538
FXUS63 KGRB 292256
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
556 PM CDT Tue Sep 29 2026

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Widespread soaking rainfall is expected over most of the area
  from this evening through Thursday morning. Rainfall amounts
  between 1 to 1.5" are forecast across portions of central and
  east-central Wisconsin.

- Patchy frost will be possible at times across northern Wisconsin
  later this week as a cooler and drier airmass settles in.

- Increasing southerly winds Wednesday will create hazardous swim
  and boating conditions on Lake Michigan.

&&

.DISCUSSION...
Issued at 1224 PM CDT Tue Sep 29 2026

Rain this evening through Thursday: A round or two of rain is
expected beginning this evening through Thursday morning. Regional
radar and surface observation show a north/south oriented band of
rain across MN along and just a head of a surface boundary slowly
moving out of the northern Plains. This band of rain is expected to
slowly push into central and north-central WI this evening as the
surface front and plume of Pacific moisture work east. On and off
rain is then expected to continue through Wednesday as the front and
weak isentropic ascent continue over the region. Weak elevated
instability (MUCAPE 100-200 J/kg) may lead to a few rumbles of
thunder Wednesday, but no organized thunderstorms are expected.
Ensemble guidance has trended lower in terms of QPF amounts through
Thursday morning with this system. Areas south of HWY 29 now having
a 20-30% chance for greater than 1" of rain and areas north have
about 20-40% for greater than 0.5" of rain.

Extended: Subsidence behind the front will usher in surface high
pressure late on Thursday, which should stick around for the better
part of the extended. As such, expect a pattern shift to cooler and
drier weather, with the exception of 30 to 50% chance of rain on
Saturday, highest across northern WI. With surface high sitting
overhead and falling temperatures, conditions should be favorable
for effective radiational cooling and frost development at times
during the early morning periods throughout the week. Will continue
to monitor trends for headline potential as we approach the end of
the growing season.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 555 PM CDT Tue Sep 29 2026

Overview: A slow-moving cold front will bring widespread rain and
deteriorating flight conditions tonight through Wednesday
morning. Then a slow, gradual improving trend late Wednesday afternoon.

Through 02Z Wed: VFR prevailing under overcast skies. Lowering
ceilings across the region reaching as low as 3.5-5 kft at KRHI,
KAUW, KCWA. S-SE winds 6-10 kts.

02Z-10Z Wed: Cold front brings widespread -SHRA/BR with lowering
MVFR/IFR cigs (500-1500 ft AGL) and vsbys 3-5SM. Low-level wind
shear hazard (LLWS 2000 ft 220-230/35-40 kt) at KAUW, KCWA, KATW,
KMTW, and KGRB between 02Z-08Z.

10Z-20Z Wed: Widespread light rain changes to a drizzle and mist.
LIFR/IFR cigs (400-900 ft AGL) with drizzle/mist (-DZ BR)
gradually lifting toward 18Z-20Z. SW-W winds 6-10 kts.

20Z-24Z Wed: Ceilings gradually lift at all terminals except for
KMTW. A return to VFR ceilings possible at KRHI, KAUW, KCWA. KGRB
and KATW likely to return to MVFR.

Confidence: High confidence in IFR cigs and LLWS tonight.

&&

.MARINE...
Issued at 1224 PM CDT Tue Sep 29 2026

Increasing southerly winds Wednesday will result in a period of
hazardous boating conditions for Lake Michigan nearshore waters.
Sustained winds of 10-15 kts are expected with gusts peaking around
25 kts. Waves are forecast to build to 3 to 6 feet. Winds are
forecast to decrease Thursday as they turn to the northwest.

High waves and strong currents will also result in hazardous swimming
conditions at Lake Michigan beaches in Manitowoc, Kewaunee, and Door
counties.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement from 4 AM CDT Wednesday through late
Wednesday night for WIZ022-040-050.
&&

$$

DISCUSSION.....GK
AVIATION.......MPC
MARINE.........GK