textproduct: Grand Rapids

KEY MESSAGES

- One more sunny day

- Showers, isolated thunder, Wed-Fri

- Cooler weekend, frost/freeze potential

DISCUSSION

Issued at 258 AM EDT Tue Sep 29 2026

- One more sunny day

High pressure over Michigan will drift east today and that will help high clouds to the west to move overhead later this afternoon. Another mostly sunny day is anticipated, once the morning fog burns off by mid morning. While much of the fog this morning will be shallow in low lying areas and river valleys, some of may be dense in spots prior to burning off.

normal high temperatures are around 70, but we'll see highs in the mid to upper 70s today.

- Showers, isolated thunder, Wed-Fri

High confidence that we'll see light to moderate rain Wednesday into Friday. GFS and ECMWF are and have been in pretty good agreement since last week in showing a cold front move east across southern Canada into Lower MI and then stall out, as a southern stream low develops in New Mexico and moves northeast. This low will not only draw Gulf moisture northward, it'll also be entrained by moisture from the tropical system that moved across Baja CA. We anticipate this to be a slow moving system, because the frontal boundary will become more or less parallel to the upper flow and the frontal boundary over the cwa will act as a conduit for a lot of the moisture. Instability is pretty low which make thunder chance around 15 percent or so. Thus, we're looking at mostly a light to occasionally moderate rainfall. QPF from Wednesday to Thursday is roughly 1-2 inches, highest over the western cwa.

- Cooler weekend, frost/freeze potential

The cold front will move through the cwa Friday, essentially ending the rainfall. H8 temperatures fall from 16c on Thursday to 6c by Saturday morning . That means the highs in the lower to mid 70s early in the week will be closer to 60 over the weekend. If skies can clear at all, we'll be looking at lows in the mid 30s over the northern cwa Friday night and Saturday night and lower 30s along US-10 Monday night; frost and freeze headlines may be needed then.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 127 AM EDT Tue Sep 29 2026

Clear skies and light winds will help fog develop during the next six hours. Shallow fog could potentially reduce visibilities to a half mile in some locations and visibilities will likely fluctuate a bit through 12z. The fog will burn off by mid morning yielding generally clear skies. High clouds will begin to move over the terminals tonight as the next cold front approaches.

MARINE

Issued at 258 AM EDT Tue Sep 29 2026

High pressure will begin move east today and south flow will increase tonight ahead of the next cold front. We've issued a small craft advisory and beach hazards statement north of Grand Haven for winds and waves valid from late this evening through Thursday morning. South winds will gust to 25 knots and waves will increase to 3-6 feet.

GRR WATCHES/WARNINGS/ADVISORIES

MI...Beach Hazards Statement from this evening through Thursday morning for MIZ037-043-050. MARINE...Small Craft Advisory from 10 PM this evening to 8 AM EDT Thursday for LMZ847>849.