Marine Weather and Tide Forecast for Mackinac Island, MI

DISCUSSION
Issued at 154 AM EDT Sat Mar 21 2026

Pattern Synopsis/Forecast: Currently a PNA pattern in the upper levels exists, with an unseasonal strong 597 dam upper high over AZ/SoCal. Due to this, the Pacific storm track is funneling moisture into northern WA/ID/MT. With fairly zonal flow over the southern CAN Rockies, a couple lee side lows have been forming here and eventually tracking to the east and south..
becoming clippers. The next clipper will bring precip chances back to northern MI today, and is currently forming over the US/CAN border near north central MT. This surface low will track along a baroclinic zone orientated NW to SE along the northern plains and great lakes states, with the center of the surface low reaching MN by mid morning today. Warm sector precip will begin to move over parts of northern MI mid to late morning today. Generally light rain and snow (or times of a mix) will fall over areas along and north of M-72, lasting through the afternoon. More moderate precipitation (mostly in the form of snow) will be seen north of the bridge. Precip will lighten up and/or stop for most places this evening, with another round of precipitation (rain, snow or both) moving through late tonight into early Sunday morning. North winds will bring in colder air for Sunday and Monday, with Monday morning low temperatuers potentially dipping into the single digits for some spots. Winds will be breezy today, with occasional gusts up to 15 to 20 mph.

A break in precipitation will be seen Monday, however quasi-zonal flow over the northern Rockies will continue into next week..
continuing the creation of lee side lows that will likely track towards MI. A few rounds of precipitation are in the forecast for next week, with temperatuers remaining near or below normal. A healthy amount of uncertainty exists in the longer term forcast, as decent spread of the overall pattern exists in the ensembles (seen in cluster analysis) as well as the global deterministic guidance. The means that details on what the precipitation looks like, timing, and amounts is still up for debate for next week.

Forecast Details: Due to the 0C 850mb line being right over northern MI, precipitation type will change over the course of today and tonight's precipitation. Drier air in the lower levels currently exists (KAPX 00z RAOB depicts stark drying just above 850 mb), and will impact the onset of precipitation. Model soundings show saturation catching up in the lower levels while the trace remains below freezing... indicating mostly snow will be seen for the onset of precipitation in the higher terrain hills of northern lower (and possibly parts of eastern upper near Presque Isle). Near surface winds eventually turn south near midday, at the same time of SW winds just above the surface advecting warmer temps over northern lower. Not only will surface temperatures warm into the high 30s and 40s, temps aloft will warm as well... resulting in most areas of northern lower seeing rain as the precipitation exits this afternoon. Eastern upper will see snow for most of the day, however as the main precipitation exits, not only will a warm nose move overhead..
lower level moisture will be stripped. Precipitation will still likely be falling, however the DGZ will not be saturated and a warm nose will likely exist. East winds will keep surface temperatuers near or just below freezing during this time. The good thing, is that the moderate precip will have transitioned back to light and become intermittent. Although freezing rain and drizzle will be seen in some spots of eastern upper late afternoon and into tonight, it will remain light and intermittent which will likely keep totals up to a couple hundredths of an inch (where ice can become measurable). The second wave of precip moving through tonight into Sunday morning will be brief and produce mostly snow as it tracks to the south across northern MI.

The lack of a prolonged window of ideal forcing and the right temp/moisture profile will result in high confidence of precipitation amounts generally remaining non-impactful across northern lower.
Eastern upper on the other hand will reside over more ideal forcing, however the window(s) remains short for most of the area. Generally 1 to 3 inches of wet snow is expected, with locally higher amounts possible near the SOO. The warm nose could not reach the SOO, and result in most of the precipitation falling as snow. If this is the case, expect some spots to see up to 5 inches of snow. As far as the ice, there is high confidence in amounts remaining local and only up to a couple hundredths of an inch.

AVIATION /00Z TAFS THROUGH 00Z SUNDAY/
Issued at 1126 PM EDT Fri Mar 20 2026

Still expecting some IFR/LIFR cigs and/or visbys tonight due to patchy fog with light/vrb winds. Latest data looks a little slower with onset of rain/snow...closer to 12-15z for CIU/PLN; some question if it reaches the ground at TVC/MBL or not, with a better chance for cigs to go MVFR/VFR after 18z behind strengthening warm front. Could stay all SN at CIU with RASN more likely for PLN/APN, with shot at all RA by late afternoon there...with most intense period closer to 18-0z. Surface low could track across the TVC/MBL area in afternoon with potential for light winds in midday/late afternoon...but otherwise expect period of stronger SE winds ahead of this (5-15kt) around 15-20z, turning to NE toward 21- 0z. Some LLWS possible, esp at mbL late in the day...but could be further north into TVC/APN if low tracks further north.

APX WATCHES/WARNINGS/ADVISORIES
MI...None.
MARINE...None.