Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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705
FXUS63 KGRR 090142
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
842 PM EST Thu Dec 8 2016

LATEST UPDATE...
Update

.SYNOPSIS...
Issued at 330 PM EST Thu Dec 8 2016

Lake effect snow showers will continue tonight and Friday.
Additional snow accumulations will be 3 to 8 inches within the
warned counties, meanwhile another 2 to 5 inches is expected for the
counties within the advisory area.  Finally, areas outside of the
headlines should see 2 inches or less through Friday.  Winds will
continue to cause blowing and drifting snow tonight.  The snow will
diminish late Friday, but still snow lightly Friday night into
Saturday.

Another accumulating snow is likely Saturday night into Monday, with
even more snow Tuesday night.  We will remain cold with highs only
30 to 35 Friday through Tuesday, then even colder air arrives by the
middle of next week with highs only around 20.

&&

.UPDATE...
Issued at 842 PM EST Thu Dec 8 2016

I have made no changes to the current forecast or headlines. I did
however increase the pop to 100% in the warning area southwest of
GRR overnight.

It seems to me the snow bands are doing what we collectively
expected... which is to consolidate into a NW to SE band from
Holland/South Haven to Battle Creek overnight. Currently we have a
band of moderate to heavy snow showers just north of GRR heading
southward, that is the mid level cold pool. Once that gets through
winds will be more northwest then west so that will help develop a
nearly stationary band as we expected. So the heaviest snow in
the warning area will be between midnight and sunrise. That area
could see over a foot of snow by mid day Friday.

Outside that band snow shower activity will be rather limited
until winds turn more westerly Friday afternoon.

&&

.SHORT TERM...(This evening through Saturday)
Issued at 330 PM EST Thu Dec 8 2016

Headlines will remained unchanged, although we may be able to drop
some/most of the advisory counties by early tomorrow morning as the
lake bands will be oriented NW to SE by then, mainly favoring the
warned counties.

We continue to see very favorable lift within the DGZ most of
tonight and into early Friday.  We will also have a surface trough
come across the CWA this evening.  This trough may produce a burst
of snow just about anywhere, even away from the lake.  This trough
and associated snow band was coming together just north of Cadillac
and Houghton Lake as of 330 PM and was dropping south.

The trough will also turn the mean low level flow from WNW to NW
this evening.  This flow holds through the night and through the
first half of Friday.  This period will see dominate snow bands that
should drop several additional inches of snow in the warned
counties.  However as the night progresses these bands may move away
from the advisory counties, which may be able to be canceled by
daybreak Friday.  We will also see the winds slowly die off late
tonight. This will reduce the blowing and drifting, and also cause
the bands to not penetrate as far inland.

The snow will continue Friday night, but should slowly fade through
Saturday.  Feel our ending time on the headlines is good as the bulk
of the heaviest snows will be over.  Any accums Friday night and
Saturday will be 2 inches or less.

.LONG TERM...(Saturday night through Thursday)
Issued at 330 PM EST Thu Dec 8 2016

What looks like a mid-winter weather pattern becomes well
established next week as arctic cold intensifies and lake effect
snow is punctuated by occasional snowstorms. The first storm takes a
track just south of Lower Michigan over the weekend with an area of
mid level F-gen providing lift for what looks like a 3 to 6 inch
synoptic snow event, which tapers off Monday.

Scattered, mostly light lake effect snow expected in the wake of the
storm early next week, then an arctic front moves through Tuesday
evening. Sfc ridging and subsidence will be keeping inversion
heights fairly low. DGZ also crashes to near the sfc, so any lake
effect should be light.

A significant storm is taking shape over the Plains by the end of
the period but snow from it should hold off until after Thursday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 712 PM EST Thu Dec 8 2016

The theme of this set TAF is to limit the lake effect at MKG,
GRR, LAN and JXN (some question there) then have them remain over
AZO and to less of an extent BTL between now and 18z. This is due
to an arctic front coming through turning winds to a more
northwest direction overnight. The area from BIV to AZO and BTL
would be in the line for the heaviest snow tonight and bands may
persist for several hours in that area (03z to 12z). Between now
and 03z MKG and GRR will be getting some snow bands yet after that
the bands should be south of both sites. The issue for JXN is just
how far east does that dominant snow band go tonight? JXN just
may get the edge of it, so we will have to watch that. LAN should
be out the snow bands for the most part through Friday.

By Friday afternoon the winds turn more westerly again so most
ares should see snow showers but they should not be all that
heavy.


&&

.MARINE...
Issued at 330 PM EST Thu Dec 8 2016

W to NW brisk flow will continue, as will the small craft advisory.
It appears we finally see lighter winds by Saturday when the lake
will calm down a bit.


&&

.HYDROLOGY...
Issued at 245 PM EST Thu Dec 8 2016

Many rivers are running above normal for this time of year but
none are going above bankfull. With no rain in the forecast there
are no immediate hydro concerns. Some river basins may develop a
healthy snowpack heading into mid December. This would be a
consideration for any future rain events and warm spells. Some ice
development during the second half of next week is likely given
the Arctic air mass moving in.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Storm Warning until 4 PM EST Friday for MIZ037-038-043-
     056-064-071-072.

     Winter Weather Advisory until 4 PM EST Friday for MIZ039-044-050-
     057-065-073.

LM...Small Craft Advisory until 7 AM EST Saturday for LMZ844>849.

&&

$$

UPDATE...WDM
SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...Ostuno
AVIATION...WDM
HYDROLOGY...Hoving
MARINE...JK



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