368
FXUS63 KGRR 041116
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
616 AM EST Thu Dec 4 2025

.KEY MESSAGES...

- Periods of light snow possible late Friday into Sunday

- Accumulating snow possible with systems Tuesday and Wednesday

&&

.DISCUSSION...
Issued at 330 AM EST Thu Dec 4 2025

- Periods of light snow possible late Friday into Sunday

The last of the light snow associated with the front that came
through yesterday is just about to exit the forecast area as of 330
am this morning. The low level flow will remain from the NW today,
with 850 mb temps down in the negative mid teens C. There is plenty
of over lake instability, however building subsidence will push
inversion heights down. This will result in a small layer of
moisture in the DGZ, which should produce nothing more than
flurries/very light snow showers with trace accumulation.

Our next system will be affecting the forecast area beginning later
Friday and Friday night. The responsible feature for this round of
precipitation is a short wave that is currently over British
Columbia. As has been the pattern for the last few days, this short
wave or clipper system embedded in the NW flow aloft will bring
light precipitation.

This system itself will be moisture starved as it moves over the
area. SW flow ahead of the system will add some moisture and
instability from Lake Michigan to potentially produce a couple of
inches of snow focused on the NW corner of the area. Elsewhere
inland, we are looking at accumulations up to an inch.

After a brief break for most of Saturday after the system moves out
early, the next short wave in the series will dive down Sunday
morning and clip the area. This short wave looks to phase with
another wave coming from the Rockies to bring more light snow to the
area. Amounts with this setup look similar to the Fri/Fri night
event with limited moisture available once again.

- Accumulating snow possible with systems Tuesday and Wednesday

We see a mostly dry period come about Monday as a fairly strong sfc
ridge and confluent flow aloft provide stronger subsidence over the
area. Can`t rule out a few flurries near the lakeshore with 850 mb
temps in the negative mid teens C again. The subsidence will really
limit the degree of saturation of the DGZ to limit snow shower
potential.

We are watching the potential for a couple of impactful systems that
could affect the area on Tuesday and Wednesday. The upper air
pattern looks to amplify a bit as a stronger ridge builds of the
eastern Pacific and Western U.S.. Instead of the rather flat upper
flow from the NW, a couple of stronger short waves will dive SE over
the region.

These short waves will be quick hitting, but will pack a punch. The
first one will have cold enough air for Lake Michigan to potentially
enhance it a bit. The second short wave is forecast to be a tad
further south, but will have some warmer air to work with. There is
enough warmer air that we could see some rain mix in over the far
southern portion of our forecast area.

Timing of these waves/frontal systems 6-7 days out is problematic,
especially in a fast flow like we have. We have an idea though of
some potentially impactful weather that we can fine tune as we get
closer to that period.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 616 AM EST Thu Dec 4 2025

Snow shower activity continues to taper off, with most flurries
done as of 11z. This is leaving just sct-bkn stratocumulus clouds
around 3500 ft. Inland terminals will see between sct-bkn clouds
continue, while KMKG and KAZO will see more coverage of clouds
being closer and downwind of Lake Michigan, with maybe a few
flurries. The clouds will scatter out even toward the lakeshore
tonight. Winds will pick up KMKG overnight, while some low level
wind shear is likely at KGRR with 35 knots at 1500 ft. The other
sites have lower winds at 1-2k ft so we did not include low level
wind shear there.

Winds from the NW much of the day will become light from the south
late this afternoon.

&&

.MARINE...
Issued at 330 AM EST Thu Dec 4 2025

We have decided to hoist a Gale Warning for the northern marine zone
for late tonight through Friday morning.

A Small Craft Advisory remains in effect through 7 pm this evening
for the entire nearshore. This is associated with the cold air
moving in behind the front that moved through yesterday. Winds will
taper off today, and waves may actually drop off early enough that
the Advisory may be able to be cancelled early.

After a brief break in the wind with a sfc ridge moving by the area,
winds will ramp up tonight ahead of the next system moving toward
the area. The strongest winds will be across the north. There is
some potential that the Gale may be needed for another zone or two,
but the confidence is not there yet.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 7 PM EST this evening for LMZ844>849.
     Gale Warning from 10 PM this evening to 10 AM EST Friday for
     LMZ849.

&&

$$

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