Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 130822

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

Synopsis/Short Term/Long Term/Marine

Issued at 305 AM EST Fri Jan 13 2017

A large area of high pressure centered over the Upper Mississippi
Valley will build eastward into the Great Lakes Region today and
tonight. This system will draw down a cold airmass from Ontario
that will result in below normal temperatures for the region. That
system tracks east of Michigan this weekend. This will result in
a gradual warming trend over the weekend as the arctic airmass
moves into Quebec.


.SHORT TERM...(Today through Sunday)
Issued at 305 AM EST Fri Jan 13 2017

With high pressure mostly in control of our weather in the short
term...the potential for precipitation will remain lower than
normal. One wave of low pressure pulls out of the Central Rockies
today and weakens as it moves into confluent flow aloft. As the
remnants of this system track through the CWA tonight...only some
mid level clouds are expected. There may be enough moisture for a
few snow showers/flurries mainly across the northern CWA.

The mid level clouds are forecasted to remain thick on
Saturday...however drying is noted for Sunday. Thus the region is
forecasted to see more in the way of sunshine and above freezing

.LONG TERM...(Sunday night through Thursday)
Issued at 305 AM EST Fri Jan 13 2017

Active weather leads off the long term with the potential for
somewhat of a wintry mess late Sunday night into Monday morning.
Mild air is expected to surge northward, bringing well above normal
temperatures through the end of the period.

A stationary front that is draped across the central portion of the
country will be the focus for active weather this weekend. Low
pressure from the southwest conus rides along the stationary
boundary into the Texas panhandle late Sunday.

Meanwhile, surface high pressure begins to vacate the Great Lakes
Region as a divergent upper level pattern develops over the Midwest.
As the southwestern low travels along the boundary, warm southerly
flow develops out ahead of the system. Precipitation then develops
through southwest Michigan by Monday morning. The main question
continues to be the timing of the onset of precipitation and how
quickly milder air replaces sub-freezing air at the surface.

The last couple of model runs have trended later with the onset of
precipitation and also backed off on amounts. Some of the better
moisture and lift doesn`t arrive until after 12z Monday. As a mid
level layer of warm at surges north, surface temperatures continue
to hover just below freezing through mid-morning. We could initially
see a very brief bout of snow, followed by a couple of hours of
freezing rain and then rain. Greater concern exists through central
Lower Michigan, where the shallow layer of sub-freezing air could
remain entrenched for several hours. If this pans out, ice
accumulations could be possible through the northern two rows of
counties through Monday afternoon. Any freezing precipitation should
transition to rain by Tuesday morning for the entire CWA.

A fairly steep ridge develops over the eastern third of the country,
making it feel more like early spring than mid-January. Aside from a
brief bout of snow mixing with rain early Wednesday, the remainder
of the time looks quite mild with periodic chances for rain into


.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.


Issued at 305 AM EST Fri Jan 13 2017

With cold air advection and a tight pressure gradient in place to
start the day...the hazardous conditions for small craft will
continue. The pressure gradient weakens during the day...thus
conditions should improve. Then tonight through Sunday the
pressure gradient remain relatively weak. This will support low
wind and wave values.


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.


LM...Small Craft Advisory until 4 PM EST this afternoon for



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