Area Forecast Discussion

KEY MESSAGES

- Scattered light showers ending by late afternoon and breezy winds subsiding toward sunset. Small craft advisories are in effect through early Wednesday morning.

- Comfortable and quiet conditions through Friday, followed by increasing heat, humidity, and thunderstorm chances (30 to 50 percent) over the weekend.

DISCUSSION

Issued at 218 PM CDT Tue Jul 21 2026

A subtle west to east sfc trough is moving swd across the area with a wind shift from nwly to more nly expected. Scattered light showers are ahead of and along the trough with drier air and isolated showers behind the trough. The cold advection will continue tnt as the 992 mb low just south of James Bay lifts newd into north central Quebec through tomorrow. Cloud cover will gradually clear through the evening with the loss of heating and the arrival of drier air. Low temps in the 40s are forecast for ne WI with lower to middle 50s over the Fox Valley.

On Wednesday, a shortwave trough will move across the nrn Great Lakes to srn Ontario, while high pressure will track from the nrn Great Plains to sw WI and ne IA. Lingering cool air aloft will lead to broken cloud cover for a time on Wed, with high temps mainly in the lower to middle 70s.

A relatively dry airmass and gradually warming temperatures back to near normal are anticipated for Thu-Fri as high pressure tracks from nrn IL to the lower Great Lakes.

Shower and thunderstorm chances return to the forecast for the weekend and early next week. Nwly flow aloft will continue with embedded shortwave troughs. There may be a couple low pressure areas that track across srn Canada or the nrn USA and affect ne WI and east central WI. High temperatures in the 80s are forecast with increasing relative humidity.

AVIATION

for 00Z TAF Issuance Issued at 620 PM CDT Tue Jul 21 2026

A deck of BKN to OVC at 060 over the north woods is anticipated to dissipate through sunset as northerly flow slowly transits it south. Gusty north-northwesterly flow will gradually subside into the overnight hours, remaining northerly into Wednesday. Primarily VFR conditions should prevail for the 00Z TAF cycle.

KOSH

Gusty north-northeasterly winds to 25kts are anticipated for the coming hours, gradually diminishing following sunset. Clouds lift and clear overnight, with northerly flow and few to scattered cu expected Wednesday. VFR conditions should prevail.

MARINE

Issued at 218 PM CDT Tue Jul 21 2026

Breezy nly winds will continue for much of the night with the Small Craft Advisory in effect until 4 AM CDT Wed. Light to modest nnwly winds are expected on Wed with lake breeze development possible by mid to late afternoon. Light wly winds Thu AM are expected to become modest sly winds for Thu afternoon.

GRB WATCHES / WARNINGS / ADVISORIES

None.