Area Forecast Discussion
Issued by NWS Green Bay, WI

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365
FXUS63 KGRB 040456
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1056 PM CST Sat Dec 3 2016

Updated aviation portion for 06Z TAF 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
degrees.

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 06Z TAF Issuance
Issued at 1054 PM CST Sat Dec 3 2016

MVFR ceilings remained across much of the region late this
evening, but were breaking up a bit over parts of central and east
central WI. Conditions will deteriorate Sunday morning as light
snow overspreads the region. Expect the snow to arrive in the
AUW/CWA areas around 12z, and RHI/GRB/ATW/MTW areas between
14z-16z. The heaviest snow should occur during the afternoon
hours, when IFR and localized LIFR conditions are likely. The snow
should start to taper off in central WI late Sunday afternoon, and
over the rest of the region in the early ti mid evening.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 9 AM to 6 PM CST Sunday FOR WIZ031-
037>039-048>050.

Winter Weather Advisory from 6 AM to 6 PM CST Sunday FOR WIZ030-
035-036-045.
&&

$$

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



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