Marine Weather and Tide Forecast for Mackinac Island, MI

DISCUSSION
Issued at 111 AM EDT Sun Mar 22 2026

Forecast: Currently, surface observations show a surface cold front boundary tracking across northern WI and the western U
P
At the same time, a ~1001 mb surface low centered over northern lower MI is gradually tracking to the east this morning. Winds will gradually turn north to northwest this morning behind the surface front. Shortly behind its passage, a band of FGEN around 850mb will move southward over northern MI. Under more ideal upper forcing (divergence from a jet aloft) paired with the lower level features and lingering moisture, light to moderate rain and/or snow with an embedded shower or two will track through this morning. Precip in some spots will likely turn to freezing rain/freezing drizzle as the precipitation exits, especially over the higher hills of northern lower and parts of eastern upper. Precipitation chances will diminish by the midday/afternoon hours. Amounts will remain light. Northwest to north winds today will become breezy with gusts up to 20 mph (up to 25 mph over coastal areas of NW lower), peaking in the mid morning and remaining brisk through the afternoon before diminishing this evening and tonight.

Cold overnight lows are in store for tonight into Monday morning, with typical cold spots potentially dipping into the single digits.
Quasi-zonal flow over the northwestern US continues through most of the forecast period will continue to generate lee side troughing over the Northern Rockies and southern CAN. The west to east upper flow will steer these towards the Great Lakes region, keeping the pattern unsettled. The next clipper will start to impact northern MI Tuesday, with precipitation chances lingering through most of the mid-week timeframe as a second clipper strengthens over the northern plains right behind the first. The cold front passage behind the larger clipper could bring in a colder airmass for the end of the work week.

Uncertainties/impacts: Higher confidence exists for amounts with this mornings precipitation remaining light, any snow accumulations will be less than an inch (if any) and any ice will a trace to a hundredth or two at max. The majority of precipitation should fall as rain, with liquid QPF remaining under a tenth of an inch. Current surface observations depict above freezing temperatures under the initial wind shift moving through northern WI and the western U.P. as very warm air was in place to the west over the northern plains yesterday. Model soundings show the Td trace staying above freezing aloft as well (indicative of precip falling along and south of the elevated boundary). Below freezing temperatures at the surface will push through later today (midday/afternoon). That doesn't rule out freezing temperatures for some local areas earlier, especially across eastern upper (near the St. Mary's river) and in the higher hills of northern lower... resulting in the chances for for freezing rain/drizzle.

There is slight uncertainty in Monday morning's low temperatures due to chances for some lake effect snow showers. Colder 850mb temperatures (-15C to -10C ) arrive overhead during this time with northwest winds around 20kts at this level. The main reason chances are so low is that background moisture is very low (-20C Tds at 850mb)
Model sounding traces of the NAM and RAP show this as well
with some lower level moisture add from the lakes but it doesn't look like enough at this time. With that said, some lake induced cloud cover could be seen over spots which could keep some locations warmer than forecasted. Although, lake induced cloud cover will have a difficult time reaching over the typical cold spots of the elevated valleys of the northern lower interior. This leads to higher confidence in typical cold spots seeing ideal radiative cooling conditions.

AVIATION /00Z TAFS THROUGH 00Z MONDAY/
Issued at 1147 PM EDT Sat Mar 21 2026

Expect lingering fog/mist thru 9-12z as light RA moves in ahead of a cold front. Still think this will begin as SN/RASN or CIU/PLN/APN.
DZ conditions could continue into the day Sunday, likely becoming FZDZ as temps fall, but could mix with SN at times. Cigs largely IFR to LIFR thru 12-15z, improving to MVFR for most all sites in the afternoon. Could try to SCT out at times, esp near mbL around midday, but expect MVFR cigs to hold after 18z for all sites, with N flow lake effect snow showers possible for coastal sites. LLWS early at mbL/TVC in particular, but should mix out after 12-15z. SE/vrb winds thru 8-12z become N and will be strongest for coastal sites (MBL/TVC/APN).

APX WATCHES/WARNINGS/ADVISORIES
MI...None.
MARINE...Small Craft Advisory from noon today to 4 AM EDT Monday for LHZ348-349.
Small Craft Advisory from 6 AM this morning to 6 PM EDT this evening for LMZ323-342-344.
Small Craft Advisory from 6 AM this morning to midnight EDT tonight for LMZ345-346.