Marine Weather and Tide Forecast for Copper Harbor, MI

DISCUSSION
Issued at 227 AM EDT Sat Oct 17 2026

Clear skies dominated the region this evening and for a majority of the overnight period so far, thanks to dry air and ridging spreading into the Great Lakes. At the time of this publishing, lingering lake induced clouds were minimal across Lake Superior and eastern Upper Michigan and high clouds have been observed streaming into western Lake Superior. Given the clear and dry conditions over Upper Michigan, effective radiational cooling has been observed across the forecast area. Lowest temperatures observed so far in the interior west have been in the mid 20s. Lakeshore temperatures range from the 30s to mid 40s and east has fallen into the upper 30s. I'm expecting continued cooling through the remainder of the night, with most interior locations likely falling into the 20s and lakeshore regions most likely to only bottom out in the 30s.

Mid-level ridging is anticipated to stretch across much of central North America today. Associated ridge axis will gradually press eastward into eastern Canada ahead of an upper level low moving through northern Manitoba Sunday, before exiting east toward Greenland Monday. Behind the northern Manitoba low on Monday, ridging will return for the Canadian and US plains east of the Rockies. At the surface, an expansive 1040-1030mb high will dominate much of eastern CONUS/Canada as it shifts east out of the Plains today into the Northeast tonight. Another high dives out of the Canadian Rockies Sunday night, helping to reinforce ridging overhead into next week. This pattern will favor dry conditions alongside above normal temperatures through at least the middle of next week.

Today and Sunday, warm air advection, characterized by 850mb temps increasing from near 0C today at 12z to ~14C by 12z Sunday, will enable 50s for highs today and 60s tomorrow. This will also be accompanied by a dry airmass, where daytime mixing will allow many spots in the interior west half to sink to 25-30% RH today and 30s elsewhere, and potentially widespread low to mid 30s Sunday.
Additionally, the strong pressure gradient associated with the strong surface high to our south and then east, a 985ish mb low moving through northern Manitoba, and a strong 925-850mb low level jet will kick off gusty southwesterly winds, especially during peak afternoon mixing each day. Currently expecting southwesterly 30-40 mph gusts to be common in the Keweenaw today with 20-25 mph elsewhere. More widespread stronger southwest winds are anticipated Sunday given the proximity of the low to our north. Current expectations are widespread 30 mph gusts with 35-40 mph being most likely in the Keweenaw, Schoolcraft and Luce counties, the Michigamme Highlands, near lakeshores, and northeast facing slopes.
Latest REFS and NBM does suggest 45mph + potential (35-60%) along the western lakeshores of Keweenaw County Sunday, which seems plausible given the stronger flow over the lake.

Winds will lighten Sunday evening, and continue to remain light through at least Wednesday morning thanks to another strong surface high migrating across the northern Plains toward eastern North America. Airmass aloft will stabilize, with 850mb temps generally remaining between +5 and 10C, varying by model. This should yield daytime highs peaking in the mid 60s for most interior locations and closer to 60F lakeside, and maybe upper 50s in the Keweenaw.
Overnight lows most nights in the 30s should be expected inland, with 40s by the lakeshores. Next best shot of rain, albeit probabilities are currently low, comes late Wednesday into Thursday.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/
Issued at 714 AM EDT Sat Oct 17 2026

VFR conditions are expected through the duration of the 12Z TAF period as high pressure passes over the region. This leaves gusty winds and LLWS as the primary impacts. Southwest winds this morning increase to around 15 kts by this afternoon. Gusts at IWD/SAW are expected between 20-25 kts with 20-30 kts at CMX. Moving into the evening hours, a strong low level jet develops introducing a LLWS threat at all sites into Sunday morning.

MARINE
Issued at 227 AM EDT Sat Oct 17 2026

Lake Superior: Winds have settled down this evening, with elevated wind observations now only focused across eastern Lake Superior.
These elevated winds will continue to fall overnight. Today, winds will turn southwesterly as high pressure shifts to our east and a low moves into Manitoba. The resulting increasing pressure gradient, in addition to a stronger low level jet coinciding with continued lake instability, will support winds climbing to 30-35kts this morning over western/northern Lake Superior and 25-30kts over the east. Ensemble and deterministic guidance isn't sold on gales, but given the 850mb airmass isn't expected to warm above +5C until early afternoon and the lake is running +12C, suspect this window will support some gale conditions. Given this, opted to issue a short duration Gale Warning for western Lake Superior. Peak significant wave heights look to climb to near 11ft, mainly between Isle Royale and the Keweenaw, extending northward into Canadian waters. Winds are expected to lighten this afternoon, before increasing again this evening. The setup will be similar to this morning's event, minus the preceding cold airmass - still cold enough for some mixing though. It should be noted though that the low level jet is anticipated to be stronger. Given this, opted to issue a Gale Watch for the western half of Lake Superior tonight through Sunday.
Largest significant waves suggested by the WW3 approach 15ft between the Keweenaw and Isle Royale, with 5-12ft elsewhere. Once the winds settle Sunday night below 20kts, anticipating these light winds to continue for a majority of the coming week.

Northern Green Bay and northwestern Lake Michigan: Northwest winds across are currently being observed, with magnitudes from the variously sited observation platforms ranging from 5 to 20kts.
Expecting similar or lighter winds to continue through at least mid- morning, at which point southwesterly winds are anticipated to increase. Increasing pressure gradient alongside stronger low level winds will support winds climbing to 25-30kts, especially outside of Little Bay de Noc. Elevated winds will continue, and will likely increase Sunday thanks to a stronger gradient over the region. Gale conditions can't be ruled out, especially in the open Bay, Big Bay de Noc, and east of the Garden Peninsula. Latest NBM and REFS probs suggest 40 percent chances or higher, which seems plausible at this time. Sunday night, winds will lighten below 20kts. By Monday, high pressure influence over the region will likely support <15kt winds through at least Wednesday.

MQT WATCHES/WARNINGS/ADVISORIES
Upper Michigan...
None.
Lake Superior...
Gale Warning until 2 PM EDT /1 PM CDT/ this afternoon for LSZ162.

Gale Watch from this evening through Sunday afternoon for LSZ162.

Gale Warning from 11 AM this morning to 5 PM EDT this afternoon for LSZ243-244-263-264.

Gale Watch from this evening through Sunday afternoon for LSZ243-244-263-264.

Lake Michigan...
Gale Warning from 5 AM to 11 PM EDT Sunday for LMZ248-250.