521
FXUS63 KGRR 040622
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
222 AM EDT Sun Oct 4 2026

.KEY MESSAGES...

- Brief Period of Rain this Morning

- Areas of Frost Possible Tonight and Monday Night

&&

.DISCUSSION...
Issued at 222 AM EDT Sun Oct 4 2026

- Brief Period of Rain this Morning

A shortwave trough is moving through this morning with plenty of
positive vorticity advection and 700 mb frontogenesis. These
showers are elevated as seen in observations with cloud bases
around 8 to 10 kft. As radar trends continue it looks like most
will see light rain before the 850 mb front clears around 9am.

Dry conditions are expected through the remainder of the forecast,
but Tuesday night into Wednesday will need to be monitored. A
decent low level jet, warm air advection ahead of the shortwave
trough and front will be present. The question is will there be
enough moisture. Currently better chances are north of the area,
but the ENS members highlight light rain across the forecast area.
If this trend continues, chances for precipitation will need to be
added.

- Areas of Frost Possible Tonight and Monday Night

High pressure builds in tonight and continues into Monday. 925 mb
temperatures will fall into the 6 to 8 C range. The inversion that
develops isn`t overly strong so expecting inland areas along and
north of U-10 to have the best chance for lows dropping into the
mid 30s with isolated colder spots. However confidence is not high
at this time as there has been a slight warming trend in the data.
In coordination with Gaylord held off on issuing a Frost Advisory
at this time due to the uncertainty.

Monday night will have a better chance for more widespread frost
as low temperatures drop into the mid to upper 30s across areas
largely east of US-131 and north of I-96. The best chances (50
percent) for lows in the low to mid 30s will be inland areas along
and north of US-10.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 222 AM EDT Sun Oct 4 2026

Light rain is moving in from the west with ceilings in the 8 to 10
kft range. Rain will quickly exit the area by 9am this morning.
Southerly winds gradually shift to the west and then northwest as
the front moves through this morning and afternoon. Wind speeds
will also pick up with gusts around 20 knots this afternoon.
Behind the front scattered clouds around 3000 feet are possible,
but could remain north of all the TAF sites before clearing this
evening.

&&

.MARINE...
Issued at 222 AM EDT Sun Oct 4 2026

Winds will pick up from the southwest as this morning`s rain
clears and then shift to the west and northwest during the late
morning and afternoon. Waves build into the 4 to 7 foot range
north of Holland with the highest waves north of Muskegon. Gusts
around 20 to 25 knots may linger longer into tonight for areas
north of Grand Haven. Additionally waves may approach 4 feet near
and south of South Haven. Therefore the Small Craft Advisory will
likely need to be adjusted for this evening into Monday morning.

Another period of Small Craft Advisory conditions looks to develop
Tuesday with strong southwesterly winds. There is the potential
that a brief period of gales develops towards Little and Big Sable
Tuesday afternoon.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory from 8 AM this morning to 8 PM EDT this
     evening for LMZ846.
     Small Craft Advisory from 5 AM early this morning to 8 PM EDT
     this evening for LMZ847>849.

&&

$$

DISCUSSION...RAH
AVIATION...RAH
MARINE...RAH