Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 092037

Area Forecast Discussion
National Weather Service Green Bay WI
237 PM CST Sat Dec 9 2017

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Sunday
Issued at 237 PM CST Sat Dec 9 2017

Timing and location of any snow, and temperatures, are the main
concerns for this part of the forecast.

Light lake effect snow showers and flurries continued across
parts of north central Wisconsin early this afternoon and there
were some flurries near Lake Michigan. Any snow should come to an
end by early evening as the mid level trough and surface system
that brought widespread snow to the area continue to move away
from the state. A surface ridge is expected to move into the
region tonight, keeping the forecast area mainly dry. Clouds
approaching from the north should help to keep temperatures from
sinking like a stone but they don`t start out very warm so single
digits and teens look reasonable for lows tonight.

Late in the night a surface front will approach from the north as
a weak mid level short wave passes north of the state. Winds also
become more favorable for lake effect, so snow chances return to
northern Wisconsin and plenty of clouds are expected for the
entire area. Warmer temperatures are in store for Sunday with
highs in the 20s at most locations.

.LONG TERM...Sunday Night Through Saturday
Issued at 237 PM CST Sat Dec 9 2017

The start of the new work week will be greeted with another in a
series of clipper systems tracking over the Great Lakes region.
Timing and track locations remain an issue with this first clipper
as well as system later in the work week.

Latest forecast guidance has indicated a more northern track of
the surface low along with the 850 trough axis. Height 850 waa
pattern spreads over more of the area between 06z Monday and 15z
Monday. Forecast soundings suggest saturation sufficient to
produce snow for most of the event, until Monday midday or afternoon
when some mid level drying is noted as CAA begins in the wake of
the mid level trough. Previous 24 hours focused higher snow
amounts over parts of central Wisconsin, while todays today
information suggests a more uniform 2 inch amount across more of
the area.

Strong cold air advection on northwest winds in the wake of the
low then turn the attention to Lake Superior snow showers Monday
night into Tuesday night. Height 850 mb temps fall to -20 C Monday
night to increase the delta T/s.

Confidence fades later in the week as progs divert on timing and
location of additional clipper systems dropping over the area in
the northwest flow.

.AVIATION...for 18Z TAF Issuance
Issued at 1148 AM CST Sat Dec 9 2017

An upper level trough to the east of Wisconsin at midday will
continue to move away from the state, taking system snow and
clouds along with it. Cold air passing over the warmer waters of
Lake Superior was bringing clouds to much of the forecast area
west of the Fox Valley, and there were some snow showers and
flurries across north central Wisconsin. Mainly VFR conditions
prevailed in the east, except for Door County, and it was mainly
MVFR in central and north central Wisconsin. Winds should
gradually back and bring and end to snow across the north by
evening as a weak surface ridge reaches Wisconsin. Most locations
should improve to VFR during the afternoon or early evening but
MVFR ceilings may return to northern Wisconsin later in the night
as a weak surface boundary approaches from the north.

Gusty northerly winds will diminish toward sunset as the surface
gradient weakens and winds decouple.



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