Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 032336
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
536 PM CST Fri Dec 3 2021

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Saturday
Issued at 233 PM CST Fri Dec 3 2021

A mix of light rain and light snow was reported this afternoon
across far northeast Wisconsin. Otherwise, skies were cloudy with
some patchy fog across central Wisconsin. Temperatures this
afternoon were in the 30s.

For the rest of the afternoon, the light precipitation will come
to an end by this evening. Any patchy fog will also dissipate as
winds shift to the west with drier air advecting into the area.
For tonight, westerly winds will be on the increase and clouds
on the decrease as temperatures drop into the upper teens and
20s. With the light precipitation this afternoon and temperatures
falling below freezing, there could be a few icy spots tonight on
roads, bridges and sidewalks across northern Wisconsin.

On Saturday, the blustery conditions will continue through much of
the day before gradually subsiding later in the afternoon. High
temperatures will be in the upper 20s far north with 30s
elsewhere.

.LONG TERM...Saturday Night Through Friday
Issued at 233 PM CST Fri Dec 3 2021

The main focus of the long-term portion of the forecast, will be the
potential for a winter storm to move through the western Great
Lakes. This storm will have the potential to produce several inches
of snow across portions of northern WI, to the north of Highway 29
and heaviest along/near the the UP border. Still varying solutions
on the exact trek of the storm system.

Saturday night through Monday: Models continue to advertise a potent
piece of energy pushing through the area this weekend along with an
intensifying surface low. The associated upper-level support is
currently offshore of the northwestern CONUS and will be sampled
better late tonight into early Saturday morning with a more vast
array of observations. There continues to be considerable variances
in the exact track of the low pressure system, which will have
significant impacts on exact location of the heaviest snow along
with any lake effect/enhanced snow on the back side of the system.
The EC/GFS take the low along the WI/UP border Sunday night, while
the NAM/UKMET are much farther north, taking the surface low north of
the WI/UP border. Ensemble guidance supports the GFS/EC solution,
which was favored for the forecast issuance. The continued variation
in model solutions has limited confidence enough to hold off on a
winter headline; however, to highlight the potential and uncertainty
have decided to issue a special weather statement.

The overall trend remains that a low is expected to intensify over
the northern Plains Saturday night before shifting eastward to
central MN Sunday morning around 15Z. Ahead of this feature,
southerly flow will advect ample deep-layer moisture northward from
the Gulf. In addition to the increasing moisture, WAA will lead to
increased isentropic upglide through much of the day Sunday. Aloft,
much of the area will remain in the right-entrance region of an
upper-level jet. All of this leads to a good chance for
precipitation late Saturday night through much of the day Sunday.
Thermal profiles would indicate much of the area will see snow at
the beginning of the event; however, surface temperatures are
expected to warm across much of central and far northeast Wisconsin
throughout the day. This will allow the precipitation to transition
to rain for those locations during the afternoon. The heaviest snow
during this time period is expected to be across the Northwoods,
where there is a better chance of seeing up 6 inches of snow from
early Saturday morning through Saturday evening. The rest of the
area is expected to see only a couple inches before temperatures warm
above freezing.

As the moisture begins to strip out of the system Sunday evening as
the dry slot passes through the area, expect a transition over to
drizzle or light freezing drizzle across much of the area, the
exception will be across the Northwoods where the deeper moisture
has a better chance of remaining in place. With that said, a farther
north low trek would allow the dry slot an warmer air to impact that
area as well. Colder air will advect into the area later Sunday
evening and the linger through the day Monday. Depending on the
exact low placement, lake effect snow will develop and impact Vilas
and Oneida Counties throughout the day Monday. 850mb temperatures
are expected to drop to -20C or colder through Monday afternoon,
which is more than favorable for lake effect/enhanced snow. The cold
air advection will allow gusty winds to mix down through much of the
day, which will lead to some blowing and drifting snow, especially
across the northwoods.

Rest of the forecast: Much colder air will arrive for Monday night
through mid week. In fact many location will see temperatures
dropping into the single digits above and below zero for overnight
low temperatures. High temperatures will be much colder as well
Monday and Tuesday with highs only in the teens and 20s. Some
moderation can be expected toward the end of the work week. The next
weather maker will brush through the area Tuesday night into
Wednesday, brining the next chance of light snow to central and
east-central Wisconsin.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 535 PM CST Fri Dec 3 2021

Clearing skies are expected tonight as a cold front exits the
area.

Lake effect clouds could produce MVFR ceilings Saturday north of
an ARV to EGV to SAW line with mostly clear skies elsewhere. Good
flying weather is expected Saturday evening.

An approaching low pressure system may bring IFR conditions and
snow to Central and North Central Wisconsin late Saturday night
and Sunday, with a mixture of snow and rain across the East
Central part of the state. Windy conditions are likely late Sunday
night and Monday with gusts over 40 knots possible.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM.....Eckberg
LONG TERM......Cooley
AVIATION.......RDM


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