Marine Weather and Tide Forecast for Copper Harbor, MI

DISCUSSION
Issued at 333 PM EDT Mon Jun 8 2026

Afternoon RAP analysis places the mid level ridge axis over the Lower Great Lakes. GOES water vapor imagery helps highlight a shortwave lifting northeast out of IA/IL. Upstream troughing reaching the PAC NW will play a role in the mid to late week shower and storm potential.

The shortwave moves overhead tonight through Tuesday, supporting scattered showers and storms with the help of isentropic ascent.
These showers and storms start late this afternoon over the west and spread eastward tonight through Tuesday. NAEFS indicates PWATs mainly around 1.75 inches, approaching the maximum of climatology for this time of year. HRRR mean 24 HR QPF ranges from 0.25 to 0.5 inches, but higher amounts of 0.75 to 1.5 inches are possible (30- 50% chance). No severe storms are expected given unimpressive shear and instability, but WPC does have a marginal risk for excessive rainfall supported by a deep warm cloud layer of 10-12 kft and lower magnitude mbE vectors (mainly 10 kts or less). Precip should largely clear the area by Tuesday afternoon in the west and Tuesday evening in the east, leaving room for a brief period of quiet weather Tuesday night into Wednesday.

A better set up for strong to severe storms arrives Wednesday afternoon/evening as an oblong closed low spins over the northern Plains/Canadian Prairie with a surface low over Manitoba. This places much of the Upper Midwest and northern Great Lakes in a ripe warm sector. The gulf connection results in PWATs rising up to around the NAEFS 99th climatological percentile with Tds in the mid to upper 60s. This coupled with steep mid level lapse rates of at least 7C/km results in supportive instability by the afternoon (500-1500 j/kg, highest west...particularly near WI where there is around 25% chance for MUCAPE values up to 2500 J/kg). Where questions remain are the timing of storms in the UP and the magnitude of deep wind shear available at the onset of storms. Main threats would be large hail and gusty winds if ideal conditions align within the CWA, however flash flooding potential also is a concern highlighted by the WPC marginal risk for excessive rainfall in the west. SPC has maintained the Slight risk for the entire CWA Troughing and an additional cold front into the early weekend keep chances for showers and weak storms in the forecast.

TEMPS: Look for above normal temps to continue through much of the week. Highs this afternoon peak in the upper 70s to mid 80s, then temps settle overnight into the mid 50s to mid 60s. The range of highs on Tuesday will be larger as showers and cloud cover lingering over the east keep temps from warming quite as high as the west.
Highs on Tuesday will be in the upper 60s to upper 80s, coldest east...particularly near Lake Superior. Lows once again will be in the mid 50s to mid 60s Tuesday night. Wednesday is the main focus for heat risk as widespread highs are expected in the 80s over Tds in the 60s. Parts of the far west approach 90 courtesy of downslope flow. Lows near 60 Thursday morning warm back up into the 80s. Temps return near normal over the weekend with highs trending toward the upper 60s to mid 70s and lows in the 40s.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/
Issued at 142 AM EDT Tue Jun 9 2026

Low pressure moving through the region will bring showers to the area through this morning. VFR conditions will fall to MVFR and IFR with the combination of very moist low levels, showers and light winds. Couldn't rule out periods of LIFR under the heavier showers.
Conditions slowly improve at CMX and IWD this morning but showers will linger into the early afternoon at SAW. Tonight fog is expected to form at CMX and SAW, thus expect IFR and LIFR conditions late tonight.

MARINE
Issued at 333 PM EDT Mon Jun 8 2026

Winds across the lake generally hold below 20 kts through Wednesday morning keeping significant wave heights below 4 ft. Showers and weak storms tonight into Tuesday may result fog development, but opted to hold off on Dense Fog Advisories for now as shower coverage is not as certain over the lake.

East to southeast winds increase to around 20 kts on Wednesday as a low pressure tracks northwest of the lake tightening the pressure gradient. Strong to severe storms are possible ahead of a cold front, starting Wednesday afternoon in the west and continuing into the overnight hours for the remainder of the lake. Additional fog development may follow heavy rain.

Shower and storm chances gradually diminish, but do remain in the forecast through late week and possibly into the early weekend as troughing remains overhead and a secondary cold front moves through.
This also is accompanied by stronger winds likely around 20-25 kts.

MQT WATCHES/WARNINGS/ADVISORIES
Upper Michigan...
None.
Lake Superior...
Dense Fog Advisory until 2 PM EDT /1 PM CDT/ this afternoon for LSZ162-240>248-263>265.

Lake Michigan...
None.