712
FXUS63 KGRB 012021
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
321 PM CDT Wed Apr 1 2026

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- A wintry mix of freezing rain, sleet, snow, and rain is
  expected, with significant ice and sleet accumulations over most
  of central, north central and far northeast WI late tonight
  through Thursday. Power outages, tree damage, and extremely
  hazardous travel are expected, especially west and north of the
  Fox Valley. Theree will be significant impacts to the Thursday
  morning commute regionwide. Ice Storm Warnings, Winter Storm
  Warnings, and Winter Weather Advisories have been issued.

- Thunderstorms will also be possible later Thursday afternoon and
  Thursday 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.

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

&&

.DISCUSSION...
Issued at 321 PM CDT Wed Apr 1 2026

Dry conditions prevailed across the region this afternoon, with
low clouds coming off Lake Michigan into east central WI, and high
clouds thickening elsewhere. Low pressure was developing over
Colorado, ahead of sharp upper level trough. This strengthening
low pressure system will impact the region with significant sleet
and ice accumulations as it approaches late tonight into Thursday.
The warm sector of this system could reach east central WI,
setting the stage for a brief period of severe thunderstorms
during the very late afternoon and evening.

Winter Weather Headlines Late Tonight into Thursday...Overall,
sleet and ice accumulations have not changed drastically. Still
expect 1/4 to 1/2 inch of ice over the roughly the southwest half
of the forecast area, with 1/2 inch to 1 1/2 inches of sleet over
the far north central and far northeast WI. East winds gusting to
30 to 40 mph may lead to power outages, especially where they
overlap with the heavier ice accumulations. Wintry impacts should
end by 18z/Thu for most areas south of Hwy 8, but temperatures
lingering near the freezing mark over far northern WI will keep
mixed precipitation in the forecast through the afternoon/evening.

Changes to headlines: Start times were delayed by a few hours due
to a lingering dry wedge around 850 mb. In addition, Waushara and
Outagamie counties were upgraded to an Ice Storm Warning, given
expected ice accumulations of two tenths to four tenths of an inch.

Severe Weather Potential late Thursday Afternoon and Evening...
The track of the surface low may bring the warm sector of the
system through east central WI late Thursday afternoon and
evening. While surface based instability is quite weak, MUCAPE
is expected to increase to 300-600 j/kg. Strong shear (0-6 km bulk
shear of 50-65 knots and 0-3 km SRH of 200-300) and strong winds
aloft (850 mb winds of 45 to 55 knots) could make up for the lack
of instability, leading to potential for a bowing line segment
moving through the Fox Valley and lakeshore areas between 6 pm and
10 pm. Damaging winds should be the primary severe threat.

Another Significant Storm Expected Late in the Week...Another
Colorado Low is expected to impact the region Friday night into
Saturday. This system will also bring potential for heavy
rainfall and thunderstorms, and a wintry mix (including possible
significant ice accumulations) over mainly northern WI.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1214 PM CDT Wed Apr 1 2026

MVFR were eroding over NC/C WI, but were holding tough in east
central WI. Given that clearing was noted upstream over central
Lake Michigan, suspect MVFR ceilings should break up in MTW by
mid to late afternoon.

After a period of VFR conditions over most of the area this
afternoon and evening, conditions will deteriorate rapidly as a
mix of sleet and freezing rain overspreads the area from SW to NE
between 06z-10z/Thu. Significant sleet and ice accumulations will
occur over much of the area late tonight into Thursday morning,
before an influx of warmer air at the surface causes a changeover
to rain from south to north. Flight conditions will lower to
IFR over most of the area once the steadier/heavier mixed
precipitation arrives.

Gusty northeast to east winds are expected through the TAF period,
and some LLWS will develop in NC/C WI late tonight into Thursday
morning.

&&

.HYDROLOGY...
Issued at 321 PM CDT Wed Apr 1 2026

Despite the uncertainty in precipitation types, the two well-
saturated systems this week 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 from 5 AM to 10 PM CDT Thursday for WIZ005-
010>013.

Ice Storm Warning from 3 AM to 1 PM CDT Thursday for WIZ018>020-
030-031.

Winter Storm Warning from 3 AM to 1 PM CDT Thursday for WIZ021-
073-074.

Winter Weather Advisory from 3 AM to 10 AM CDT Thursday for
WIZ022-039-040-050.

Ice Storm Warning from 1 AM to 10 AM CDT Thursday for WIZ035>038-
045.

Winter Weather Advisory from 1 AM to 10 AM CDT Thursday for
WIZ048-049.
&&

$$

DISCUSSION.....Kieckbusch
AVIATION.......Kieckbusch
HYDROLOGY......Kieckbusch

NWS GRB Office Area Forecast Discussion