NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 202322
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
622 PM CDT Mon Apr 20 2026

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

-Minor to moderate flooding continues on the Menominee and Wolf
 Rivers and associated tributaries, with major flooding expected
 on the Wolf River at New London through Tuesday night. Water
 levels have crested in most areas, and due to an extended period
 of dry weather, a gradually drop is anticipated through the week.

-Showers and thunderstorms are expected Thursday night into
 Friday. Heavy rainfall may accompany any thunderstorms. There is
 a 50-70% chance of rainfall in excess of 1/2 inch, but higher end
 amounts to 1-2 inches could occur.

-Temperatures will be much above normal from Tuesday through
 Friday, with highs in the 60s and 70s expected away from Lake
 Michigan.

&&

.DISCUSSION...
Issued at 304 PM CDT Mon Apr 20 2026

Partly sunny skies and gusty south to southwest winds were
observed across the region this afternoon. Temperatures were in
the middle 40s to middle 50s, except upper 30s and lower 40s near
Lake Michigan due to a pronounced lake breeze.

Quiet weather is expected tonight, with south winds keeping
low temperatures 15 to 20 degrees warmer than last night. A weak
surface low/trough will move through the region with no
precipitation on Tuesday. Much warmer gets drawn into the region
ahead of the trough, with high temperatures rising into the 60s
and lower 70s, except 50s and lower 60s due to a lake/bay breeze.
High pressure returns Tuesday night into Wednesday, with continued
dry and mild conditions inland from Lake Michigan. Throughout
this period, low afternoon humidity is anticipated, which may
result in an uptick in wildfire potential.

South winds develop Wednesday night and gust to 25 to 35 mph on
Thursday, resulting in an increase in Gulf moisture over the
region. There is a 20 percent chance of showers in our far western
counties late Thursday afternoon, but showers and embedded storms
become more numerous Thursday night, as a cold front moves
through. Models are a bit slower with the timing of the front, so
precipitation is likely to linger into Friday. With PWATs
increasing to 1.20-1.50 inches and marginal instability (MUCAPE of
500-1000 j/kg), would anticipate locally strong storms and
potential for heavy rainfall. Current probabilistic forecasts call
for a 50-70% chance of rainfall amounts in excess of 0.50 inch.
The 90th percentile forecasts show rainfall totals in the 1-2 inch
range, and offer a glimpse of the higher-end potential for this
event. The frontal showers should taper off Friday afternoon or
evening, with mainly dry conditions anticipated over the weekend.

Above normal temperatures are anticipated from Tuesday through
Friday, with the cold frontal passage only bringing modest
cooling for the weekend.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 617 PM CDT Mon Apr 20 2026

VFR conditions will continue through Tuesday evening. Mid and
highs will move across the region tonight, with mostly sunny
skies expected on Tuesday. Some fair weather cumulus will develop
across eastern WI during the mid to late afternoon. Low level
wind shear will develop around 02z tonight from 220-240 degrees
at 35-45 kts. The wind shear will come to an end overnight. Weak
cold front will move across the area Tuesday morning, shifting
winds to the northwest. During the afternoon, a lake breeze
boundary will develop around 18z at KMTW/KSUE, spreading westward
to KGRB/KATW/KOSH between 21z Tue and 00z Wed.

&&

.HYDROLOGY...
Issued at 304 PM CDT Mon Apr 20 2026

Minor to moderate flooding continues on the Menominee and Wolf
Rivers and associated tributaries, with major flooding expected
on the Wolf River at New London through Tuesday night. Water
levels have crested in most areas, and due to an extended period
of dry weather, a gradually drop is anticipated through the week.

Those living near rivers should continue to monitor the latest
Flood Warnings and statements from the National Weather Service
in Green Bay.

See the discussion section above for information pertaining to
precipitation forecasts for the Thursday night to Friday period.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

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