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fxus63 kgrr 130540 
afdgrr

Area forecast discussion
National Weather Service Grand Rapids Michigan
1240 am EST Fri Dec 13 2019

Latest update...
aviation

Synopsis...
issued at 330 PM EST Thu Dec 12 2019

- some light snow and freezing drizzle possible tonight central
Lower

- Lake effect snow potential Saturday night into Sunday

- low pressure system Monday night into Tuesday mainly misses US
to the south

&&

Discussion...(this evening through next thursday)
issued at 330 PM EST Thu Dec 12 2019

A warm air advection precipitation event is expected across
central lower Michigan tonight. Some light accumulations of snow
are expected up along U.S. 10 where an inch or two of snow is
certainly possible. It would not be out of the question to see a
few reports around 3 inches by Friday morning up near Baldwin and
Reed City. Temperatures are forecast to be marginal for freezing
precipitation with many areas transitioning to some light rain or
drizzle overnight with temperatures above freezing in most areas.
There is a chance for some freezing drizzle, especially across
interior central lower Michigan from roughly Reed City to the east
towards Clare and Harrison. At this time there is not enough
confidence to issue a Winter Weather Advisory as we feel
precipitation amounts will be light and Road/air temperatures will
be marginal. We will be monitoring trends though through the
evening and overnight and update forecasts as necessary.

The next item of note is some lake effect snow that gets going
Saturday night into Sunday. Moisture depth with this evening looks
limited once again especially Saturday night. The better chances
for accumulating snow may come on Sunday where the dgz begins to
become saturated. Some light accumulations of an inch or two are
certainly possible towards Lake Michigan.

On Monday night into Tuesday an area of low pressure is forecast
to move from the Ohio Valley into New England by the deterministic
models. This is not a favorable track for the GRR forecast area
for heavy snow. For heavy snow we would want to see the low track
a bit further to the north. The ensemble members in the Euro show
the same thinking with many members showing little to no snow at
our further Southeast Point at Jackson. There are a few members
showing amounts around 4 inches there. Most other locations would
see little to no snow even with Jackson getting 4 if that
occurred. The feeling right now is the track is not conducive for
a heavy snow swath into our area at this time, but we are
monitoring. Also of note, the depth of the low is not too
significant, moving by the Great Lakes above 1000mb's. Plenty of
time to watch this system, but it appears the trend as been a
little further to the south with time.

&&

Aviation...(for the 06z tafs through 06z Friday night)
issued at 1232 am EST Fri Dec 13 2019

VFR conditions are expected to prevail through the early morning
hours at west Michigan taf sites. We could see a few patches of
drizzle or even freezing drizzle impact mkg or GRR, but potential
is low and amounts would be very light. Low-level jet core that
has been bringing low-level wind shear across the area will shift
east and weaken through 10z. General trough pattern over the
western Great Lakes will allow clouds to lower through the day
today as additional moisture seeps into the area, but the only
site that may drop to MVFR looks like mkg. Low-level moisture and
light winds tonight may cause some visibility issues, but impacts
look to be after 06z.

&&

Marine...
issued at 330 PM EST Thu Dec 12 2019

Core of the strongest winds are moving through the area as of mid
afternoon. At 2,000ft to 3,000ft a core of 50-60 knots of wind is
moving through from west to east between this afternoon and about
1000pm this evening. These winds are beginning to mix down over
Lake Michigan, with Big Sable Point touching gales in the last
couple of hours. We issued a Gale Warning a bit earlier this
afternoon from Holland to the north. South of Holland a Small
Craft Advisory remains in effect. Waves will fall below Small Craft Advisory
criteria towards Friday morning. Once the Gale Warning ends, we
will need to reissue the Small Craft Advisory for the northern four zones, north of
Holland.

A Lakeshore flood advisory remains in effect until 7am Friday, but
the worst of conditions will be this afternoon and evening in the
height of the winds and waves.

The next wave event will come Saturday night into Sunday in
northwest flow cold air advection. 4 to 7 footers are expected in
this event.



&&

Hydrology...
issued at 330 PM EST Thu Dec 12 2019

The amount of water in our rivers will continue to trend down over
the coming days. The Maple River at Maple Rapids is still above
flood stage, but is also safely trending lower. The bigger impact
over the last 24 hours has been the start of ice freeze up processes
on some of our rivers, specifically parts of the Muskegon river and
the White River. A small ice jam has formed south of Big Rapids, as
the near-zero temperatures overnight caused rapid ice growth. With
warmer temperatures now moving into the area for the next several
days, river levels should resume a downward trend in this area.

&&

GRR watches/warnings/advisories...
Michigan...Lakeshore flood advisory until 7 am EST this morning for miz037-
043-050-056.

Lm...Small Craft Advisory until 7 am EST this morning for lmz844>849.

&&

$$

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