Green Bay, Wisconsin 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

618
FXUS63 KGRB 302257
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
557 PM CDT Sun Mar 30 2025

Updated aviation portion for 00Z TAF issuance
and new information added to update section

.UPDATE...
Issued at 543 PM CDT Sun Mar 30 2025

The potential for significant icing is ending as the warm layer
aloft erodes and precipitation changes to sleet/snow from
northwest to southeast. Have cancelled the Ice Storm Warning and
just gone directly to the Winter Storm Warning (which was set to
begin at 7 pm in most areas). Hazardous travel will develop as
snow and colder temperatures shift east this evening. Deformation
zone snows are expected to impact the region this evening, and
will gradually end in eastern WI late tonight. Snowfall amounts
of 2 to 4 inches are expected most areas, with only an inch or two
in the Fox Valley/lakeshore areas. There is concern for
additional power outages over northern WI as trees laden with
ice/snow and winds gusting to 25 to 35 mph cause more branches to
break and fall on power lines.

&&

.KEY MESSAGES...

- Rain/freezing rain will transition to snow from northwest to
  southeast this afternoon into tonight. Additional ice
  accumulations up to 0.25 inches is anticipated across the
  Northwoods through early this evening before transitioning to
  snow. Snow accumulations of 1 to 4 inches is forecast for
  locations north and west of the Fox Valley. Up to 1 inch of snow
  and a light glaze of ice is forecast for locations in the Fox
  Valley and lakeshore areas. Additional power outages and tree
  limb damage is anticipated for locations mainly across the
  Northwoods due to the recent icing, wet snow, and gusty winds
  expected through tonight.

- The recent, ongoing, and any additional widespread
  rainfall/precipitation this week will lead to rising river and
  stream levels and minor flooding for some locations.

- Another impactful period of precipitation is likely Tuesday into
  Wednesday with potential for accumulating snowfall, rainfall,
  and thunderstorms.

&&

.DISCUSSION...
Issued at 440 PM CDT Sun Mar 30 2025

Short Term...Tonight and Monday

The ongoing wintry precipitation associated with a low pressure
system moving across the Midwest remains to be the main focus from
this forecast period.

This evening through Monday morning...As of this afternoon, the
surface low pressure system was located over southern Lake MI and
slowly tracking northeast. Meanwhile, the deformation zone and areas
of f-gen were beginning to set up over northern WI. This coincided
with a large band of precipitation over the Northwoods producing
rain, freezing rain, sleet, and snow. Another band of broken rain
and freezing rain was lifting across east-central WI this afternoon.
As the surface low continues to track northeastward this evening and
overnight, the elevated warm layer producing the wintry mix will
also move eastward across the area. This will lead to a gradual
transition to a brief period of a wintry mix to all snow from west
to east through early this evening. The snow will then come to an
end by early Monday morning.

Additional ice accumulations of 0.05 to 0.25 inches will be mainly
focused across the Northwoods and will mainly fall through early
this evening before switching over to snow. Therefore, kept the Ice
Storm Warning as is with an end time of 7 PM this evening. Minor ice
accumulations or a light glaze are possible elsewhere as the brief
period of the wintry mix moves over other locations.

Snow accumulations have increased from the previous forecast as the
surface low will deepen as it moves further northeast this evening,
allowing for a better organized deformation zone to develop over the
area. Snow accumulations of 1 to 4 inches is forecast by early
Monday morning for locations north and west of the Fox Valley with
up to an inch in the Fox Valley and lakeshore areas. In addition to
the snowfall, gusty northerly winds of 25 to 30 mph are expected
overnight. The combination of the ongoing ice impacts (several
thousands without power across the Northwoods), wet snow, and gusty
winds will likely lead to additional impacts with more power outages
and tree limb damage. Therefore, after collaborating with
surrounding offices, decided to issue a Winter Storm Warning into
this evening/night for the areas where the Ice Storm Warning remains
in effect until 7 PM. The Winter Storm Warnings will then expire
from northwest to southeast as the snow comes to an end tonight.

Monday...Surface high pressure will reign over the area for Monday,
bringing the return of sunshine. However, temperatures will remain
below normal due to the colder air filtering down with the high
pressure. Highs to range from the low 30s to low 40s.

Long Term...Monday Night Through Sunday

Another messy system is taking shape for the middle of this week,
which may bring potential impacts to the region. P-type appears to
be another challenge with this system as models have the surface low
passing somewhere over the Upper Mississippi Valley. Depending on
where the low track sets up, there is also potential for the area to
be in the warm sector, which could present the potential for
thunderstorms. There is also potential for the area to see
accumulating snow as well. With many important details to still be
worked out, be sure to monitor the forecast for changes. A less
active pattern with dry conditions is then anticipated through the
end of this week.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 543 PM CDT Sun Mar 30 2025

Poor flying conditions will continue tonight, though improving
conditions will occur from west to east later this evening and
overnight. A wintry mix of rain, freezing rain, sleet, and snow
will change to all snow from west to east this evening, then taper
off overnight. Most places will have IFR/MVFR conditions, though
LIFR vsbys will occur with the heavier snow in parts of NC/C/NE
WI. VFR and occasional MVFR conditions should return from west to
east Monday morning as high pressure builds over the area.

Gusty N winds will gust to 20 to 30 kts tonight, then gradually
subside on Monday.

&&

.HYDROLOGY...
Issued at 440 PM CDT Sun Mar 30 2025

Recent rainfall has led to saturated ground across much of the
area with rises on area rivers/streams, including near bankfull
or minor flooding at a few locations, especially in the Wisconsin
and Oconto areas. With additional precipitation continuing through
tonight and another bout of impactful rain/snow likely for mid-
week, additional river rises and elevated river levels are likely
into the coming week.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 10 PM CDT this evening for WIZ005.

Winter Storm Warning until 1 AM CDT Monday for WIZ010>012-018-
019-030-035.

Winter Storm Warning until 4 AM CDT Monday for WIZ013-020>022-
031-036-037-073-074.
&&

$$

UPDATE.........Kieckbusch
DISCUSSION.....Kruk/Kruk
AVIATION.......Kieckbusch
HYDROLOGY......Kruk