Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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610
FXUS63 KGRR 090545
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1245 AM EST Sat Dec 9 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 325 PM EST Fri Dec 8 2017

A low pressure system will move in from the northwest and bring
snow tonight into Saturday. Snow may become heavy at times
overnight near Lake Michigan. Some light snow showers and flurries
will linger Saturday and a band of heavier lake effect snow will
affect areas from near Saugatuck southward. A few light snow showers
and flurries are expected Sunday and another low pressure system
will bring more snow early next week.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 325 PM EST Fri Dec 8 2017

A low pressure system will move in from the nw tonight and bring
snow accumulations of 2 to 4 inches to most of our fcst area by
mid morning Saturday. Higher snow accumulations of 4 to 6 inches
are fcst across our lakeshore counties tonight due to sw flow lake
enhancement.

Our previous headlines looked excellent and remained unchanged.
We decided to also issue a winter wx advisory for Mason/Oceana
counties for tonight due to sw flow lake enhancement (thx for
coord on this APX).

Light snow showers and flurries will linger across our fcst area
from mid morning tomorrow through tomorrow afternoon but with very
light additional accumulations. The exception to this is in far
western Allegan and Van Buren counties which will likely be
clipped by a dominant north/south oriented les band as winds
become northerly and h8 temps fall to -12 to -14 C in the
afternoon.

Therefore several inches of additional snow accumulation are
expected tomorrow from near Holland/Saugatuck southward near the
Lake MI shoreline. Lighter lake effect snow showers will linger
west of US-131 Saturday evening as winds back to the nw. The light
snow showers will taper off to flurries overnight.

A cold front will approach from the north and cause development
of light snow showers Sunday into Sunday night. Synoptic snow tied
to the next clipper system will not move in until Monday.

.LONG TERM...(Monday through Friday)
Issued at 325 PM EST Fri Dec 8 2017

The cold pattern with periodic lake effect snow showers continues
through next week. Additional snow accumulations and occasional
impacts are likely, especially near and west of Highway 131.

Models are in good agreement on timing of the next clipper system
diving southeast through the region on Monday, but the track and
strength of this feature are still a bit uncertain.

Potential exists for a swath of several inches of synoptic snow
along and north of the track of the upper low/vort max Monday,
followed by a period of potentially significant north-northwest flow
lake effect on the back side of the system on Monday night and
Tuesday.

A relative lull in the lake effect appears to occur later Tuesday
night into Wednesday morning as sfc ridging and lower inversion
heights are present. Confidence decreases beyond that regarding the
timing and frequency of the next clipper-related boosts to snow
coverage and intensity, but the pattern remains conducive for more
snow showers and additional accumulation - especially near and west
of Highway 131.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1245 AM EST Sat Dec 9 2017

Snow is expanding across all of the terminals early this morning,
with the heaviest near the lakeshore as expected. We will see the
trend continue through sunrise as the low approaches. The heavier
snow will then rotate out, leaving lighter snow from mid-morning
through much of the afternoon. Conditions are likely to at least
drop down to IFR sporadically, with more widespread IFR along the
lakeshore.

The IFR will then trend up later in the morning, and especially
this afternoon as the low moves away. Winds will shift from SSE,
to more N as the low moves away. Snow showers will then gradually
diminish this evening away from the lakeshore.

&&

.MARINE...
Issued at 325 PM EST Fri Dec 8 2017

A small craft advisory remains in effect through Saturday night
into Sunday. Brisk west to southwest winds will veer to the
northwest Saturday and cause significant wave action into Sunday.


&&

.HYDROLOGY...
Issued at 113 PM EST Fri Dec 8 2017

Rivers are running near or a little above normal. No flooding or
significant rises in river levels are expected. Accumulating snow is
expected tonight into Saturday and again late Sunday through Tuesday.

Temperatures have been near to below freezing since Tuesday night.
Similar temperatures are expected to persist through the end of next
week. This will allow ice to begin forming on area rivers.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory until 7 PM EST this evening for MIZ064-
     071.

     Winter Weather Advisory until 8 AM EST this morning for MIZ037-
     043.

     Winter Weather Advisory until 9 AM EST this morning for MIZ050-
     056-057.

LM...Small Craft Advisory until 9 AM EST Sunday for LMZ844>849.

&&

$$

SYNOPSIS...Laurens
SHORT TERM...Laurens
LONG TERM...Meade
AVIATION...NJJ
HYDROLOGY...63
MARINE...Laurens



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