Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 130545
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1245 AM EST Fri Jan 13 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 PM EST Thu Jan 12 2017

High pressure will build in from the northwest and bring fair
weather with decreasing cloud cover tonight. Fair weather will
continue Friday. A weak upper level disturbance will bring a few
light snow showers and flurries Friday night. Dry weather is
forecast Saturday through Sunday. A low pressure system moving
slowly northeast toward the Great Lakes region will bring
potential for freezing rain Sunday night into Monday before milder
air moves in and precipitation changes over to rain.

&&

.SHORT TERM...(This evening through Saturday night)
Issued at 330 PM EST Thu Jan 12 2017

Short term fcst concerns are minimal. High pressure will build in
from the northwest and result in decreasing cloud cover tonight
and partly cloudy skies for Friday. However it will be seasonably
cold Friday with high temperatures only reaching the lower to
middle 20`s.

A weak upper level disturbance will bring potential for a few
light snow showers and flurries Friday night. The relatively best
chc for those will be well to the north of I-96 in an area of
stronger mid level pva. A ridge of high pressure will then bring
wx with seasonable temps Saturday through Saturday night.

.LONG TERM...(Sunday through Thursday)
Issued at 330 PM EST Thu Jan 12 2017

Main focus of the long term is on a potential impact event late
Sunday night into Monday night. It appears we may see a period of
freezing rain from late Sunday night into Monday. Both the GFS and
ECMWF indicate a surge of warmer air ahead of a system lifting out
of the plains states toward the Great Lakes. Some low level colder
air will hang on from late Sunday night at least into some of Monday
making a mix of precipitation possible. The highest concern at this
early stage would be for a period of freezing rain that could exceed
a tenth of an inch across Central Lower Michigan. We are a long way
out at this point so we have plenty of time to watch run to run and
model to model consistency.

Otherwise most of Sunday looks quiet as the precipitation should not
move in until late at night. The precipitation looks to flip to just
rain on Tuesday in the warmest surge of air (850mb temps of +7C). We
have very low pops in the forecast for Wednesday and Thursday but
for the most part these periods look dry with warmer than normal
temperatures.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1245 AM EST Fri Jan 13 2017

Lake effect cloud cover is expected to develop tonight on the
10-15 kt northwest wind. Marginal MVFR conditions are likely with
an overcast ceiling around 2500 ft. The only change made was in
the onset of the cloud cover, which was pushed back by a couple of
hours. KJXN may avoid it, remaining VFR into Friday.

Winds gradually diminish to around 5 kts as they turn out of the
north and eventually east by late in the day. As a result, MFVR
cigs break to give way to VFR conditions. A bit of light snow is
possible very late in the TAF period for KMKG and KGRR as a weak
system approaches from the west.

&&

.MARINE...
Issued at 330 PM EST Thu Jan 12 2017

A small craft advisory remains in effect through mid afternoon
Friday afternoon. Brisk northwest winds will cause wave heights to
stay up around 4 to 6 feet tonight. Wave heights will slowly
subside Friday as winds veer to the north to northeast and
diminish.


&&

.HYDROLOGY...
Issued at 330 PM EST Thu Jan 12 2017

Rivers are running above normal across the area due to rain, melted
snow and ice jams. The Grand River at Comstock Park and at Robinson
Township have active warnings for minor flooding. Multiple sites
also have active advisories. A period of colder than normal
temperatures through the weekend may allow river ice to thicken.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 4 PM EST this afternoon for
     LMZ844>849.

&&

$$

SYNOPSIS...Laurens
SHORT TERM...Laurens
LONG TERM...Duke
AVIATION...JAM
HYDROLOGY...63
MARINE...Laurens



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