Area Forecast Discussion
Issued by NWS Green Bay, WI

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340
FXUS63 KGRB 122037
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
237 PM CST Fri Jan 12 2018

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Saturday
Issued at 234 PM CST Fri Jan 12 2018

Lake effect clouds and flurries should diminish across the northwoods
tonight with mostly clear skies elsewhere. Light northwest winds and
subzero temperatures should make for wind chills of 20 to 25 below
in central and northcentral Wisconsin where wind chill advisories
are in effect. Wind chills of 10 to 20 below zero are expected
across the east. Saturday will be sunny and very cold with highs
10 to 15 degrees below normal.

.LONG TERM...Saturday Night Through Friday
Issued at 234 PM CST Fri Jan 12 2018

Forecast concerns mainly center around the potential snowfall late
Sunday into Monday night, with a sprinkle of bitter cold also thrown
into the mix.  The gfs and ecmwf remain in good agreement with this
system, so will continue to use a blend for this part of the
forecast.

Saturday night through Monday night...Arctic high pressure will be
sliding southeast from the northern Mississippi Valley to the Ohio
Valley on Saturday night. The pressure gradient will be considerably
more relaxed than on Friday night, and many locations will likely
see their winds decouple.  Where this occurs, temps will likely fall
into the teens to low 20s below zero, mainly over central and north-
central WI.  Scattered locations may see their winds remain in the 3-
5 kt range, which combined with the cold, will drop their wind
chills to 20-30 below zero.  So no matter how you slice it, it will
be cold, and a wind chill advisory may be needed for central and
north-central WI.  Clouds will then be on the increase from the
northwest from late Saturday night into Sunday ahead of a digging
upper trough and associated reinforcing cold front.  Enough forcing
and moisture will move into central and north-central WI for light
snow to arrive on Sunday afternoon.

The bulk of the snowfall will occur on Sunday night and Monday as
low pressure swings across southern Wisconsin.  Northern WI is
expected to be positioned in the deformation zone, with inverted
troughing providing a focus for snowfall.  Lake enhancement off Lake
Michigan and Lake Superior could also enhance snowfall.  Though the
snowfall will likely be light (and also fluffy in nature), the long
duration of snowfall and high snow to liquid ratios could bring a
widespread 3 to 5 inches of accumulations, and potentially higher in
the lake enhanced areas.  The light snow will gradually diminish on
Monday night as the low finally moves away.

Rest of the forecast...High pressure will then return to the area on
Tuesday and Wednesday.  Temps will remain below normal, with wind
chills of 10 to 20 below on Tuesday night.  Moderating temps remain
on track to arrive late next week.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1135 AM CST Fri Jan 12 2018

Lake effect clouds will continue to produce MVFR ceilings
of 2000 to 3000 feet north of a Merrill to antigo to Iron Mountain
line through late afternoon or early evening, along with snow showers
north of Rhinelander. These clouds should gradually dissipate overnight.
Mostly clear skies elsewhere this afternoon through Saturday.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Wind Chill Advisory from 9 PM this evening to 9 AM CST Saturday
for WIZ005-010>012-018-019-030-035-036.
&&

$$

SHORT TERM.....RDM
LONG TERM......MPC
AVIATION.......RDM



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