Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 071557
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1057 AM EST Thu Dec 7 2017

LATEST UPDATE...
Update

.SYNOPSIS...
Issued at 304 AM EST Thu Dec 7 2017

A reinforcing shot of arctic air moves in today leading to
unseasonably cold temperatures and lake effect snow showers.
Slick travel conditions will be possible. An area of high pressure
builds up the Ohio Valley for tonight into Friday diminishing the
snow showers. A widespread accumulating snow event is expected
for Friday night into Saturday as an area of low pressure tracks
through.

&&

.UPDATE...
Issued at 1052 AM EST Thu Dec 7 2017

No headline or significant fcst changes are necessary late this
morning. Snow showers will continue across the advisory area
through mid to late afternoon with additional accumulations mainly
under an inch or less near to west of US-131. Isolated higher
amounts to near 2 inches are possible west of US-131 where the
heaviest les bands are most persistent before tapering off late
this aftn.

&&

.SHORT TERM...(Today through Saturday)
Issued at 304 AM EST Thu Dec 7 2017

The leading edge of a reinforcing shot of arctic air was pushing
through the forecast area at this time. As this front sinks
southeast over the next couple of hours...the steadier snow
showers ahead of it will track through Kalamazoo and Battle Creek.
A northwesterly flow was setting up behind this front where lake
effect snow showers were strengthening. The northwest flow then
persists through the day supporting the steadiest snow showers
where we have the headlines out. We will need to monitor the
Interstate 94 corridor for possible expansion further inland of
the headlines due to the potential for stronger snow showers
today.

A more significant wave of low pressure tracks southeastward
through the CWA Friday night and Saturday. Widespread impacts are
becoming more likely with this event. The combination of deep
moisture...favorable lift and lake enhancement supports an
increased potential for more than 4 inches of snow for western
parts of the forecast area.

.LONG TERM...(Saturday night through Wednesday)
Issued at 304 AM EST Thu Dec 7 2017

The long term begins with a deep upper trough moving across eastern
Michigan and a sfc low over Ontario. Snow from this system will be
winding down and most locations will probably be dry Saturday night
through Sunday evening.

A clipper is progd to move southeast from Manitoba to southern
Ontario Sunday evening and dragging a cold front through the cwa
Monday. Light snow is likely with this system. Lake effect snow that
develops behind it as h8 temps fall to -17c will be limited to the
lake shore and perhaps the far eastern cwa if boundary layer winds
can get enough of a easterly component off of Lake Huron to bring a
few bands through Mid Michigan.

Another clipper is shown by both the ecmwf and gfs to move from
northern Minnesota southeast across Chicago Tuesday night. This
should bring light synoptic snow to the cwa during this time leading
to some minor accumulations.

Highs through the period will range from the upper 20s to mid 30s.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 614 AM EST Thu Dec 7 2017

Bands of lake effect snow will impact the TAF sites today. IFR and
lower look likely at times today. The heaviest snow will be west
of KLAN and KJXN. As we go through the afternoon...the snow
showers are forecasted to gradually weaken and by evening...the
bulk of the impacts should be gone.


&&

.MARINE...
Issued at 304 AM EST Thu Dec 7 2017

Small craft advisory conditions continue throughout the nearshore
area. The cold airmass will persist as west to northwest flow
lingers into Friday as high pressure builds up the Ohio
Valley...keeping the conditions hazardous.


&&

.HYDROLOGY...
Issued at 329 PM EST Wed Dec 6 2017

Several rounds of snow are expected over the next week due to a
combination of lake effect processes and passing low pressure
systems. The first round of more widespread snow will occur late
today through Thursday afternoon, bringing several inches of snow to
counties near the lakeshore. Total liquid equivalent (melted snow)
through Thursday evening will be below one-quarter of an inch for
most locations, but locations in Allegan, Van Buren, and Kalamazoo
counties could see locally higher totals up to one-half inch. No
issues with flooding or rivers are expected. Another round of more
widespread snow is expected to start mid-day Friday and last through
Saturday afternoon. This looks to bring another tenth to one-quarter
of an inch of liquid equivalent, and again not cause any issues
aside from accumulating snowfall.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory until 4 PM EST this afternoon for MIZ037-
     038-043-044-050-056-057-064-065-071>073.

LM...Small Craft Advisory until 7 PM EST Friday for LMZ844>849.

&&

$$

UPDATE...Laurens
SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...04
AVIATION...MJS
HYDROLOGY...HLO
MARINE...MJS



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