333
FXUS63 KGRR 160605
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
205 AM EDT Thu Oct 16 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 /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 204 AM EDT Thu Oct 16 2025

Surface high pressure is sprawled across the Great Lakes tonight
which is resulting in light winds and clear skies. We have some
occasional ground fog occurring, formed through radiational
cooling processes, but most sites are VFR. We expect VFR weather
to continue throughout the next 24 hours actually as the high will
only have slipped slightly to the east during that time.

The cloud bank that is off to our west early this morning with
cloud bases of 3,500 to 8,000 feet will remain west of the TAF
sites today. Some high level cirrus clouds will filter in from
the west after sunrise with bases at or above 20,000 feet.

In the 00z to 06z time frame this evening we will see clouds
spread in from the west with bases around 10,000 feet. Winds
through the TAF period of 06z to 06z will be light, either calm
(like this morning) or east to southeast around 5 knots today.

&&

.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...Duke
MARINE...Thomas