Lansing, Michigan 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

697
FXUS63 KGRR 040815
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
315 AM EST Wed Dec 4 2024

.KEY MESSAGES...

- Light Snow Through This Afternoon

- Lake Effect Snow, Blowing Snow, and Windy Tonight into Thursday

- Potential for rain arriving Sunday night

&&

.DISCUSSION...
Issued at 313 AM EST Wed Dec 4 2024

- Light Snow Through This Afternoon

An upper-low diving towards the region is driving a surface low
north of the area today.  The warm air advection wing of this system
will keep light snow ongoing today, especially near and north of I96
. Accumulations will generally be 3 inches or less by this afternoon
keeping travel impacts minimal. There is a low chance of drizzle or
freezing drizzle late this morning into the early afternoon once the
DGZ dries out.

- Lake Effect Snow, Blowing Snow, and Windy Tonight into Thursday

Bottom line up front, have upgraded the current Winter Storm Watch
into a Winter Storm Warning from this evening to early Friday.
Osceola, Mecosta, and Calhoun were also added to the warning. All
remaining counties across West Michigan are under a winter weather
advisory for the same timeframe.

The first phase of the event is expected this evening when an arctic
front sweeps across the area. Surface based instability and strong
low-level convergence likely leads to the development of snow
squalls along the front. Snow squalls will lead to rapid reduction
of visibilities to near zero and rapid changes in road conditions.
Of particular concern is that these squalls will track along the
I96, I69, I94, US131, and US127 corridors during the evening
commute. The arctic air behind the front will also lead to any
lingering moisture on the roadways quickly freezing. Winds may gust
over 40 mph along the front as well given strong mixing.

Behind the front snow there may be a brief lull in snow showers
before lake effect snow ramps up this evening. Given low-level theta
e lapse rates in the negatives and boundary layer winds exceeding 40
knots these snow bands will be able to reach well inland. Two snow
maxima are expected. Northwest flow drives the heaviest lake effect
snow bands tonight into Thursday across the Grand Haven to Holland
to Battle Creek region, and potentially further east if organized
banding persists. Second, as low-level flow becomes more northerly
into the day on Thursday, several CAM solutions suggest that lake-
effect bands are able to get a Lake Superior connection leading to
an additional snowfall maximum across the northwestern CWA and
enhance snow across the rest of the warning area from enhanced
moisture if this occurs. Snowfall totals will vary across counties
due to the banded nature of lake effect snow. Across the warning
area a general 6 to 10 inches of snow with locally higher amounts
possible is favored. In the advisory area where lake effect snow
squalls will be more scattered in the post frontal environment a
general 2 to 6 inches of snow is expected with locally higher
amounts possible.

A deep  mixing layer tapping into the aforementioned strong boundary
layer winds will lead to wind gusts exceeding 40 mph bringing
concerns for scattered power outages and blowing snow in addition to
the heavy lake effect snow tonight into Thursday. Travel conditions
will be hazardous due to occasional whiteouts from snow and blowing
snow along with snow covered roads Tonight into Thursday morning.
The Thursday morning commute will be particularly impacted, with
snow and winds continuing to affect the Thursday evening commute as
well. Snow diminishes Thursday night as surface ridging advances
into the area.

- Potential for rain arriving Sunday night

A mid level low that will be over the Southwest U.S. on Friday will
lift out into the Plains Sunday and through the Great Lakes region
Monday.  Warm and moist air advection ahead of this feature will
warm temperatures up enough for rain to be the main precipitation
type with this next system.  An upper level wave digs into the Upper
Plains behind the initial wave for Monday.  The upper wave then
tracks into MI for Tuesday. This feature will extend the
precipitation here in MI into Tuesday.  As the column cools later
Tuesday and more so Tuesday night, any remaining precipitation will
mix with and change to snow. Deterministic qpf values from the
models generally support around a quarter inch across northern zones
with around a half inch over southern Lower MI.  Ensemble values
show a fair amount of spread, but at this time potential impacts
from this event look low.  Melting snow will add to the runoff, so
we will have to monitor the water equivalent values after the
current system is done.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1244 AM EST Wed Dec 4 2024

Strong gusty winds will generate some impacts through the period.
Ahead of an arctic front south to southwest winds will gust over
25 knots at times through the morning. Then as the front moves in
this afternoon, the winds will veer to the west and gusts will top
30 knots and occasional brief gusts could reach 40 knots,
especially after 00z Thursday. Overall, not much precipitation is
expected through the morning, with the focus remaining north of
KGRR, however that will change as the front moves in during the
afternoon. We will see rain and snow arriving and there is still a
small chance for a short period for freezing drizzle. As the
arctic air flows in during on the backside of the front for the
late afternoon hours the snow will expand. IFR and lower
conditions are expected. Blowing snow will become an increasing
concern, especially after 00z Thursday when the strongest winds
arrive and snow intensity increases.

GRR Airport DSS Update
The potential for visibilities to fall under a mile has increased
for later this afternoon. The rapid fall in temperature from 3 pm
to 11 pm today is likely to make untreated surfaces icy. Peak
wind gusts Wednesday evening and into Thursday could reach 45 mph.

&&

.MARINE...
Issued at 313 AM EST Wed Dec 4 2024

Current Gale Warning is already verifying as southwest gales
continue through the day. This evening gales turn northwesterly with
widespread strong gales and isolated storm force gusts tonight into
Thursday with peak gusts along the initial arctic front and again in
the hours before daybreak on Thursday. Waves of 15 to 20 feet are
expected along with the strong winds. No changes to the gale warning
will be made at this time. Snow squalls are expected to develop
along and behind the arctic front this evening into Thursday causing
rapid reductions in visibilities to under one quarter mile at
times.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Storm Warning from 5 PM this afternoon to 1 AM EST Friday
     for MIZ037>039-043>045-050-056-057-064-065-071>073.
     Winter Weather Advisory from 5 PM this afternoon to 1 AM EST
     Friday for MIZ040-046-051-052-058-059-066-067-074.
MARINE...Gale Warning until 1 PM EST Thursday for LMZ844>849.

&&

$$

DISCUSSION...Thomas/MJS
AVIATION...MJS
MARINE...Thomas