Marine Weather and Tide Forecast for Harper Woods, MI

DISCUSSION

Moist near surface conditions are persisting across Southeast Michigan this afternoon evidenced by widespread stratus ceilings at 2.0 kft agl. Satellite imagery supports a rather thick cloud deck outside of the downsloping area in the Saginaw Valley. Suspect it is in this area that clearing will begin as daytime heating wanes. The southern forecast area will likely be a different story as some model data supports keeping moisture in place. In fact, models suggest some additional low level moisture advection from the east overnight. For the grids did continue optimistic sky trends in the north, but did hand edit a more pessimistic overcast forecast in the south late tonight and a good part of Friday. Lows tonight will range from the lower 50s north to lower 60s in the Detroit heat island. Heat indices Friday are expected to be in the middle to upper 70s.

On Saturday, the next wave of low pressure will be driven by right entrance region dynamics of a fairly zonal upper level jet streak.
Plan view progs of moisture show a surface warm frontal surge occuring between 12-15Z with 900-700mb thetae return during the mid to late afternoon hours. Respectively steep lapse rates are expected above 12.0 kft which could yield MUCAPEs/SCAPEs up to 3000 J/kg.
Given the larger scale forcing both with the jet forcing aloft and warm advection, difficult to pin down any short time windows for precipitation. Rather, looks like there will be chances throughout the day and will need to account for the timing and evolution of upstream MCS activity. Will take destabilization during the afternoon to sustain any deep convection and it is late in the day that 0-6km bulk shear is forecasted to increase between 40 to 50 knots. At this point, Swody3 has Southeast Michigan in a General Thunderstorm designation.

1000-500mb geopotential height rises over the Great Lakes will allow for surface high pressure across the region Sunday through Tuesday.
Forecast soundings suggest mid-upper level dry air during the time period with subsidence varying between 6.0 and 16.0 kft agl. A very comfortable period early next week.

MARINE

High pressure arrives from the west tonight causing gusty northwest winds to weaken and veer north to northeast. Small Craft Advisories remain in effect along the Lake Huron nearshore where 4+ foot waves will persist through this evening. The high spreads directly overhead on Friday causing winds to go light and variable. By Saturday, wind organizes out of the south as the high departs east and a warm front lifts into the Great Lakes. This will bring the next round of humid, unstable weather with scattered showers and storms this weekend. Wind speeds and wave heights will hold below advisory criteria but may be locally higher in and around thunderstorms. The cold front clears the area Sunday with moderate north wind to wrap up the weekend.

PREV DISCUSSION
Issued at 130 PM EDT Thu Jul 17 2025

AVIATION...

General trend is for low cloud (sub-5.0 kft) to linger through early Friday morning as cooler post-frontal flow has activated Lake Michigan and Lake Huron. There is a low chance for clouds to scatter this evening, but would be brief as winds veer to the NE and redirect downstream moisture overhead. High pressure slides across lower Michigan tonight, which lowers inversion heights and increases chances for MVFR conditions through 12z Friday. Winds eventually shift offshore Friday morning as diurnal heating ramps up to result in a clearing trend that persists through the rest of the TAF period.

For DTW/D21 Convection... Thunderstorms are not in the forecast through Friday.

THRESHOLD PROBABILITIES...

* High for ceiling 5000 ft or less today, moderate this evening, high between 04z and 12z Friday.



DTX WATCHES/WARNINGS/ADVISORIES
MI...Beach Hazards Statement until midnight EDT tonight for MIZ049.

Lake Huron...Small Craft Advisory until midnight EDT tonight for LHZ421-441>443.

Small Craft Advisory until 4 PM EDT this afternoon for LHZ422.

Lake St Clair...None.
Michigan waters of Lake Erie...None.