711
FXUS63 KGRR 191617
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1117 AM EST Sun Jan 19 2025

.KEY MESSAGES...

- Lake Effect Snow Through Tuesday Night

- Very Cold Temperatures Through Mid-Week

- Moderating Temps and Additional Snow Chances Late Next Week

&&

.DISCUSSION...
Issued at 304 AM EST Sun Jan 19 2025

- Lake Effect Snow Through Tuesday Night

Increasing radar returns suggest that lake effect snow has begun to
develop across the lakeshore this morning. Intensity of snow showers
is expected to increase through the day today as a mid-level
shortwave and the arrival of the cold core aloft cause inversion
heights to climb to 10-15 kft. Winds then shift to westerly tonight
causing snow to expand inland given favorable low-level instability.
These showers continue through Tuesday night before diminishing as
upper-level ridging arrives. There are some signals that Monday
Night into Tuesday we may see some banding set up between I94 and
I96 as a high to our south leads to increased wind convergence.
Specifics as to how this could evolve are unclear.

Near the lakeshore, accumulations look to to be in the 8-12 inch
range through Wednesday morning with locally higher amounts
possible. Given the long duration of this event, with amounts below
warning criteria in any given 24 hour window this looks to be a high
end advisory event at this point. Have extended the current advisory
to early Wednesday morning. Inland towards US131, snow looks to be
in the 3-6 inch range for the most part so have issued a winter
weather advisory from early this evening through Tuesday evening.
Further east a widespread 1-4 inch snowfall is expected. Some
blowing snow is also possible.

In terms of impacts, expect dangerous travel conditions due to
snowfall and reduced visibilities, especially for roads like US31,
131, and I94 near and west of US131 where we have seen pile-up
accidents happen in similar kinds of events. This will only be
compounded by the fact that bitter cold temperatures will render
salt largely ineffective. Even areas that receive lighter amounts
may still see areas of slick conditions as a result. If you need to
travel, drive with caution and plan for extra travel time.

- Very Cold Temperatures Through Mid-Week

In addition to the snow, dangerously cold conditions are expected in
the early part of next week as an increasingly bitter airmass
arrives. Between tonight and Wednesday highs will be in the single
digits with lows near to below zero, especially where any breaks in
lake-effect cloud cover can occur.

Wind chills fall areawide to the -15 to -25F range Monday into
Wednesday, coldest inland away from the warm influence of the lake.
A Cold Weather Advisory will likely be needed, long in duration
given increased winds pair with the modest daytime heating for
little improvement in wind chill. Will will allow subsequent shifts
to finalize exact timing given advisory level wind chills are 24-36
hours our. Our coldest conditions are expected Tuesday and Wednesday
mornings. In particular, Wednesday morning will feature winds
shifting to southwesterly removing lake influence from parts of our
southeastern CWA. Given the fresh snowpack and potential clearing we
may see wind chills fall below -25F (30-50 percent chance). Given
conditions this cold lead to frostbite times of 30 min or less,
ensure you bundle up when outdoors.

- Moderating Temps and Additional Snow Chances Late Next Week

The arrival of mid-level ridging briefly ends snow for Wednesday
before a northern stream wave and associated clipper arrives for the
Thursday/Friday timeframe. 850mb temps near -10C will be enough to
support lake enhancement to the light synoptic snowfall. Southwest
flow will mean our northwestern forecast area will be favored for
the best lake enhancement. Ridging and the associated arrival of
warm air will cause highs to climb into the 20s for Thursday into
the weekend bringing a welcome relief to the bitter conditions.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 625 AM EST Sun Jan 19 2025

Lake effect snow bands will lead to occasional impacts at the TAF
sites for this forecast period. The northwest low level winds
will focus the main banding to the southwest of KGRR this
morning. Then the winds start to back to the west northwest and
eventually west through the afternoon and into the evening. As a
result the snow will work its way inland. Outside of the bands of
snow, conditions will vary from VFR to MVFR as the clouds drift
by. However in any of the bands of snow, IFR and lower conditions
will be possible. Aviators should continue to monitor the latest
forecasts given the risk for rapidly changing conditions.

&&

.MARINE...
Issued at 1117 AM EST Sun Jan 19 2025

The SCA is extended out to 9 AM Wednesday and the Heavy Freezing
Spray Warning until 1 pm Wednesday. Ice should be covering an
increasing amount of the nearshore waters the next few days and
may cover most if not all of the nearshore waters by Thursday.
Most river mouths could become ice bound as well. A reminder that
the current forecast for wave heights is for ice free areas.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory until 1 AM EST Wednesday for MIZ037-043-
     050-056-064-071.
     Winter Weather Advisory from 4 PM this afternoon to 7 PM EST
     Tuesday for MIZ038-044-057-065-072.
MARINE...Small Craft Advisory until 9 AM EST Thursday for LMZ844>849.
     Heavy Freezing Spray Warning until 1 PM EST Wednesday for
     LMZ844>849.

&&

$$

DISCUSSION...Thomas
AVIATION...MJS
MARINE...Ostuno