Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 061924

Area Forecast Discussion
National Weather Service Louisville KY
224 PM EST Tue Dec 6 2016

.Short Term...(This evening through Wednesday night)
Issued at 215 PM EST Tue Dec 6 2016

Potent shortwave now east of the area, after having brought over an
inch of rain in many locations across southern IN and central KY,
will continue east northeast the rest of this afternoon. In its
wake, one more vortmax, now over northern Arkansas, will cross the
region this evening. Forecast soundings from the GFS/RAP and to a
lesser extent the NAM show this feature, via a saturated layer at
500 mb and above. There is plenty of dry air underneath this layer,
save for near the surface. Any ice crystals aloft should sublimate
through this dry air.

High pressure will ridge in from the west during the day Wednesday,
under partly cloudy skies, with more upper clouds all from making us
sunny. Wednesday night cloud cover will increase again as a
reinforcing cold front approaches. Models have continued the trend
of showing a dry passage with this front. Even the NAM joined that
dry party, reversing its trend from the 00Z run. The SREF spreads
show a little more uncertainty, with some higher values near the
KY/TN border late Wednesday night. Thus will keep in slight chance
for light snow, but no accumulations, down there.


.Long Term...(Thursday through Tuesday)
Issued at 215 PM EST Tue Dec 6 2016

...Unseasonably Cold Later This Week...

Reinforcing cold shot moving in Wednesday will allow Arctic high
pressure to spill southward into our region.  Expect temperatures
Thursday through Saturday to run some 10-20 degrees below normal,the
first time we`ve run with average temperatures that far below normal
was back in mid May. Surface high pressure should be right over the
area Saturday morning, so our cold spots easily could see mid teens
or lower for lows.

The slightest chances for precip in this cold regime are possible
just northeast of our area Friday, in the flow off Lake Michigan. A
few models hint at light QPF in this plume, but with this package we
are forecasting that plume to stay out of our area.

By Saturday night the surface high will push east of the area,
allowing a return flow to start warming us up. Flow aloft will be
zonal but should back to southwesterly Sunday, as the next cold
front approaches. Models have slowed the timing of precip a little
since this time yesterday`s runs, now keeping the bulk of the rain
during the daytime period...which more than likely would be rain.
Still given uncertainty in timing, will be continuing our rain/snow
mix wording.

High pressure building in behind that front should make us cold and
dry again by Tuesday.


.Aviation...(18Z TAF Issuance)
Issued at 1204 PM EST Tue Dec 6 2016

IFR conditions are expected to continue across the region this
afternoon and into tonight.  Rain band continues to push on off to
the east.  The back edge of the rain band will clear KSDF and KBWG by
06/18Z and should clear the KLEX area by 06/20-21Z.  After the rain
ends, low-level moisture will be plentiful and some residual drizzle
will persist for several hours.  Overall trend in the data is to
keep lower ceilings in the forecast than previously thought.  For
now, plan on keeping ceilings under IFR for the afternoon and
evening hours and then letting ceilings slowly rise overnight.  VFR
conditions probably will not occur until around 07/12Z.  Winds have
shift to the northwest at KSDF and KBWG and will remain that way
through the TAF period with speeds of 5-10kts.  Winds at KLEX will
start out of the south and then shift the southwest around 06/18-19Z
and then to the northwest by 06/19-20Z.


.LMK Watches/Warnings/Advisories...


Short Term...RJS
Long Term...RJS
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