617
FXUS63 KGRR 261045
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
645 AM EDT Sat Sep 26 2026

.KEY MESSAGES...

- Dry through Tuesday

- Rain chances increase mid week

- Above normal temperatures expected

&&

.DISCUSSION...
Issued at 350 AM EDT Sat Sep 26 2026

- Dry through Tuesday

Overall the theme of the forecast has not changed much in the past
couple of days. The first point remains the same in that we will
see dry weather through the weekend and at least into Tuesday. The
east coast low will keep ridging in place across the Great Lakes
both at the surface and aloft. BUFKIT overviews remain very dry
and all ensemble members of the GFS and ECWMF rain dry as well
through Tuesday. Bottom line a high confidence forecast that
conditions remain benign and dry for the next 4 days.

- Rain chances increase mid week

The setup changes as we head into mid week. The reason for this is
largely a shortwave moving across Canada in zonal flow. The
shortwave acts to flatten the ridge over the Great Lakes and pulls
the east coast system northward into the westerlies. What this
means for the Great Lakes is some active weather as the ridge that
was over the region will be gone.

Models show good chances for rain beginning as early as Tuesday
night, but more likely on Wednesday. At this point details are not
certain in the mid to late week time frame but it does look like
good opportunities for rain. The first opportunity will come on
Wednesday with a cold front associated with the aforementioned
Canadian shortwave. The front looks to hang up across the Southern
Great Lakes with additional rain into Thursday and perhaps Friday.

The item of note here is that moisture in the mid and upper
levels, associated with what will be former Hurricane Polo, could
potentially interact with the front in the Southern Great Lakes
during this time frame. PWATs are forecast by the GFS to reach
2.00 inches which is very high/record for late Sept/early Oct. It
is a long way out on day 5 and 6 so we have time to watch it, but
it has our attention. Heavy rain events of the past have had
similar setups with remnant moisture streaming northward from
former tropical systems. One event that comes to mind is September
of 2008 when moisture from Gustav, Lowell and Ike all made it`s
way north into Lower Michigan. We are not by any means saying we
are looking at an event like that, but some heavy rain is
possible this upcoming week. 1-2 inches of rain seems plausible.
Individual ensemble members are indicating higher than that.

- Above normal temperatures expected

Normal high temperatures this time of year are in the 60s and for
much of the 7 day forecast we are looking at highs in the 70s.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 645 AM EDT Sat Sep 26 2026

VFR weather is expected at the TAF sites over the course of the
next 24 hours. For the most part we are expecting clear skies. The
one caveat is that we are watching the potential for some
fog/stratus to form yet this morning and again tonight. There is
some patchy fog around this morning, but it is not impacting the
TAF sites at this time. Lansing looks most in line to see this
potentially move in for a couple hours this morning. Confidence
was not high enough to include and anything that develops should
burn off/lift by 14z or so. Winds are expected to remain light.

&&

.MARINE...
Issued at 350 AM EDT Sat Sep 26 2026

Conditions are expected to remain quiet on the big lake into early
next week. A ridge of high pressure will remain situated over the
Great Lakes region resulting in light winds and limited wave
action. Waves in the next few days will be 2 feet or less and for
most of the time less than a foot.

&&

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

&&

$$

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