623
FXUS63 KGRB 310503
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1203 AM CDT Sat Oct 31 2026

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- Spotty light rain and sprinkles (30-60% chances) for Halloween.
  Rainfall amounts less than 0.10 inch.

- Unsettled conditions much of next week, with widespread showers
  (70-95%) and gusty winds Monday afternoon through Wednesday,
  peaking Monday night into Election Day. Shower chances lingers
  into Thursday.

- The probability of 48-hour rainfall totals over 1" from Monday
  afternoon through Wednesday afternoon range from 60-75% north
  and west of the Fox Valley to 40-60% over Fox Valley east to
  Lake Michigan.

- Above normal temperatures continue through the middle of next
  week.

&&

.DISCUSSION...
Issued at 1130 PM CDT Fri Oct 30 2026

Mid-level warm air advection across southwest WI is lifting an
arcing band of showers toward central late this evening. However,
with such a dry surface layer in place, don`t anticipate more than a
sprinkle reaching the ground overnight. As a surface low lifts
closer to the region Saturday an draws addtioanl moisture into the
region expect some isolated to scattered showers to develop during
the afternoon and evening. Rainfall amounts will be fairly light
with most places seeing only a few hundreths. High pressure then
builds back in on Sunday returning dry conditions to the region to
finish the weekend.

A slow moving, moisture-laden system arrives Monday afternoon/
evening and sticks around into at least Thursday. Rain is likely
Monday night into Tuesday (80-95%) with the initial surge of
moisture and forcing. Then chance/likely PoPs will continue into
Wednesday, then taper off on Thursday as the system finally exits to
our east. Chances for exceeding 0.50 inch rain Monday Night through
Tuesday are 70-90% with chances for exceeding 1.00 inch between 70-
80% northwest of the Fox Valley, and 40-60% over east-central WI.
Higher end projections take rainfall to 1.5 to 2.25 inches.
Certainly looking like a soaking rain at times. Some elevated
instability and impressive dynamics with the initial WAA surge
Monday night to include some thunder, especially across central and
north-central WI.

Temperatures will trend back above normal this weekend, with highs
on Halloween mainly in the 50s and in the low to mid 60s on Sunday
through Wednesday. Temps cool off behind the large system at the end
of the week.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1203 AM CDT Sat Oct 31 2026

High pressure centered over the central Great Lakes will shift
east as a storm system moves northeast across the central Plains.
Deeper moisture ahead of this system is already moving into
central and southern Wisconsin with ceilings falling from 10 kft
AGL at ISW to sub 3 kft AGL over northeast Iowa. A cluster of
light rain showers is also moving into MFI and ISW late this
evening.

With backing winds aloft, moisture will continue to increase
across the region through the TAF period. Ceilings will
consequently lower with the cluster of showers impacting
AUW/CWA/ATW/GRB/MTW during the predawn hours. Tentative timing is
from 07-11Z Sat. No impacts to visibility are expected, but
ceilings will likely fall from 10 kft to 6 kft in the process.

MVFR ceilings will likely arrive to AUW/CWA/RHI this afternoon
with some potential for IFR ceilings at RHI this evening.
Visbilities may also fall to MVFR in mist this evening as well
but confidence is lower with that. Spotty light rain showers and
sprinkles will be possible through the day but little to no
impacts are expected.

&&

.MARINE...
Issued at 1130 PM CDT Fri Oct 30 2026

A slow moving low pressure system will move across the Great Lakes
Monday night into Wednesday morning, bringing gusty south to
southeast winds and large waves on the bay and Lake Michigan. A
Small Craft Advisory will likely be needed. Winds will shift to
the north on Thursday, possibly gusting to near 25 kts as the
system departs to the east.

&&

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

&&

$$

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

NWS GRB Office Area Forecast Discussion