Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 131702
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1202 PM EST Sat Jan 13 2018

LATEST UPDATE...
Hydro

.SYNOPSIS...
Issued at 330 AM EST Sat Jan 13 2018

Arctic air will be entrenched over the Great Lakes this weekend
with lake effect snow showers expected at the Lake Michigan
shoreline. A more widespread snow will impact the region beginning
Sunday night and continuing through Tuesday. Accumulations of 2 to
4 inches are likely during this time, with localized higher
amounts possible.

&&

.SHORT TERM...(Today through Monday)
Issued at 330 AM EST Sat Jan 13 2018

Northerly flow backs slightly more nw today as big system tracks
into New England, so lake effect snow showers currently offshore
early this morning will begin to impact coastal communities. A
north-northwest flow regime typically lead to accums being
restricted to areas south of Holland and north of Whitehall, so
thinking 1-3" is the way to go today for places like South Haven
and Ludington.

Inversion heights are shown to be around 6-7K feet which isn`t
too bad, and another shortwave is dropping in from the northwest
today. The South Haven bufkit overview indicates some fairly
strong omega in the DGZ so there could be some heavier snow
showers along the coast between Holland and Benton Harbor for a
while today. This could impact travel for sections of I-196 and
I-94 in Allegan and Van Buren counties.

Lake effect should weaken tonight as the sfc high currently over
the nrn plains moves across the area and inversion heights lower.
However some localized additional 1 inch amounts possible as low
level flow over Lk MI backs more westerly. On Sunday the low level
flow goes southerly so any lingering lgt lake effect should be
north of Grand Haven.

Widespread, mainly light, snow breaks out on Sunday night in
response to good isentropic lift ahead of the approaching system.
This looks to produce around an inch of snow areawide. Additional
widespread accumulations of 1-3" look likely on Monday as upper
low approaches from the northwest and the sfc low/occlusion come
into the area. It also appears that a lengthy south to north
oriented lake effect band will be present over the center of Lake
MI and could come onshore somewhere depending on wind direction.
That could lead to some localized higher snow amounts at the
coast.

.LONG TERM...(Monday night through Friday)
Issued at 330 AM EST Sat Jan 13 2018

The upper low moves into Northern Lower Michigan, but weakens and
opens to a wave on Tuesday.  The snow will continue as this occurs,
but it should become lighter.  Its also somewhat questionable how
much lake effect we see on the backside of the system, since the
models indicate the flow should be almost due northerly, perhaps
keeping the best banding offshore.  This at least favors the
immediate shoreline having the best chance for snow, while it should
be mainly dry east of U.S. 131 Monday night through Tuesday night.

Surface and upper ridging will signal a bit of a pattern change by
Wednesday night, lasting into Friday.  Although the models are not
in good agreement, temperatures will not be as cold.  The ECMWF
warms us much more than the GFS or it`s ensemble members, so believe
the ECMWF is running a bit too warm.  Even so temps should return to
normal, if not slightly above normal by the end of the work week.
With the ridging building we should remain dry and even turn off the
lake effect as warm air aloft moves in with the ridging.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 700 AM EST Sat Jan 13 2018

Frequent MVFR to IFR vsbys at the lakeshore today including the
MKG terminal due to lake effect snow showers. Inland at the other
terminals expect VFR to MVFR cigs of 2500-3500 ft with flurries
occasionally producing 4-6 mile vsbys. For tonight skies should
clear inland but ocnl snow showers persisting at the lakeshore.

&&

.MARINE...
Issued at 330 AM EST Sat Jan 13 2018

NNW winds of 15 to 25 and waves 4-8 ft today.

&&

.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...Small Craft Advisory until 6 PM EST this evening for LMZ844>849.

&&

$$

SYNOPSIS...Meade
SHORT TERM...Meade
LONG TERM...JK
AVIATION...Meade
HYDROLOGY...63
MARINE...Meade



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