Marine Weather and Tide Forecast for Grand Ledge, MI

DISCUSSION
Issued at 326 AM EDT Sun Jun 15 2025

- Dry today and Monday

A line of showers has developed along a weak h8 convergent boundary from CAD southwest across LDM to Wisconsin. This will likely dissipate later this morning. Otherwise, IR loop shows a bkn-ovc mid deck over the northern two rows of counties with mainly bkn high clouds covering the rest of the cwa.

Expect a mix of clouds and sun today across the cwa with highs around 80 and dewpoints in the upper 50s. The high over Ontario the past several days will move east Monday, resulting in higher heights and warmer temperatures; highs in the mid 80s.

- Increasing humidity, showers/storms mid week

Dewpoints will surge into the mid 60s Tuesday and the air will feel rather summer-like, compared to the lower humidity values of late. Southwest flow will increase Tuesday ahead of a low that will move toward the state Wednesday. Moisture transport vectors increase considerably Tuesday night into Wednesday. Instability will also increase, and with it, so will chances for showers and thunderstorms. There hasn't been much change in ECMWF ensemble mean QPF over the past few model runs. Still looking at a half inch to inch of rain across much of the cwa. In fact, each ensemble member produces precipitation. LREF ensemble mean suggests a 50-70% chance of half inch of of rainfall during this time frame an a 25-35% chance of an inch. Precipitable water values increase to 1.75 inches late Tuesday into Wednesday, pointing toward some heavier rainfall possible. Any rainfall would be beneficial given the dry conditions in place across much of the cwa.

As for chances for strong/severe storms mid week, some model discrepancies exist between the operational ECMWF and GFS models.
Specifically, the GFS is a bit quicker moving the trailing cold front across the cwa compared to the ECMWF, which would lower the chances for strong/severe convection. We'll start to get a better indication on timing over the next day or so as the time frame in question comes into the CAMs.

Precipitation chances will linger into Thursday when the trailing upper wave moves through.

- Hot next weekend

A building dome of high pressure over the MS/western OH Valleys will result in an increase in heat across the Great Lakes. We may be looking at 90 degrees by Saturday/Sunday. If dewpoints push 70 degrees, heat indices will increase to the mid 90s.

AVIATION /06Z TAFS THROUGH 06Z MONDAY/
Issued at 123 AM EDT Sun Jun 15 2025

High broken clouds cover the terminals early this morning. IR loop also shows bkn-ovc mid clouds north of I-96. This deck is expected to sink south today resulting in 6-10k ft ceilings at most of the TAF sites.

An onshore wind will develop at MKG by early afternoon. Otherwise, expect northeast winds again today.

MARINE
Issued at 326 AM EDT Sun Jun 15 2025

High pressure over Ontario will produce a northeast wind flow this morning. A lake breeze will develop this afternoon. However, wind speeds will remain in the 5 to 15 mph range.

Thunderstorm chances will increase late Tuesday and continue through Thursday.

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