646
FXUS63 KGRR 131138
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
638 AM EST Tue Jan 13 2026
.KEY MESSAGES...
- A few rain showers today and tonight, changing to snow Wed morning
- Becoming much colder and snowy this weekend and beyond
&&
.DISCUSSION...
Issued at 334 AM EST Tue Jan 13 2026
- A few rain showers today and tonight, changing to snow Wed morning
The next system to affect the area is rapidly advancing toward the
area this morning, evident by water vapor imagery and the regional
radar composite. This system will not be impactful for the area, but
will set the stage for a more impactful system late tonight and
Wednesday morning.
We are looking at a high probability/low amount light rain event
coming through late this morning/early this afternoon with the wave
to our NW. As has been the case with most of these weak systems
coming in from the WNW, this one also has limited moisture
available. Forecast soundings/RH cross sections show very little
moisture available below 6k ft, and a sufficient melting layer for
just about all rain. It looks like that we will see a brief period
of light showers, and then dry out for much of the rest of the day
with even some partial clearing possible for the afternoon.
This wave will be still moving out when the next wave will arrive
with a vengeance late tonight. We maintain longer wave troughing
behind today`s wave, and we see a northern stream wave with origins
up near the arctic diving south quickly toward the area later
tonight. We will see some precipitation break out as light drizzle
or scattered showers ahead of this wave this evening and early
overnight.
Then we will see the sfc arctic front associated with the wave
diving south rush through arriving at the U.S.-10 corridor around
06z tonight, and exit the I-94 corridor by 11-12z. This front is
expected to have a line of more intense showers, starting as rain,
and quickly changing to snow, likely associated with strong wind
gusts. Snow amounts will not be much with this front, but the
impacts will come with the abrupt change, including temps going from
the mid-upper 30s to mid 20s within about 2-3 hours causing wet sfcs
to freeze rather quick.
If there is a bright side to this transition, it is that it should
occur mostly before the morning commute, vs happen right during the
commute which would cause more impacts. Right now, given duration,
snow amounts, winds, some blowing snow, etc...there does not look to
be enough to justify a headline at this time with this alone. This
scenario looks like Special Weather Statement type of situation.
Now, lake effect will get going almost immediately as the cyclonic
flow and cold pool aloft will move overhead. Inversion heights will
rise to about 7-8k ft, delta t`s will increase to about 20C, and low
level lapse rates increase to almost 8c/km. Lake effect will favor
the far NW and SW corners of the forecast area with the flow
becoming from the NNW. This lake effect combined with the impacts
from the front earlier may be enough to justify some winter
headlines. We still have a little bit of time to fine tune the
details on this.
The lake effect will wind down over our area Wednesday evening and
night. This will be the result of the flow going more NNE (offshore)
and a temporary upper ridge coming in and lowering inversion heights
with the cyclonic flow moving out briefly.
- Becoming much colder and snowy this weekend and beyond
After the break on Thursday, the next wave will arrive on Friday. We
see some warming take place ahead of the sfc system, along with
precipitation breaking out. Then, the long wave upper low and
cyclonic flow aloft settles over the area once again. This will
reactivate the lake effect as much colder air comes back in. With
short waves embedded in the large scale low, we are looking at
multiple spikes in lake effect intensity.
The flow will be constantly adjusting based on the short waves and
associated sfc reflections. This will be tough to pin down amounts
at this time. What does look likely though is areas generally along
and west of U.S.-131 will be the most impacted. This continues right
through the end of the period next Monday. Needless to say, we will
see snow accumulations add up steadily over the three day period
from Sat-Mon for western areas. This will be accompanied by max
temps likely not reaching 20F after Sat.
&&
.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 638 AM EST Tue Jan 13 2026
Quite a complicated period of weather for the next 24 hours for
the terminals. We start out VFR at all sites, with mid clouds
around 10k ft over the area. However, a core of wind of 50+ knots
around 2-4k ft up is moving overhead. We kept the low level wind
shear in with the speed and directional shear, even as sfc winds
gust a bit. Some light rain showers will pass through the
terminals mainly this morning from NW to SE. These are expected to
only last a couple of hours, and remain VFR.
We will scatter out a bit this afternoon, and winds will be gusty
from the SW and eventually W. Low level moisture will start moving
back in from north to south around 22z or so. Ceilings will then
go MVFR after 00z as low level moisture increases ahead of a
front. Rain showers will become more widespread by 06-08z. The
front will then approach as pass through, changing all
precipitation to snow quickly, and it could briefly be intense.
Winds will become very gusty also.
&&
.MARINE...
Issued at 334 AM EST Tue Jan 13 2026
We will be upgrading the Gale Watch to a Gale Warning for late
tonight through Wednesday. This looks to be a solid Gale event as
the gradient will be quite tight in the wake of the front dropping
through, along with strong cold air advection over the warmer waters
of Lake Michigan.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 4 AM EST Wednesday for LMZ844>849.
Gale Warning from 4 AM Wednesday to 1 AM EST Thursday for
LMZ844>849.
&&
$$
DISCUSSION...NJJ
AVIATION...NJJ
MARINE...NJJ
NWS GRR Office Area Forecast Discussion
