textproduct: Green Bay

KEY MESSAGES

- Patchy-areas of frost expected late tonight into Monday morning.

- Below normal temps continue today, with temps warming closer to seasonal norms mid-late week.

- Chances (30-70%) for rain showers and a few storms return Monday night into Tuesday night.

DISCUSSION

Issued at 352 AM CDT Sun Sep 7 2025

Today into Monday: Patchy frost and some low clouds/ground fog will continue early this morning, mainly north and west of the Fox Valley. Otherwise, look for quiet early September weather conditions across the region today as the upper trough/low shifts into Quebec and high pressure builds across the Great Lakes. Northwest, cyclonic flow over the warmer waters of Lake Superior will result in some lingering clouds, and possibly a stray shower/sprinkle, over northern WI early this morning, with most locations seeing mostly clear skies. Daytime cumulus clouds are expected to develop later today, as surface temps climb into the mid 50s to mid 60s. Look for the daytime cu to fade in the evening, with mostly clear skies expected tonight. Could have some patchy ground fog overnight into early Monday as well, especially north and west of the Fox Valley. Better conditions for frost will develop tonight, with less clouds and lighter boundary layer winds. Have lowered low temps a little, especially in the typical cold spots of north-central WI. Most lows look to drop into the 30s, with some warmer readings near the bay/lake. The highest HREF probabilities of <37 degrees (40-60%) across Shawano, Marathon, Lincoln, Langlade and Oneida counties. This will be where the greatest threat for areas of frost would develop, with a Frost Advisory possibly being needed. After a sunny start, look for some mainly mid-upper clouds to spread across the region later Monday morning and afternoon, as a strong push of WAA arrives (going from 3C to 12C through the day). This could kick off a sprinkle or two, as some of the CAMs are indicating, but thinking the drier air should win out. The WAA will bring in slightly warmer temps as well, with highs mainly in the upper 60s to low 70s.

Monday Night into Tuesday Night: The next chance for rain showers and a few storms returns as return flow sets up over the western Great Lakes, and a shortwave trough and cold front approach from the northwest. Chances for rain (30-70%) will spread east across the area Monday evening/night and continue on Tuesday as the front and trough move into and across the region. Have confined the chance for thunder mainly northwest of the Fox Valley where modest MUCAPEs up to ~300 J/kg are forecast. No severe weather is anticipated.

Rest of the week: Some light precip may linger into Wednesday, depending on how progressive the front/trough is, then models are in fairly good agreement showing another stretch of dry weather from Wednesday into Friday as high pressure builds in. Temps will climb back closer to seasonal norms by mid-week, with highs in the low to mid 70s for most locations.

AVIATION

for 06Z TAF Issuance Issued at 1001 PM CDT Sat Sep 6 2025

Plan on scattered to broken stratocu especially north and far northeast, including RHI and possibly GRB at times. Isolated showers or sprinkles may occur overnight mainly over northern WI, though most of the activity will remain over Upper Michigan. Skies will become mostly clear elsewhere. Given the light winds and clearing skies, patchy brief ground fog may occur.

On Sunday, expect another round of generally VFR stratocu to develop in the afternoon. Northwest winds may briefly gust over 15 kts in the afternoon at most sites. Both cloud cover and winds will diminish late in the day, with skies becoming mostly clear on Sunday night.

GRB WATCHES/WARNINGS/ADVISORIES

None.