330
FXUS63 KGRR 011937
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
337 PM EDT Mon Sep 1 2025

.KEY MESSAGES...

- Quiet weather continues through Tuesday

- Cooler and more active weather Wednesday into the weekend

&&

.DISCUSSION...
Issued at 337 PM EDT Mon Sep 1 2025

- Quiet weather continues through Tuesday

We have a few more forecast periods of quiet weather, tonight
through Tuesday night. Surface ridging will continue to hang on
providing dry weather. Highs will push to around 80 degrees on
Tuesday providing one last day of summer like warmth. Lows tonight
and Tuesday night will mainly be in the 50s which is close to
normals for this time of year.

- Cooler and more active weather Wednesday into the weekend

A fairly significant pattern shift will take place on Wednesday as
an upper low diving southeast out of Canada plows into the Great
Lakes aloft. At the surface a cold front will lead the charge,
passing through our area in the afternoon and evening. The front
will be accompanied by showers and thunderstorms. 850mb LIs drop to
around -2C, with MUCAPE values likely eclipsing 1,000 j/kg in spots.
We are in the day 3 (Wed) general thunder outlook given the
instability parameters and the forcing from a strong cold front. The
stronger shear will be post frontal, but even with that said, not
out of the question to see some hail given cooling temperatures
aloft and a nose of 60+ F dew points. PWAT values will be around 1.4
inches so some brief locally heavy rain is likely.

Beyond Wednesday, upper troughing settles in as the upper low holds
in the Great Lakes region. 850mb temperatures will be very fall like
in the single digits C above zero. Highs will be in the 60s from
Thursday onward for the most part with 50s are even likely across
Central Lower Michigan.

Another cold front will move through on Friday increasing shower
chances once again. Given the cold air aloft and an early September
sun angle really can`t rule out showers any afternoon between
Thursday and Sunday.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 123 PM EDT Mon Sep 1 2025

Skies are mostly clear mixed with a few flat cumulus, which will
dissipate with sunset. Winds are generally light and will become
variable overnight.

&&

.MARINE...
Issued at 123 PM EDT Mon Sep 1 2025

High pressure is creating light winds and low wave heights on the
lake, which will continue into Tuesday. A small craft advisory may
be needed Wednesday as the high moves east and the gradient
tightens ahead of the next cold front resulting in increasing
winds and waves.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.

&&

$$

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