Marine Weather and Tide Forecast for Plymouth, MI

AVIATION

Dry and stable conditions persist today as high pressure slowly migrates across the eastern Great Lakes toward New England. Light wind will emerge out of the south to southwest this morning, generally holding below 10 kt through the afternoon. Potential exists for FEW to SCT coverage of VFR diurnal cu, otherwise mainly clear skies prevail. Benign conditions overnight with just some high cloud arriving late, associated with a slow moving cold front over the Midwest.

D21/DTW Convection...No thunderstorms expected through Wednesday morning.

DTW THRESHOLD PROBABILITIES

* None

PREV DISCUSSION
Issued at 353 AM EDT Tue Aug 4 2026

DISCUSSION...

Another pleasant day is in store for SE Mi as high pressure maintains primary influence while drifting into upstate NY by this evening. Temperatures respond to the core of cooler and less humid air exiting eastward along with the surface high. Full sun and wind returning SW over the region are able to lift readings into the mid 80s, especially in the Tri Cities area. The warmer temperatures occur with typical mid summer humidity as surface Td creeps up to around 60 F most areas by this evening.

After dry and mild conditions tonight, the forecast focus turns to the broad central Canadian low pressure system that is pulling a cold front slowly into the northern/western Great Lakes during Wednesday. Emphasis is on slowly as model projections show it taking about 36 hours to move from the west end of Lake Superior this morning into central Lower Mi by Wednesday evening. The leading moisture axis has also been mostly inactive at night due to weak low level jet forcing as the system approached from the Plains Sunday night and into the upper Midwest early this morning. That could change tonight into Wednesday morning as upper level jet entrance region forcing becomes more favorable for larger scale vertical motion and to support a stronger low to mid level wind field. Longer lasting showers/storms from surface based convection this afternoon then have a chance to combine with a nocturnal component tonight and graze the Saginaw Valley by Wednesday afternoon.

The front takes the remainder of Wednesday afternoon and night to make progress into southern Lower Mi. It does so while a component of surface based convection develops along and near the boundary as the broad mid level trough and entrance region of the upper jet maintain support for larger scale ascent. Consensus of 00Z regional and global deterministic models show a generous QPF response to the favorable larger scale environment focused within the low level frontal zone that takes all of Thursday and much of Thursday night to reach the Ohio border. The weak link in the severe storm parameter space is mainly lower end CAPE values in an otherwise respectable SW unidirectional flow. This is in line with the Day 3 general thunder outlook with an eye toward a marginal risk for excessive rainfall.

The extended range model output gives the front a chance to settle south of the Ohio border by Friday morning where it dissipates during the day. It leaves a tenuous scenario in place for dry weather Friday and Saturday while the large closed low remains anchored over far northern Ontario. The system has a chance to produce another cold front in the Great Lakes by Sunday.

MARINE...

High pressure influence lingers across the central Great Lakes today as the center of the surface ridge slides across Appalachia into the Northeast. Winds increase throughout the day, taking on a southwesterly orientation. This is generated by the return flow configuration and low pressure moving into Hudson Bay from northern Ontario. An attendant cold front will move in from the west and briefly stall out over Lake Huron Wednesday. This provides the first opportunity for showers and a few thunderstorms for the latter half of the week. Several disturbances are expected to ripple through atop the boundary, preserving rain/storm chances through Thursday as the front resumes forward progress toward the southern waterways.
The pressure gradient response appears rather minor through this period, ensuring low probabilities for any long-fused headlines before the end of the week. Drier weather may briefly return Friday and/or Saturday, but the front will stall out again in the vicinity, keeping low chances for thunder nearby.

DTX WATCHES/WARNINGS/ADVISORIES
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.