Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 161730

Area Forecast Discussion
National Weather Service Grand Rapids MI
1230 PM EST Tue Jan 16 2018


Issued at 330 AM EST Tue Jan 16 2018

Occasional light snow will persist today but will be followed by
dry weather and gradually moderating temperatures the rest of the
week. Highs over the coming weekend should be in the 40s, with
increasing chances for rain by next Monday.


Issued at 850 AM EST Tue Jan 16 2018

Based on current radar trends and a quick look at the hi-res
models I have increase to the chance of snow to near 100% over SW
MI for the next 2 hours then allow it to taper off.

UPDATE Issued at 645 AM EST Tue Jan 16 2018

Will let the advisory for Allegan and Van Buren counties expire at
7 am as recent radar shows a diminishing trend.


.SHORT TERM...(Today through Thursday)
Issued at 330 AM EST Tue Jan 16 2018

For now will keep the advisory going for Allegan and Van Buren
counties. The heavier snow showers temporarily lifted north into
Ottawa and Kent Counties overnight, but latest radar trends
suggest they will be shifting back toward these counties early
this morning. Also a mesolow looks to be present just offshore of
South Haven. If heavier snow showers do not redevelop in the
Advisory area over the next couple hours, will cancel/expire.

Otherwise, ocnl light snow/flurries will continue to fall over
much of the area this morning with mid level cyclonic shear zone
overhead. Also an area of enhanced low level convergence related
to a sfc trough extends along/near the I-96 corridor. Both of
these features are progged to move slowly southeast with time, so
will have a decreasing pop trend later today.

Impressive temperature contrast exists on either side of the I-96
sfc trough feature, with single digit readings to the north and
south but teens along/near it. The low level FGEN related to the
temperature contrast and the convergence should continue to
promote the development of snow showers from GRR to the south and
east through mid morning. Another sfc trough dropping south through
eastern lwr mi today should aid in snow shower development for
place like Clare, Mt Pleasant and Alma.

While the synoptic system finally departs tonight, backing low
level flow should send lake effect snow showers back into areas
west of Highway 131. The lake snows will end early Wednesday
however due to the incoming warm advection. Wednesday and Thursday
look like dry but breezy days with slightly milder temps.

.LONG TERM...(Thursday night through Monday)
Issued at 330 AM EST Tue Jan 16 2018

Warmer weather and the potential for a late weekend storm is the
focus of the long term.

Zonal flow aloft Thursday night through Saturday will increase
temperatures across the Great Lakes. High temperatures will be in
the 40s Saturday through Monday. Models show a cold front trying to
move south across Lower Michigan Saturday, but it looks like it will
stall out over northern Lower due to strengthening south flow over
the Midwest ahead of the next storm.

Precipitation chances will increase from Saturday night through
Sunday night as a developing storm moves from the southern Plains
northeast to the Great Lakes. Both the ecmwf and gfs show sfc
cyclogenesis over the Texas panhandle in response to a strong short
wave moving across the southern Rockies. This low is progd to move
northeast along the aforementioned cold front and draw up abundant
moisture from the Gulf. Present storm tracks show the cwa being on
the southern side of the system, which means rain beginning Saturday
night and continuing through Sunday. It`s possible that we could see
a mix of some freezing rain and/or snow over the the northern cwa
Sunday night as the low moves through. Elevated lifted indices over
Illinois are in the -1 to -2c range Sunday evening so some thunder
might not be too far away.

Heavy rain is a possibility with this system and could lead to
localized flooding. Colder air will flow back into the cwa late
Monday as the low moves east and northwest winds develop. This would
lead to the rain mixing with and changing to light snow.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1209 PM EST Tue Jan 16 2018

A few small bands of light snow remain scattered across the area
early this afternoon. They are shrinking in coverage, but will
take a few more hours before they clear all of the terminals. KMKG
looks to stay out from under those bands, with the eastern and
southern terminals more likely to see them. We believe they will
be mainly MVFR, but a local spot of IFR remains possible.

This will move out, then we will watch the band of lake effect
over Lake Michigan push onshore tonight. The western terminals
will see the biggest impacts from these, as they diminish pushing
inland. MVFR again looks likely with some chances of local IFR
mainly due to vsbys in the snow showers. These should move out by
15-16z everywhere. Winds will become gusty around 14-16z Wed with
gusts up to around 25 knots likely.


Issued at 1230 PM EST Tue Jan 16 2018

The ice jam continues along the Muskegon River in Mecosta County.
Latest information from Emergency Management is that little rise has
been noted since impacts from the jam were reported Monday evening.
Little or no additional impacts have been reported. Previously
open waters have since frozen with ice chunks that have built in
on the back side of the jam, but seem to be stable. Given the
little noticeable changes, we could be seeing the peak, but it
does not rule out ice movement and further fluctuation. Residents
should continue to monitor levels and pay close attention to
latest updates that are provided.

Sites elsewhere are showing some affects as a result of river ice,
but seem to be stable. Minor fluctuations have been noted with
overall downward trends on rivers at or near bankfull. Only one
advisory remains in effect, but is likely to be dropped sometime
late this evening or overnight.

Colder temperatures will allow ice to continue to build over the
next couple of days. There is concern in the upcoming weekend and
into early next week as temperatures rise and precipitation
chances increase. We could see a repeat of last week with melting
snow and rainfall. In addition to weakening ice, runoff could
cause rivers to rise and lead to additional ice jams.




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