Marine Weather and Tide Forecast for Monroe, MI

AVIATION

A mid level low pressure system will remain nearly stationary just east of Se Mi today. Ample low level moisture circulating around this system will sustain areas of light showers and drizzle into the afternoon. Some low level moisture advection from the north overnight in combination with nighttime boundary layer cooling has resulting in nearly widespread IFR based stratus. Model RH plan views and soundings indicate a gradual eastward shift in these lower clouds during the day. This and some degree of boost from daytime heating will result in a trend toward MVFR based ceilings. The timing of this transition carries a high degree of uncertainty. The overall consensus suggests a mid to late afternoon transition to MVFR, although a much earlier transition is possible across the Detroit metro terminals with a subtle downslope. Despite shallow level afternoon mixing depths frequent wind gusts around 20 knots are expected given the strength of the low level wind fields. A secondary upper low dropping into the northern Great Lakes tonight will help drive a region of dry air across Se Mi, offering a return to VFR conditions for the overnight period.

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

THRESHOLD PROBABILITIES...

* High for ceilings below 5000 feet today and this evening. Low overnight.

PREV DISCUSSION
Issued at 347 AM EDT Thu May 22 2025

DISCUSSION...

Stacked low pressure rotates in place over the eastern Great Lakes today as a departing upper jet streak exit region orphans it off.
Abundant moisture remains in place with model soundings showing saturated profiles up to 700mb into this afternoon. Forcing for ascent is disorganized around the barotropic system but filaments of deformation will continue to bring about scattered light showers and intervals of mist/drizzle through the day. Much of this will be focused over the Thumb and eastern CWA Breezy wind around 15 to 25 mph maintains a feed of cool air from the northwest, keeping temps mainly in the lower to mid 50s. By this evening moisture depth will begin to erode, suggesting a gradual diminishing of showers tonight.
Clouds will remain pervasive through the night holding lows in the lower 40s.

The low releases eastward and gets absorbed into a late season nor'easter on Friday. Cold cyclonic flow persists across the Great Lakes with 850mb temps falling to near 0C, extending the chilly streak another day with highs again in the 50s. The breezy northwest wind sticks around another day as well. A lobe of vorticity passing overhead cools the mid-levels during peak heating to induce weak instability and support a scattered coverage of showers.

By this weekend weak geopotential height rises will commence over the area which should allow upstream high pressure and drier air to nudge in from the west. We will still sit within an active northwest flow pattern with several lobes of vorticity passing through the Great Lakes each day through Monday. With some lingering low-level moisture around, these waves may be sufficient to generate isolated showers during the daylight hours. Otherwise more sun will start to break through the clouds and high temperatures will rebound into the 60s. By Tuesday into the midweek, a series of upper low mergers results in another broad upper trough taking residence over the area. This favors continued below normal temps and potential for showery conditions.

MARINE...

A meandering low pressure system over Lake Erie will continue to maintain northeast flow over Lake Huron and Saginaw Bay, and northwest flow across Lake St. Clair and Lake Erie. This will sustain elevated wave heights and gust potential across Lake Huron and especially the Saginaw Bay, given the favorable fetch. As a result, Small Craft Advisories remain in effect through the day.
Periods of on and off rain showers also continue today, with greatest coverage expected across Lake Huron.

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.