Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 132022
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
322 PM EST Sat Jan 13 2018

LATEST UPDATE...
Synopsis/Short Term/Long Term/Marine

.SYNOPSIS...
Issued at 322 PM EST Sat Jan 13 2018

Ongoing snow showers near the lake shore will diminish tonight but
probably not completely shut off before the arrival of a clipper
late Sunday brings more light snow to West Michigan. The clipper
will produce another inch or two as it moves across the state.
Lingering snow showers will occur through Wednesday in the north
flow behind the departing low. By midweek temperatures will begin to
warm as high pressure builds in and the upper flow becomes more
southerly.

Highs around 20 tomorrow will warm to around 40 by Saturday.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 322 PM EST Sat Jan 13 2018

Forecast concerns deal with the approaching clipper.

Latest vis loop shows lake effect clouds developing over the western
portion of the lake. Given very cold temps over the lake, we`re
likely to see light snow showers continue mainly west of US-131
through Sunday.

A clipper will approach Michigan late Sunday. The south winds ahead
of the low will produce a north/south lake band that could become
important Monday. The clipper has a large upper trough associated
with it, but it lags a bit behind the sfc low and this could be a
reason that the ecmwf has backed off considerably on snow accums.
The gfs is more bullish and produced 2-4 inches of snow across the
cwa from 00z Monday through 00z Tuesday. Earlier runs of the ecmwf
were doing something similar to the gfs but have backed way off on
pcpn, mainly due to not pushing that lake band onshore. The ecmwf
now only produces an inch or two of snow with this system, which is
a key reason we have not issued a advisory for Sunday night/Monday.
It`s still possible that the northwest cwa could see higher snowfall
given lake influences, especially if that dominant lake band comes
near the coast. So that`s something we`ll continue to watch. The
snow will diminish Monday night as the sfc low starts to peel away
to the east.





.LONG TERM...(Tuesday through Saturday)
Issued at 322 PM EST Sat Jan 13 2018

The mid level low opens up to a positive tilted trough as it moves
away from the region on Tuesday.  Thus the snow will be decreasing
in coverage and intensity through the day.  The DGZ is moist to
start the day...but becomes unsaturated for most areas by the end of
the day.  Northerly winds will exist on the lakeshore.  With the
atmosphere plenty cold enough for lake effect...we should see some
mainly west of a Big Rapids to Kalamazoo line.

Surface ridging in WI Tuesday night flattens out as it builds east
into MI on Wednesday.  Thus any lake effect should quickly diminish
Tuesday night into Wednesday.  Warm air advection strengthens on
Wednesday as the arctic airmass shifts off into eastern Canada. Here
in MI we will see a moderating trend to the temperatures along with
breezy conditions Wednesday into Friday.  With the Gulf cut
off...there is not much chance for precipitation.

The Gulf starts to open up Saturday as a stronger mid level waves
tracks eastward through the Southern Rockies.  This also leads to
deep warm air advection.  Thus we will likely see well above normal
temperatures for Saturday along with the potential for showers.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1232 PM EST Sat Jan 13 2018

Snow showers will be dropping down from the northwest through the
afternoon with localized mainly MVFR impacts. Tonight the flow
starts to turn and the snow showers over Lake MI may impact KMKG.
Will feature a prolonged MVFR period setting up later tonight and
continuing Sun AM...otherwise conditions look to be mostly VFR
tonight into Sun AM for much of the region.


&&

.MARINE...
Issued at 322 PM EST Sat Jan 13 2018

Canceled the small craft advisory a couple of hours early. Wind will
pick up again Sunday afternoon and a SCA may be needed again.

&&

.HYDROLOGY...
Issued at 1202 PM EST Sat Jan 13 2018

The colder temperatures that have moved back into the region will
cause ice to reform and solidify on area rivers into next week.
Additional flooding is not expected and rivers will likely be locked
down by the end of the weekend. Will still need to monitor rivers
for potential ice jam flooding.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&

$$

SYNOPSIS...04
SHORT TERM...04
LONG TERM...MJS
AVIATION...MJS
HYDROLOGY...63
MARINE...04



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