420
FXUS63 KGRR 120545
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
145 AM EDT Sat Sep 12 2026

.KEY MESSAGES...

- Low chance of Rain on Saturday

- Showers and Thunderstorms Possible Late Monday into Tuesday

&&

.DISCUSSION...
Issued at 145 AM EDT Sat Sep 12 2026

- Low chance of Rain This Weekend

Surface high pressure moves east today and return flow brings
some moisture. There could be a few showers this afternoon and
again on Sunday as a weak surface boundary moves through today
followed by an area of mid-level frontogenesis on Sunday. For
today, we will follow the hi-res ARW model and have slight chance
POPs across the northern zones where the better moisture and lift
is located. For Sunday, low chance POPs will extend across the
central forecast area.

- Showers and Thunderstorms Possible Late Monday into Tuesday

A shortwave trough ejects out of the northern Rockies with a
surface low tracking into Canada early next week. A trailing cold
front is expected to touch off showers and thunderstorms Monday
night and Tuesday. Instability and deeper moisture is across
northern Lower Michigan pooling ahead of the cold front, which
sinks south through the forecast area on Tuesday. Precipitable
water surges close 2 inches, so heavy rain potential is there as
the front will be moving slowly and MBE vectors are less than 10
knots.

The front stalls across the southern zones on Wednesday, with a
showers and thunderstorms possible into Thursday as a surface low
tracks along the front across southern Lower Michigan.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 145 AM EDT Sat Sep 12 2026

VFR conditions will continue through Saturday evening. Southwest winds
will increase this morning with some gusts over 20 knots possible
during the afternoon.

&&

.MARINE...
Issued at 145 AM EDT Sat Sep 12 2026

Winds and waves will briefly be hazardous to small craft today
before subsiding this evening. Stronger winds are expected Tuesday
when southwest gales are expected.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement from 8 AM EDT this morning through this
     evening for MIZ037-043-050.
MARINE...Small Craft Advisory from 8 AM this morning to 8 PM EDT this
     evening for LMZ847>849.

&&

$$

DISCUSSION...Ostuno
AVIATION...Ostuno
MARINE...Ostuno