Marine Weather and Tide Forecast for Pentwater, MI

DISCUSSION
Issued at 325 PM EDT Sun Apr 12 2026

- Excessive rainfall threat this week

Multiple chances for showers and thunderstorms tonight, Monday night, Tuesday night, and beyond will lead to an increasing flood threat after what has already been an abnormally wet spring since the beginning of March. Rivers have come down from their crests last week but will be prone to go back up again as thunderstorms dump rain onto fairly moist soil. The usual caveats of convective hit-or-miss rain swaths are in play, but any well developed storms that repeat over the same areas will be in an environment with PW values 1.25 to 1.5 inches, near the climatological maximum this time of year, so rainfall production should be efficient.

The river forecasts issued Sunday morning contain forecast rainfall through Monday morning. River forecasts are susceptible to change tomorrow once tonight's actual rainfall is counted and Monday night's thunderstorm rainfall enters the forecast. An areal flood watch covers portions of central Michigan (and to the north) through Wednesday morning, but could be extended south in the next day or two as the thunderstorm threat eventually migrates that direction.

- Severe thunderstorms possible Monday night through Tuesday night

This evening... a well mixed warm sector has moved into southern Michigan up to Muskegon-Alma. A convectively enhanced shortwave ejecting out of the south-central Plains today will bring another potential for showers and isolated storms this evening as low- level wind fields increase ahead of the wave. The relatively dry air beneath the showers may facilitate mixing down gusts over 40 or 50 mph in some locations into tonight, as multiple runs of the HRRR have been depicting.

Monday evening... Thunderstorms are likely to develop in the vicinity of a frontal wave and surface low over Wisconsin and Michigan during the evening and overnight. CAMs show a variety of solutions regarding if and where storms develop over the area on the warm advection side Monday evening, so confidence is on the lower side for now. If storms develop, elevated supercells with wind and hail hazards are possible. A squall line late in the night may then arrive in west-central Michigan with a wind hazard.

Tuesday... a lingering tail of convection during part of the morning can't be ruled out, but much of the day is likely to be rain-free before the next shortwave arrives in the evening or night. A plume of 1000-2000 J/kg of CAPE will be stretched over much of the Midwest including Michigan, with sfc-500 mb shear around 40 knots, so severe weather hazards are again possible.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/
Issued at 747 PM EDT Sun Apr 12 2026

Rain with a few embedded thunderstorms will expand over the area between 00-06Z. Ceilings will gradually lower to MVFR with IFR conditions at GRR into Monday morning and LIFR at MKG. Winds will remain elevated with gusts in the 25 to 35 knot range this evening with low level wind shear around 40 to 50 knots present.
Rain exits the area between 6-12Z Monday with southwest winds gusting 20 to 25 knots. Ceilings will gradually lift toward the end of the TAF forecast. Our next chance for rain should hold off until 00Z Tuesday.

MARINE
Issued at 325 PM EDT Sun Apr 12 2026

Hazardous winds and waves for small craft continue through much of Monday, followed by a slight lull, then reinvigorating again Monday night into Tuesday morning. So far today, the cool and stable marine layer has prevented a lot of gale force winds aloft from mixing down (there have been 40 mph wind gusts crashing to the ground a couple miles inland). Some southwesterly gales are possible late this evening, as have been depicted by the HRRR, as showers and scattered thunderstorms move over the lake. Additional thunderstorm hazards over the lake are possible between Monday evening and Tuesday night.

GRR WATCHES/WARNINGS/ADVISORIES
MI...Flood Watch through Wednesday morning for MIZ037>040-043>045.
MARINE...Small Craft Advisory until 4 PM EDT Monday for LMZ844>849.