Flooding in Wisconsin, April 16 to 22, 2026

Area Forecast Discussion
National Weather Service Green Bay WI
702 AM CDT Thu Apr 16 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

-Minor to major flooding is ongoing or forecast to occur on
 several rivers. Expect many rivers to continue rising into this
 weekend, with the greatest impacts expected on the Menominee and
 Wolf Rivers where major or record breaking flooding has been
 observed.

-Severe thunderstorm risk is increasing for Friday evening.
 Strongest storms are expected across central and north-central WI
 with all severe hazards possible.

-Thunderstorms Friday will produce locally heavy rainfall. If this
 occurs over the flood sensitive areas of central and east-central
 WI flood concerns may be exacerbated.

-Beginning Sunday a prolonged period of mostly dry weather is
 expected through at least the middle of next week.

&&

.DISCUSSION...
Issued at 217 AM CDT Thu Apr 16 2026

Short Term...Today...Tonight...and Friday

Today...

Widespread dense fog this morning will begin to dissipate after 8-9
AM with most of the fog cleared out by 10 AM. A few scattered
showers may also develop across central and east-central WI early
this morning along a stalled boundary that is snaked from Green Bay
back toward southwest WI. There may be a few rumbles of thunder, but
no stronger storms are expected. Will need to watch precipitation
rates as these showers pass over the flood sensitive areas of
central and east-central WI, but based on upstream treads don't
expect this round of precipitation to exacerbate ongoing flooding.
Any lingering precipitation should clear out early this afternoon as
a ridge builds in. This will leave dry conditions across the region
for the remainder of the day.

Severe Thunderstorms and Heavy Rain Potential Friday...

Beneath a stout cap a highly unstable airmass will be building
during the day Friday. Southerly winds will usher in a tough of 60+
dew points as far north as HWY 8 along with temperatures well into
the 70s away from Lake Michigan. A plume of 7-8 C/km mid-level lapse
rates associated with an EML will also be overspreading the region
at this time. This will result in an increase of surface based
instability to around 2000 J/kg late Friday afternoon. Forecast
soundings from across central WI also show strong low and deep layer
shear across the warm sector with 40-45 kts in the 0-6km layer and
25-30kts in the 0-1km layer. As the cap erodes late in the afternoon
isolated discrete super cells  may be able to initiate across
central WI within an area of subtly convergent surface winds. Any
storms that do develop within the warm sector will pose a large hail
(1-2") and tornado risk. Stronger and more widespread forcing will
then arrive between about 5-6 PM as a sharp cold front and upper
level trough push in from the west. With the cloud layer shear
oriented nearly parallel to the cold front storms mode will likely
transition from discrete cells to a line of storms. As this occurs
the severe wind threat will increase as will the QLCS tornado risk.
One area of uncertainty is how far east surface based storms will
persist. Surface winds will be out of the southeast most of Friday
which will keep a stable marine boundary layer across our far
eastern counties.

Along with the severe threat thunderstorms will also bring a risk
for heavy rain. PWATs in increase to near 1" Friday afternoon which
in near the 99th percentile for this time of year. HREF 90th
percentile hourly precipitation values which should be a good proxy
for hourly rainfall rates within the strongest storms are around
0.75-1" per hour. With fast flow through the cloud layer (40-45kts)
storms should not sit over one location too long, however, any areas
that see multiple storms could see upwards of 1.5-2" of rain Friday
evening into early Saturday morning. As has been the case the last
few days the greatest risk for flooding will be where there is
ongoing river flooding or across parts of central and east-central
WI where soils will still be saturated. On the back side of this
system much cooler air may result in a brief chance over to snow,
mainly across northern WI Saturday morning. However, with the ground
thawed don't expect any accumulations.

Long Term...Friday Night Through Wednesday

Saturday night through Wednesday

High pressure will build in across the western Great Lakes region
Saturday night, then slowly track east through the central Great
Lakes during the early part of next week. The high will provide a
much needed reprieve from precipitation for the area. Another cold
front is slated to track through the region Monday night or
Tuesday as the parent low tracks through southern Canada. This
system is expected to track through the region mostly dry as the
best moisture and lift will be closer to the upper level support
across southern Canada. Therefore, impacts from this upcoming
system early next week are expected to be minimal. Mainly dry
weather is expected to last through at least the middle part of
next week.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 701 AM CDT Thu Apr 16 2026

LIFR conditions will linger for another few hours across central and
eastern WI as dense fog lingers over the area. Across northern WI
clouds and fog have already cleared out as an upper ridge pushes
into the region. That clearing trend should continue east across most
of the area this morning with nearly all terminals becoming VFR for
the rest of the day. The one exception will be MTW where linger
marine fog may come onshore at times and create LIFR/IFR conditions.
Did include a TEMPO group for the return of patchy fog across east-
central WI early Friday, however, confidence in this fog is lower
than the last couple of nights.

&&

.HYDROLOGY...
Issued at 217 AM CDT Thu Apr 16 2026

Multiple rivers, namely the Wolf, Menominee, and Wisconsin Rivers,
continue to read in minor to moderate flood stage, with the
Menominee River now in major flood stage due to the additional
influence of snow melt from the Upper Peninsula. Home evacuations
are ongoing along the Wolf River. High flows and rising water levels
have also resulted in several dams being compromised or overtopped.
If you live near a river or stream, continue to monitor the latest
hydro forecasts and Flood Warnings from the National Weather Service
in Green Bay.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 10 AM CDT this morning for WIZ005-
010>013-018>022-030-031-035>040-045-048>050-073-074.
&&

DISCUSSION.....GK/Kurimski
AVIATION.......GK
HYDROLOGY......GK

Hazardous Weather Outlook
National Weather Service Green Bay WI
1019 AM CDT Thu Apr 16 2026

WIZ005-010>013-018>022-030-031-035>040-045-048>050-073-074-171530-
Vilas-Oneida-Forest-Florence-Northern Marinette County-Lincoln-
Langlade-Menominee-Northern Oconto County-Door-Marathon-Shawano-
Wood-Portage-Waupaca-Outagamie-Brown-Kewaunee-Waushara-Winnebago-
Calumet-Manitowoc-Southern Marinette County-
Southern Oconto County-
1019 AM CDT Thu Apr 16 2026

This Hazardous Weather Outlook is for north-central and northeast
Wisconsin.

.DAY ONE...This Afternoon and Tonight

Areas of dense fog may redevelop across eastern Wisconsin tonight.

Flooding is expected to continue due to recent heavy rainfall.
FLooding concern is greatest near rivers, streams, and creeks.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

Thunderstorms, some potentially severe with locally heavy rain,
will impact the area Friday afternoon and evening. Hazards include
large hail, a few tornadoes, and damaging winds. Flooding may
occur, especially in urban areas, and locations already impacted
by heavy rain earlier in the week.

Flooding will occur on some area rivers and streams into next
week.

.SPOTTER INFORMATION STATEMENT...

Spotters are requested to report any flooding to the National
Weather Service in Green Bay.

LMZ521-522-541>543-171530-
The Bay of Green Bay south of a line from Cedar River MI to Rock
Island Passage-Lake Michigan from Washington Island to Sheboygan-
1019 AM CDT Thu Apr 16 2026

This Hazardous Weather Outlook is for portions of northwest Lake
Michigan and the waters of Green Bay.

.DAY ONE...This Afternoon and Tonight

Areas of fog are expected across the nearshore and open waters
through tonight. A Dense Fog Advisory is in effect.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

Thunderstorms will occur Friday night. Any thunderstorms could be
hazardous to boaters.

JM