Area Forecast Discussion
Issued by NWS Louisville, KY

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447
FXUS63 KLMK 190037
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
737 PM EST Sat Nov 18 2017

.Forecast Update...
Issued at 736 PM EST Sat Nov 18 2017

Convective line has pushed east of the CWA and in coordination with
SPC have gone ahead and dropped the severe thunderstorm watch.
Surface cold front continues to push east of I-65 and will be
heading for the I-75 corridor.  Cold air is pushing through southern
Indiana and north-central KY.  Temps have dropped into the 40s along
the I-65 corridor and upper 30s just entering our northwest CWA.  In
the near term, expect temperatures to continue to drop during the
rest of the evening and into the overnight period.

Upstream radars show a band of precipitation working through
southern IN and far western KY.  This is a band of rain showers that
will affect primarily the northern half of the CWA this evening
bringing few hundredths of precipitation to the region.  Much of
this precipitation should exit our forecast area by midnight with
cloudy skies remaining across the region.  Some clearing may take
place late tonight in the far west.  As lapse rates steepen late
tonight and northwest flow becomes more dominant, a few snow
flurries will be possible from southern Indiana and into the
Bluegrass region of central KY.  These flurries should continue into
the morning hours on Sunday, but will not result in any
accumulations.

Gradient winds will remain an issue this evening as winds will
remain in the 15-25 MPH range with gusts reaching up to 40-45 MPH at
times.  The gradient will begin to relax and speeds are expected to
diminish as the evening goes on.  Based on upstream observations,
our suspicion is that we`ll likely be able to let go of the wind
advisory later this evening prior to its expiration time.

Updated forecast, graphical, and text products have been issued.

&&

.Short Term...(This evening through Sunday night)
Issued at 208 PM EST Sat Nov 18 2017

...Damaging Winds Possible This Afternoon And Evening...

A strong cold front continues to progress eastward toward southern
Indiana and central Kentucky. A QLCS has developed along the
boundary, draped from central IN back through southern IL and the MO
bootheel. This convection was located in the exit region of a 140 kt
upper jet streak. A 90 kt mid-level speed max was also rounding the
base of a potent shortwave trough. The dynamic nature and very
strong wind fields of this system have been well advertised, and the
narrow convective band may be able to transport gusts of 60-70 mph
to the surface. Outside of thunderstorm activity, widespread wind
gusts of 45-50 mph are likely, with peak gusts up to 55 mph. The
strongest winds are still expected in the 3-8 PM EST time frame,
which is also when the cold front will be crossing the forecast
area. A Severe Thunderstorm Watch has now been issued for all of
central KY and southern IN. A Wind Advisory remains in effect for
the whole region through late tonight.

A narrow plume of 250-500 J/kg MLCAPE is forecast just ahead of the
QLCS as it marches east, but this zone should gradually narrow and
decrease into the early evening hours as the line pushes east of I-
65 and approaches I-75. The overall damaging wind risk should be
diminished near and east of the I-75 corridor, but this will
continue to be re-assessed through the event. Still can`t rule out a
brief tornado or two given the magnitude of the low level
shear/helicity, but veered low-level winds should help inhibit
tornadogenesis.

Behind the cold front, we could have some lingering showers late
this evening. But expect winds to remain fairly gusty through 06z
tonight as cold air advection ramps up. There`s quite a large
temperature gradient with this potent system, and 850 mb temps are
forecast to plummet below 0 C tonight. The atmosphere will remain
well mixed, with overnight lows in the low to mid 30s.

Low clouds will tend to linger behind the front overnight. In fact,
areas near and east of I-65 may stay mostly cloudy until Sunday
afternoon. It will be chilly with a northwest breeze, with highs in
the upper 30s to mid 40s. Sunday night will feature mid-level height
rises as surface high pressure builds over the Tennessee Valley.
Lows will drop into the mid 20s in most places by Monday morning.

.Long Term...(Monday through Saturday)
Issued at 229 PM EST Sat Nov 18 2017

Weather through the upcoming holiday week looks pretty quiet, with a
dry forecast for holiday travel and Thanksgiving Day itself. After
highs in the low 50s on Monday, temps should moderate into the
mid/upper 50s on Tuesday ahead of another wave of low pressure.
Moisture looks really limited however, so a dry cold front will
likely push through Tuesday evening-Tuesday night. This front will
bring another shot of cold air, with highs in the low 40s for
Wednesday. Thanksgiving Day looks to start out cold, with morning
lows in the 20s. Highs in the mid 40s look reasonable for now. The
forecast continues to look dry for Black Friday shoppers as well,
with overnight lows a bit below freezing. Highs should warm to
around 50.

&&

.Aviation...(00Z TAF Issuance)
Issued at 613 PM EST Sat Nov 18 2017

Surface cold front is pushing through the I-65 corridor now.  Has
already pushed through KHNB and is in the process of pushing through
KSDF and KBWG.  Should pass through KLEX in the next few hours.
Winds out ahead will continue to be gusty with sustained 15-25kts
with gusts up to 40kts at times.  Shower and storm activity will
push east of KLEX by 18/23-19/00Z.  Some additional showers upstream
near St. Louis will drop down and affect mainly KHNB/KSDF and KLEX
later this evening and into the overnight period.  Winds overnight
will remain elevated out of the northwest with speeds of 15-20kts
and gusts in the 25-30kt range early, but the winds are expected to
weaken overnight.  Ceilings will likely remain MVFR overnight.
Models are too quick to clear things out, so we`ll likely have low
clouds lingering into the morning hours on Sunday.


&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...Wind Advisory until 1 AM EST /midnight CST/ Sunday for
     INZ076>079-083-084-089>092.

KY...Wind Advisory until 1 AM EST /midnight CST/ Sunday for
     KYZ023>043-045>049-053>057-061>067-070>078-081-082.

&&

$$

Update.......MJ
Short Term...EBW
Long Term....EBW
Aviation.....MJ



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