221
FXUS63 KGRR 081802
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
202 PM EDT Tue Sep 8 2026

.KEY MESSAGES...

- Showers and isolated thunderstorms expected this afternoon into
  Wednesday

- Low chance of rain Saturday

- Additional showers and storms Monday

&&

.DISCUSSION...
Issued at 201 PM EDT Tue Sep 8 2026

- Showers and isolated thunderstorms expected this afternoon into
  Wednesday

Radar shows a line of showers ahead of a cold front approaching the
northwest CWA at present, which should slowly expand south and east
into the evening and tonight. HREF mean MUCAPE shows just a few
hundred joules suggesting little severe threat though scattered
thunderstorms are possible. High PWATs and 30+ knots of shear may be
sufficient to support gusts over 30 mph with water loaded
downdrafts and heavy rainfall. The front will clear the area
Wednesday afternoon taking the rain and thunder chances with it.
Up to 1/4" of rain is expected south of I96 with 1/4"-1/2" expected
north.

Dry air behind the front along with high pressure will keep fair
conditions in place later Wednesday through Friday.

- Low chance of rain Saturday

Our next chance of precipitation, albeit a low one, arrives Saturday
as a weak shortwave drives a front through. Between the best
dynamics being displaced from the area, and little in the way of
moisture return ahead of the front, PoPs are low with little
precipitation favored to occur.

- Additional showers and storms Monday

A stronger system takes aim at the region Monday as the upper-level
jet moves south into the region. A deepening low associated with
this will lead to potentially breezy conditions as well as the
chance for showers and storms. NBM probabilities suggest a 30-40%
chance of over 1" of rainfall, highest across the northwest CWA, so
will need to monitor for potential heavy rainfall.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 200 PM EDT Tue Sep 8 2026

Afternoon cumulus clouds with bases around 4,000 feet are
developing under thickening high clouds at or above 12,000 feet.
Tonight, the cumulus should diminish and ceilings around 8,000
feet will begin to produce rain showers. Will have to monitor
trends to see if a chance of thunderstorms will need to be added
overnight after 02 Z, as instability at 8,000 feet will increase
and may allow for convection into air colder than -10 C. MVFR
ceilings are favored to develop from north to south Wednesday
morning.

&&

.MARINE...
Issued at 201 PM EDT Tue Sep 8 2026

Ongoing Small Craft Advisory/Beach Hazards Statement look to be in
good shape. Increasing southwest winds will support gusts to around
25 knots and 3-6 foot waves between tonight and Wednesday Evening.
Highest waves expected near and north of Holland. Isolated
thunderstorms are also possible over the waters tonight. Winds
diminish Wednesday night and stay below hazardous levels before
increasing again on Saturday.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement through Wednesday evening for MIZ037-043-
     050-056.
MARINE...Small Craft Advisory until 8 PM EDT Wednesday for LMZ846>849.

&&

$$

DISCUSSION...Thomas
AVIATION...CAS
MARINE...Thomas