972 FXUS63 KGRB 130854 AFDGRBArea Forecast Discussion National Weather Service Green Bay WI 354 AM CDT Sat Sep 13 2025
Forecast discussion for routine morning forecast issuance
.KEY MESSAGES...
- Showers end early this morning.
- Areas of fog develop late tonight into early Sunday morning. Patchy dense fog could result in locally hazardous travel conditions.
- Mainly dry with above normal temperatures through early next week. A chance of showers and thunderstorms during the mid to late part of the week, with a significant cool down possible Friday and Saturday.
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.DISCUSSION... Issued at 350 AM CDT Sat Sep 13 2025
Showers associated with a strong short-wave trough were moving out of the region early this morning, but a NW-SE oriented band of thunderstorms on the nose of 25-30 kt LLJ was ongoing just southwest of the forecast area. These storms could brush the far SW/S part of the forecast area early today, but most of the rain should be gone by 14z-15z. Although some surface-based instability will develop across the southwest half of the forecast area this afternoon, significant CINH and a building upper ridge should prevent convection from forming. High temperatures should warm into the middle 70s to lower 80s. Good radiational cooling conditions should set up tonight, with partly cloudy skies and light east winds, so areas of fog look like a good bet. Patchy dense fog could result in locally hazardous driving conditions into early Sunday morning.
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 during the mid to late part of the next work week, as the upper ridge shifts east and an upper trough and cold front edge east across the region.
Temperatures will remain above normal through much of the next week, with highs reaching the upper 70s to middle 80s on most days. A cool down is expected Friday into Saturday in the wake of the cold frontal passage.
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.AVIATION...for 06Z TAF Issuance Issued at 1006 PM CDT Fri Sep 12 2025
First batch of showers continues to spread east across the area during the late evening hours, but overall coverage/strength has not been overly impressive. Limited/no instability has kept the lightning away from the TAF sites as well. Most models continue to back off on the overall coverage of the second round of showers/storms, so have removed thunder from the northern/eastern TAF sites, as the threat is under 15%. However, will add a PROB30 at AUW/CWA as they are closer to the better instability. Mainly VFR conditions are expected for most of the night, with MVFR conditions possible in the heavier rain/storm. Some lower clouds may develop overnight into Saturday morning as southeast flow prevails. Lingering showers are possible into Saturday morning, with partial clearing in the afternoon, but additional clouds are expected Saturday night, along with some fog, especially after 06z.
Low clouds and dense fog will linger across/near Lake Michigan into Saturday morning, impacting MTW at times into Saturday morning. Additional fog is possible across the rest of the area after the second area of showers exits.
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.GRB WATCHES/WARNINGS/ADVISORIES... None.
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DISCUSSION.....Kieckbusch AVIATION.......Bersch
NWS GRB Office Area Forecast Discussion