Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 171523

Area Forecast Discussion
National Weather Service Grand Rapids MI
1123 AM EDT Fri Mar 17 2017


Issued at 330 AM EDT Fri Mar 17 2017

A mixture of precipitation is expected today ahead of a low pressure
system moving our direction from Northern Minnesota. Light snow will
spread into the area this morning with accumulations of 1 to 2
inches possible. The snow may mix with some freezing rain for a time
in the late morning and midday hours. Precipitation should then
change over to light rain or drizzle during the course of the
afternoon. As the low moves through the area tonight some light rain
and light snow are expected with little in the way of accumulation
of snow. Conditions will gradually dry out on Saturday as the low
moves away to our southeast. High pressure building in for Saturday
night and Sunday will bring dry weather. Temperatures today and
through the weekend will be near normal for this time of year.


Issued at 956 AM EDT Fri Mar 17 2017

Local radar shows a band of moderate to heavy snow moving east
across the cwa. Visibilities are quickly falling to a quarter
mile at a few locations. A quick inch of snow is possible as this
band moves east late this morning and early afternoon. No changes
to the winter weather advisory. The dgz will become unsaturated by
noon and a brief period of freezing rain/drizzle is possible.


.SHORT TERM...(Today through Sunday)
Issued at 330 AM EDT Fri Mar 17 2017

Will be continuing the Winter Weather Advisory with this forecast
issuance. We did push back the timing in all areas to have a start
time of 800am. The models have delayed the onset just a bit which is
why we pushed the timing back a few hours.

The other change with this model run is that there looks to be less
in the way of freezing rain and a bit more snow. The progression
looks to be snow over to drizzle or rain. There may be a few hours
where some spotty freezing rain occurs in the mid to late morning
hours. With the threat of at least some freezing rain did not really
consider discontinuing the headline, but the impacts with this
winter weather advisory may be limited. It appears that an inch or
two of snow is now possible which is up from an inch or less in the
forecast yesterday. Also, some of the higher resolution models are
showing some isolated 3 inch amounts.

Dew points are still in the teens F over Southwest Lower Michigan,
so wet bulb affects should trend things towards snow this morning. A
warm nose does push in above 5000ft which will try to bring in the
threat of some freezing precipitation later this morning and midday.
Enough warming should trend precipitation to drizzle and light rain
this afternoon as the DGZ becomes unsaturated. Precipitation rates
in the snow this morning could be moderate to locally heavy in
bursts, given good upglide noted on the 290K isentropic surface.

A bit of light rain and snow will continue tonight into Saturday
morning as the surface low and upper shortwave drift southeast
through the area. Not expecting any impact from what snow occurs
tonight into Saturday as surface temperatures will be marginal.

Saturday night and Sunday look dry and quiet as surface high
pressure moves through the Great Lakes.

.LONG TERM...(Sunday night through Thursday)
Issued at 330 AM EDT Fri Mar 17 2017

We are looking at two systems that will likely impact the area in
the long term. One at the beginning for Sun night and Mon, and the
second right at the end of the period and more likely just beyond.
These systems look like they will not create serious impacts as they
should be mainly rain.

The system on Sun night and Mon is looking less and less impressive
over time as it will tend to be weakening as it moves into the area.
This system will be a weakening front on the southern flank of a
stronger system well north in Canada. Even though it will be
weakening, it will try to draw some Gulf moisture north in the area,
bringing the chcs of rain to the area late Sun night and Mon. Colder
air will follow in the wake of the system, but it appears that it
should wait to come in after pcpn comes to an end.

We are looking at a cool period for the mid week portion of the
forecast. We will see a Canadian ridge build over the region that
will usher in the cold air. Temps will drop sufficiently that lake
effect would be in play. We do not expect any lake effect here
however as the flow should be from the NNE.

We are bringing in a chc of pcpn right at the end of the forecast
period next Thu. The upper trough and cold air expected to be in
place mid-week will be pushed out by a ridge. Deep S/SW flow will
eventually develop and bring a wet pattern to the region. The models
are showing it coming late on Thu, and more so beyond this forecast
period. We tend to side with a slower arrival as these amplified
upper air patterns end up delaying the arrival of these types of
systems a bit.


.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 744 AM EDT Fri Mar 17 2017

Snow will spread in from the west this morning, taking conditions
from VFR to MVFR rather quickly. There will be bursts of snow that
may dip conditions to IFR at times as well through early
afternoon. The precipitation may mix at times with a bit of
freezing rain, but it is not expected to be the dominant
precipitation type. This afternoon the snow will transition over
to a drizzle or light rain. Conditions will drop into the IFR
category this afternoon as ceilings dip below 1000ft.

Tonight the IFR conditions will be persistent as the lower
ceilings hang on through the night. Some drizzle and light fog is
expected to continue tonight. Winds today will be southeast at 7
to 15 knots.


Issued at 330 AM EDT Fri Mar 17 2017

Opted to extend and issue headlines for the wind that comes in
tonight into Saturday behind the front. So, we have small craft
advisories that now extend through Saturday evening.

The first push of wind is a southerly flow today that should ramp up
waves north of Grand Haven. There is a lull this evening into the
overnight hours before the next surge of wind behind the low
passage. Waves increase in all areas tonight after 500am continuing
into Saturday evening.


Issued at 1123 AM EDT Fri Mar 17 2017

River levels are running around normal to a little below normal.
With less than a half inch of precipitation expected through this
weekend and then no additional precipitation until Friday, no
flooding is expected across the area into next weekend.


MI...Winter Weather Advisory until 4 PM EDT this afternoon for

LM...Small Craft Advisory until 8 PM EDT Saturday for LMZ846>849.

     Small Craft Advisory from 4 AM to 8 PM EDT Saturday for LMZ844-



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