416 FXUS63 KGRB 080208 AAA AFDGRBArea Forecast Discussion...UPDATED National Weather Service Green Bay WI 908 PM CDT Sun Sep 7 2025
New information added for marine and beach hazards
.KEY MESSAGES...
- Patchy-areas of frost late tonight into Monday morning. Frost Advisory along and north of highway 29.
- Below normal temps continue tonight, 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.
- Conditions hazardous to small craft, along with dangerous swimming conditions, expected on the bay and lake Monday evening into Tuesday evening.
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.DISCUSSION... Issued at 904 PM CDT Sun Sep 7 2025
Diurnally driven stratocumulus clouds will dissipate after sunset, providing for mostly clear skies and light winds as a ridge of high pressure tracks through the western Great Lakes region. Temperatures will therefore plummet tonight under these conditions, with lows ranging from the middle to upper 30s across the north to the middle 40s along the lakeshore. The cold temperatures across the north will likely lead to frost along and north of Highway 29 with temperatures in the middle to upper 30s; therefore, will issue a Frost Advisory for these areas overnight into early Monday morning.
Strong warm air advection will commence on Monday as the high pushes off to the east and surface winds turn to a southerly direction. This will allow surface temperatures to warm into the upper 60s across the north, with around 70 degrees across central and east-central Wisconsin. While the CAMs indicate some sprinkles are possible with this surge of warm air, model soundings indicate quite a bit of dry air will be in place. Therefore, virga is the most likely scenario from any clouds that develop with the warm air advection.
A cold front will slowly track through the region from Monday night through Tuesday night, which will bring showers and thunderstorms to the region. The best chance for precipitation will be across the north Monday night into Tuesday, with lesser chances across east-central Wisconsin Tuesday into Tuesday night as the front loses a lot of its dynamics as it washes out across the Great Lakes. Any thunderstorms should be on the weak side as instability will only clock in at a few hundred J/kg.
Some light precipitation 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. There appears to be another shot at precipitation next weekend as a low pressure system tracks through the western Great Lakes; however, timing is still uncertain this far out.
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.AVIATION...for 00Z TAF Issuance Issued at 629 PM CDT Sun Sep 7 2025
Stratocu clouds will slowly clear out this evening. Patchy low clouds and ground fog could occur again overnight into early Monday morning. Confidence remains too low to include in this set of TAFs. After mostly clear skies to start the day, warm air advection will produce a swath of mid clouds (080-120) across the area by Monday afternoon. The warm air advection will eventually lead to showers and storms developing Monday evening, mainly over north-central WI.
Winds will shift to the west and decrease to under 5 kts this evening and overnight. South-southwest winds of 10 to 20 kts are expected Monday afternoon.
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.MARINE... Issued at 904 PM CDT Sun Sep 7 2025
Gusty south to southwest winds and building waves will result in conditions becoming hazardous to small craft starting Monday evening. The strongest winds on the bay will diminish on Tuesday afternoon, while conditions hazardous to small craft will linger into Tuesday evening on Lake Michigan. A Small Craft Advisory has been issued for the Bay of Green Bay from 7 pm Monday through 1 pm on Tuesday, while the Small Craft Advisory on Lake Michigan runs through as late as 10 pm on Tuesday evening. The higher waves will also result in dangerous swimming conditions for beaches on Lake Michigan, so a Beach Hazards Statement has also been issued.
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.GRB WATCHES/WARNINGS/ADVISORIES... Frost Advisory from 1 AM to 8 AM CDT Monday for WIZ005-010>013- 018>021-030-031-073-074.
Beach Hazards Statement from Monday evening through Tuesday evening for WIZ022.
Beach Hazards Statement from Monday evening through Tuesday evening for WIZ040-050. &&
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DISCUSSION.....Kurimski AVIATION.......JLA MARINE.........JLA
NWS GRB Office Area Forecast Discussion