Grand Rapids, Michigan 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

749
FXUS63 KGRR 060536
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
136 AM EDT Sat Sep 6 2025

.KEY MESSAGES...

- Cool with chances for showers through the weekend

- Small chances for showers Monday night into Tuesday

- Mainly dry with a slow warming trend Wednesday through Friday

&&

.DISCUSSION...
Issued at 339 PM EDT Fri Sep 5 2025

- Cool with chances for showers through the weekend

We will remain under a deep through aloft through much of the
weekend. 850mb temperatures of +2 to +4 C are expected through
Sunday night which means cool weather will continue. Highs will be
in the upper 50s to middle 60s with lows in the upper 30s to
lower 40s. Normal highs are in the 70s and normal lows in the 50s,
so we will be well below normal...the fall feel to the air will
continue.

Lake temperatures are around +20C which puts delta t`s in the
upper teens C over the lake through the weekend. Therefore there
will be plenty of instability over the lake. The instability
combined with cyclonic flow should result in isolated to scattered
rain showers off of Lake Michigan. The deepest moisture will
occur on Saturday and Saturday night when upper shortwaves will be
moving through. We expect the highest chances for rain in those
two periods, increasing into the 30-50 pct range.

- Small chances for showers Monday night into Tuesday

Small chances for rain showers exist Monday night into Tuesday on
the backside of departing high pressure that will be moving off to
the east. Return flow and increasing moisture main bring us some
showers during this time frame as shown by the ECWMF. The GFS is
dry, so confidence in this time frame is on the lower side.

- Mainly dry with a slow warming trend Wednesday through Friday

We look to be mainly dry mid to late week as we have followed the
ECMWF for guidance in this time frame. The ECMWF has a building
ridge. The GFS has a trough moving through the area. Given the
range in the forecast though forecast confidence is on the lower
side. We have a dry forecast at this point from Wednesday through
Friday.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 136 AM EDT Sat Sep 6 2025

We are starting out this forecast period with lots of clouds over
all of the terminals. KMKG and KGRR are seeing ceilings of around
5k ft agl, while the other sites are mainly seeing high clouds
20-25k ft agl. No showers are around per the radar. We do not see
conditions changing much until late morning, when we will see
diurnal clouds develop around 5k ft at the aforementioned sites
that do not have them already. In addition, winds will become
gusty with gusts to 20-22 knots as we see the heating of the day
mix better winds down. This is already happening at KMKG closer to
the warm lake.

Conditions will not be favorable for much in the way of shower
activity until mid-evening when a strong wave approaches the area.
This wave will bring scattered showers to all sites. Have handled
these with a prob30 with some isolated MVFR conditions possible
under the heavier showers. These will continue through the end of
this forecast period.

&&

.MARINE...
Issued at 339 PM EDT Fri Sep 5 2025

Hazardous winds and waves persist this afternoon with gusts to 30
knots and waves up to 10 ft being recorded at observation sites this
afternoon. Have expired the Gale Warning but conditions hazardous to
small craft will continue through the weekend. Waves of 6-10 feet
with gusts to 30 knots will continue into Saturday before a brief
lull develops late Saturday. With another burst of wind Saturday
night bringing waves of 3-6 feet, the short duration of the lull
warrants keeping headlines in place through the weekend. Have
extended the Small Craft Advisory/Beach Hazards Statement through
Sunday afternoon.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement through Sunday afternoon for MIZ037-043-
     050-056-064-071.
MARINE...Small Craft Advisory until 5 PM EDT Sunday for LMZ844>849.

&&

$$

DISCUSSION...Duke
AVIATION...NJJ
MARINE...Thomas