Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 230532
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
132 AM EDT Mon Oct 23 2017

...Updated Aviation Discussion...

.Forecast Update...
Issued at 935 PM EDT Sun Oct 23 2017

HRRR, RAP, and GEM are handling the current precip shield well,
which is not moving eastward very fast. Also, the cold front has
slowed down its forward progress some. Those models still pick up
the pace for rainfall eastward as the night goes on and as the low-
level jet develops. Have adjusted the grids to lean a little more
towards these models and also to pick winds up a little for the
daytime tomorrow, in the wake of the cold front.

Issued at 610 PM EDT Sun Oct 23 2017

Cold front shows up well on radar mosaic, now nearing the IL/IN/KY
border. Rain shield is enhancing to our west, over southern IL along
this front. Latest short-range model guidance continues to scattered
showers this evening along and west of the I-65 corridor and then a
more solid band of rain moving in overnight, as the low-level jet
picks up. Current forecast looks good, but will continue to tweak as
near-term guidance comes in, and with latest radar trends. We should
be able to handle the rainfall amounts, as flash flood guidance is
around 4 inches in the BWG vicinity. The lowest values are 2.5-3
inches along and northeast of a Huntingburg, IN to Bardstown, KY and
Liberty, KY line. Current rainfall total forecast is for 1-2 inches,
so we should stay well under any concerns.

&&

.Short Term...(This evening through Monday night)
Issued at 345 PM EDT Sun Oct 22 2017

Currently, a cold front extends from eastern Wisconsin to Houston,
Texas ahead of a deep upper level trough. As the trough crawls
slowly to the east it will push rain ahead of it. The tight pressure
gradient leading the trough is fueling gusty southerly winds today
and keeping temperatures seasonably warm in the upper 70s and a few
places will cross into the low 80s. Winds are 10-15 mph with gusts
to around 20-30 mph.

Tonight, rain will enter the vicinity of our western counties near
sunset. Rain chances will continue to slowly move east as the night
continues. Showers will intensify as moisture being carried up from
the Gulf of Mexico wraps around a surface low after 4z. With
precipitable water values in the 1.5 to 1.7 inch range, expect an
efficient soaking rain. Rain is not expected to cause issues due to
the current dry conditions. Temps will be mild tonight in the upper
50s/lower 60s.

Monday, rain will be the heaviest in the morning while showers are
on the leading edge of the front. After the front moves through and
moisture wraps around a low pressure center, more scattered showers
will work their way through the rest of the day.  Mon highs will
reach the 60s.

Monday night, Rain chances will remain in the area at sunset, but
chances will drop from west to east as the night continues.  Temps
will cool off into the 40s.

.Long Term...(Tuesday through Sunday)
Issued at 315 PM EDT Sun Oct 22 2017

Tuesday - Thursday...

A deep, broad trough will drop into the Midwest Tues bringing
noticeably cooler temps for Tues/Wed.  Highs will be limited to the
50s both days with Wed being the cooler day.  Vorticity max`s
rotating through the base of the trough will be enough to spark isld
to sct rain showers Tues/Tues night with maybe a few lingering in
the northern Bluegrass for Wed.

Thursday morning lows look to drop into the 30s across the entire
area with patchy frost possible.  The upper trough will move out of
the region Thu, however, allowing temps to reach the low to mid 60s
for highs.

Friday - Sunday...

There continues to be low confidence regarding the timing of a
potential strong cold front and upper trough for this weekend. While
the 12Z GFS/GFS Ensembles/Canadian all seem to push the front and
associated precip through Fri-early Sat, the 12Z ECMWF continues to
show a much slower arrival and progression eastward of the front and
associated precip (Fri night-Sunday).  The official forecast sides
with the consensus which is on the faster side but timing may change
in coming forecasts.  Either way, rain showers and another cool down
look on track for the end of the week and through the weekend.

&&

.Aviation...(06Z TAF Issuance)
Issued at 125 AM EDT Sun Oct 23 2017

Unsettled TAF period with several weather items to contend with
across central Kentucky and southern Indiana. An axis of rain with
embedded heavy rain will slowly lift from middle TN into central KY
and southern IN through the morning hours. Plan on steady rain with
embedded pockets of IFR visibility. Rainfall rates could approach 1
inch per hour in places, especially at BWG and HNB. The rain will
reach LEX the latest, not until closer to 10-12z. LLWS will be a
threat at HNB/BWG/SDF through sunrise ahead of the cold front as a
strong low-level jet sets up. Winds at 2000 ft will be around 40 kts
out of the south/southeast.

Once the surface low and front passes, and winds becomes out of the
west, there`s a good signal that low MVFR signals will spread across
the area. Upstream observations are in the 800-1500 ft, so IFR
ceilings are possible, especially at HNB and BWG. Rain will become
more scattered late morning, as westerly winds begin to pick up with
gusts to around 18-20 kts possible. The lower ceilings will likely
persist into the afternoon hours.

Slowly improving conditions are expected this evening as the whole
weather system lifts to the northeast, however wrap around stratus
will likely stay over SDF and LEX and could potentially be in the
MVFR range.

&&

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

$$

Update...RJS
Short Term...KDW
Long Term...AMS
Aviation...ZT


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