596
FXUS63 KGRR 291939
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
239 PM EST Sat Nov 29 2025

.KEY MESSAGES...

- Widespread snow event through Sunday morning remains on track

- Below average temps and periodic chances of snow showers next week

&&

.DISCUSSION...
Issued at 239 PM EST Sat Nov 29 2025

- Widespread snow event through Sunday morning remains on track

At this time, we will not be making any changes to the headlines
currently in place.

The event has unfolded as expected so far with light snow having
developed across all of the forecast area already. Regional radar
imagery shows stronger radar returns to our SW that are poised to
move in through this evening as expected. The isentropic ascent/warm
air advection driving this part of the system is relatively light,
interacting with an already saturated atmosphere.

The main part of the event remains poised to move in beginning in
the next few hours from south to north, and lasting off and on
through a good chunk of tonight. The heavier snow is just about to
move in over the far SW corner of the state as of 230 pm EST. It is
at that time that we have the enhanced forcing with the main short
wave that will traversing the area, along with some upper level jet
coupling going on.

The majority of the forecast area in the sweet spot for the
widespread snow. with some margin for error if the axis of the best
forcing changes a bit. Model consensus continues generally showing
the going forecast snow amounts we have been advertising for the
last couple of days with good run to run consistency in model
solutions and ensemble means.

We believe the only way that the forecast could deviate from the
current forecast is for the U.S.-10 corridor to end up with more
snow that currently forecast. Perusing all of the 12z data does not
give us enough confidence to upgrade at this time. Something to
watch up there is some possible enhancement from Lake Huron/Saginaw
Bay with the flow from the east over Clare and Osceola counties that
might bump their totals up compared to Mason and Lake counties.

The synoptic snow then moves out first thing Sunday morning, which
will transition to some lake effect snowfall for much of Sunday.
Lake effect parameters are fairly decent for most of the day as we
will see the upper jet surrounding the state with the cyclonic
flow/upper cold pool overhead. Delta t`s increase to around 20C with
inversion heights likely at or just above 10k ft.

The favored area for lake effect will be at the lakeshore counties
with the flow expected to be from the NNW much of the day. We can
not rule out needing the headlines to be extended, or transitioned
to an advisory for Sunday. Inversion heights will lower Sunday night
as ridging aloft builds in.

- Below average temps and periodic chances of snow showers next week

Not a lot of detail can be put into the forecast for Monday and
beyond, but the general pattern is fairly straight-forward. We are
looking at an upper flow pattern that will be predominately from the
NW through next weekend.

What this means is that we will be seeing short waves embedded in
the upper flow coming right at the area, providing periodic snow
shower chances just about everyday at some point. It is tough to
time any of these with much confidence beyond about 2-3 days. The
upper jet will be such that we are not looking at significant lake
effect with the jet core north of the area much of the time. As
stronger short waves come through, the jet core may temporarily drop
south of the area, allowing for enhanced snow chances along with
lake effect/enhancement.

Temperatures in this pattern will be generally below average through
the period. This does not look like any prolonged period of any
abnormally cold weather for this time of the year.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 108 PM EST Sat Nov 29 2025

Low pressure is centered in South Central Iowa as we approach
18z. Widespread snow is occurring to the east of the low across
Iowa, Wisconsin and Illinois. The eastern edge of the snow has
pushed through all of Southwest Lower Michigan with all 6 TAF
sites in the area now snowing.

Conditions will continue to deteriorate as we work through the
remainder of the afternoon and into the evening hours. Regional
radar loops show a surging large band of heavy snow encompassing
much of Northern Indiana and Northern Illinois stretching back
into Iowa. This band of snow will surge into the TAF sites this
afternoon and remain parked over the area during the evening hours
and into tonight. The heaviest snow at the bulk of the TAF sites
will fall between 22z and 07z. Snowfall rates of 0.50" to 1.00"
per hour are anticipated during that time frame. Conditions have
reached IFR at most TAF sites with a trend towards LIFR and VLIFR
as we work into the evening.

Conditions will try to improve late in the TAF period between 12z
and 18z as the system snow will be exiting to the east. We should
improve to MVFR during this time.

&&

.MARINE...
Issued at 239 PM EST Sat Nov 29 2025

The Small Craft Advisory for tonight into Sunday remains intact with
no changes. We will be upgrading the Gale Watch to a Warning for
Sunday morning and afternoon for the entire nearshore.

Winds will be coming up through this evening ahead of the system,
but will be offshore in nature and warm advection in nature,
limiting the wind gusts that reach the sfc. This will lead to the
marginal Gale force winds staying out over the open waters of mid-
lake.

It is a different story on Sunday. We will see offshore winds switch
to become from the NW (onshore). We will also see cold advection
over the lake mixing down to the sfc over the warmer lake. It is
much more likely we hit gales on Sunday vs. tonight.

&&

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

&&

$$

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