textproduct: Green Bay

KEY MESSAGES

- Periods of showers and a few thunderstorms will continue into tonight. Additional rainfall up to 1 inch will be possible south of Highway 29, but the threat for flooding has diminished as the heaviest rainfall remains anchored further south.

- A Beach Hazards Statement and Small Craft Advisory have been issued into this evening for areas south of Algoma. Additional advisories will likely be required from Sunday morning through Tuesday as strong northeast winds and high waves develop.

- A quieter and drier weather pattern will settle into the region early to mid next week. Patchy frost will be possible at times across the northwoods.

DISCUSSION

Issued at 122 AM CDT Sat Sep 19 2026

The latest RAP analysis and satellite and radar imagery show a broad upper-level trough over the western United States with lower amplitude shortwave energy moving across the Dakotas and Minnesota. At the surface, a warm front extends from northern Iowa to central Illinois, with low pressure organizing over Iowa. A potent 30 to 35 knot low-level jet riding over the warm front is supporting a line of deep thunderstorms from southeast Minnesota into southern Wisconsin (south of Wood and Manitowoc counties) where localized rainfall rates exceed 1 inch per hour. Because the main convective core remains south of the area, the risk for flooding across central and east-central Wisconsin has ended. Over northern Wisconsin, high pressure centered over northern Ontario and Quebec continues to feed cooler, drier air southward. This has kept areas north of Highway 10 mostly dry early this morning.

Periods of rain continue through tonight: As the shortwave energy and associated surface low move east across the area today, rain is expected to gradually increase in coverage from west to east. Broad upper-level ascent in the right rear quadrant of an upper jet streak combined with low-level warm advection will generate efficient rainfall production, supported by precipitable water values in the 90th to 95th percentile. Additional rainfall amounts of 0.25 to 1.00 inch are expected generally south of Highway 29 through this evening before the low exits to the east overnight and brings precipitation to an end.

Quiet weather returns for next week: For the long term period from Sunday through Friday, a prolonged stretch of quiet and dry weather is anticipated across north- central and northeast Wisconsin. Shortwave energy originating from the western trough will slowly migrate across the central Plains and southern Great Lakes toward the East Coast during the week, keeping deep moisture and rain chances suppressed well south of the local area. Strong high pressure centered over northern Ontario and Quebec will maintain an expansive plume of dry air across northern Wisconsin, keeping rain probabilities below 10 percent through Friday. Under clear to partly cloudy skies, efficient radiational cooling on Monday and Tuesday nights will drop overnight low temperatures into the mid to upper 30s across north-central Wisconsin, leading to patchy frost formation in low- lying areas. A steady warming trend will take place throughout the week as afternoon high temperatures rise from the low and mid 60s on Monday and Tuesday into the low and mid 70s by Friday.

AVIATION

for 06Z TAF Issuance Issued at 1045 PM CDT Fri Sep 18 2026

Poor flying conditions expected for most of the TAF period as low pressure moves across the region, bringing low clouds, reduced visibility, and periods of rain. A storm is also possible, mainly south of Hwy 29, but chances too low to include, with higher storm chances just south of the area. First large area of rain is exiting late this evening, with the heaviest rain overnight staying south of Hwy 10. Lighter rain and some drizzle, along with some fog, is expected at times further north overnight into Saturday morning. Some brief heavier rain is possible late Saturday morning and Saturday afternoon across central and east- central WI. Rain showers could linger across east-central WI into Saturday night. Ceilings will continue to fall late this evening and settle mainly in the IFR range overnight into Saturday, with a few LIFR conditions possible at times. Reduced visibilities to high end IFR to low end MVFR are likely in the heavier downpours.

East/southeast winds will be rather steady overnight into Saturday morning, then will shift to the northeast Saturday afternoon/ evening. Gusts to 14-20 kts are expected at times.

MARINE

Issued at 122 AM CDT Sat Sep 19 2026

Gusty southeast winds up to 25 knots ahead of the low will build waves to 3 to 6 feet along the Lake Michigan shoreline south of Algoma today. Consequently, the Small Craft Advisory and Beach Hazards Statement have been extended through 10 PM this evening. Following a brief lull in winds and waves late tonight, northeast winds will increase to 15 to 25 knots early Sunday morning following the passage of the surface low. These strong northeast winds will persist into Tuesday as a high-pressure system builds across northern Ontario and Quebec, resulting in building waves of 4 to 7 feet and a high risk of dangerous rip currents along the Lake Michigan coast. A new Small Craft Advisory and Beach Hazards Statement will likely be needed from roughly 7 AM Sunday through Tuesday for waters south of Sturgeon Bay, with additional advisories likely required for Green Bay and northern lake zones.

GRB WATCHES/WARNINGS/ADVISORIES

Beach Hazards Statement through this evening for WIZ040-050.