825
FXUS63 KGRR 152249
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
649 PM EDT Wed Oct 15 2025

.KEY MESSAGES...

- Pleasant Fall Day Tomorrow

- Wet Pattern Sets Up Friday through the Weekend

&&

.DISCUSSION...
Issued at 307 PM EDT Wed Oct 15 2025

- Pleasant Fall Day Tomorrow

High pressure continues to build into the area tonight into
Thursday. Winds will be light and variable with temperatures
dropping tonight into the 30s to around 40 along the lakeshore.
Some patchy frost is possible along the US-127 corridor and is
expected to be more widespread north of M-20. Mostly sunny skies
Thursday and afternoon temperatures in the mid to upper 60s will
result in a pleasant fall day for any outdoor activities.

- Wet Pattern Sets Up Friday through the Weekend

An approaching upper level trough will bring rounds of rain Friday
through Sunday with the best chances Saturday into Sunday.
Southwest flow ans warm air advection with precipitable water
values around 1.5 inches will spark off some showers late Thursday
night with 20 percent pops lingering into Friday, best chance for
showers will be during the morning hours with the afternoon
largely staying dry. Friday night into Saturday positive
vorticity advection, warm air advection, the low level jet, and
some upper level jet divergence move in bringing another round of
rain with embedded thunderstorms. At this time there aren`t any
clear dry breaks with rain likely through the day (60-80 percent).

Sunday as the trough axis moves through there is a consistent
signal for a surface low to develop rapidly overhead. Additional
rainfall through Sunday along with gusty northwest winds are
expected. NBM probabilities of an inch or more of rain Friday
through Sunday are in the 40 to 70 percent range across much of
the area with the lowest probabilities of 20 to 30 percent in the
Jackson, Calhoun, Ingham County area.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 634 PM EDT Wed Oct 15 2025

No significant impacts to aviation are expected over the next 24
hours. The cloud deck has retreated from most sites and should
clear AZO and BTL shortly. Expect clear skies tonight with a few
mid to high clouds possible Thursday. Light winds will veer to
east or southeasterly overnight, with the exception of MKG where a
westerly lake breeze will develop in the afternoon.

&&

.MARINE...
Issued at 307 PM EDT Wed Oct 15 2025

At present, marine conditions are relatively benign as high pressure
dominates the forecast. Winds of 15 knots or less and waves near or
below a foot are expected through tomorrow. Ongoing northeast flow
will become southeasterly for Thursday.

The aforementioned high pressure system slides east Thursday night,
resulting in an increasing pressure gradient as a low deepens across
the Northern Plains and Central Canada. Increasing south to
southwest flow develops late Thursday Night, peaking Friday Night,
and continuing into Saturday. 20-25 knot sustained winds with this
system will drive waves of 4-8 feet, highest near and north of
Holland. Gusts to 30 knots are likely, with a low (around 10
percent) potential for Gales across the waters. Isolated
thunderstorms are also possible Saturday.

A signal is emerging for a potentially stronger wind/wave event
Sunday. Model guidance is beginning to align on the idea that a
second low pressure system develops and deepens across the Central
Great Lakes. Where this system develops and how deep it gets remain
in question which means uncertainty in the wind forecast is still
present. Even with this uncertainty, the potential for gales is
increasing across Lake Michigan. Waves to 10 feet may also occur.
Refinement of the forecast and gale potential will occur over the
next few days as guidance comes more into alignment.

&&

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

&&

$$

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