Winter Storm Warning 5, NWS Grand Rapids, MI

Area Forecast Discussion
National Weather Service Grand Rapids MI
1257 PM EST Wed Dec 21 2022

LATEST UPDATE...
Aviation

.UPDATE...
Issued at 1217 PM EST Wed Dec 21 2022

After coordinating with nearby offices, we are planning to issue
a Winter Storm Warning for our eastern counties from Thursday
evening until Saturday morning (likely 7 am). For our western CWA
very likely we will issue a blizzard warning from Thursday evening
through Saturday afternoon.

The latest model trends over the past 3 runs of those model have
stopped backing off on QPF and continue to support the idea of
sustained winds in the 25 mph range with gusts to 40 mph on
Friday. So the reason to have a blizzard warning over the western
counties is that there would be significantly more snow during the
day on Friday to blow around then there would be over our eastern
counties.

&&

.DISCUSSION...(Today through next Tuesday)
Issued at 315 AM EST Wed Dec 21 2022

- Major winter storm late Thursday through Saturday -

Bottom line up front... a winter storm watch remains in effect
for our entire fcst area from Thursday afternoon through Saturday
evening (no headline or major fcst changes with this early morning
fcst issuance). An overall short to medium range guidance
consensus continues to show potential for significant snow
accumulations from late Thursday afternoon through Friday with
blizzard conditions Friday.

It is noticed though that overall medium range guidance trends
the past 12-24 hours suggest that the low will track a bit
further east than it looked yesterday at this time. This is
particularly noticeable in the 00Z deterministic ecmwf and 00Z eps
which has a 982 mb low just nw of Toronto by 12Z Fri (yesterday
the ecmwf ensemble mean suggested a 980 mb sfc low would be
located further nw over Lake Huron by 12Z Fri).

This shift further east is significant in that it causes cold air
to move into our area sooner (no pcpn type issues Thur eve). It
also no longer supports a trowal this far southwest and has less
qpf and less snowfall for our area while now showing potential
for heavier snow over eastern lower MI in closer proximity to the
sfc low. My gut feeling is that all the cold dense arctic air
already pouring into the upper midwest across MN/WI/IA could force
the low on a bit further east track as suggested by latest
model trends which would mean potentially less synoptic snow
accumulations in our area.

All things considered though a consensus blend of latest short to
medium range guidance still supports significant snow late
Thur/Thur night through Friday. Some of our guidance is likely
underdone with snowfall amounts since falling temps through the
day Friday will lead to increasingly favorable snow ratios. Snow
combined with very strong winds will cause blizzard conditions
regardless of how much snow ultimately falls across our area.

So at this time our forecast and messaging will remain very
consistent with previous forecasts and we still expect a major
winter storm with significant snow and blizzard conditions and
scattered to potentially numerous power outages Friday into
Saturday.

Future shifts will need to continue to monitor guidance trends
very closely in terms of low strength and track. It will make all
the difference in terms of total snow accumulations and therefore
just how impactful this storm becomes in our area (the difference
between blizzard conditions at times Friday versus a crippling
snowstorm that makes travel very difficult if not impossible for
days on end if we end up with one to two feet of snow and drifts
much higher than that). The furthest west 00z deterministic
gfs/00z gefs ensemble low position over Saginaw Bay at 12Z Fri
with trowal in our area are the solutions most conducive to
highest end synoptic snow accumulations.

By Saturday we expect significant impacts from cold temps and
windy conditions and blowing and drifting snow. Several additional
inches of lake effect snow are likely in our favored nw flow snow
belt regions. However the magnitude of wind speeds Saturday will
limit airmass residency time over Lake MI and carry les far inland
such that all of our area will get lake effect snow showers.
However the greatly dispersed nature of lake effect snow showers
across our area will tend to limit accumulations in any particular
location given the strong winds. Very cold thermal profiles
Saturday will also result in a very fine powdery snow which will
also limit potential accumulations somewhat.

In the nearer term... tranquil wx will continue today with partly
cloudy skies and seasonably cold temps.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1257 PM EST Wed Dec 21 2022

There are two area of concern in the very short term. First it he
IFR light snow that has been happening at MKG since 09 am this
morning. That is a lake effect event with very shallow moisture
associated with it. That should be ending very soon (by 19z for
sure) due the warmer air moving in at mid levels moving in.

The second area of interest is the MVFR cigs associated with the
warm front. There is an area of MVFR cigs just north of the
surface warm front. That will bring several hours of MVFR cigs to
most of our TAF sites between 3 pm to 6 pm I-94 group and 4-8 pm
for I-96 group. Once the warm front gets north of this area cigs
should lift and leave mostly mid and high clouds.

The system coming into tomorrow will bring snow but that will not
start till well after the 18z end time of the TAFS.

&&

.MARINE...
Issued at 315 AM EST Wed Dec 21 2022

Storm force winds are likely to develop late Thursday night
through Saturday and will cause wave heights to build into the 15
to 20 foot range by Friday. In addition freezing spray is expected
as arctic air moves in Friday through the weekend.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Storm Watch from Thursday afternoon through Saturday
     evening for MIZ037>040-043>046-050>052-056>059-064>067-
     071>074.

LM...Storm Watch from late Thursday night through Saturday evening
     for LMZ844>849.

&&

UPDATE...WDM
DISCUSSION...Laurens
AVIATION...WDM
MARINE...Laurens

Hazardous Weather Outlook
National Weather Service Grand Rapids MI
400 AM EST Wed Dec 21 2022

MIZ037>040-043>046-050>052-056>059-064>067-071>074-220900-
Mason-Lake-Osceola-Clare-Oceana-Newaygo-Mecosta-Isabella-Muskegon-
Montcalm-Gratiot-Ottawa-Kent-Ionia-Clinton-Allegan-Barry-Eaton-
Ingham-Van Buren-Kalamazoo-Calhoun-Jackson-
400 AM EST Wed Dec 21 2022

This hazardous weather outlook is for portions of southwest Lower
Michigan.

.DAY ONE...Today and Tonight

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

Snow will develop Thursday afternoon and become heavy at times
Thursday night and Friday. Snow will be accompanied by very gusty
winds and falling temperatures Friday leading to blizzard or near
blizzard conditions which will continue into Friday night.
Additional lake effect snow is expected Saturday into Sunday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed.

LMZ844>849-220900-
St Joseph to South Haven MI-South Haven to Holland MI-
Holland to Grand Haven MI-Grand Haven to Whitehall MI-
Whitehall to Pentwater MI-Pentwater to Manistee MI-
400 AM EST Wed Dec 21 2022

This hazardous weather outlook is for portions of southwest Lower
Michigan.

.DAY ONE...Today and Tonight

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

Storm force winds and dangerously high waves are expected late
Thursday night through Saturday evening. Freezing spray is also
expected Friday through the weekend.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed.