595
FXUS63 KGRR 220645
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
245 AM EDT Tue Sep 22 2026

.KEY MESSAGES...

- Slight chance of a rain shower South on Wednesday

- Dry weather with slowly warming temperatures into next week

&&

.DISCUSSION...
Issued at 245 AM EDT Tue Sep 22 2026

- Slight chance of a rain shower South on Wednesday

We continue to see the upper low over Eastern Iowa as of this
morning, continue to weaken and lose its moisture and associated
precipitation. The frontal system that was the focus of the heavy
rain over the region this past weekend, has now completely
separated, and the dry low level flow from the NE eat away at much
of the rain.

Today looks to be a dry day, while the best small chance of rain
looks to be over the south on Wednesday afternoon.

We look to have some diurnal cumulus development again today, but
not as extensive as yesterday. This is likely due to the upper level
temps moderating, and resulting instability weaker. We continue to
have fairly dry conditions below 15k ft, minus the cumulus clouds.
Forecast soundings show this well. There will not be much vertical
development with a fairly strong inversion around 4-5k ft,
especially with low boundary layer dew points.

This changes a bit later tonight and Wednesday for southern areas.
Most model guidance indicates that some low level moisture will
rotate around the low to our south and up and over the southern
portion of the forecast area. This added moisture in conjunction
with weak short waves in the vicinity will be just enough for a few
light showers.

- Dry weather with slowly warming temperatures into next week

The amplification of the upper air pattern is still expected to
take shape with the low expanding over the Eastern Seaboard, and the
upper ridge building to our west over the upper Plains. It might be
taking a little longer for everything to fall in place than
previously thought, which is fairly common with upper lows. It still
looks like we will see the upper ridging build over the area, and
hold in place through early next week. We will be under the
confluent flow downstream of the ridge, providing plenty of
subsidence for the area.

Temperatures again will remain cool through Wednesday with the upper
low and cold pool aloft nearby. Temperatures will moderate then as
warmer air builds in and we see much more sunshine.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 135 AM EDT Tue Sep 22 2026

Any lower clouds that were around yesterday afternoon and evening
have dissipated/moved out of the area as of early this morning. We
are left with only some high clouds. This should remain the case
through the night.

High clouds will thicken up once again, and some sct-bkn clouds
around 3500-4000 ft will develop. More widespread lower clouds are
expected at the I-94 terminals. Winds will become gusty by
afternoon with gusts 20-25 knots expected once again. The winds
will diminish toward sunset. The 3500-4000 ft clouds actually look
to stick around with the upper low rotating just south of the
area.

&&

.MARINE...
Issued at 245 AM EDT Tue Sep 22 2026

We continue to see the brisk offshore winds over the nearshore
waters this morning, and continue through Thursday, before winds
settle down a bit. The setup responsible for this continues to be
the relatively strong gradient between the sfc high to our north,
and the low to our south. The offshore component keeps the winds
just below criteria.

We will see much lighter winds by Friday, and continue through the
weekend.

&&

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

&&

$$

DISCUSSION...NJJ
AVIATION...NJJ
MARINE...NJJ