345
FXUS63 KGRR 010445
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
1145 PM EST Wed Dec 31 2025
.KEY MESSAGES...
- Accumulating Snow Through Tonight
- Light Snow Showers Thursday Evening
- Snow or Mixed Precipitation Possible Sunday into Monday
&&
.DISCUSSION...
Issued at 313 PM EST Wed Dec 31 2025
- Accumulating Snow Through Tonight
An upper low moving across Lake Superior is helping push through a
surface cold front across Lower Michigan this afternoon, with
synoptic lift and abundant low level moisture moving over Lake
Michigan to provide a flare up in lake enhanced snowfall. Some
blowing snow has also been observed at airport observation sites
such as MKG. Saturation of the DGZ with 3-6 ubar/s of lift per the
18z RAP13 guidance is moving through at this time with decent
snowflake growth bringing visibilities down to 3/4 mile at times
at numerous airports including GRR, LAN, and AZO. NAM12 925-850mb
omega values look intense for a time from BIV to AZO and LWA
between now and 00z or so. During this period, higher impacts to
travel are likely for anyone venturing out this New Year`s Eve.
Beyond 00z, lake effect snow showers will migrate closer to the
coast as low level flow shifts from W to NW. Some lighter lift
within a saturated DGZ continues for the lakeshore counties plus
Lake and Kalamazoo into tonight, but not for Newaygo/Kent/Barry.
Given a dropoff in snow shower activity for those three counties,
have decided to trim back the expiration time of the Advisory to
10pm tonight, while leaving the rest of the counties at 7am
Thursday. The evening shift can reevaluate as needed. Additional
accumulations between now and 10pm for Newaygo/Kent/Barry look to
be 1"-2", with 1"-4" through Thursday morning for the remainder
of the Advisory area.
- Light Snow Showers Thursday Evening
The lake effect snow showers should either wind down completely or
be reduced to flurries later Thursday morning before another brief
flare up Thursday afternoon into the evening. This is the result
of a subtle upper shortwave showing up in the numerical guidance
and some light snow occurring at the surface (MN into WI)
underneath an 850mb thermal gradient. This features moves over the
lake after 18z Thursday and 1000-700mb RH increases from below 60%
to nearly 100% between 18z Thursday and 03z Friday. With light
lift noted in this layer, some lake effect snow showers will
likely redevelop with around 1" of new accumulation possible.
- Snow or Mixed Precipitation Possible Sunday into Monday
Attention then turns to the next system slated to impact the state
Sunday night into Monday. Unlike recent systems, this one will
emanate from the SW United States and ride up over a developing
upper ridge as seen at 500mb across the central U.S. on Sunday.
Warm air advection is indicated at 850mb with -10C to start the
day but around 0C to end it. At the surface, a warm front is
forecast to lift through the region Sunday night into Monday. A
strong LLJ of 50 kts will accompany this synoptic system. WAA snow
and potentially mixed precipitation could occur especially near
and north of I-96. Current ECE probabilities for 1" or more across
this region is 60-80% and 3" or more is 20-30%. Can`t rule out
mixed precipitation either with the elevated warm layer nosing in.
While this doesn`t look like a significant storm yet, it could
impact Monday travel conditions.
&&
.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1145 PM EST Wed Dec 31 2025
Key changes:
- None before 12Z
- Added PROB30 for MVFR restrictions in snow Thursday afternoon
VFR conditions should prevail at all terminals overnight with the
possible exception of MKG, which could see intermittent MVFR
ceiling restrictions with lake effect snow (LES). Visibility
restrictions with LES should be limited given its weakening and
disorganized nature. Only other change was to mention PROB30 at
all terminals due to an expected uptick in lake enhanced snow
Thursday afternoon.
GRR Airport DSS Update
No changes to the airport briefing information provided from the
day shift.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory until 7 AM EST Thursday for MIZ037-038-
043-050-056-064-071-072.
MARINE...Small Craft Advisory until 7 PM EST Thursday for LMZ844>849.
&&
$$
DISCUSSION...Hoving
AVIATION...TJT
NWS GRR Office Area Forecast Discussion
