Marine Weather and Tide Forecast for Port Sanilac, MI

AVIATION

Minimal aviation weather concerns in the near term as the region remains under the influence of high pressure. Cloud cover through the early evening will be generally confined to cirrus streaming in from the west. There is a brief (couple hour) window in the process of winds veering southerly overnight for southeasterly winds to draw in remnant low VFR (~3kft) stratocu from Lake Erie over the southern terminals. Coverage is still not expected to be more than SCT however with this low cloud pushing north of the terminals late tonight as southerly flow strengthens. Clipper system is then set to sweep over lower MI Tuesday morning bringing widespread MVFR/IFR light snow and breezy southwesterly winds. Main accumulating snowfall occurs mid-morning with the southern terminals seeing an inch or less with around an inch for FNT/MBS. As snow tapers off late morning as mid-level dry air arrives, the still saturated low levels offer a transition to freezing drizzle/mist through early Tuesday afternoon. Little if any ice accums forecast. Southwest winds gust 20-25kts most of daytime Tuesday.

DTW THRESHOLD PROBABILITIES...

* Low for ceiling at or below 5000 ft through late tonight. High by Tuesday morning.

* High for initial p-type as snow Tuesday morning before transitioning to a light freezing drizzle/mist midday Tuesday.

PREV DISCUSSION
Issued at 421 AM EST Mon Dec 8 2025

DISCUSSION...

Chilly start today with readings in the single digits, outside of Metro Detroit and the Lake Huron coastline. Initial wind chills will not deviate much compared to temperatures given light to calm gradient winds. Sub-700 mb anticyclone passes over Lower Michigan today leading to a layer of subsidence between 3 kft and 12 kft with a maximum 35C dewpoint depression. Meanwhile, moisture spills in aloft along a low amplitude shortwave trough, leading to a canopy of high clouds as lower column trajectories across the Huron basin generate patches of stratocumulus, downwind of the southern coast.
Given the shallow mixed-layer and 925 mb temperatures around -10C, daytime highs will struggle to break much beyond the mid-upper 20s while the resident arctic airmass holds (10-15 degrees below seasonal normals).

The surface pressure field transitions from high pressure to low pressure dominant overnight as a clipper digs into the Upper Midwest. Gradient flow strengthens, starting out southerly, and foreshadowing the consequential warm sector arrival within the occlusion of the primary (southern) surface reflection. A plume of Pacific moisture associated with this circulation accompanies the VortMax promoting the quick onset of nocturnal precipitation. The elevated warm front modifies the lower levels, setting up an inversion between the 2-6 kft AGL layer. Initial precipitation falls as snow between 07Z and 11Z (from west to east). In spite of nocturnal warming, surface temperatures should be plenty cold for accumulation into the early morning hours on Tuesday. DGZ depths are sufficient, but not much QPF to work with, so expect only a coating to an inch. Interesting note about the 07Z NBM snowfall percentiles through Tuesday (18Z). Quite a big difference between the 50th and 75th percentiles, with 0.3-1.0 inches for the former, and 1.0-2.5 inches for the latter. Outgoing forecast falls between the two ranges. Ensured a minimum accumulation of around a quarter inch, but allowed for over an inch for The Thumb where mixed precipitation chances will be lower.

Precipitation type concerns arise during the daylight hours Tuesday as forecast soundings reveal issues with DGZ depth and duration of saturation. After the initial burst of morning snow, the surface to 10 kft layer warms above -10C and begins to dry out (down to 5 kft)
upon increasing zonal flow. At the same time, the omega sign reverses leading to subsidence within the mid-levels. This extends to ice nucleation problems limiting snow generation aloft. Higher potential exists for an all-snow scenario north of I-69 which is where the higher daytime QPF should fall. As for the southern half of the forecast area, a mix of low SLR (wet/fine snow) and freezing drizzle could lead to a thin glaze of ice, generally atop existing snowpack. Temperatures will be near/above freezing late afternoon and evening, so ice accretion will be more questionable on other surfaces. High temperatures arrive around sunset.

The next VortMax and 985 mb surface low arrive Tuesday night into Wednesday as the active quick-hitting pattern holds. Temperatures will be slow to drop below freezing early Tuesday night as the next round of precipitation gets underway. Latest model data shows a similar progression with snow to start before switching over to primarily rain late Tuesday night or early Wednesday morning.
Precipitation type differences exist between the northern and southern parts of the CWA with a much lower likelihood for a liquid transition to the north. Higher snowfall totals are therefore predicted along/north of M-46 where precipitation should continue exclusively as snow all day Wednesday. Winter Weather Advisory considerations will need to be made for the northern counties in subsequent forecast updates. Kept inherited NBM snowfall with totals in the 3-5 inch range. Further south, drying in the mid and upper levels ensures a period of cold low stratus rain until midday. Once the system's cold front swings through, expect a flip back to snow across Southeast Michigan for the foreseeable future. Additional accumulations will be lighter along the back end of the event Wednesday and into Thursday with temperatures dropping below normal overnight.

The colder post-frontal airmass works in concert with periodic trajectories for sufficient fetch for some lake effect snow chances through the end of the workweek. Some evidence exists for a third clipper on Friday, but positioning within the mean flow is questionable as it would pertain to the local area. Could get some synoptic driven snow if things fall into place. The next release of arctic air remains on track for arrival by Saturday. 850 mb temperatures could drop below -20C as colder than normal temperatures lock-in for the weekend.

MARINE...

Northerly winds continue to decrease this morning as high pressure settles over the Central Great Lakes, leading to light winds today, but shifting to the southwest and then ramping up this evening.

Still looking at brief southwest gales possible late tonight into Tuesday morning as low pressure tracks through the northern Great Lakes. The strongest winds looking to be over Saginaw Bay/Central Lake Huron. Snow will likely cause some precip drag, which should help limit the magnitude and duration of any gales that develop.

A larger and stronger low pressure system is then on track to move through Lower Michigan Tuesday night into Wednesday producing widespread snow and even rain over Lake St. Clair and Lake Erie. The southwest low level jet ahead of the looks to be very strong, and low level profiles do not appear to warm quick enough to stabilize the near water surface. Thus, it is looking like increasing chance of gales of western Lake Erie, with potential to briefly reach aoa 40 knots.

Rush of cold air behind the passage of the low will then support strong northwest winds late Wednesday and Wednesday evening.
Isolated, brief gusts to gales will be possible, but the pressure gradient quickly relaxes by Thursday morning.

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