659
FXUS63 KGRR 150440
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
1140 PM EST Sun Dec 14 2025
.KEY MESSAGES...
- Lake effect into early Eve then light snow in north Tomorrow
- Warmer, rainy and windy Thursday
- Snow with mixed precipitation events into the weekend
&&
.DISCUSSION...
Issued at 337 PM EST Sun Dec 14 2025
- Lake effect into early Eve then light snow in north Tomorrow
So bottom line upfront. Have allowed the Winter weather advisory
to expire. However, periods of snow showers in a narrow band of
lake effect continues. This persistent band is along the coast and
looking at most MDOT webcams, while it is snowing, it is less
impactful with light accumulations. The flow continues to shift
and the main bands could affect the Muskegon to Holland region
over the next few hours.
These bands will continue to diminish into the evening as flow
cuts off and weak thermal ridge builds into the midwest.
Downsloping flow begins the work week with a weak trough moving
through the Upper Great Lakes tomorrow. This weak clipper could
bring light snowfall north of the I 96 corridor and mainly along
and north of the US 10 corridor. Any accumulations will be light.
- Warmer, rainy and windy Thursday
The big story for the week will be the warmup and potential rain
midweek. A large surface low with good mid level forcing will move
through Southern Canada and draw warm southwesterly flow into
Michigan Tuesday evening into Thursday.
The warm air advection by Tuesday evening should be around +7C at
850mb. To put that in perspective, it was around -25C this
morning. Lows this morning were preliminary 0F, normal is 25F and
record is -1F. So by Wednesday morning, the low forecast is 30F.
That warm air will continue to advect into the region through
Wednesday and into Thursday. Lows projected Wednesday morning to
be 10 degrees above normal and 7 degrees above normal Thursday.
Models remain consistent in bringing a large upper level system
through the region Thursday. There is some question on position
and that will determine how much QPF we receive. Rain is still
expected. with showers likely Thursday. Slightly anomalous PWATS
give credence to around 0.5 inch to .75 inch of QPF range so far.
Strong low level jet remains possible along with this system so
strong southwesterly winds will remain possible Thursday.
What this transition period does to the snowpack remains to be
seen. However, given the rain and persistent warm air advection,
we should expect to loose much of the snowpack.
- Snow with mixed precipitation events into the weekend
The large upper level low will quickly move eastward Thursday
evening. Strong northwesterly flow with -15C at 850mb should
advect into the region by Friday morning. This should allow for
some lake effect with perhaps an inch or two of snow Thursday
night into Friday. Given the robust system, a rain/snow mix at
times is probable. So a wintry mix through this timeframe is
plausible. Temps drop back down to near normal on Friday before
potentially getting back into the upper 30s on Saturday.
&&
.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1140 PM EST Sun Dec 14 2025
The lake effect snow showers that had persisted most of the
weekend have now pretty much ended across the terminals except
maybe an isolated flurry at most. We have kept the cloud cover in,
which for the most part is low end MVFR with ceilings 1-2k ft
agl. We do expect this low cloud cover to gradually move out of
most of the terminals through tomorrow morning, except KMKG. Only
mid-high clouds will persist once the low clouds move out.
Winds will become gusty by mid morning at all of the sites, with
wind gusts of 22-30 knots expected. These will diminish by late
afternoon. We will also see the lower clouds move back in by late
afternoon to early evening on Monday. These will likely be around
2500 ft initially, then going down to 1500 ft.
For the KGRR 06z update, no precipitation expected through Monday.
&&
.MARINE...
Issued at 337 PM EST Sun Dec 14 2025
The longer duration Small Craft advisory continues into Monday
morning. While there will be a lull this evening, the winds will
pick up late tonight with gales expected tomorrow of 35 to 40 kts
at times Monday morning. Waves remain expected to peak around 10
feet Monday morning.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 4 AM EST Monday for LMZ844>849.
Gale Warning from 4 AM to 3 PM EST Monday for LMZ844>849.
&&
$$
DISCUSSION...Ceru
AVIATION...NJJ
MARINE...Ceru
NWS GRR Office Area Forecast Discussion
