Marine Weather and Tide Forecast for Port Sanilac, MI

DISCUSSION

A mixture of scattered light showers, drizzle, and mist continues into the evening as stacked low pressure remains in place over southern Ontario. Drier air currently over the northwestern Great Lakes, seen on water vapor imagery as well as evident on visible satellite, is wrapped into southeastern Michigan late this evening/tonight resulting in steady top-down column desaturation.
Loss of moisture should allow for a fairly rapid tapering off of lingering showers across the region. Some clearing skies possible late tonight mainly over the southern CWA as the main surge of drier air pushes into northern IN/OH; however with continuing cool cyclonic flow below the upper trough still in place overhead, low moisture is not expected to be fully scoured out resulting persistent cloud cover through Friday. Another mid-level wave drops out of the southern James Bay over Lake Huron daytime Friday steepening lapse rates as the mid-levels cool offering isolated to scattered showers the latter half of the day- best chances focused towards the Thumb.

Shortwaves finally push east of the region Friday night-Saturday as they merge with the remnants of the Nor'easter, though low amplitude upper troughing holds across the Great Lakes. Another shot at afternoon pop-up isolated/widely scattered showers comes Saturday as a lobe of vorticity embedded with mid-upper flow provides renewed steepening of lapse rates below weak upper divergence. Similar story for Sunday as yet another vort max tracks over the central Great Lakes. Some temperature recovery (ie back into the 60s) can be expected this weekend as flattening upper flow supports modest height rises and more breaks in cloud cover weakening lingering thermal troughing and allowing 850mb temps to climb from -1-0C Sat AM to 2-3C by Sunday PM. Any further moderation is stalled this coming work week as broad upper troughing redevelops over the eastern CONUS maintaining seasonably cool conditions.

MARINE

A low pressure system will continue to meander across Lake Erie and Lake Ontario through Friday, before phasing with a second low pressure system over New England. This will maintain northwest flow to end the week. The slight backing of wind direction through this evening in conjunction with a weakening pressure gradient will relax wave heights across the Lake Huron shoreline by late tonight. This will allow ongoing Small Craft Advisories to end late tonight.
Otherwise, on and off rain showers will continue through the week.

PREV DISCUSSION
Issued at 217 PM EDT Thu May 22 2025

AVIATION...

Cool north flow with relatively moist conditions in the lowest 9.0 kft agl will maintain MVFR ceilings this afternoon. Cyclonic northwesterly flow will eventually force the dry air over Lake Michigan to advect across the terminals. The combination of dry air and loss of daytime heating is expected to result in VFR ceilings this evening and tonight.

For DTW/D21 Convection... No thunderstorms expected through the period.

THRESHOLD PROBABILITIES...

* High for ceilings below 5000 feet this afternoon.



DTX WATCHES/WARNINGS/ADVISORIES
MI...None.
Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ421-422- 441>443.

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