Marine Weather and Tide Forecast for Harbor Springs, MI

DISCUSSION
Issued at 256 PM EDT Fri Jun 26 2026

Pattern Synopsis/Forecast: Low amplitude/quasi-zonal flow pattern across CONUs to start the weekend; digging trough/-PNA pattern along the west coast. Short wave trough that crossed the upper Lakes Thursday heading across southeast Ontario/northern New England; water vapor imagery shows another well-defined wave across Minnesota. Still a little residual low/mid level cyclonic flow across Michigan in the wake of the passing short wave trough...
though northerly flow has dried things out (precipitable water values below 0.75 inch)
At the surface
broad ridge of high pressure across northern Ontario/Manitoba extending into the upper Great Lakes; west-east frontal zone stretches from the central Plains/Ohio Valley and into southern New England.

Digging trough and eventual closed low developing over the western U.S. (pretty impressive -3 to -4 sigma 500mb height anomalies) a harbinger of things to come across the eastern CONUS. Strong ridge builds in response to the upstream troughing...initially centered over the middle/lower Mississippi Valley and expanding north into the Great Lakes later Sunday into Monday. 590+dam 500mb heights into northern Michigan by Monday (which would be a +2 to +2.5 sigma 500mb anomaly)...heights that exceed those occurring in prior June heat waves (16-19 June 1995 and 29 June-1 July 2018 for example).
This pattern configuration...with 594dam 500mb heights flirting with southern Lower Michigan...is expected to remain in place through most of next week although the amplitude of the ridge may get blunted by short wave energy coming over the top of the ridge.

High pressure over Hudson Bay will continue to have an influence on the upper Great Lakes through Saturday. Rising heights will eventually (one would think) have to push a warm front northward across the upper Lakes...perhaps on Monday. If we can get on the warm side of that boundary (Tuesday)...push the potential MCS corridor to the north of Michigan and get some capping aloft (which 582+dam thickness would aid the cause) that will increase the probability for significant heat unencumbered by convective remnants (which happens way too often).

Primary Forecast Concerns:

Mostly dry through Sunday: Will likely see patchy/areas of fog develop tonight...especially across northeast Lower and adjacent to Lake Huron...and up around Whitefish Bay. Fog over northwest Lower will likely be more patchy and develop late...but that should burn off during the morning with a nice Saturday afternoon expected.
Better surge of moisture headed into the upper Midwest/Wisconsin Sunday...although dew points across northern Michigan will still be in the comfortable 50s. Temperatures should continue to creep up Sunday afternoon with more areas likely getting into the 80s.

Rain chances Sunday night/Monday as warm air pushes northward: The push of warmth and moisture expected to spawn some convection across Wisconsin/Lower Michigan Sunday evening which should propagate northeast. Warm front lifting north across the upper Lakes Monday will keep the threat for convection going though consensus forecast PoPs are pretty muted (capping??). Monday should also be the onset of a noticeable increase in humidity.

Significant heat wave in the offing next week...especially from Tuesday and beyond: It has been an up-and-down month for temperatures in June; a warm spell for the first two weeks...but we've been below normal every day since 14 June (which will include today and perhaps Saturday as well). But we will break that string and then some to wrap up June and head into July...with the upcoming hot weather being the main impact this forecast cycle. Now how extreme will this get? NBM trying to forecast 100+F highs from Alcona county south to Arenac county starting Tuesday; perusing the raw and bias corrected member distributions for OSC...there is no overlap at all in the interquartile ranges of the two distributions.
We don't see that in other locales (e.g., GLR/HTL) which makes me suspicious that the bias correction is going a bit wild (a couple of bias corrected members are over 110F at OSC on Wednesday and Thursday). Would prefer to at least cut the NBM with some of mean raw model guidance to keep the forecast more "responsible" for days 4+; still forecasting temperatures in the mid-upper 90s east of I-75 for Tuesday through Thursday so the hype machine can continue unabated.

Forecast versus record highs starting Tuesday (30 June) are as follows:

KGLR: Tue 92/98 (2018)...Wed 90/96 (1966)...Thu 91/96 (1966).
KHTL: Tue 93/99 (1927)...Wed 93/103 (1931)...Thu 95/99 (1921).
KTVC: Tue 94/99 (1931)...Wed 93/103 (1931)...Thu 91/100 (1966).
KAPN: Tue 95/99 (2018)...Wed 93/100 (1031)...Thu 95/98 (1966).
KPLN: Tue 91/94 (2018)...Wed 90/97 (2018)...Thu 88/93 (1966).

So we will be close and several records will be threatened...
provided of course that we don't get rogue clouds/convection rolling in at some point during that stretch. And while it seems reasonable that we could remain capped at least across northern Lower...that is too much of a mesoscale stretch at a decidedly synoptic scale time frame.

Tuesday should see the first day of several with dew points in the vicinity of 70F; wet bulb globe temperatures will be in the high to extreme category (extreme south of the bridge) each afternoon from Tuesday through Thursday. Heat indices 95F to 100+F across northern Lower would necessitate Heat Advisories...perhaps getting up to 105F in spots on Tuesday afternoon. Heat may be mitigated a bit by Friday but it will still be uncomfortable.

AVIATION /00Z TAFS THROUGH 00Z SUNDAY/
Issued at 740 PM EDT Fri Jun 26 2026

Some fog is likely at most TAF sites late tonight. Kept TVC VFR, but IFR at the others. LIFR is most likely at mbL/PLN. Quickly becoming VFR Sat morning, and staying that way thru the day.
Light winds.

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