738
FXUS63 KGRR 010754
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
354 AM EDT Tue Sep 1 2026

.KEY MESSAGES...

- Small chances for showers and storms today

- Additional shower and storm chances Wednesday through Friday

- Above normal temperatures through the 7 day forecast

&&

.DISCUSSION...
Issued at 354 AM EDT Tue Sep 1 2026

- Small chances for showers and storms today

Light southwest flow is in place this morning along with dew
points around 70F. Upstream a cold front is situated from the U.P.
southwest across Wisconsin and into Iowa. We remain in the warm
sector today with building instability. MUCAPE values even at this
early hour range from 2,000 j/kg in Southwest Lower Michigan to
around 4,000 j/kg in Iowa. The front remains upstream today and
only slowly sags into the area tonight while losing definition.
Aloft, it is difficult to pick out much of any shortwave activity
upstream early this morning and model data moving through the day
shows little energy aloft either. The bottom line is a threat for
some isolated showers and storms is certainly there today/tonight,
but there is little to truly pinpoint timing or areas. Confidence
in morphology of storms today is low as is the threat for storms
at all. Would not be surprised to see some isolated activity
during the heat of the day today, but have kept the forecast dry.
We do have some small pops around 20 percent this evening based on
a consensus of short term models and blends. SPC has the area in
a marginal risk today, which is related to an increase in wind
fields at 850mb and 500mb after 00z. Again, we will need a
kicker/lifting mechanism and at this point that component is
nebulous.

Have held off on any heat headline today as index values are
marginal only in the far south. We could see heat index values
approach 100 from AZO over to JXN this afternoon, but most areas
should hold in the 90s for maximum apparent temperatures today.

- Additional shower and storm chances Wednesday through Friday

The surface front will remain in the area on Wednesday which may
provide a focus for showers and thunderstorms. Multiple shortwave`s
are forecast to be moving through the generally zonal flow aloft
on Wednesday as well. Strong instability will remain in place on
Wednesday making for better chances for showers and storms. SPC
has some of our far eastern areas towards the U.S. 27/127 corridor
in a Slight risk for severe weather. Cannot rule this out given
strong winds aloft remaining in place.

Additional shower and thunderstorm activity is expected on
Thursday and Friday as well before high pressure builds in for the
weekend. That said, quite a few ensemble members of both the GFS
and the ECMWF indicate precipitation potential into the weekend as
well. Suffice it to say, forecast confidence in precipitation in
the coming days is not high owing to transient weaker shortwaves
aloft and a weak surface pattern most days.

- Above normal temperatures through the 7 day forecast

We are expecting above normal temperatures through much of the
period with the warmest days being today and Wednesday. A slow
cooling trend is noted into early next week. It will take until
next Monday before we see temperatures approaching normals for
this time of year.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 148 AM EDT Tue Sep 1 2026

VFR weather prevails across the area at 06Z with mainly clear
skies and no restrictions to visibility currently. Winds aloft
will subside considerably in the hours that remain through
sunrise. The lowering in wind speeds aloft may allow for some
fog to develop around sunrise or in the 11z-13z time frame. Have
included this at the western TAF sites. At this point only
expecting some MVFR fog.

Otherwise expecting VFR weather with some scattered to potentially
broken cumulus development today during the heat of the afternoon.
Bases will be VFR up around 5,000 feet. Above that some cirrus
will continue to advect in from the west with bases at or above
20,000 feet.

The item to keep an eye on today is the small potential for
showers and thunderstorms this afternoon and evening. At this
point feel the threat is too small to include in the TAFs,
generally less than 10 percent. If confidence increases we will
include going forward, but for now we have dry TAFs.

&&

.MARINE...
Issued at 354 AM EDT Tue Sep 1 2026

As forecast, waves subsided below advisory levels yesterday
evening. Sub advisory conditions are now expected the next couple
of days at least. The pressure gradient will be fairly slack it
appears as a weak boundary sags into the area today and remains
near through the end of the work week. Without a low of some
depth and/or a building high winds will remain on the lighter
side. Waves look to be 2 feet or less the next few days. The
caveat however as always is thunderstorms. We are expecting at
least some periodic thunderstorm activity through Friday which
will bring a local uptick in wave action as the storms and
associated localized wind move through.

&&

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

&&

$$

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