Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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683
FXUS63 KGRR 230531
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1231 AM EST Tue Jan 23 2018

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 PM EST Mon Jan 22 2018

More rain will continue into tonight, but of the lighter variety.
Very late tonight, or around daybreak, the rain will switch over
the snow. The snow will be the steadiest through Tuesday morning,
however with temperatures near or slightly above freezing, the
snow accumulations will be limited. Most areas will see less than
an inch on grassy areas. Areas toward Highway 10 will see around
an inch. Scattered light snow showers will continue Wednesday
afternoon into Wednesday night. the colder air will hang on
through mid week, with highs on Wednesday only around 30.

Another warm up arrives by Friday into Saturday when temperatures
should once again be in the 40s. Then it appears to cool down
again sunday and monday. Light rain should return Friday night,
which should switch to snow Saturday night and last into Sunday
night.

&&

.UPDATE...
Issued at 953 PM EST Mon Jan 22 2018

Expect scattered rain showers to continue overnight as the upper
low approaches from the southwest. Also can`t rule out a tstm as
area of steeper mid level lapse rates around 7-7.5C currently just
to our south and west heads northeast. Have added isolated tstms
to the fcst tonight.

Any chance of snow looks very low until after 12z Tuesday since
sfc temps remain rather mild. If some snow were to mix in, it`d
be after 09Z and mainly south of I-96 since the coldest H8 air
/near -4C/ curls in from the southwest around the bottom of the
sfc low.

Will have areas of fog in the fcst overnight in the northern 2/3
of the cwfa where the sfc low is tracking and where baggy
pressure gradient/light winds will be present. Also, a few sites
near and north of I-96 are currently reporting 1/4 mile
visibilities.

&&

.SHORT TERM...(This evening through Wednesday night)
Issued at 330 PM EST Mon Jan 22 2018

Low pressure will cross the state late tonight. Rain showers will
continue, then change to snow toward daybreak Tuesday. A steady
snow is expected Tuesday morning, but most places will see less
than an inch of accumulation. Roads are only expected to be wet.

Precipitation will remain spotty within the dry slot which will
be over the CWA this evening. but then steadier pcpn will return
late tonight and into Tuesday morning. This will initially start
as more rain, but then begin to switch to snow from west to east
as the colder air wraps in. Still appears we won`t have any
accums through 12z Tue, so it appears the morning commute will go
OK, and no headlines are planned.

But the steady snow will continue through much of Tuesday
morning. This will be falling on a sloppy wet ground, after
roughly the inch of rain that occurred today. The far north, near
Highway 10 should see around an inch of snow, perhaps toward two
inches in northern Clare County, otherwise less than an inch is
expected.. The snow will move out toward mid day. this will be
followed by some light lake effect into Tuesday evening, this
will only add another dusting since the delta T`s are marginal.

A short wave comes through Wed morning, leading to slightly
colder air moving in. Feel this will perk up the lake effect
again by Wednesday afternoon and into the night. Again the delta
T`s are marginal, but slightly better moisture arrives. Accums
are expected to remain under an inch in this time frame and mainly
for areas west of U.S. 131.

.LONG TERM...(Thursday through Monday)
Issued at 330 PM EST Mon Jan 22 2018

Ridging both at the surface and aloft will bring benign weather
on Thursday and Friday. We have a dry forecast through both days
with temperatures moderating from the 30s on Thursday to the 40s
on Friday.

Models diverge on Saturday which leads to a lower confidence
forecast for the weekend. The GFS and Canadian have a weakening
surface trough and therefore little in the way of precipitation
associated with it. The ECMWF develops a wave of low pressure on
a front which moves northeast through our area. We have a chance
for showers in the forecast for Saturday and Saturday night for
now and we will see how the models trend. The precipitation in
the forecast is a nod to the ECMWF.

Colder air flows in for Sunday and Monday and we have some small
chances for snow showers in the forecast. The surface pattern
features a high building in so not expecting anything significant
in regard to snow. Highs cool back into the upper 20s and lower
30s by next Monday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1227 AM EST Tue Jan 23 2018

Low pressure is moving through the state and a cold front will
follow in a few hours. Cigs/vsbys are varying widely and
will continue to do so through the night. A general shift toward
mvfr conditions will occur later this morning as colder air flows
into the state. Wrap around moisture will initially develop as
mixed rain and snow before changing to snow showers mid day.

&&

.HYDROLOGY...
ISSUED AT 330 PM EST MON JAN 22 2018

Snow has melted or nearly melted across west Michigan as of Monday
afternoon. Rain that fell across the area last night and this
morning averaged between 0.25 and 0.5 inches along and south of a
line from South Haven to Mason, and between 0.5 and 0.9 inches to
the north of there. Additional rainfall today is expected to be
lighter, with most areas receiving less than an tenth of an inch of
rainfall.

Additional precipitation is expected tonight and early Tuesday on
the backside of low pressure tracking through the area. The heaviest
amounts of precipitation, a combination of rain and melted snow,
through Tuesday afternoon would be most likely to occur over
portions of Central Michigan. Amounts are not expected to be heavy
enough to cause additional flooding, but potential for ice jams will
still exist as river levels rise. A relatively dry stretch of
weather is then expected Tuesday night through Friday.

Rises on many rivers across the area are already being observed as
water runs off the frozen ground. Some of the slower responding
rivers will continue to see these rises continue through the end of
the week. The only River Flood Warning in effect as of Monday
afternoon was for the Looking Glass River near Eagle. Sycamore Creek
near Holt may near warning criteria, and the advisory could need to
be upgraded later this evening. The Portage River near Vicksburg is
the only other river that could exceed flood stage by Tuesday night.
Numerous river flood advisories are in effect. Please see the latest
Flood Advisory statement for more information. The rainfall and
warmer temperatures (both today and late this week) will aid in the
breakup of river ice, and will continue to provide concern for ice
jams. The most likely impacts from these would be minor flooding
upstream of the ice jam.

&&

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

$$

UPDATE...Duke
SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...Duke
AVIATION...04
HYDROLOGY...HLO



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