Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 212103
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
303 PM CST Sun Jan 21 2018

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Monday
Issued at 303 PM CST Sun Jan 21 2018

Another mild across the area with temperatures in the middle 30s
to middle 40s. Several issues to deal with for this afternoon
into early tonight. Dense fog formed this morning from near
Oshkosh to Manitowoc. The fog has not lifted and will probably not
lift until later tonight. A dense fog advisory was issued for
Winnebago, Calumet and Manitowoc counties until 6 am. Also, dense
marine fog has spread northward across the area as far north as
Northport/Deaths Door. Issued a dense marine fog advisory until
6 am Monday for this region.

The impending winter storm is expected to bring light precipitation
to the area later tonight, then the heaviest precipitation is
expected to fall Monday into Monday night. Bufkit soundings at
Green Bay stradling the line between rain and heavy snow. To
complicate matters, road temperatures will drop to or a few
degrees above freezing tonight. Current thinking is clouds and
easterly flow will keep air temperatures several degrees above
freezing, thus expecting rain/snow mix across the Fox Cities east
to the lakeshore. For locations just north and west of the Valley,
some freezing rain and snow is expected as air and road
temperatues will hover around the freezing mark. Any slight
shift in the 850mb thermal gradient could make a significant
difference in snow and ice amounts along with precipitation types.

The main storm system will move across southern Wisconsin Monday
afternoon. Models are in fairly good agreement with amount of
warm air working into the region. However, any deviation to the
south would have significant impacts on the snow totals from
Wisconsin Rapids into the Fox Valley and lakeshore region. Have
posted winter storm warnings from Marathon county into Marinette
county north to the Michigan border. Snow totals in this region
should range from 6 to 11 inches with minor ice accumulations
of a tenth or two. Winter weather advisories have been posted
just south of the warning area for 3 to 6 inches of snow along
with ice accumulations of a tenth or two. Presuming that the
mild stretch of mild air along with temperatures a few degrees
above freezing should keep the precipitation from freezing across
the Fox Valley and lakeshore region based on the road temperature
forecast. It will be close! Gusty northeast/north winds expected
on Monday.

.LONG TERM...Monday Night Through Sunday
Issued at 303 PM CST Sun Jan 21 2018

Focus will be on the winter storm Monday night, including
precipitation type, snow and ice accumulations, and headlines.

Models are in good agreement with a low pressure system moving
from the WI/IL border region to Lake Huron Monday night. Moderate
to heavy snow is expected to be ongoing across north central and
far northeast WI during the evening, as the deformation zone and
RRQ of an upper level jet pull through. A crosshairs signature
(core of strongest lift coincident with dendritic growth zone) is
evident in this area early in the evening, so inch an hour
snowfall rates are possible. Additional accumulations of 3 to 5
inches are expected over the far north. A mid-level dry slot over
central and east central WI should eventually lift far enough
north to temporarily change snow over to light freezing rain or
freezing drizzle. A secondary band of precipitation associated
with the passing upper low and H8 circulation may get close to
east central WI late, but models keep the main impacts to our
south. Although light snow and ice accumulations will still be
possible overnight, we will keep the end time of the winter
weather headlines at midnight.

Northeast to north winds will be quite strong Monday night,
especially in east WI. A gale warning is in effect for the Bay
and northern Lake Michigan through early evening.

High pressure and quiet weather is expected for the mid to late
part of the work week, with a nice warmup anticipated on Friday.
A cold front will bring a chance of rain or snow showers Friday
night into Saturday.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1054 AM CST Sun Jan 21 2018

Low clouds and fog continue across portions of the southern
Fox Valley early this afternoon. Otherwise, a winter storm will
approach the area tonight, bringing increasing chances for snow
and mixed precipitation. Mainly a rain/snow mix towards 12z
at KGRB/KATW/KMTW. Towards KY50/KISW/KMFI, will probably be
a mix of freezing rain/sleet/snow. To the north, it should be
mainly light snow. Expect CIGS and VSBY`s to drop through the
night with poor flying conditions expected. Mainly rain is
expected across the Fox Valley/lakeshore and a rain/snow mix
across Door county and across Wood/Portage counties by late
morning on Monday. The precipitation is expected to change
over to all snow over the rest of the region Monday
afternoon into Monday evening as colder air works into the
region. Tight gradient in snow amounts with locations
north of a Wausau to Marinette line could see over 6 inches
of snow with only a few inches south of highway 10.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 6 AM CST Monday for WIZ048>050.

Winter Weather Advisory from 3 AM Monday to midnight CST Monday
night for WIZ020-022-031-035>037-074.

Winter Storm Warning from 3 AM Monday to midnight CST Monday
night for WIZ030.

Winter Storm Warning from 6 AM Monday to midnight CST Monday
night for WIZ005-010>013-018-019-021-073.
&&

$$

SHORT TERM.....Eckberg
LONG TERM......Kieckbusch
AVIATION.......Eckberg



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