Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 111204

Area Forecast Discussion
National Weather Service Grand Rapids MI
704 AM EST Wed Jan 11 2017


Issued at 320 AM EST Wed Jan 11 2017

Low pressure will move across southern Lower Michigan later today
and Thursday bringing a mixed bag of precipitation with rain
across the south and snow and ice across the north. Colder air
will move in for Friday and the weekend.


.SHORT TERM...(Today through Friday)
Issued at 320 AM EST Wed Jan 11 2017

Precip type is issues dominate the near term forecast as wave of low
pressure scoots along a baroclinic zone with arctic air filtering
in from the north. Fortunately there has been decent consistency
in the model guidance and it appears that the blended forecast
captures a consensus that is also consistent with the previous
forecast. So no significant changes were made.

Area of f-gen forcing should result in narrow bands of precip
forming across the northern forecast area by 18Z. Precip type will
start off snow across the far northern zones with mix of sleet
and freezing rain south of there through this evening. Shallow
arctic air moves south overnight, bring the threat of an icy mix
into the I-96 corridor after midnight. Although QPF is progged to
be light...there could be enough icing to impact travel by
Thursday morning so this will need to be watched and a winter
weather advisory may be needed.

.LONG TERM...(Friday night through Tuesday)
Issued at 320 AM EST Wed Jan 11 2017

In the grand scheme of things, the pattern remains very busy.
Fortunately, much of what affects southwest Michigan through the
period is light in nature up until the beginning of next week.

A rather impressive 590mb high builds over the southeastern U.S.,
which results in a dominant ridge pattern for the southeastern third
of the country. This places the southern Great Lakes Region into a
zonal pattern. While zonal flow is not immune to wet weather, we are
departed far enough north, away from the main moisture flow over the
heart of the Midwest.

High pressure that resides at the surface, over the Great Lakes,
begins to gradually breakdown and move eastward through the weekend.
Meanwhile, a couple of weak upper level shortwaves eject out of the
central U.S., weakening as they move eastward. The only realized
result of this comes late Friday and Saturday in the form of a few
light snow showers. It is not likely to amount to much, if anything.

A bulk of the moisture holds off for late in the period, as the
southwestern upper level low finally makes some progress toward the
east. Once again, much of southwest Lower Michigan is placed in the
warm sector with both long range models. Though we likely start out
as snow late Sunday into early Monday, snow changes to rain as
much of the area is overcome by mild southerly influence.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 704 AM EST Wed Jan 11 2017

VFR conditions this morning will become IFR by late afternoon as
low clouds and rain move in. The rain will transition to snow
tonight and a brief period of freezing rain is possible. Winds
will be south today around 10 knots then go north tonight.


Issued at 320 AM EST Wed Jan 11 2017

Will let the gale warning expire at 7 am and be replaced with a
small craft advisory through 7 pm.


Issued at 1147 AM EST Tue Jan 10 2017

Various ice jams on area rivers continue to be monitored. Warmer
temperatures, rainfall, and snow melt will combine to elevate
river levels for the remainder of the week. It is uncertain if
the ice jams will release given these circumstances. Typically we
need temperatures closer to 50 degrees for a few days to break
them up, if the ice is thick enough. Currently the jam downstream
of Robinson Township appears to be holding but the readings at
Robinson have been unchanged in the last 3 days, with stable ice
covering the river. Added flow behind the jam may back up river
levels if the jam doesn`t break up. A Flood Watch has been issued
given the uncertainty in how the river will respond over the next
few days, with the possibility that a rise above flood stage may
occur. Another jam on the Grand River has occurred near the Fish
Ladder at Grand Rapids, which is backing up flow a bit. Currently
this backwater has reached Comstock Park. No flooding is occurring
at this time though rises above bankfull may occur as rain and
snow melt add to the levels.

Other jams are likely occurring on the Flat River near Smyrna and
also the Looking Glass River near Eagle. Combined rainfall and
snow melt will add to these river stages and further rises above
bankfull are likely.


LM...Small Craft Advisory until 7 PM EST this evening for LMZ844>849.



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