758
FXUS63 KGRR 011726
AFDGRR

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

.KEY MESSAGES...

- Next Chance for Rain late Wednesday

&&

.DISCUSSION...
Issued at 123 AM EDT Mon Sep 1 2025

- Next Chance for Rain late Wednesday

A highly amplified and somewhat blocky flow regime more typical of
autumn than late summer persists across North America over the
next week. We start off with a surface high moving east and
moderating temperatures as upper ridging builds across the
northern Great Lakes through the first half of the week. This is
followed by an upper low diving southeast from Canada and carving
out a longwave trough across the central and eastern CONUS by late
in the week. Moisture streaming up from the south will converge
with the trough axis and a surface low trailing a cold front by
Wednesday afternoon and evening with showers and thunderstorms
possible.

Diurnally driven showers with some lake enhancement are possible
on Thursday through next weekend with shortwave troughs and
vorticity maxima rotating around the upper low in broad cyclonic
flow regime along with steep mid level lapse rates. Unusually cold
airmass for early September builds in by the end of the week with
temperatures well below normal. Some scattered frost is possible
in the northern interior zones if skies clear and winds decouple
from Thursday night into the weekend.

&&

.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...Ostuno
AVIATION...04
MARINE...04