NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 011201
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
701 AM CDT Wed Apr 1 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- A wintry mix of freezing rain, sleet, snow, and rain is expected
  to bring significant ice and sleet accumulations mainly to
  central and northern WI tonight through Thursday. Power outages,
  tree damage, and extremely hazardous travel are expected for
  central and northern WI, with impacts to the Thursday morning
  commute. Ice Storm Warnings, Winter Storm Warnings, and Winter
  Weather Advisories have been issued.

- Thunderstorms will also be possible Thursday into Thursday
  evening, and may become strong to severe in the Fox Valley and
  lakeshore areas.

- Heavy rainfall, mixed precipitation, and thunderstorms are
  possible late Friday into Saturday. Wintry impacts remain
  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 529 AM CDT Wed Apr 1 2026

Significant Winter Storm Tonight into Thursday...A Colorado Low
brings the next chance for precip tonight through Thursday
evening in the form of all precip types. Although there is still
some disagreement in low track, models have still come into better
agreement with the low tracking northeast from eastern CO to
eastern Upper MI tonight through Friday. This paints the track of
the low moving directly overhead Thursday night. Prior to the low
moving overhead, strong WAA/isentropic lift and f-gen, paired with
an abnormally moist atmosphere (PWATs increasing to 1-1.25
inches) due to surging Gulf moisture, will result in widespread
heavy precip from tonight into Thursday. As the precip lifts
northeast over the area tonight into Thursday morning, surface
temps hovering around freezing with a decent elevated warm layer
would support mainly sleet and freezing rain. The elevated warm
layer will stick around through Thursday, but surface temps will
warm above freezing from south to north late Thursday morning into
Thursday afternoon, causing a switch to all rain. All
precip will come to an end by late Thursday night with the
departure of the low.

Issued an Ice Storm Warning for portions of central WI, where
confidence is highest for ice accumulations of 0.25 inch or
higher. Across the north and far northeast WI, issued a Winter
Storm Warning where a mixture of snow and heavy sleet, combined
accumulations of 1 to 2 inches, and ice accumulations up to 0.25
inch are expected. For locations in east-central WI and along the
lakeshore, issued Winter Weather Advisories as the potential for
significant icing or sleet is lower, but disruptions to travel and
possible power outages remain a possibility. Northeast to east
winds gusting to 30-35 mph across the entire forecast area will
also play a role in potential impacts from icing, including power
outages and damage to trees. The main area of uncertainty is in
the advisory areas with how surface temps will behave tonight into
early Thursday, including road temps, which may stay a little
above freezing, reducing the hazards on roads, and keeping ice
accumulations to mainly elevated surfaces. Another consideration,
area-wide, is the high precip rate, making it harder to have
freezing rain accumulate on surfaces.

By late Thursday afternoon, a chance for thunderstorms will arise
in east-central WI as temps look to warm into the upper 40s to mid
50s. While there appears to be enough instability and shear to
generate a marginal chance of strong/severe storms, the severe
threat will ultimately depend on the exact track of the surface
low and if portions of east-central WI will be in the warm sector.
If these strong storms develop, hail and damaging winds will be
the main threats, along with brief heavy downpours.

Another Significant Storm Expected Late in the Week...Another
Colorado Low is expected to impact the region late Friday into
Saturday. This system will also bring warmer and very moist air to
the region, as the Gulf will still be open. Similar to the
midweek system, there are uncertainties in low track and thermal
profiles, but northern WI appears to have the greatest chance of
having significant wintry impacts with this system, mainly in the
form of freezing rain/icing.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 701 AM CDT Wed Apr 1 2026

MVFR cigs prevailed across the region this morning as low-level
winds remained out of the northeast, allowing for moisture off of
Lake Superior to generate a stratus cloud deck. The main question
is how long these MVFR cigs will prevail. Across the east-central
and north-central WI TAF sites, there are signs these cigs will
continue through the late morning before scattering out. For the
central WI TAF sites, cloud trends would suggest the MVFR cigs to
scatter out by mid-morning. VFR mid-level clouds will then
prevail across all terminals through this evening before a potent
system approaches from the southwest.

Occurring mainly after 06z Thu, cigs will lower to MVFR with the
arrival of the mixed precipitation from the system, including
sleet, freezing rain, snow, and rain. Towards the end of this TAF
period and through at least Thursday afternoon, IFR/LIFR
conditions will become widespread with the mixed precipitation
continuing.

Northeast to east winds are expected today, gusting to 20 to 25
kts. Gusts may approach 30 kts after 06z Thursday at times for the
central and east-central WI TAF sites as well.

&&

.HYDROLOGY...
Issued at 529 AM CDT Wed Apr 1 2026

Despite the uncertainty in p-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 2 AM to 10 PM CDT Thursday for WIZ005-
010>013.

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

Winter Storm Warning from 2 AM to 1 PM CDT Thursday for WIZ021-
073-074.

Winter Weather Advisory from 2 AM to 10 AM CDT Thursday for
WIZ022-039-040-050.

Ice Storm Warning from midnight tonight to 10 AM CDT Thursday
for WIZ035>037.

Winter Weather Advisory from midnight tonight to 10 AM CDT
Thursday for WIZ038-045-048-049.
&&

$$

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