Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 040425
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1125 PM EST Sat Dec 3 2016

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 PM EST Sat Dec 3 2016

Quiet weather expected tonight with lows falling into the mid to
upper 20s. A trough of low pressure will slide through the Great
Lakes on Sunday and Sunday evening, bringing a period of light to
moderate snow. Total snowfall amounts of 1 to 3 inches are
expected. Dry weather returns on Monday. Colder air and lake-
effect snow are expected from mid to late week.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 330 PM EST Sat Dec 3 2016

Light accumulating snow is expected across West and Central Michigan
on Sunday, with totals ranging from 1 to 3 inches. Total snowfall
amounts by Monday morning will be lightest toward Lansing and
Jackson, with slightly higher totals possible further northwest.
Snow is expected to begin in the lakeshore counties by 9-10 AM.

A potent shortwave trough swings out of the Plains on Sunday and
goes negative tilt as the trough axis sweeps through Lower Michigan
Sunday night. Favorable synoptic lift will be in place as SW flow
advects in deeper moisture. The DGZ looks to be saturated from
roughly 13-14z tomorrow through 03z Monday. Modest omega is present
in the DGZ, with even better forcing slightly below the DGZ.

P-type still looks like all snow, with both the NAM and GFS
forecasting wet bulb zero heights below 1500 ft through the day.
Surface wet bulb temps will likely rise to right around 32 F
during Sunday afternoon, particularly across the western half of
the CWA, so some melting is likely. Accumulations will be most
likely on grass. Some roads, especially bridges and overpasses,
could become slushy during moderate snow. Road surfaces could also
quickly become icy Sunday evening and Sunday night and temps drop
back below freezing. Highs Sunday afternoon will likely be in the
low to mid 30s.

Persistent slick roads could affect traffic Monday morning, as
surface temps will remain a bit below freezing.

.LONG TERM...(Tuesday through Saturday)
Issued at 330 PM EST Sat Dec 3 2016

Extended begins with Lower Michigan in between northern and southern
stream with light mixed precip or rain before the Arctic air arrives
after Wednesday. Looks like an extended period of lake effect snow
showers. Amounts of several inches are possible but should be capped
by DGZ and inversion heights remaining under 10 kft during much of
the event. Best chances for snow will be Wednesday night through
Thursday night.

By Friday we are looking at Plains cyclogensis with a warm air
advection pattern developing. Lake effect will be winding down but
synoptic snows could be moving in on Saturday in advance of the
low.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1115 PM EST Sat Dec 3 2016

A mix of vfr/mvfr conditions will continue overnight into Sunday
morning due to lingering low clouds. Conditions will gradually
deteriorate to primarily mvfr and then eventually ifr on Sunday as
light snow moves in and cigs/visbys lower. Conditions will then
deteriorate further to a mix of mainly ifr/lifr late Sunday
through Sunday evening due to very low cigs and significantly
reduced visbys in light snow.

&&

.MARINE...
Issued at 331 PM EST Sat Dec 3 2016

Quiet marine conditions are expected through Sunday. Southwest
winds will increase to 15 to 20 kts Sunday night, causing waves to
build into the 2 to 4 foot range.


&&

.HYDROLOGY...
Issued at 150 PM EST Sat Dec 3 2016

The Maple Rapids remains about a half foot below bankfull stage.
One to three inches of snow is expected on Sunday, containing
about 0.2 inches of meltwater equivalent. Much of this snow should
melt on Monday and Tuesday, which may push the Maple River above
bankfull. Additional chances for precipitation will arrive the
latter part of next week, most likely in the form of lake effect
snow. This moisture should have little impact on rivers in the
short term.

&&

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

$$

SYNOPSIS...EBW
SHORT TERM...EBW
LONG TERM...Ostuno
AVIATION...Laurens
HYDROLOGY...CAS
MARINE...EBW


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