issuance)
Issued at 143 PM EDT Wed Apr 18 2018

The main concern for this TAF period will be the winds. Gusty winds
have already developed at all sites except SDF. Winds there are
expected to pick up over the next hour as the warm front continues
to lift to the north of the region. Late this afternoon the pressure
gradient will tighten up ahead of a cold front and sustained winds
and gusts will increase.

The cold front and scattered showers will move through from 21Z-01Z.
Behind the front, winds will shift to westerly. Guidance shows some
enhanced wind gusts right behind this front, particularly at SDF,
HNB, and LEX. After 03-06Z winds will come down a bit, but still be
quite gusty through the remainder of the overnight hours. A stratus
deck will then build in tomorrow morning with MVFR ceilings likely.


&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...Wind Advisory until 2 AM EDT /1 AM CDT/ Thursday for INZ076>079-
     083-084-089>092.

KY...Wind Advisory until 2 AM EDT /1 AM CDT/ Thursday for KYZ023>043-
     045>049-053>057-066-067-078-082.

&&

$$

Update...ZT
Short Term...RAS
Long Term...RAS
Aviation...EER



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