824
FXUS63 KGRB 021039
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
539 AM CDT Thu Apr 2 2026

Forecast discussion for routine morning forecast issuance

.KEY MESSAGES...

- A wintry mix of freezing rain, sleet, snow, and rain is expected
  through this evening, with significant ice accumulations from
  central to northern WI. Power outages, tree damage, and
  extremely hazardous travel are expected, especially west and
  north of the Fox Valley. There will be significant impacts to
  the morning commute regionwide, and to the evening commute
  across northern WI. Ice Storm Warnings, Winter Storm Warnings,
  and Winter Weather Advisories remain in effect.

- Thunderstorms are also possible late this afternoon and evening,
  and may become strong to severe in the Fox Valley and lakeshore
  areas.

- Heavy rainfall, mixed precipitation, and thunderstorms are possible
  Friday night into Saturday. Wintry impacts should be focused
  over northern WI. A Winter Storm Watch has been issued.

- Flooding concerns arise this weekend into early next week following
  the passage of the two moisture rich systems.

&&

.DISCUSSION...
Issued at 539 AM CDT Thu Apr 2 2026

Ice/Winter Storm Today through this Evening...The mixed
precipitation has arrived this morning from the southwest as a
result of WAA and increasing f-gen over the area ahead of an
approaching Colorado Low. The freezing rain, sleet, snow, and
rain is expected to continue lifting northeast throughout the day.
As warmer air lifts into the area from the south, a transition to
all rain is expected across central and east-central WI by this
afternoon, while the wintry mix continues across northern WI. As
the surface low tracks across the forecast area late this
afternoon into this evening, models indicate the potential for
convection and thunderstorms to develop over the Fox Valley and
lakeshore areas. Meanwhile, CAMs and forecast soundings indicate
locations across northern WI will still be dealing with freezing
rain through late this evening. Therefore, wintry impacts should
end by 18z today for most areas south of Hwy 64, but temperatures
lingering near the freezing mark over far northern WI will keep
mixed precip impacts in place through the evening.

East winds gusting to 30 to 40 mph this morning will likely lead
to power outages and broken tree limps, especially where they
overlap with the heavier ice accumulations.

Including what has already fallen this morning, total ice
accumulations have increased across portions of far northern WI,
but generally, are still in the 0.25 to 0.50 inch range for
locations north and west of the Fox Valley, with 0.10 to 0.25
inches elsewhere. Combined total snow and sleet accumulations are
still in the 1 to 2 inch range, mainly across northern WI, but
little to no impacts are anticipated from the snow/sleet.

Changes to headlines: Added Oneida and Forest counties to the Ice
Storm Warning due to the increased signal for ice accumulations
over 0.25 inches. Otherwise, extended the end times for locations
across the north to account for the lingering freezing rain
impacts expected into the late afternoon and through the evening.

Severe Weather Potential Late this Afternoon and Evening...Despite
the track of the surface low being a little further southeast,
there is still some potential for the warm sector to reach into
portions of east-central WI late this afternoon and evening.
While surface based instability looks to remain just south of the
forecast area, MUCAPE is expected to increase to 300-600 j/kg.
Strong shear (0-6 km bulk shear of 50-65 knots) and strong winds
aloft (850 mb winds of 45 to 55 knots) could make up for the lack
of instability, leading to damaging winds being the primary
threat if strong or severe storms can make it into the area,
mainly during the 6 pm to 10 pm time frame. Hail would be a
secondary threat.

Another Significant System Late Friday through Saturday...Another
Colorado Low is expected to impact the region Friday night into
Saturday. The signal for freezing rain has increased across
northern WI, with ensemble probabilities for 0.25 inches of ice of
40 to 50%. Given the nature of this system and the increasing
icing signal, a Winter Storm Watch was issued for northern WI.
This system will also bring the potential for heavy rainfall and
thunderstorms.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1039 PM CDT Wed Apr 1 2026

Conditions will deteriorate after midnight tonight as a powerful
low pressure system impacts the region. VFR ceilings late this
evening will transition to MVFR/IFR between 06z and 10z as a
wintry mix overspreads the terminals from southwest to northeast.

Expect a prolonged period of hazardous flight conditions through
Thursday morning. Significant icing and sleet accumulations are
likely, especially at RHI, AUW, and CWA, where heavy sleet and
freezing rain will persist longest. A transition to rain is
expected from south to north Thursday afternoon as warmer air
arrives, though IFR ceilings will likely remain through the end of
the period. Some areas from RHI to the U.P. border may remain as a
wintry mix until the end of the TAF period.  LLWS is forecast at
all sites tonight through Thursday afternoon with 40-60 kt winds
at 2k ft. Gusty east to northeast surface winds of 20-30 kt will
also persist. Confidence is high in the transition to IFR, but
medium on the exact timing of the changeover from freezing to
liquid precipitation.

With passage of the surface low, there will be a chance of
thunderstorms between 02/23Z-03/03Z across east central Wisconsin.
Have added a prob30 to show the most probable timing. If
thunderstorms develop, gusty winds and small hail will be
possible. While most areas will see rain by this point, areas near
and north of RHI may still see a wintry mix through the evening.

&&

.HYDROLOGY...
Issued at 539 AM CDT Thu Apr 2 2026

The combination of today`s and Friday night-Saturday`s well-
saturated systems will lead to flooding concerns, with a signal
for river and stream rises this weekend into early next week
across the forecast area. Minor flooding would likewise be
possible in low-lying and poor drainage areas.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 1 AM CDT Friday for WIZ005-012-013.

Winter Storm Watch from Friday evening through Saturday morning
for WIZ005-010>013-018-019.

Ice Storm Warning until 1 AM CDT Friday for WIZ010-011.

Ice Storm Warning until 4 PM CDT this afternoon for WIZ018-019.

Ice Storm Warning until 1 PM CDT this afternoon for WIZ020-030-
031-035>037.

Winter Storm Warning until 1 PM CDT this afternoon for WIZ021-
073-074.

Winter Weather Advisory until 10 AM CDT this morning for WIZ022-
039-040-048>050.

Ice Storm Warning until 10 AM CDT this morning for WIZ038-045.
&&

$$

DISCUSSION.....Kruk
AVIATION.......MPC
HYDROLOGY......Kruk

NWS GRB Office Area Forecast Discussion