Marine Weather and Tide Forecast for Mackinaw City, MI

SHORT TERM /THROUGH SATURDAY/
Issued at 229 PM EDT Fri May 16 2025

Current Overview / Pattern Synopsis:

Vertically stacked / cut off low pressure over Minnesota will slowly trek eastward through the forecast period, with attendant secondary cold frontal boundary sweeping through the Great Lakes this evening into tonight. Convective response from a wave along this front well underway across Iowa and Illinois, and with strengthening low level jet dynamics, should bring another round of showers and thunder to the area tonight. In the wake of the FroPa, cold air advection will be the rule through Saturday... and with some lingering low level moisture coupled with steep low level lapse rates (and a touch of diurnal heating) anticipating shower coverage to fill right back in through the day Saturday as a borderline autumn feel intrudes into the region over the next several days.

Forecast Details:

Dry conditions hold across much of the area into this evening, with the exception being some shower potential across the far SW as the convective activity to our southwest intrudes. Current thoughts are that with ample mixing and steepened low and mid level lapse rates (latest guidance suggests the mixing layer may approach 600mb), moisture intrusion aloft courtesy of a returning low level jet will allow for some instability to develop this evening, bringing a returning shower and storm chance.

The steep lapse rates aloft coupled with textbook "inverted-V" low level convective profiles (more reminiscent of the Plains as opposed to northern Michigan) suggest the environment may be conducive for some gusty winds / dry microburst development to accompany as well due tue negatively buoyant influences of rapid evaporative cooling from water loading. Some of the initial storms may feature strong to even severe gusts due to ample shear leading to well tilted updrafts, but this particular threat probably wanes rather quickly after the convective environment becomes contaminated with moisture throughout the profile following the development of storms.

Hail will also be possible in the event that updrafts overachieve due to strong lift in the hail growth region and ample shear. As such, SPC has expanded the area of Marginal Risk for severe storms (Level 1/5) to include all of northern lower Michigan. The greatest overall storm chances favor NW lower. It should be noted that this is a conditional threat, with non-zero higher end potential due to aforementioned dry microburst potential. The front will pass late this evening into tonight, taking with it the potential for thunder across northern lower as cold air advection slowly builds due to the occlusion, but that drier air will become more evident as that subtle cold air advection lets lows slip to 45-55 tonight. The occluded nature of the system will allow for prolonged rainfall through much of the night across far NE lower into the eastern Yoop, which may see some downpours through daybreak Saturday before the cold air advection regime drives us to a shallower convective regime.

Eventually, anticipating cold air advection to go into overdrive Saturday, with breezy W to NW winds bringing a raw feel to the day... shallow convection seems a likely bet with diurnal heating, so certainly some dry showers on the table throughout much of the day Saturday as highs struggle to break out of the 50s for most, with 60s becoming more likely the closer one gets to Lake Huron and Saginaw Bay.

LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/
Issued at 229 PM EDT Fri May 16 2025

Pattern Forecast: At the start of the period Saturday night, closed upper level low pressure is expected to be situated near the southern Ontario/Quebec border with attendant broader area of surface low pressure in the same vicinity. Some lingering low-level moisture continues to wrap around the backside of that departing low pressure Saturday night, but a general drying trend in store for the remainder of the weekend as mid-level ridging folds over the western Great Lakes. Canadian surface high pressure noses in from the northwest by later Sunday and associated dry air will fight low pressure that's expected to trek across the Plains, mid-MS Valley ino the Ohio Valley early-mid next week.

Forecast Details: A few lingering light/isolated showers may continue to dot the map Saturday evening, but with a general drying trend anticipated through Saturday night. Occasionally breezy northwest winds continue with lows falling into the 40s area-wide.
Cooler than normal temperatures, with highs in the 50s and perhaps low 60s on occasion in southern parts of the forecast area, are expected to prevail Sunday through the end of the forecast period.
Pocket of colder air under ~1035mb high pressure to our north largely responsible for this reprieve in warmer weather with the primary focus revolving around potential frost chances, especially Sunday night through Tuesday night. Blended guidance favors lows each night in the lower to mid 30s over inland areas, and while that seems feasible for now, will have to monitor overnight wind/cloud trends for the potential of localized colder temperatures.

With respect to precip chances next week, longer range ensemble guidance continues to favor plenty of dry time across northern Michigan as dry northeast winds fend off associated moisture with low pressure passing by to our south/southwest. However, by later Wednesday/Thursday, as low pressure treks up the eastern seaboard, at least low potential exists for that system to retrograde a bit and provide some increased low-level wrap around moisture and isolated to scattered shower chances.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/
Issued at 136 PM EDT Fri May 16 2025

VFR CIGs will be the rule through the afternoon amid a breezy SW flow gusting to 25kts at times, especially for mbL, TVC, and mbL.
Cold front approaches this evening, bringing the development of showers and thunderstorms after 00z, with potential for another night of CBs. Some of these storms may produce gusty winds with their passage. This should clear from west to east around or just after 06z, perhaps a little later for CIU and APN. Winds turn more westerly Saturday with MVFR to IFR CIGs at times as cooler air and showery weather prevail.

APX WATCHES/WARNINGS/ADVISORIES
MI...None.
MARINE...Small Craft Advisory until 2 AM EDT Sunday for LMZ323-341-342- 344>346.