textproduct: Grand Rapids

KEY MESSAGES

- Chance of showers and isolated thunderstorms this weekend

- Drier and more comfortable Monday

- Midweek shower/storm chance

DISCUSSION

Issued at 348 AM EDT Sat Aug 15 2026

- Chance of showers and isolated thunderstorms this weekend

Quasi-stationary front with active convection remains stuck over Illinois and Indiana. With an 850 mb ridge moving east of the area, some higher low-level moisture (increasingly muggy dew points) will drift into southern Lower Michigan this weekend. Limited upper-level shortwave forcing, thin CAPE, and weak vertical shear will make for generally meager convection today, often along zones of temporarily increased surface confluence. PWAT will be rather high, so despite the model trends to back away from heavier mean QPF solutions, rain totals around 0.5 to 1 inch remain possible but will be patchy and isolated, and mainly near and south of I-96.

Anticipating muggy air with dew points in the lower to mid 70s on Sunday. Areas of fog are possible in the morning given the moist, still air and the potential for skies to partially clear Saturday night. 850 mb temperatures on Sunday will be a little warmer while 500 mb heights fall as the upper-level ridge flattens out a bit. As a result, CAPE should climb toward 1000 J/kg during the day. Scattered thunderstorms may develop in the vicinity of a cold front and/or midlevel MCV. Heavier downpours will remain the mode in any thunderstorms, and hit-or-miss heavier totals greater than an inch are possible.

- Drier and more comfortable Monday

Behind the cold front, high temperatures Monday may not be much cooler, though will be noticeably less humid as air from the northern plains flows through. A good amount of sunshine is also expected.

- Midweek shower/storm chance

Late Tuesday into Wednesday, somewhat increased low-level moisture returns from the central CONUS, then upper-level heights fall and a cold front sags through, associated with an upper- level low over Hudson Bay and a trough digging into Ontario and the northern Great Lakes. Instability builds and scattered thunderstorms may develop with hit-or-miss beneficial rain.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 710 AM EDT Sat Aug 15 2026

Patchy fog ongoing at RQB and MOP expected to mix out shortly with VFR likely in that area of central Michigan. Conditions will generally be worse farther south with chances for MVFR ceilings and occasional rain showers. Confidence is fairly low in timing any flight category changes. Rain showers in southern Michigan this afternoon could produce temporary IFR visibility.

MARINE

Issued at 348 AM EDT Sat Aug 15 2026

Offshore flow today will keep waves low at West Michigan beaches while larger waves build in the open waters toward Wisconsin. More of a west wind at 10 knots is expected on Sunday, making waves about 1 to 3 feet. Scattered showers and isolated thunderstorms may occasionally develop over the lake this weekend.

GRR WATCHES/WARNINGS/ADVISORIES

MI...None. MARINE...None.