Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 032047

Area Forecast Discussion
National Weather Service Green Bay WI
247 PM CST Sat Dec 3 2016

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Sunday
Issued at 246 PM CST Sat Dec 3 2016

The latest rap analysis and satellite/radar imagery show high
pressure stretching from northern Ontario, across the Great Lakes to
the Gulf Coast early this afternoon.  Low clouds have shown little
signs of dissipating so far today, due to a sharp inversion at 850mb
based off the 12z GRB sounding.  Still some spotty flurries showing
up on radar, and will keep a mention of flurries to the end of the
afternoon. Looking upstream, light rain and snow is moving northeast
over Nebraska and Kansas early this afternoon ahead of the next
shortwave trough.  As this trough moves into the western Great Lakes
on Sunday, snow accumulation potential and impacts are the main
forecast concerns.

Tonight...High pressure will be sliding to the east as height falls
occur over the northern Plains ahead of the next shortwave.  Because
of thermal troughing and a sharp inversion across the state, the low
clouds are going to be tough to dislodge.  Minor warm advection does
occur late and models do show low level moisture thinning out after
midnight, but think the low clouds will likely stick around through
the evening. But even if the low clouds break up, mid-clouds will be
arriving from the southwest ahead of the next trough.  Moisture
looks to become deep enough for light snow to push into central
Wisconsin after about 3 am which could yield a tenth or two by
daybreak.  With the ample cloud cover, increased min temps a couple

Sunday...Light snow will continue to spread northeast across the
region during the morning hours and then continue through the
afternoon. Forcing in the form of isentropic ascent and mid-level
fgen only looks modest, but the shortwave does become negatively
tilted as it swings through the region during the afternoon.
Moisture looks a little more robust over eastern WI than farther
west, but complications arise from having max temps projected to
rise above freezing, partially due to a southeast and south wind
through the day. Thinking is that wind speeds may not be strong
enough to have much of an impact over the Fox Valley, but will
likely have some influence on ptype along the Lakeshore where rain
could mix with snow from the late morning through the afternoon. But
with temps around 33 or 34 in the Fox Valley, think snow will
partially melt on roadways, and that could still create hazardous
travel. Given snow amounts of 2-3 inches from the Fox Valley to
central WI, will issue a winter weather advisory for snow.  Amounts
will be less along the lakeshore and also over northern WI.

.LONG TERM...Sunday Night Through Saturday
Issued at 246 PM CST Sat Dec 3 2016

Winter like cold temperatures will arrive by the
middle of the week and continue through the remainder of the
forecast period.

Some light snow will be ending Sunday night as the upper trough
exits the area. The a flat upper ridge moves in for Monday and
Monday night with dry weather. Upper troughs passing by to our
north and south could produce some light snow Tuesday afternoon
or evening but there is not much moisture available, so snow
amounts should be a dusting to an inch.

A sharp upper trough drops south towards the region Wednesday and
moves slowly across the Great lakes Thursday and Friday. Arctic
high pressure builds in as the upper flow becomes northwest bringing
the coldest air of the season to Wisconsin. The air is not expected
to be super cold, just 5 to 10 degrees colder than normal. It will,
however, feel very cold to many people as the weather has been so
mild during the last two months. Snowfall of any significance seems
to be limited to the snowbelt areas in the far north Thursday
night and Friday.

.AVIATION...for 18Z TAF Issuance
Issued at 1145 AM CST Sat Dec 3 2016

A strong winter inversion will lead to mvfr clouds hanging around
into the evening.  Some suggestions that cigs will improve to vfr
later in the evening or early overnight, but not entirely sold on
that idea.  Otherwise, the most significant impacts revolve around
light snow arriving Sunday morning.  Expectations are for the light
snow to spread across the region during the morning hours, dropping
ceilings and visibilities to ifr/lifr with amounts of 1 to 3 inches.
Snow will continue through the afternoon before ending in the

Winter Weather Advisory from 9 AM to 6 PM CST Sunday FOR WIZ031-

Winter Weather Advisory from 6 AM to 6 PM CST Sunday FOR WIZ030-


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