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Displaying AFOS PIL: AFDGRR Received: 2018-03-13 07:14 UTC

FXUS63 KGRR 130714

Area Forecast Discussion
National Weather Service Grand Rapids MI
314 AM EDT Tue Mar 13 2018

Synopsis/Short Term/Long Term

Issued at 257 AM EDT Tue Mar 13 2018

A cold northwest flow will persist through tonight. This will lead
to continued snow showers which will be most numerous along the
lakeshore. A few slick spots will be possible. An area of high
pressure will settle in over Ontario for the middle part of the
week. This system will act to keep the weather on the colder than
normal side.


.SHORT TERM...(Today through Thursday)
Issued at 257 AM EDT Tue Mar 13 2018

The main issue in the short term deals with the potential for
impacts from the snow showers today and tonight. Models are in
reasonable agreement in showing a mid level shortwave pivoting
down the backside of the trough. This feature moves through
western parts of the CWA this morning. The lift associated with it
will likely lead to an increase in the snow shower activity...some
of which could be briefly heavy. It appears the duration of the
snow showers will limit the potential impacts due to the lack of
accumulations. The models do show an overall diffluent low level
flow today which could also cut back on any amounts. For now will
hold off on headlines. I suspect we could see a few SPS's through
the day for short duration impacts.

NVA moves in this afternoon but another shortwave drops down for
this evening. Initially the low level flow is shown to be mostly 
northerly. Thus the immediate lakeshore region will stand the best
chance for snow showers. Will feature the highest potential for 
snow showers there. Later at night the flow backs with time as
high pressure tries to ridge in from the west. Subsidence
increases which should support a diminishing trend to any snow
shower activity. 

.LONG TERM...(Thursday night through Monday)
Issued at 257 AM EDT Tue Mar 13 2018

Much of the long term will be quiet and cool, with the best chance 
of pcpn coming at the end of the period and just beyond.

A few snow showers of the lake effect variety may linger through Thu 
night into Fri before they come to an end. Colder air pouring into 
the area from the North will be sufficient for some lake effect. The 
snow showers will come to an end as sfc ridging builds in.

The period from Fri afternoon through Sun night looks dry at this 
time, and has now for a few model runs. The cyclonic flow from much 
of this week will move NE of the area as upper ridging tries to push 
east. The ridge gets pinched as a strong upper low emerges from the 
Rockies. The strong upper low to our NE will shunt the low over the 
weekend to our South. This will keep the area dry, with seasonable 

Dry weather will be maintained Sun before pcpn makes headway into 
the area on Mon. An upper ridge in the wake of the Sat low to our 
South, will move through on Sun. It will move east thereafter, and 
the next low ejecting from the West Coast trough will be allowed to 
approach the area. A lot of uncertainty exists with the track of the 
Mon low as the upper low across NE Canada will likely influence the 
track. This is due to the uncertainty of waves moving around the 
low, and how they would interact. It does look like temps will be a 
bit milder wither way into Mon, before likely cooling down after 


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 130 AM EDT Tue Mar 13 2018

Snow shower trends will be the main focus of the 06z fcsts.
Occasional waves of snow showers are occurring mainly just
offshore of the area early this morning. It does look like as a
more organized wave aloft will come through in the next few hours,
and snow showers could reach inland to KGRR and KAZO. The best
concentration will remain near the lakeshore at KMKG. Inland areas
will see VFR cloud cover spread in from the North with the wave,
but snow shower chances there are fairly low. VFR conditions will
prevail, but some reductions in vsbys in any snow showers could
briefly drop as low as IFR.

We may see a brief break in the snow showers, before another wave
approaches later in the morning. This wave will also have some
daytime instability helping the chcs of snow showers, even at
inland locations. Again, conditions will be VFR, but localized
IFR will be possible under the heavier snow showers. Winds will 
pick up by afternoon with some gusts topping 20 knots. Snow 
showers and wind gusts will diminish toward sunset Tue night.


Issued at 330 PM EDT Mon Mar 12 2018

River levels will continue to fall this week. No heavy precipitation 
is forecast and snowmelt will be gradual.