236
FXUS63 KGRB 300252
AFDGRB

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

Updated aviation portion for 06Z 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 06Z TAF Issuance
Issued at 951 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 Wednesday
afternoon while MVFR/IFR ceilings continue over central to east-
central WI through Wednesday evening.

Through 12Z, the cold front will bring bring widespread
-SHRA/BR with lowering ceilings to IFR 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.

12Z-20Z Wed: Widespread light rain changes to a drizzle and mist.
Widespread LIFR/IFR ceilings (400-900 ft AGL) with drizzle/mist
(-DZ BR) very slowly lifting to IFR/MVFR toward 16Z-20Z at KRHI,
KAUW, KCWA. The greatest improvements will likely occur at KRHI.
SW-W winds 6-10 kts.

20Z Wed-01Z Thu: Further ceiling improvements are expected at
KRHI, KAUW, KCWA but only very small improvements are possible
over the Fox Valley and Lakeshore.

01Z-06Z Thu: Guidance is showing ceilings deteriorating again over
central and east-central WI and back to low end MVFR or IFR. Some
potential for fog to develop by late in the taf period over areas
where clearing occurs.

Confidence/Outlook: High confidence in LIFR/IFR ceilings 06-18Z
Wed.

&&

.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