Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 111523
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1023 AM EST Mon Dec 11 2017

LATEST UPDATE...
Hydro

.SYNOPSIS...
Issued at 328 AM EST Mon Dec 11 2017

A low pressure system will track south southeast from Northwest
Minnesota early this morning to near Chicago by late this
afternoon. That will bring snow to the area today into this
evening. Tonight and arctic front comes through bringing in the
coldest air of the season with very strong winds. Heavy lake
effect snow squalls are expected near the Lake Michigan shore
tonight into Wednesday morning. Travel in that area will be
challenging Tuesday. Outside of that expect snow showers and highs
only in the lower 20s. We get a break between systems Wednesday
but by late Wednesday the next system will bring more snow to the
area into Thursday.

&&

.SHORT TERM...(Today through Tuesday Night)
Issued at 328 AM EST Mon Dec 11 2017

I have decided (in coordination with our Gaylord and North Webster
offices) to issue a Winter Storm Warning for all of our lake shore
counties for tonight through Tuesday into Wednesday morning. This
is a dangerous situation as there will be heavy snow squalls from
with winds will be gusting to over 40 mph resulting in near zero
visibilities in the heavier snow bands.

We have a clipper type low tracking south southeast toward
Chicago for late this afternoon. That will keep all of our CWA in
the snow from the warm advection / isentropic lift part of the
event. This will bring two periods of snow. The first one is the
warm advection part of the event, which will last only about 3
hours in any one place. It will for the most part occur from
around 8 am near Muskegon end by Jackson by 1 pm. That should be a
1 to 2 inch snowfall event. The second part of this is the
deformation zone snow band that from most of the high resolution
models (for several runs in a row) to occur near I-94 from around
4-5 pm till around 9 pm. This will have heavier snow with it, more
like 2 to 3 inches. I considered an advisory for this event but
the event tonight into Wednesday morning seems to this forecast to
be a much more significant event so to keep the headlines simple
I only have headlines for the Lake Effect event tonight into
Wednesday morning.

With the coldest air of the season crossing water that is still
over 40 degrees, and 850 temperature near zero, that is by far and
away a very unstable setup. Bufkit time sections show strong lift
in the DGZ from around midnight tonight till around early
Wednesday morning. The inversion heights are near 10000 ft. Given
there is 40 knots in the mixed layer for wind gusts, this seems
like an event that would need a warning.

I put an advisory for the counties next to the warning area as
there will be some snow squalls that get into those counties. The
inland counties near route 10 will have a Lake Superior connection
and some upslope to help the cause.

Inland of all that it will just be windy and cold Tuesday into
Tuesday night.

.LONG TERM...(Wednesday through Sunday)
Issued at 328 AM EST Mon Dec 11 2017

More cold air and intervals of snow showers will continue through
the end of the work week. We will then see a decent shot at a period
of milder weather for next weekend, with a mix of pcpn types
possible.

Snow showers will be trending down a bit by Wed after the decent
lake effect event expected for Mon night into Tue night. The chance
of snow will remain on Wed however, especially for Western and
Southern areas. This is the result of the next short wave rounding
the long wave trough. This wave is expected to dive mostly south of
the area. It could clip the Western and Southern portion of the area
with some light snow. The track of the low will produce an offshore
flow, so the lake should not be much of a factor.

Lake effect will ramp up a bit on Thu in the wake of the Wed system.
Colder air on the order of around -14- to -16C will pour in over the
relatively warmer waters of Lake Michigan. The flow will be W/SW as
another system will be approaching the area with the low north of
the CWFA. A slight moderation in temps will occur on Fri with the
low level SW flow.

A better moderation in temps is still expected next weekend with
chcs of rain/snow. The long wave trough that has been sitting over
the region over the last week will get pushed out with the strong
wrn ridge getting beat down some by a strong Pacific Jet. The
transition will bring more chcs of pcpn. These will gradually shift
North as the jet flattens out a bit, and the systems are a bit
further North.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 644 AM EST Mon Dec 11 2017

Currently most of the GRR TAF sites are MVFR. However there is a
storm tracking toward northern Indiana which has a large area of
light snow in front of it. This will move through all of the GRR
TAF sites between now 16z or so. We then get a brief period early
to mid afternoon when the snow will stop.

The system snow will move out of the area by 9 pm or so. Then the
lake effect kicks in that will bring gusty winds and snow squalls
to MKG, SBN likely become solid IFR while the other TAF sits
should become VFR.

&&

.MARINE...
Issued at 328 AM EST Mon Dec 11 2017

With 45 knots in the mixed layer it made sense to just go ahead
with the Gale Warning for tonight into Tuesday night.

&&

.HYDROLOGY...
Issued at 1023 AM EST Mon Dec 11 2017

Rivers are running near normal levels. No flooding or significant
rises in river levels are expected. Snow is forecast periodically
through the week.

Temperatures have been near to below freezing since last Tuesday
night and similar temperatures are expected to persist through the
end of this week. This should allow ice to begin forming on area
rivers, especially on the Muskegon River in Central Lower
Michigan.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Storm Warning until 7 AM EST Wednesday for MIZ037-043-050-
     056-064-071.

     Winter Weather Advisory until 7 AM EST Wednesday for MIZ038-039-
     044-057-065-072.

     Winter Weather Advisory until 1 AM EST Tuesday for MIZ051-052-
     058-059-066-067-073-074.

LM...Gale Warning from 7 PM this evening to 7 PM EST Tuesday for
     LMZ844>849.

&&

$$

SYNOPSIS...WDM
SHORT TERM...WDM
LONG TERM...NJJ
AVIATION...WDM
HYDROLOGY...63
MARINE...WDM


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