FXUS63 KGRB 251101 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 601 AM CDT Sat Oct 25 2025 Updated aviation portion for 12Z TAF issuance .SYNOPSIS... An upper-level disturbance is poised to traverse the area today, bringing a chance for light rain primarily south of a Merrill to- Algoma line. The forecast is expected to remain relatively tranquil through mid-week. A shift to a west-northwest 500 mb flow pattern is anticipated later in the work week, bringing a sharper 500 mb trough on Friday that will increase the likelihood of rain. && .KEY MESSAGES... - An upper level disturbance will bring a 15-40% chance of light rain for locations south of a Merrill to Algoma line today. - Uncertainty in the chances of rain Tuesday-Wednesday, currently at 15-30%, as Canadian high pressure and system passing well south of the area don't bode well for rain to reach our area. - High temperatures over the next week will be near or a few degrees above normal each day. - Persistent southeast to south winds may bring high waves and hazardous conditions for small craft on Lake Michigan south of Sturgeon Bay Sunday afternoon into Monday. && .DISCUSSION... Issued at 219 AM CDT Sat Oct 25 2025. && .SHORT TERM...(Today through Sunday)... An upper- level disturbance is forecast to move across the region today. This disturbance will bring a 15-40% chance of light rain to locations situated south of a Merrill to Algoma line. Model guidance, including the NAM, GFS, and ECMWF, suggests the precipitation currently visible on radar across Minnesota and far western Wisconsin will largely dissipate as it reaches central Wisconsin around or shortly after 12Z. Therefore, despite some impressive radar returns to our west, the overall rain chances are being held steady, focusing on light amounts where it does occur. High pressure will build across the area tonight, leading to another chilly night. Overnight lows are expected to drop into the middle 20s to middle 30s. The high pressure system will slide east on Sunday. We anticipate mostly sunny skies with highs reaching the 50s to around 60 degrees. A southeast wind at 5-15 mph is forecast during the day. .LONG TERM...(Sunday night through Friday) Uncertainty remains regarding the chance of rain early to mid- week (Tuesday and Wednesday). The presence of Canadian high pressure over the western Great Lakes and a low- pressure system expected to track well south of our area are the primary factors mitigating rain chances during this time. Current model runs show precipitation potentially skirting close to our western counties later Tuesday, before shifting south Tuesday night and Wednesday. This pattern does not favor significant rainfall for the forecast area. Confidence increases for a better chance of precipitation late in the work week, specifically on Friday. The 500 mb pattern is expected to transition to a west-northwest flow, which will usher a fairly sharp 500 mb trough across the area, increasing the likelihood of showers. If the timing remains consistent in future model runs, we will likely need to increase the probabilities for rain during the Friday period. Daytime high temperatures throughout the period are forecast to be around or slightly above normal. && .AVIATION...for 12Z TAF Issuance Issued at 532 AM CDT Sat Oct 25 2025 Some light showers or sprinkles will move across portions of central and east-central WI, mainly this morning. Otherwise, VFR conditions should prevail through Sunday afternoon. Winds today will be under 10 knots from the south or southeast, then light and variable tonight. Gusty southeast/south winds will develop on Sunday with gusts up to 20 knots. && .GRB WATCHES/WARNINGS/ADVISORIES... None. &&$$ DISCUSSION.....Eckberg AVIATION.......Eckberg