Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 112318
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
518 PM CST Thu Jan 11 2018

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Friday
Issued at 251 PM CST Thu Jan 11 2018

Rain will change to freezing rain or freezing drizzle
and then to snow in eastern Wisconsin while the rest of the forecast
area will have light to moderate snow.

Decided to include additional counties in the winter weather advisory
even though amount of freezing or frozen precipitation will be light,
since rapidly falling temperatures will produce icy roads and sidewalks
during the evening commute. The precipitation will end by midnight
over all but Vilas county as the system exits. Some lake effect snow
showers will continue there into Friday.

Temperatures will fall to values close to normal and highs Friday
will be 5 to 10 degrees below normal with subzero wind chills in
most places.

.LONG TERM...Friday Night Through Thursday
Issued at 251 PM CST Thu Jan 11 2018

Forecast concerns continue to revolve around the cold
temperatures and snowfall potential during the Sunday night
through Monday night time period. Models are in good agreement
through early next week, so used a blend of the ecmwf/gfs for this
forecast.

Friday night through Sunday...Arctic high pressure will be sliding
across the area from northwest to southeast on Friday night and
Saturday.  Outside of a few light snow showers over northern Vilas
county from lake effect processes, the rest of the region will see
clear and cold conditions.  The pressure gradient is expected to
remain tight enough for a 5 to 10 mph wind, which combined with the
cold results in 20 to 25 degrees below zero wind chills over central
and north-central WI on late Friday night into Saturday morning.  A
wind chill advisory may be needed during this time.  The surface
high will shift to the southeast of the area on Saturday night into
Sunday.  With an influx of high clouds and lighter winds, wind
chills are anticipated to be slightly warmer on late Saturday night
into Sunday morning, but could still see scatterd 20 to 25 below
wind chills where winds do not decouple.  Clouds will continue to
increase on Sunday ahead of the next clipper.  Light snow could
begin to move into central and north-central WI areas during the
afternoon.

Rest of the forecast...A digging upper trough will then slowly
develop across the region on Sunday night and Monday before exiting
late Monday night into Tuesday.  This looks like a prolonged light
snow event with inverted troughing/shortwave energy with some
support from lake effect processes providing the forcing.  Potential
snow amounts in the 2-4" range appear possible, and could become
locally higher near the lakeshore if the onshore flow occurs as
models indicate.  High pressure then returns for Tuesday and Tuesday
night before temps moderate for the middle and end of the week.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 518 PM CST Thu Jan 11 2018

A mix of IFR and MVFR conditions existed over the TAF sites as
rain continued to transition to snow from west to east. At TAF
time locations west of Shawano to Iron Mountain were all snow,
with locations to the east all rain or a mix of rain and snow. As
cooler temperatures advect into the area some flash freezing is
possible on airport runways this evening. The precipitation will
end from west to east this evening, leaving mainly MVFR conditions
across the TAF sites during the overnight hours. Conditions are
expected to become VFR on Friday with gusty northwest winds.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 10 PM CST this evening for WIZ005-
038-039-048-049-073-074.

Winter Weather Advisory until 8 PM CST this evening for WIZ013-
020-021-031-037-045.

Winter Weather Advisory until 6 PM CST this evening for
WIZ010>012-018-019-030-035-036.
&&

$$

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



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