Marine Weather and Tide Forecast for Copper City, MI

DISCUSSION
Issued at 144 PM EDT Sun Sep 20 2026

Early afternoon GOES WV imagery and RAP analysis show a cut-off low over WY, shifting east toward Northern Plains. Further upstream there is a ridge over the Pacific Northwest and a trough off the coast of CA. High pressure of 1027 mb has become centered over northwestern Ontario with a cold front now south of the UP. Low level cloud cover is beginning to decrease in coverage as drier air filters in and 850 mb temps marginally warm up ~1-2C, but stubborn scattered clouds persist in the west into tonight. This helps keep afternoon highs cooler than normal in the mid 50s to mid 60s. Breezy northeast winds, particularly near Lake superior where gusts of 20- 30 mph have been observed, taper off through this evening as the pressure gradient weakens and the shallow inversion develops. This supports a high swim risk along Lake Superior shores into tonight, possibly into early Monday morning for Marquette County. When low clouds clear out, mid to high level clouds take over for tonight courtesy of the western cut-off low which breaks up as it moves east over the northern Plains. Although this is not an ideal radiative cooling set up, 5-10 degrees colder than normal lows are expected with 30s for the interior and low to mid 40s near the Great Lakes shores. Patchy frost is possible (10-20% chance), but opting for no headlines given limited coverage and low confidence.

Although high pressure continues to strengthen through the middle of the week over Quebec, extending ridging over the Great Lakes, the upper level troughing moving east over the Midwest supports mostly cloudy skies through Monday before clear skies return Tuesday through Wednesday night. The split flow that sets up over eastern Canada/CONUS helps this high pressure persist into the weekend, possibly keeping dry weather until early next week. That said, the NBM currently has low PoPs between 15-24% returning on Sunday. The cooler temps gradually trend to above normal by the weekend as southerly flow returns. Decreasing cloud cover and lighter winds yields better frost potential Monday night (20-60% chance in the interior, highest west). Tuesday night could also bring patchy frost to the interior (10-40% chance).

AVIATION /00Z TAFS THROUGH 00Z MONDAY/
Issued at 711 PM EDT Sun Sep 20 2026

VFR conditions are present save for SAW at MVFR at the start of the 00z TAF period. SAW should lift to VFR within the next few hours as diurnal cu wanes. Light winds and mostly clear skies expected overnight into Monday.

MARINE
Issued at 144 PM EDT Sun Sep 20 2026

Building high pressure to the north tapers off northeast winds mainly below 20 kts this evening, save for gusts in the low 20 kt range over northern Lake Michigan and the southeastern waters of Lake Superior tonight. Significant wave heights on Lake Superior, especially in the south and west, between 4-7 ft this afternoon fall to ~4 ft or lower for tonight. Waves in the northern Bay of Green Bay and northern Lake Michigan linger between 1-4 ft through mid next week given persistent northeast to east flow is expected. Winds become easterly for Monday as the high strengthens over Quebec.
Aside from northeast winds channeling in the far western nearshores of Lake Superior, yielding gusts up to 25 kts, winds lakewide primarily hold below 20 kts. High pressure remains dominant through the forecast, keeping the pressure gradient weak and winds largely 20 kts or less.

MQT WATCHES/WARNINGS/ADVISORIES
Upper Michigan...
Beach Hazards Statement until 8 PM EDT this evening for MIZ005- 006.

Lake Superior...
None.
Lake Michigan...
None.