Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 250449
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1049 PM CST Fri Feb 24 2017

Updated aviation portion for 06Z TAF issuance

.SHORT TERM...Tonight and Saturday
Issued at 244 PM CST Fri Feb 24 2017

Main forecast concern to be on lingering snow amounts tonight as
the surface low pulls away, but the trailing mid-level shortwave
trough yet to pass through.

The 20z MSAS surface analysis showed the center of the storm now
over SW Lower MI with the shortwave trough still over the Upper
Midwest. The water vapor imagery did indicate the dry slot had
worked into eastern WI where the precipitation had changed mainly
to freezing drizzle or drizzle. Light snow stretched from the
central Plains into western Upper MI associated with the main
deformation zone.

The surface low will continue to track northeast into southeast
Ontario tonight, while the mid-level shortwave trough sweeps
across WI. Gradually cooler air associated with the trough should
keep precipitation type as all snow over central WI, while the
wintry mix of drizzle, freezing drizzle and snow over eastern WI
will eventually turn to all snow later this evening as the dry
slot exits to the east. Additional snow accumulations to be 2-3"
for central WI (local 4" over Vilas county with lake enhancement),
1-2" for eastern WI. Brisk north-northwest winds will persist
tonight which would bring some more drifting of the fresh snow.
Since the heavier snow and stronger winds have diminished, prefer
to downgrade the winter storm warning for central WI to a winter
weather advisory (except Vilas) and keep headlines intact for
eastern WI. Min temperatures will range from 10 to 15 degrees
north-central WI, to the lower 20s near Lake MI.

Light snow will likely linger over eastern WI into Saturday
morning, but additional accumulations would mainly be less than an
inch. Weak lake effect snow showers will also linger into Saturday
for Vilas county as trajectories are marginal in the morning
before becoming unfavorable Saturday afternoon as winds back more
to the west. Accumulations over Vilas county will also be an inch
or less. Otherwise, slowly improving conditions are expected by
Saturday afternoon as a ridge of high pressure builds toward the
western Great Lakes region. Central WI may be able to see some
afternoon sunshine, while eastern WI should remain mostly cloudy.
Max temperatures will be below normal for a change with readings
only in the lower to middle 20s north, middle to upper 20s south.

.LONG TERM...Saturday Night Through Friday
Issued at 244 PM CST Fri Feb 24 2017

As the mid level trough lifts out of the area a brief quiet
period is expected Sunday morning. A quick moving short wave then
rides through northern and central Wisconsin Sunday in the late
morning to evening. Colder temperatures aloft coupled with
temperatures in the middle thirties near the surface are expected
to keep precipitation in the form of snow with little accumulation
across the area.

An active weather pattern then continues in the middle of next
week although timing continues to be a bit messy. A broad upper
trough with accompanying surface low will bring in a large swath
of precipitation overnight Monday into Tuesday. Timing, exact
placement, and strength of the low are still variable, but
precipitation is expected to stay in the area through Tuesday
night. Current blended tracks of the low allow for sufficient
warming in the lower levels to bring in mixed precipitation and
rain through much of the afternoon before returning to snow
as colder cyclonic flow comes in behind the low overnight. Another
system will then follow this one as a clipper sets itself up to
arrive Thursday into Friday.

Near normal temperatures are expected for Sunday followed by a
slight warming ahead of the large trough and low pressure system,
then cooling into the end of the work week.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1049 PM CST Fri Feb 24 2017

Surface low pressure will track through southeast Ontario
overnight, then continue northeast over western Quebec Saturday
morning. Expect primarily MVFR cigs/IFR vsbys to continue through
the overnight hours. Mainly snow is expected out to the west, as
freezing drizzle changes to all snow across the east after
midnight. In addition to the precipitation, windy conditions are
expected with a tight pressure gradient across the western Great
Lakes. Winds will diminish Saturday evening as winds decouple.
The precipitation will gradually diminish from west to east on
Saturday as a ridge of high pressure builds into the region. VFR
conditions should return Saturday morning and continue into
Saturday night.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 AM CST Saturday for WIZ010>013-
018>022-030-031-035>040-045-048>050-073-074.

Winter Storm Warning until 6 AM CST Saturday for WIZ005.
&&

$$

SHORT TERM.....Kallas
LONG TERM......Uhlmann
AVIATION.......Kurimski


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