Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 161156
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
656 AM EST Tue Jan 16 2018

LATEST UPDATE...
Update/Aviation

.SYNOPSIS...
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.

&&

.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 12Z TAFS through 12Z Wednesday morning)
Issued at 655 AM EST Tue Jan 16 2018

MVFR to IFR conditions today with occasional light snow
restricting vsbys to 2-4 miles. Snow coverage decreasing later
today/tonight although MVFR to VFR cigs persisting. However lake
effect snow showers will push inland from Lk MI tonight as winds
turn westerly, impacting MKG after 00Z and possibly GRR/AZO after
06Z.

&&


.HYDROLOGY...
Issued at 313 PM EST Mon Jan 15 2018

Observations through Southwest Lower Michigan show overall stability
on area rivers. This is expected to be the case through the next few
days with highs near or below freezing through Thursday.

Next weekend`s temperatures may be a factor in raising concerns for
additional ice jams. Guidance places a strengthening system over the
Midwest, which results in strong southerly flow and temperatures in
the 40s through the area. Precipitation then streams in by early
next week, yielding amounts that exceed one inch through portions of
Western Michigan.

There is still plenty of time for forecast details to be worked out
and trends will need to be monitored over the next several days.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.

LM...None.
&&

$$

UPDATE...Meade
SYNOPSIS...Meade
SHORT TERM...Meade
LONG TERM...04
AVIATION...Meade
HYDROLOGY...JAM


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