Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 152343
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
543 PM CST Fri Dec 15 2017

.UPDATE...

An initial band of light snow associated with warm air advection
is lifting east northeast through the area this evening.
Visibility isn`t restricted below 8-9 miles, so just an area of
flurries at this time. It`s still expected to intensify later
tonight and mainly north of Milwaukee and Madison.

&&

.AVIATION(00Z TAFS)...

MVFR CIGS cover most of southern Wisconsin at the start of the TAF
period. Look for the band of light snow across the area early on
to gradually lift north through the night. The TAF sites are only
expected to see a dusting with less than 1/4 inch of snow, or
less...and mostly before 06z Saturday. The better accumulating
snow will be located to the north and become more
widespread/intense in that area later this evening and through the
overnight hours. VFR CIGS should return to the TAF sites between
about 05-07z Saturday and remain there through the remainder of
the TAF period. Look for light and variable winds to become
easterly after sunrise on Saturday.

&&

.PREV DISCUSSION... (Issued 303 PM CST Fri Dec 15 2017)

SHORT TERM...

Tonight and Saturday...Forecast confidence high.

As the upper level flow backs in the wake of the passing upper
trough this morning, low to mid level warm advection will develop
with a focused area of sfc-850 mb frontogenesis over the nrn
forecast area. Expect some very light snow from Madison to
Milwaukee in the evening that will then shift nwd and become a
little heavier toward central WI for late evening into Sat AM.
Total snow accums of 1-2 inches for Fond du lac and Sheboygan
Counties with a dusting farther south from Madison to Milwaukee.

Saturday night through Tuesday night...Forecast confidence
medium.
l
Ely sfc flow will prevail Sat nt into Sun. A shortwave trough will
track from the srn Great Plains through the Ohio River Valley for
Sun-Sun eve. The nrn extent of the light rain and snow may reach
the WI/IL border but only slight chances for now. A quasi-zonal
flow will continue through the middle of the week with above
normal temps. A dry cold front, from a strong low well north in
Canada, will pass on Tue with high pressure to follow for Tue nt.

LONG TERM...Wednesday through Friday...Forecast confidence
low to medium.

High pressure will gradually move ewd on Wed with temps several
degrees cooler from Tue but still above normal.

A large upper trough will dig sewd from the Pacific NW Tue nt,
becoming a cut off upper low over the desert SW by Fri. A vorticity
maximum from the digging upper trough will break away and move
newd to the Great Lakes ahead of a large polar trough digging
sewd from Canada. Thus, a sfc trough/cold front will move sewd
across the region with mild air and some rainfall ahead of it and
some snowfall afterward. A wave of low pressure along the trough
is expected with the chances of strong cyclogenesis low at this
time. Polar air will return to the region at the end of the
week with arctic air possible if more of an intrusion occurs. The
cold would continue through Christmas Day.

AVIATION(21Z TAFS)...Cigs of 1-3 kft will continue ewd across
srn WI with periodic flurries through late afternoon. Cigs of 1-3
kft will then prevail tnt as light snow develops and shifts nwd.
Vsbys with the snow will range from 1-3 miles with the longest
duration of snow and reduced vsbys toward central WI. The Cigs
will rise above 3 kft from Madison to Milwaukee and swd by
midnight while Cigs will remain low to the north where the light
snow will continue and accumulate. The snow will taper Sat AM but
with Cigs remaining low north of Madison and Milwaukee through the
day.

MARINE...Brisk wly winds will subside by early evening thus the
Small Craft Advisory will be allowed to expire at 6 PM CST. Modest
ely winds will then prevail for Sat into Sun AM. Waves of 3-4 feet
are expected mainly north of North Point Lighthouse.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory until 6 PM CST this evening for LMZ643>646.

&&

$$

Update...Davis
Tonight/Saturday and Aviation/Marine...Gehring
Saturday Night through Friday...Gehring


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