textproduct: Grand Rapids

KEY MESSAGES

- Areas of fog tonight and Tuesday morning

- Thunderstorms possible later Wednesday, less likely Thursday

DISCUSSION

Issued at 305 PM EDT Mon Aug 24 2026

Upper low over western Quebec is wobbling east out of the region and releasing it's influence. Narrow surface ridge will wash across the Lower Peninsula tonight and early Tuesday. As a consequence the fresh northwest flow will quell out early this evening. The light flow and very good radiative cooling potential will support some fog development tonight. Fog will lift into a cumulus field by late morning. Otherwise, a quiet late summer day is in store Tuesday with partly cloudy skies and highs around 80F.

The next shortwave in the westerlies, currently over the southern Canadian Prairies will carve into the Great Lakes region on Wednesday. The wave will undergo some level of capturing by the larger Hudson Bay closed low over the next day or so. This process will induce height falls to the north of the wave centroid, coaxing the best forcing north. Therefore, the main forcing across Western Lower Michigan will be the attendant cold front - with the primary wave ascent shunted north across the northern Lakes region.

An uptick in south-southwest flow on Wednesday in advance of the cold front, will squeeze in some better moisture content and actionable instability - MLCAPE values approaching 1-kJ/kg. Showers and scattered thunderstorms are expected to develop along the advancing buoyancy gradient during the mid/late afternoon, with a second impulse of development along the cold front during the evening hours. Still plenty of timing wiggle room in the forecast, given this system still has two more diurnal convective cycles to augment the forcing before arrival. Severe potential will be limited with only modest deep layer shear due to weakening mid-level flow.

Not much a of cool down on Thursday behind the front with ample late summer sun. A stray shower or storm is certainly possible along and south of I-96, with some lingering modest instability lingering.

Overall flow pattern appears poised to support greater ridging aloft over the Great Lakes region as we progress through the upcoming weekend and into next week. Global ensembles are starting to gel around the notion of a period of above average temps starting Sunday.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1248 PM EDT Mon Aug 24 2026

Occasionally gusty northwest flow will temper through the late afternoon. A couple pockets of small scale cumulus will linger around AZO/BTL and LAN for the next couple of hours, as near surface drying continues. Center of the incoming high will slide just to the south - staging very light wind conditions tonight. Fog formation is expected overnight - with the best potential across the interior where soil moisture availability is higher. Fog is expected to thin and dissipate by mid morning.

MARINE

Issued at 305 PM EDT Mon Aug 24 2026

Northwest winds are slowly relaxing this afternoon and the wave field continues to follow. Winds will become light tonight as high pressure moves across the region. South-southwest winds will emerge on Tuesday - with speeds increasing into the 10-15 kt range north of Muskegon during the afternoon. Speeds will continue to slowly climb through Tuesday night as the next system approaches from the west. Waves will quickly respond early Wednesday - likely warranting small crafts and beach hazards.

GRR WATCHES/WARNINGS/ADVISORIES

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