161
FXUS63 KGRR 121959
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
259 PM EST Fri Dec 12 2025
.KEY MESSAGES...
- Light Lake Effect Snow through Saturday
- Arctic Cold into Early Next Week The Moderating
&&
.DISCUSSION...
Issued at 256 PM EST Fri Dec 12 2025
- Light Lake Effect Snow through Saturday
A shortwave trough and advancing arctic front is currently across
Wisconsin with low level convergence generating an area of snow.
The snow should expand as it gets a boost from Lake Michigan with
the trough raising inversion heights to around 10 kft this
evening. Lake effect snow will perk up in southwest flow behind
the front,switching to northwest overnight.
Given strong lake instability and persistent onshore flow, we
expect some localized amounts over 4 inches of snow before
inversion heights fall and snow showers decrease on Saturday
night. However, snow amounts will be limited in most places to 1
to 3 inches by inversion heights at or below 5 kft and small flake
size, as the DGZ is near or below the ground.
- Arctic Air into Early Next Week then Moderating
Arctic air surges in on Saturday, with a lobe of the polar vortex
reaching Lower Michigan Saturday night. We will see apparent
temperatures fall to near of below minus 10F away from Lake
Michigan and a Cold Advisory may be needed.
850 MB temperatures near or below minus 20C and should result in
high temperatures being confined to the teens on Saturday and
Sunday then slowly moderating into Monday. The surface high moves
east with milder Pacific air arriving for mid-week and the
potential for rain on Thursday. Colder air moves in for the end
of the week, completing a freeze-thaw-refreeze cycle.
&&
.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1200 PM EST Fri Dec 12 2025
A mix of MVFR and VFR cigs are expected across the terminals this
afternoon before solid MVFR sets in overnight through the end of
the TAF period. After 00z, lake effect snow showers set in from
northwest to southeast with periods of MVFR visbys likely and a
20-30% chance of IFR visbys. Light snow showers likely linger near
the lakeshore through the day but become less widespread and
robust after 12z Saturday through the end of the TAF window. Wind
gusts increase tonight into Saturday to 20-25 knots, possibly as
high as 30 knots near the lakeshore, in post frontal cold air
advection.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory from 7 PM this evening to 7 PM EST Saturday
for LMZ844>849.
&&
$$
DISCUSSION...Ostuno
AVIATION...Thomas
NWS GRR Office Area Forecast Discussion
