Marine Weather and Tide Forecast for Onekama, MI

DISCUSSION
Issued at 155 AM EDT Sun Apr 19 2026

Pattern Synopsis and Forecast:

Deep upper trough, extending from Hudson Bay and northern portions of Quebec down into the Upper Midwest, will be our feature of note for today. Additionally, secondary cold front will move through the area as well. Trough axis with cold pool aloft and steepening low to mid level lapse rates will result in minor instability today, aiding in snow shower development. Low level convergence along the frontal boundary will help as well. Given this pattern, conceptually, cellular snow/rain showers are likely with aid from the frontal boundary. Looks to be a little better region of enhancement generally south of M-32 given better sfc convergence along with the best axis of non zero convective instability during the daytime hours. One would think the main concern with any of these snow showers would be short lived drops in visibility, perhaps some graupel as well. Colder low level temps tonight may produce a few light lake induced snow showers, the main story being the seasonably cold lows. Expect low 20s most areas with teens across our notoriously colder spots.

That troughing complex pulls away early next week, with drier conditions overall as high pressure builds overhead on Monday. Quick moving upper trough across Canada and attendant boundary late Monday night into early Tuesday will try to clip eastern upper for a shower or two, but looks like the better forcing and moisture will be displaced too far to the north. Either way, this is not a big deal and does not add any more hydrologic stress on the area, on the contrary in fact with subsiding water levels across our river systems.

A welcomed dry stretch of weather is expected much of next week as heights begin to rise, especially mid to late week. Meanwhile, a deep trough made up of many pieces of energy dives into western and central portions of the CONUS, driving a moist (dewpoints >50F and PWATs 150-200% of normal) airmass into northern Michigan.
Instability a little in question at this time, but there is the potential for some healthy rains with this type of pattern sometime during the later Thursday through Friday night time frame. Current probs from LREF and NBM generally suggest a low to medium potential (~10 to 50%) for 0.5" or more of rain. We'll have to monitor the subtleties of this setup moving forward.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/
Issued at 622 AM EDT Sun Apr 19 2026

Primarily VFR conditions expected through this taf period, with passing mainly higher based clouds...along with the potential for a few light snow showers at times today. Suppose any brief heavier snow shower may temporarily drop visibilities to MVFR. Gusty northwest winds today...with northwest winds steadily decreasing in speed tonight.

HYDROLOGY
Issued at 155 AM EDT Sun Apr 19 2026

Current flows across area rivers remain anomalously high, with plenty still exhibiting cfs values at a 2% annual exceedance probability (or 50 year average return interval). Combining this with some of our flood inundation mapping tools suggest inundation still occurring across portions of northwest and northeast lower MI (for example portions of Cheboygan, Alpena, and Wexford counties).
Some improvement noted across other locales though standing water likely remains in poor drainage places and areas of saturated soils.
Thus, areal and river flooding is still occurring, although river levels and flows are dropping to some extent across the area. This will continue to be the trend through a good portion of this upcoming week as a dry period is expected, so we should expect a slow but significant improvement in the ongoing flooding and subsequent river levels across northern Michigan, as indicated by the latest HEFS River Flood guidance. Flooding will linger longer across the Tip of the Mitt and any lakes that have elevated water levels that are impinging on houses. Worth noting that an active period is likely late this week and beyond, with the potential for noteworthy precipitation. Something to consider moving forward.

APX WATCHES/WARNINGS/ADVISORIES
MI...None.
MARINE...Small Craft Advisory until 5 AM EDT Monday for LHZ345>349.
Small Craft Advisory until 5 AM EDT Monday for LMZ323-341-342- 344>346.
Small Craft Advisory until 5 AM EDT Monday for LSZ321-322.