Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 072353
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
653 PM EST Thu Dec 7 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 325 PM EST Thu Dec 7 2017

Lingering lake effect snow showers will taper off late this
afternoon and evening as high pressure briefly builds in tonight
into Friday. The next low pressure system will bring accumulating
snow Friday night into Saturday. The cold weather pattern will
continue through next week with occasional snow showers.

&&

.SHORT TERM...(This evening through Saturday night)
Issued at 325 PM EST Thu Dec 7 2017

Lingering snow showers attm will taper off late this afternoon and
evening. Although wnw flow lake effect snow showers continue in
progress attm we believe most of the accumulating snow has already
fallen and will let the advisory headline expire as scheduled at
21Z. Dry wx is then anticipated overnight into Friday morning before
the next low pressure system approaches from the nw.

This system will be stronger and bring widespread snow Friday
night and Saturday resulting in hazardous travel conditions. The
snow will be enhanced by moisture from Lake Michigan and the dgz
will be saturated. Very strong mid to upper level pva will also
develop late Friday night and dynamics look favorable. Deformation
zone snow will linger into Saturday afternoon.

This system will bring three to six inches of snow across our
fcst area from Friday night through Saturday afternoon with
highest amounts expected west of US-131 and lowest amounts over
our eastern fcst area. A solid three to four inches of snow is
forecast for the US-131 corridor.

Light lake effect snow showers will linger Saturday night mainly
west of US-131 in a northwest flow regime but little additional
accumulations (under an inch).

.LONG TERM...(Sunday through Thursday)
Issued at 325 PM EST Thu Dec 7 2017

The pattern remains supportive of lake effect snow through next
Thursday but daily wind direction and timing/track of clipper type
systems is not totally clear.

A clipper on Monday looks to bring a widespread light snow as it
tracks overhead or just south of MI, but also provides northeasterly
low level flow which shuts off the lake component for at least
Monday, and possibly into Tuesday as well for much of the area.

However there is some suggestion of a potentially significant north
or north-northwest flow lake effect event right along or just off
the coast on Tuesday. There could be localized big snows for parts
of Allegan/Van Buren and Mason/Oceana counties Tuesday if a NNW flow
occurs, or the heavier bands may remain just a tad offshore if the
more northerly flow verifies. Either way, the land breeze/meso high
Tuesday night would probably send that snow completely offshore
through Wednesday morning.

Better potential for a westerly component to the low level flow is
indicated as we head into Wednesday and Thursday. Tuesday night`s
mid lake convergence band would be sent inland on Wednesday
afternoon, with additional NW flow snow showers likely on Thursday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 653 PM EST Thu Dec 7 2017

Conditions should improve this evening as lake effect snow showers
diminish with MVFR and patchy IFR becoming primarily VFR
overnight. Lake effect snow showers will begin to bring MVFR
conditions after 18Z on Friday and possible IFR closer to Friday
evening. Winds will be west to southwest around 10 knots with some
gusts to 20 knots.

&&

.MARINE...
Issued at 325 PM EST Thu Dec 7 2017

The small craft advisory has been extended through Saturday
afternoon. Brisk west winds generally in the 15-25 kt range through
Friday will continue to result in wave heights of around 4-8 feet
through then. Winds will veer to the northwest and increase to 30
kts Saturday.


&&

.HYDROLOGY...
Issued at 325 PM EST Thu Dec 7 2017

Snow showers will diminish in coverage and intensity through the
late afternoon and evening, although a few light snow showers will
continue overnight along and west of US 131. Liquid-equivalent
(melted snow) from snow this afternoon through tonight will be less
than 0.10 inch.

The next widespread snow event will occur from Friday evening into
Saturday, bringing several more inches of snow accumulation to the
region. Liquid-equivalent (melted snow) from this next event looks
to range between 0.10 to 0.50 inches, highest near Lake Michigan and
gradually decreasing as you go inland. No flooding or significant
rises in river levels are expected. Additional snow is expected
during the late Sunday through Tuesday timeframe.

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...None.
LM...Small Craft Advisory until 7 PM EST Saturday for LMZ844>849.

&&

$$

SYNOPSIS...Laurens
SHORT TERM...Laurens
LONG TERM...Meade
AVIATION...Ostuno
HYDROLOGY...HLO
MARINE...Laurens



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