Winter Weather Advisory 20, NWS Green Bay, WI

Brown County, WI, Calumet County, WI, Door County, WI, Florence County, WI, Forest County, WI, Kewaunee County, WI, Langlade County, WI, Lincoln County, WI, Manitowoc County, WI, Marathon County, WI, Marinette County, WI, Menominee County, WI, Oconto County, WI, Oneida County, WI, Outagamie County, WI, Portage County, WI, Shawano County, WI, Vilas County, WI, Waupaca County, WI, Waushara County, WI, Winnebago County, WI, Wood County, WI

Area Forecast Discussion
National Weather Service Green Bay WI
1059 PM CST Sat Dec 25 2021

Updated aviation portion for 06Z TAF issuance

.SHORT TERM...Tonight and Sunday
Issued at 137 PM CST Sat Dec 25 2021

Main forecast issue will be the potential of light snow across
northern WI tonight.

The 19Z MSAS surface analysis showed a very weak area of high
pressure over eastern WI and a second high pressure over south-
central Canada. Visible satellite imagery indicated a band of mid
clouds streaming east across WI with surface reports over central
MN of light snow.

A mid-level shortwave trough is forecast to move across northern
sections of the Great Lakes region tonight, accompanied by the
left exit region of the upper jet. Low-level moisture is lacking
with this system, thus do not anticipate much in the way of
accumulation. In fact, have limited pops to the northern third of
WI with perhaps up to an inch over Vilas County. Otherwise, drier
air will try to lift north into WI overnight and bring some
decrease in clouds to central/east-central WI. Min temperatures to
range from 10 to 15 above north-central WI, lower to middle 20s
near Lake MI.

This drier air will hold over the area through Sunday morning,
however clouds are expected to increase Sunday afternoon ahead of
the next system moving into the central Plains. East winds will
also be on the increase Sunday afternoon as the pressure gradient
tightens between the surface low and high pressure over Ontario.
Gusts could approach 20 mph by late in the day. Max temperatures
to range from the middle to upper 20s north, upper 20s to lower
30s south.

.LONG TERM...Sunday Night Through Saturday
Issued at 137 PM CST Sat Dec 25 2021

A well-developed low pressure system will move northeast out of
Colorado on Sunday and bring a mix of rain and snow to northeast
Wisconsin starting Sunday evening and lasting through Monday
morning. It continues to look like dry air will work into the
mid-levels of the storm system over our region from late Sunday
night through midday Monday when precip type will transition to a
very light rain/freezing rain or drizzle. Before the transition
occurs, though, enough precip should fall for a few inches of snow
accumulation. Highest accumulations, likely in the range of 2-4
inches, will fall over northern WI. Lower amounts of 1-2 inches,
plus some minor ice accumulations, are likely over central WI. In
addition to the wintry precip, windy conditions will develop over
portions of central to east-central WI on Monday afternoon with
gusts to 35 mph. High pressure then will build into the region on
Monday night as winds slacken.

After a brief period of dry weather on Tuesday, a similar storm
system will rapidly push into the region by Tuesday afternoon and
deliver more snow to north-central WI and a wintry mix to the
remainder of the region. Behind this second system, though,
colder air and blustery conditions will follow in for Wednesday
and Thursday. Sub-zero lows will be possible across the
northwoods.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1059 PM CST Sat Dec 25 2021

VFR conditions prevailed across the region late this evening as
dry air prevented MVFR cigs from reaching far north-central WI
associated with a nearby weakening upper-level disturbance.
Despite the dry air, MVFR cigs may briefly reach some locations in
far north-central WI before Sunday morning.

VFR conditions are expected through early Sunday evening before
the next system arrives. This stronger weather system will spread
from southwest to northeast Sunday evening through Monday morning
and bring IFR/LIFR conditions with snow, a wintry mix, and gusty
east winds of 20 to 30 kts.
&&

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

SHORT TERM.....Kallas
LONG TERM......ML
AVIATION.......Hykin

Hazardous Weather Outlook
National Weather Service Green Bay WI
202 PM CST Sat Dec 25 2021

WIZ005-010>013-018>022-030-031-035>040-045-048>050-073-074-262015-
Vilas-Oneida-Forest-Florence-Northern Marinette County-Lincoln-
Langlade-Menominee-Northern Oconto County-Door-Marathon-Shawano-
Wood-Portage-Waupaca-Outagamie-Brown-Kewaunee-Waushara-Winnebago-
Calumet-Manitowoc-Southern Marinette County-
Southern Oconto County-
202 PM CST Sat Dec 25 2021

This Hazardous Weather Outlook is for north-central and northeast
Wisconsin.

.DAY ONE...Tonight

Slippery road conditions are possible across northern Wisconsin
due to light snow accumulations up to 1 inch.

.DAYS TWO THROUGH SEVEN...Sunday through Saturday

Accumulating snow remains likely from Sunday night into Monday
morning. Snowfall totals could range from 1 to 3 inches across
the region, with 2-4 inch amounts over north-central Wisconsin.
Minor ice accumulations less than 0.10 inches will also be
possible. Expect hazardous travel Sunday night into Monday
morning, including the Monday morning commute.

Accumulating snow is also possible on Tuesday afternoon into
Tuesday night that could lead to hazardous travel.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed tonight.

LMZ521-522-541>543-262015-
The Bay of Green Bay south of a line from Cedar River MI to Rock
Island Passage-Lake Michigan from Washington Island to Sheboygan-
202 PM CST Sat Dec 25 2021

This Hazardous Weather Outlook is for portions of northwest Lake
Michigan and the waters of Green Bay.

.DAY ONE...Tonight

The probability of widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Sunday through Saturday

The probability of widespread hazardous weather is low.

AK/ML