730 FXUS63 KGRB 140910 AFDGRBArea Forecast Discussion National Weather Service Green Bay WI 410 AM CDT Sun Sep 14 2025
Forecast discussion for routine morning forecast issuance
.KEY MESSAGES...
- Areas of fog, locally dense, will impact travel this morning and again late tonight into early Monday. A Dense Fog Advisory is in effect for the eastern half of the forecast area this morning.
- Mainly dry through Tuesday, with a chance of showers and thunderstorms returning late Tuesday night into Wednesday and continuing into Saturday.
- Much above normal temperatures today through mid-week, with a significant cool down expected from Friday into the weekend. The warmest day is expected on Tuesday, when highs reach 10 to 15 degrees above normal.
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.DISCUSSION... Issued at 410 AM CDT Sun Sep 14 2025
Fog Trends: The fog forecast is a bit tricky early this morning. Low stratus has expanded over NC/C WI, where the boundary layer flow is a bit stronger, and this has prevented vsbys from bottoming out in most places. In far eastern WI, where many areas have clear skies, fog has been slow to develop or vsbys have been variable. Suspect that fog will settle into these areas within the next couple hours. In between, from IMT-EZS-CLI, vsbys have been at or below 1/4sm for several hours. Given recent trends and model vsby forecasts, have opted to issue a Dense Fog Advisory for most of far northeast and east central WI through 9 am. Will monitor trends to see if any adjustments need to be made. Fog potential will return late tonight, with models showing the best chance for widespread (and locally dense) fog over far northeast WI.
Precipitation Trends: Dry weather returns for the rest of the weekend and early next week as strong upper level ridging occurs, and high pressure over Ontario ridges into NE WI. A chance of showers and storms arrives late Tuesday night or Wednesday, as the upper ridge shifts east. A cold front is expected to sag south across the area during the Wednesday night to Thursday night period. In addition, an upper low over the Northern Plains will track toward the Upper Mississippi Valley by the weekend. These features will keep a chance of showers and thunderstorms in the forecast through at least Saturday, but most of this activity should be scattered, with the best chances occurring during peak heating.
Temperature Trends: Temperatures will remain well above normal through most of the work week, with highs peaking in the mid to upper 80s (10 to 15 degrees above normal) on Tuesday. A post- frontal cool down is expected late in the week, with highs dropping into the 60s by the weekend.
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.AVIATION...for 06Z TAF Issuance Issued at 1100 PM CDT Sat Sep 13 2025
A pesky, small patch of stratus will continue to shift east of the Fox Valley and into central WI late this evening. Otherwise, look for low clouds and fog to continue developing late this evening and into Sunday morning, bringing IFR/LIFR and some VLIFR conditions to most areas. SREF/HREF probabilities of under a 1/2SM VSBY in the 50-90% range from the Fox Valley north and westward. Some lake fog is also expected, which will impact MTW. After the low clouds and fog burn off Sunday morning (by ~15z), look for VFR conditions for the rest of Sunday. Additional low clouds and fog will be possible again Sunday night, but likely after 06z.
Light and variable winds are expected tonight, with southeast winds up to ~10 kts on Sunday.
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.GRB WATCHES/WARNINGS/ADVISORIES... Dense Fog Advisory until 9 AM CDT this morning for WIZ012-013- 020>022-031-037>040-048>050-073-074. &&
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DISCUSSION.....Kieckbusch AVIATION.......Bersch
NWS GRB Office Area Forecast Discussion