412 FXUS63 KGRB 051714 AFDGRB

Area Forecast Discussion National Weather Service Green Bay WI 1214 PM CDT Fri Sep 5 2025

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- Scattered to isolated showers at times today and Saturday, mainly during the afternoon. Greatest chances in north-central Wisconsin.

- Blustery conditions today with westerly winds gusting to 25 to 35 mph.

- Dangerous swimming conditions and gale force gusts are expected through mid-morning.

- Near-record cold maximum temperatures are possible through this weekend. Frost potential Sunday and Monday morning. Moderating temperatures early next week, but remaining below normal.

.DISCUSSION... Issued at 434 AM CDT Fri Sep 5 2025

Precipitation Trends...The strong surface low pressure system that brought widespread rainfall to the area overnight was located over central Upper MI early this morning. Despite the majority of the rainfall exiting to the northeast, additional areas of rain have developed early this morning north of Highway 29 in association with steeper mid-level lapse rates. Anticipate these showers to come to an end this morning as the low shifts further northeast of the area. However, with upper-level cyclonic flow expected to reside over the western Great Lakes region today through the weekend, light shower/sprinkle activity is expected each day, especially during the afternoon hours. Most locations won`t see measurable precipitation with this shower activity, except in far north-central WI where Lake Superior will provide some lake-enhancement.

Surface high pressure will gradually build into the area on Sunday, putting an end to the shower activity, except perhaps over far northeast WI where the cyclonic flow will linger the longest. Dry weather is expected for Monday as the high pressure system gradually departs the area, bringing return flow over the area with warmer, moist air. Meanwhile, a shortwave dropping from the north will combine with this moisture/return flow and bring the next chance for showers and potentially thunderstorms to the region sometime between late Monday and Wednesday.

Blustery Today...The departure of the surface low has brought a pressure rise/fall couplet and a tight pressure gradient over the area early this morning, resulting in gusty southwest winds. Locations in central and east-central WI have gusted the highest (35- 40 mph), where mixing into the strong low-level jet occurred. As the low continues to depart this morning, the associated cold front will cause winds to turn northwest/west today. The continued close proximity to the low and added CAA will result in blustery conditions today with gusts to 25 to 35 mph. Winds will gradually subside overnight tonight.

Temperatures/Frost Potential...An abnormally cold airmass will continue to reside over the area through the weekend, resulting in well below normal temperatures. Several sites set new record low maxes for Thursday, with additional records potentially in jeopardy today and Saturday. See the climate section for more details about records. The addition of the surface high pressure system moving into the region Sunday into Monday, may allow for a couple periods of frost development in portions of the region Sunday morning and Monday morning with low temperatures forecast in the mid 30s to low 40s. The return flow early next week will allow temperatures to rise into the 60s and low 70s, but remain below normal.

.AVIATION...for 18Z TAF Issuance Issued at 1214 PM CDT Fri Sep 5 2025

Gusty westerly winds of 20 to 30 knots along with MVFR/VFR cigs and a few light showers and sprinkles prevailed across the area early this afternoon. These conditions will continue this afternoon as a shortwave tracks through the western Great Lakes region. While all of the TAF sites could see a light shower or sprinkle through this evening, the coverage will be too isolated and brief to include in the TAFs. Winds will gradually diminish late this evening and pick up again Saturday morning with gusts to around 15 knots. CIGs will eventually rise to VFR everywhere by Saturday as bases slowly rise, rising the latest across north- central Wisconsin.

.MARINE... Issued at 434 AM CDT Fri Sep 5 2025

Southwesterly winds increased rapidly early this morning over the waters, with some marine sites reporting gale force gusts. Anticipate the window for gales will come to an end by mid-morning, therefore did not make any changes to the current Gale Warning in effect until 10 AM. Also, did not make any changes to the Beach Hazards Statement in effect until 10 AM for Lake Michigan beaches as the strong winds are bringing high waves and dangerous swimming conditions. Following the Gale Warning, a Small Craft Advisory will be needed for the Bay of Green Bay and the nearshore waters along Lake Michigan through late this evening as gusty westerly winds continue. While there is a non-zero chance for a waterspout this morning, the greater potential will be east of our waters.

.CLIMATE... Issued at 434 AM CDT Fri Sep 5 2025

The unseasonably cold airmass will bring additional chances of setting record low maximum temperatures today (9/5) and Saturday (9/6). Here is a look the current records and forecast values for Green Bay, Rhinelander, and Wausau.

Green Bay

Date Record Low Max Forecast High ---- -------------- -------------

9/5 60F(1981) 58F 9/6 58F(1965) 60F

Rhinelander

Date Record Low Max Forecast High ---- -------------- -------------

9/5 55F(2017) 50F 9/6 55F(1956) 56F

Wausau

Date Record Low Max Forecast High ---- -------------- -------------

9/5 57F(1956) 54F 9/6 56F(1965) 58F.

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

DISCUSSION.....Kruk AVIATION.......Kurimski MARINE.........Kruk CLIMATE........Kruk/Bersch

NWS GRB Office Area Forecast Discussion