729
FXUS63 KGRR 291017
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
617 AM EDT Tue Sep 29 2026

.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 /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 615 AM EDT Tue Sep 29 2026

Visibilities have been bouncing around between LIFR and VFR
overnight as patchy fog, sometimes dense, continues to affect the
terminals. Fog will burn off by 14z leading to VFR conditions
through the remainder of the period. We`re not expecting a repeat
of the fog after midnight due to cloud cover advecting across the
region and limiting the radiational cooling.

&&

.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.

&&

$$

DISCUSSION...04
AVIATION...04
MARINE...04