Area Forecast Discussion

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.