415
FXUS63 KGRR 300806
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
306 AM EST Sun Nov 30 2025

.KEY MESSAGES...

- Transition to lake effect near lake shore today

- Accumulating snow possible Monday afternoon/night

- Cold week ahead

&&

.DISCUSSION...
Issued at 306 AM EST Sun Nov 30 2025

- Transition to lake effect near lake shore today

Surface obs reveal low pressure over central Lake MI early this
morning. Regional radar shows snow extending west to eastern IA
which means we have several hours of synoptic snow to go before
we transition to just lake effect snow showers. Spotter reports
indicate 3-6 inches of snow have fallen so far. During the past
few hours, radar echos have increased to 30 dbz or greater
indicative of heavier snowfall and flake size has increased quite
a bit since midnight concurrent with the strongest isentropic
lift. Pressure advection is maximized through 09z, after which
pressure advection becomes more neutral. At that point, expect the
snowfall rates to begin to decrease. That said, several more
inches of accumulation is anticipated prior to the synoptic system
moving east.

Boundary layer wind progs indicate we`ll see NNWly winds develop
around noon combined with deep moisture to produce lake effect
snow showers. Given the wind direction, the lake shore counties
will see the largest impact with several more inches of snow.

We`ll keep the winter storm warning going through 10 am and see
how the lake effect evolves. We may need to extend the warning for
a few lake shore counties.

Winds will increase this afternoon as the low moves by and high
pressure builds in behind it. This may result in blowing and
drifting snow which could create hazardous travel conditions.

- Accumulating snow possible Monday afternoon/night

Boundary layer winds will become southwesterly Monday ahead of the
next upper trough. H8 temperatures combined with deep moisture
will result in a southwest lake effect event Monday afternoon and
night. Several inches of snow are possible centered on northern
Ottawa, Muskegon, southern Oceana counties as this event unfolds
and headlines may be needed.

- Cold week ahead

Highs around 30 are expected Monday through Wednesday. An arctic
cold front will pass through the state Wednesday with the coldest
air of the season behind it. H8 temperatures are progd to fall to
around -18c behind it; surface high temperatures in the lower 20s
are anticipated Thursday and Friday along with more lake effect
snow.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1158 PM EST Sat Nov 29 2025

IFR conditions will prevail most of the time through 12Z with some
patchy LIFR possible in heavier snow. Conditions will improve on
Sunday morning as the snow moves out but lake effect snow showers
will still bring areas of IFR conditions near MKG and AZO.
Conditions will improve to VFR away from Lake Michigan by Sunday
afternoon.

Winds will be east around 10 knots before switching to west by 12Z
and northwest by 16Z.

&&

.MARINE...
Issued at 306 AM EST Sun Nov 30 2025

No changes to the marine headlines. Surface low over central Lake
MI will move east today and winds will become NNWly. As high
pressure builds in behind the departing low, winds will increase
to gales late this morning and continue through the afternoon.
Once the gales decrease this evening, we`ll likely need another
small craft advisory.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory until 10 AM EST this morning for
     MIZ037>040.
     Winter Storm Warning until 10 AM EST this morning for MIZ043>046-
     050>052-056>059-064>067-071>074.
MARINE...Small Craft Advisory until 10 AM EST this morning for LMZ844>849.
     Gale Warning from 10 AM this morning to 8 PM EST this evening
     for LMZ844>849.

&&

$$

DISCUSSION...04
AVIATION...Ostuno
MARINE...04