Marine Weather and Tide Forecast for Harbor Springs, MI

SHORT TERM /THROUGH FRIDAY/
Issued at 325 PM EDT Thu May 22 2025

Pattern/synopsis: Primary upper low center is just north of eastern Lk Superior, and is moving southward. Secondary circulation center, evident in visible satellite imagery this afternoon, is a bit north of YYZ. This is still associated with the main surface low.

Forecast: Upper low swings south and then se-ward, ending up over northern Lk Huron Fri morning. It shears out eastward on Friday, with a substantial trof lingering back over OSC-PLN-ERY by late afternoon. Deeper moisture has been edging eastward today, with synoptic precip mostly confined to far se Chip Co, and the ne lower MI coast near and south of Rogers City.
However, as the upper low approaches and especially departs, deep moisture will be pushed back to the sw for a period. Clouds and pops will be on the increase tonight in eastern upper MI, and eventually far northern lower MI overnight. Before then, main focus will continue to be near APN/Rogers. Around 0.10-0.15" of rain tonight in central and western Chippewa Co, less elsewhere.

Friday will see the most extensive precip chances, with spotty showers/light rain possible across most of northern MI. The far south is the possible exception. Better moisture starts to depart eastward as the afternoon proceeds, with precip decreasing in the TVC area first. Progged QPF is around 0.10" in parts of far eastern upper MI, less elsewhere.

Parts of nw lower, eventually migrating down toward HTL, will see partial clearing early tonight. Clouds do fill back in from the north late. May be a few mid 30s down by CAD/Lake City, but winds are likely to stay up enough to limit frost potential.
Upper 30s to around 40f elsewhere
Friday, mainly cloudy
and awfully cold for the Friday heading into Memorial Day weekend.
Upper 40s to lower 50s for highs.

LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/
Issued at 325 PM EDT Thu May 22 2025

Upper low merrily spins over northern New England this weekend.
Lingering upper troffing will contribute to a somewhat slow recovery from the chilly wx. Moisture lingers long enough for a chance of showers Fri evening in eastern upper MI. And cloud cover will be slow to diminish, as the low levels remain somewhat soupy. That is likely to limit frost potential Fri night, at least. But Saturday looks more cloudy than not, and max temps will still be stuck in the 50s. There could be a diurnal shower or two Sat afternoon. There will be a diurnal contribution to cloud cover on Saturday, so we should some breaks form heading into Sat night. That looks like a better chance for frost, and a mention will be added to the HWO.

Better temps appear likely for Sunday and beyond, finally, nearer 60f for highs Sunday and into the 60s after that. A stray diurnal shower is possible again Sunday afternoon. GFS/ECMWF agree an on upper low being generated in the northern plains early to mid week. If so, that would pump some warmer air into at least the southern lakes by midweek. A general frontogenetical pattern should also lead to increasing precip chances by Tue into Wed.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
Issued at 139 PM EDT Thu May 22 2025

Varying conditions across the forecast area this afternoon...with partly/mostly sunny VFR conditions at KTVC/KMBL...more mid level VFR cloudiness at KCIU/KPLN...and IFR ceilings in light rain at KAPN
Expect conditions at KAPN to improve after 21Z
but over time expecting at least MVFR ceilings to develop at all terminals after midnight (and IFR Friday morning).

APX WATCHES/WARNINGS/ADVISORIES
MI...None.
MARINE...Small Craft Advisory until 11 PM EDT this evening for LHZ348- 349.
Small Craft Advisory until 11 PM EDT this evening for LMZ323- 341-342-344>346.