687
FXUS63 KGRR 042012
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
312 PM EST Thu Dec 4 2025

.KEY MESSAGES...

- Periods of light snow late Friday and again Sunday

- Accumulating snow possible with systems mid to late week

&&

.DISCUSSION...
Issued at 312 PM EST Thu Dec 4 2025

- Periods of light snow late Friday and again Sunday

As noted previously, we are looking at a brief window of lake effect
flurries by the lakeshore this afternoon thanks to a thin layer of
convective cloudiness in the DGZ. Surface observations and satellite
indicate a land breeze induced convergence band that is slowly
pushing offshore between Little Sable Point and Holland, which
will similarly displace the area of flurries offshore.

No changes in expectations regarding the next system beginning later
Friday and Friday night. The 04/12Z HRRR looks scary in terms of
forecast reflectivity during this time, especially over Lake MI,
but this is likely related to the HRRR`s Thompson microphysics
scheme that has a penchant for creating water-coated crystals.
This yields large simulated reflectivity, but not necessarily
large precipitation rates. Best accumulations still look to be
over the northwest forecast area. Lake Michigan, being
substantially warmer than the surrounding coastal areas, will be
able to induce a thermal pressure trough that could enhance
convergence along the eastern lakeshore, but even with this in
play, we are dealing with limited moisture, sub-optimal crystal
growth, and therefore modest accumulations.

Farther south, along and south of Grand Rapids, there is a signal
for brief freezing drizzle Friday night towards midnight that,
from a time of day/week perspective, may pose limited risks, but
could still be sneaky in terms of causing slippery travel on
overpasses and other exposed areas.

Our next accumulating snow episode arrives Sunday morning. This will
be associated with somewhat more phasing between the northern and
southern streams. However, it appears that the best PV forcing
manages to bifurcate our area, meaning limited snowfall
accumulations for much of southwest Lower MI, albeit a better
chance for some snow along and south of I-96 compared to Friday
night.


- Accumulating snow possible with systems mid to late week

As noted previously, we expect at least one potentially impactful
system towards mid-week with a seasonably deep surface low expected
to cross Lower MI around Wednesday. Any time a surface low is
forecasted to cross directly over the forecast area, this often
sets the stage for a potentially diverse and complex precipitation
type forecast that is also highly susceptible to change based on
the track of the surface low. This system is no exception and will
be a chief focus for concern in the coming days.

There is a signal for yet another shortwave trough and round of
winter precipitation towards the end of the work week - but all
we can really say now is that the latter half of the week looks to
be unsettled with perhaps a favoring of more lake effect by the
weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1221 PM EST Thu Dec 4 2025

VFR conditions will continue through Friday morning. Winds will
shift southwest overnight with some gusts near Lake Michigan over
20 knots beginning late tonight. Areas of LLWS can be expected
across parts of western Lower Michigan late tonight into Friday
morning.

&&

.MARINE...
Issued at 312 PM EST Thu Dec 4 2025

Have maintained the Gale warning and added a Small Craft Advisory
for all remaining marine zones to the south that will last well
into Saturday. It still looks like the Whitehall to Pentwater
region immediately south of the Gale warning could see 2-3 hours
of gale conditions tonight, but this is a pretty borderline
situation and have therefore elected to leave things as is for
now.


&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory from 10 PM this evening to 7 PM EST
     Saturday for LMZ844>848.
     Gale Warning from 10 PM this evening to 10 AM EST Friday for
     LMZ849.

&&

$$

DISCUSSION...TJT
AVIATION...Ostuno
MARINE...TJT