Marine Weather and Tide Forecast for Big Bay, MI

DISCUSSION
Issued at 350 PM EDT Tue Aug 4 2026

RAP analysis this afternoon shows today's cold front currently draped across the central UP as it progresses eastward. Southerly flow ahead of the front this morning generated widespread 20 mph gusts across the eastern UP and a few as high as 30 mph. Behind the front this afternoon, WNW'ly surface winds show gusts to 20 mph, with temperatures in the high 60s. Frontal passage has limited daytime heating somewhat in the western UP, though locations in the eastern UP are currently in the high 70s.

As this morning's ridge exits the region, a mid-level Canadian low sets up in conjunction with a Four Corners high. This pattern persists for next couple days while the Canadian low propagates slowly eastward. Combined anticyclonic flow from the NE quadrant of the Four Corners and cyclonic flow along the southern half of the Canadian low creates robust NW'ly mid-level pressure gradient flow across the Upper Midwest for the next few days. Weak surface ridging builds in on Wednesday for a dry day tomorrow; on Thursday, a pair of shortwaves orbit through but with no expected precipitation given a lack of substantial moisture. With surface ridging building in over the next few days, winds will be mostly light but with some periods of elevated gusts as LLJs form, dissipate, and rotate around the Canadian low.

What weather we do experience may be initiated by shortwaves orbiting around the slow-moving Canadian low, whose surface feature sits in northern Ontario this afternoon. The next shortwave with notable moisture and precipitation chances appears to be Friday evening, when the NBM shows an anomalously strong LLJ moving overheard. Along with this, the NBM shows up to 50% chance of SBCAPE greater than 500 J/kg along the WI border Friday afternoon, and 30 knots of 0-500mb shear. NBM probability of 6-hr precip exceeding 0.1" is around 50% for at least some point on Friday afternoon and evening, and the 90th percentile of 6-hr distributions top out at 0.6" at this point in time. All told, severe weather is not expected for this event at this time.

Further out, differences in LREF clustering in 500 mb heights begin around Day 6 (Aug 8-9) in the timing and strength of trough entering into the PNW from the Pacific (though the strength of this trough is so weak such that the question is not 'how strong?' but rather 'trough or zonal?'). That said, the influence on this region for days 6-9 are all very similar, with the Canadian low and Four Corners high still in place leading to local NW'ly mid- level flow.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
Issued at 100 PM EDT Tue Aug 4 2026

Expect VFR conditions through the rest of the period once SAW improves this afternoon. While some -SHRA and maybe a few rumbles of thunder could be seen over SAW this afternoon, expect the -SHRA chances to move eastward away from the terminal as we continue into the late afternoon to evening hours. With high pressure moving in, but with upper-level clouds looking to remain overhead early tonight, thinking the terminals will generally remain FG-free. That being said, there is still a <30% chance that some patchy FG could be seen at and around IWD and SAW early Wednesday morning.

MARINE
Issued at 350 PM EDT Tue Aug 4 2026

Westerly flow builds in this evening as the cold front and accompanying thunderstorm chances exit the eastern reaches of Lake Superior. Winds decrease throughout the night tonight, with gusts to 25 knots remaining over the open western Lake Superior and nearshore zones west of the Keweenaw until 00Z. Winds are light (<10 knots)
until Wednesday evening, when southerly gusts to 20 knots build into Lake Superior. This southerly flow remains through Thursday, peaking in the early morning hours of Friday near 30 knots over Lake Superior before diminishing to 15 knots by Friday evening.
Waves remain below 2 feet before building to 3.5 feet by Friday morning, then decrease to 1 ft by Saturday afternoon.

MQT WATCHES/WARNINGS/ADVISORIES
Upper Michigan...
Beach Hazards Statement until 10 PM EDT this evening for MIZ014.

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