484
FXUS63 KGRR 071845
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
245 PM EDT Mon Sep 7 2026

.KEY MESSAGES...

- Showers/storms likely Tuesday night into Wednesday

- Rain possible Saturday

- Stronger system possible Monday with rain and wind

&&

.DISCUSSION...
Issued at 245 PM EDT Mon Sep 7 2026

- Showers/storms likely Tuesday night into Wednesday

High pressure continues in control of the weather this afternoon
with seasonable temperatures for early September and much lower
humidity levels compared to last week. This drier weather will
continue through most of the day Tuesday for most areas.

Very late on Tuesday, the rain chances will begin to increase across
the NW corner of the area, with rain spreading SE through Wednesday
morning. This increase in rain chances will be via a 30+ knot low
level jet advecting decent moisture ahead of the incoming cold
front.

The thunder threat looks to be a scattered to numerous one with
fairly low chances of anything severe. The low level jet moving in
will provide enough elevated instability Tuesday night for thunder.
It is not very strong, only around a few hundred J/kg at best. This
is due to the timing of the front approaching during the coolest
time of the day, and with a lack of support aloft from a cold
pool/short wave.

Showers and storms will be most likely in the morning, then
gradually moving out from NW to SE during the afternoon hours. This
is a bit too early for any significant destabilization to occur
during peak heating.

We can`t rule out an isolated shower on Thursday afternoon as a weak
upper trough will be moving through. This trough could combine with
some lake breeze convergence to pop a shower or two. The vast
majority of the area and day will be dry.

- Rain possible Saturday

High pressure will be over the area Thursday night and Friday,
before shifting east of the area Friday night. There is a short wave
moving into Ontario that will drag another cold front into the area
on Saturday.

This front looks to have much less rain potential with it for
multiple reasons. The first is that the upper support once again
stays north of the area, limiting the upper level synoptic support.
In addition, the front does not have a good strong moist flow ahead
of it from the Gulf. If anything, the trend in the data has been for
less and less rain to be expected.

- Stronger system possible Monday with rain and wind

We see a brief break on Sunday before the next system approaches on
Monday. This system has the potential to be a much stronger system
than the two systems earlier in the period.

We will see a stronger upper low drop into the Pacific NW by next
weekend. It will then rotate eastward across the northern tier of
the country late next weekend into early next week. It is expected
to support a stronger sfc low over the Upper Midwest that will be
driven ENE, and approach the region.

We could see the initial rain with this system as early as late
Sunday night into Monday morning with a leading short wave, and/or
the warm air advection low level jet supporting the chances. Then,
after a period of potentially being in the warm sector, the cold
front will move in fairly strong. This system looks like right now
that it will have a favorable feed of rich Gulf moisture ahead of
it. Of course details with regard to timing and exact track this far
out are still uncertain. This system could cause some impacts with
rain, storms, and wind.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 158 PM EDT Mon Sep 7 2026

Afternoon cumulus clouds at or above 4,000 feet will dissipate
around sunset. There is a slight chance of patchy fog early
Tuesday morning, though it may be kept in check by 15 knot winds
at 500 feet.

&&245

.MARINE...
Issued at 245 PM EDT Mon Sep 7 2026

No marine headlines will be needed until likely late Tuesday. High
pressure over the  area this afternoon is bringing light winds and
low waves.

Winds will increase on Tuesday, likely hitting Small Craft Advisory
criteria late in the day with the stronger winds ahead of the front.
These conditions will then likely last through most of Wednesday on
the back side of the front with the cooler air moving in.

We will see a lull in the higher winds/waves then late Wednesday
through most of Friday. We could be looking at headlines being
needed Friday night and Saturday in association with the next system
moving through.

&&

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

&&

$$

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