Marine Weather and Tide Forecast for Pentwater, MI

DISCUSSION
Issued at 340 PM EDT Fri Apr 18 2025

- Warm with periods of showers/storms tonight

Low confidence forecast with respect to severe weather potential and coverage this evening. Warmer, more humid air continues to flow in from the south with temps in the 70s and dew pts in the mid to upper 50s. Despite lingering cloud cover, some sfc based cape is now developing south of I-96 and that is expected to grow and expand farther north with time through this evening. However RAP guidance continues to show 200-300 J/KG of CIN persisting for several hours.

Mid level lapse rates of 8-9 C/KM are present over srn Lwr MI so if the cap can be broken by either the shortwave approaching from the southwest and/or the cold front slowing leaning in from the northwest then strong to severe storms could quickly develop.
Large hail and damaging winds are the main threat. Will have the highest pops early this evening north and west of a MKG to MOP line, expanding/moving south and east with the slow moving cold front through the night.

Shower and storm threat ending late tonight or Saturday morning as the cold front settles south of the state but considerable cloudiness lingering, especially south.

- Another wet and breezy system Sunday through Monday

Shower potential ramping up again later Sunday and Sunday night as wound-up low tracks from the Plains toward Wisconsin. Best shower and storm potential should be 06Z-18Z Monday when the sfc occlusion and negative tilt upper trough is swinging through, although some wrap-around showers will linger in the cold advection Monday afternoon and night. Another aspect from this system will be winds; with brisk easterly flow preceding it and strong westerly flow on the back side.

- Mild with small chances of rain Tuesday through Thursday

Tuesday and beyond features occasional (but for now low) shower chances with ripply zonal flow aloft and decent baroclinicity overhead/nearby. There are no major cold intrusions shown and temperatures for the mid to late week period are expected to be a bit above normal.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/
Issued at 147 PM EDT Fri Apr 18 2025

Showers and storms will be the main focus for any aviation concerns through the TAF period. This mornings convection brought widespread rainfall along with some strong thunderstorms. Daytime heating should couple with the added moisture to bring several opportunities for showers and storms this afternoon and evening.
Models show the potential for mid afternoon convection which could bring periods of TSRA to MKG, GRR and LAN. There is more instability through the western portion of SW MI so have VCTS at MKG and GRR and it is more likely to see TSRA between 22Z to 00Z.
While there is the potential at LAN, it could be just west of them so have PROB30 group accordingly.

Showers and a few storms will remains likely at all TAF sites between 02Z to 08Z. There is some LLWS concerns out ahead of the line so have shear in the TAF's until 08Z.

Behind the front will be an increase of low clouds with lowering cigs into Saturday morning. That will bring MVFR to IFR cigs between 08Z to 12Z. IFR looks more widespread with conditions improving to MVFR after 12Z and VFR after 15Z.

MARINE
Issued at 340 PM EDT Fri Apr 18 2025

We're seeing a lull in winds and waves currently but will keep the small craft advisory going into Saturday morning since the cold frontal passage tonight will bring a period of increased northerly winds. Occasional thunderstorms are also expected over Lk MI tonight.

GRR WATCHES/WARNINGS/ADVISORIES
MI...None.
MARINE...Small Craft Advisory until 11 AM EDT Saturday for LMZ844>849.