Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 270827

Area Forecast Discussion
National Weather Service Grand Rapids MI
327 AM EST Sun Nov 27 2016

Synopsis/Short Term/Long Term/Marine

Issued at 305 AM EST Sun Nov 27 2016

A ridge of high pressure pushes east of Michigan today. This
system will act to keep the weather dry into the evening. A warm
front will lift northward through the region later tonight into
Monday. Thus showers will arrive. A cold front will track eastward
through the area Monday night into Tuesday morning causing periods
of showers.


.SHORT TERM...(Today through Tuesday)
Issued at 305 AM EST Sun Nov 27 2016

Overall the pattern still looks rather wet later tonight into
Monday night. A couple of items to monitor include a possible
wintry mix at the onset for route 10...impactful wind gusts Monday
night and perhaps thunderstorms.

The temperature tonight will cool off to near freezing for
interior parts of Lower MI. The low levels will be dry. So as the
elevated precipitation moves is forecasted to
weaken...which would delay the arrival in places like Mount
Pleasant and Harrison. This initial area of precipitation is
expected to weaken as it moves in...with generally light amounts
expected later tonight into Monday AM. Generally when we have
light precipitation/rather than moderate or heavy/ surface temps
do tend to diurnally rise as the precipitation moves in. So will
feature plain rain in the forecast...thinking the evening near
freezing temperatures will rise a few degrees later at night into
Monday AM.

The wind at 850 mb climbs to 50 to 60 knots Monday night as the
cold front moves in. How high the gusts go will depend on how
deeply we mix. There is a risk for stronger nocturnal mixing with
the front pushing in. Thus an elevated risk for impactful wind
gusts exists. Will continue to highlight this in the HWO. In
addition...weakness in the surface based stability shows up. The
risk for thunderstorms is not zero...and they may need to be added
to the forecast. Even without thunder...organized lines of
showers could enhance the gusts.

.LONG TERM...(Tuesday night through Saturday)
Issued at 305 AM EST Sun Nov 27 2016

No major changes have been made to the going forecast for the long
term. We are looking at a gradual cooling trend through the period,
along with unsettled conditions.

We will see mainly quiet weather at the beginning of the period,
with temps still a bit above average. This will come with the
initial front having passed through the area, and the secondary
surge of colder air poised to move in from the west. This secondary
front will approach the area Tue night into Wed, and bring another
chance of a few showers.

Once the secondary cold front moves through, we will see the cold
pool aloft and upper troughing linger over the area through most of
the rest of the long term. The cold pool aloft and occasional short
waves moving through will be responsible for keeping the chance of
showers in.

The arrival of the colder air will also bring the chance for some
snow to at least mix in at times. The air is not exceptionally cold,
so rain and/or snow will remain possible. We continue to expect that
snow accumulation potential will be limited with the marginal
sfc temps and wet bulb zero heights.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1246 AM EST Sun Nov 27 2016

Some lower clouds based around 1500-3500 ft are persisting along
the lakeshore early this morning. This is likely due to the added
moisture coming in off of Lake Michigan above a shallow layer at
the sfc where winds are from the SE. Pieces of these clouds are
then occasionally breaking off, and moving inland along I-96. We
have this accounted for at KGRR and KLAN in addition to KMKG. This
will persist until the winds start to back a bit and the
trajectory does not come off of the lake.

We have included in some light fog along the I-94 corridor. Some
is starting to form under mainly clear skies. Winds aloft should
limit the fog from becoming too dense.

Otherwise, a decreasing cloud trend should take place on Sun.
Some high clouds will come in later.


Issued at 305 AM EST Sun Nov 27 2016

The high pressure ridge slides east of the region today resulting
in backing low level winds. An offshore flow develops today and
into tonight. The pressure gradient starts of today relatively
light but tonight it tightens up. Thus the wind will
increase...and during the evening values over 20 knots will start
pushing up from the south. Close call later tonight for gales.

The pressure gradient remains tight into Tuesday as a cold front
pushes through the zones. Hazardous boating conditions for small
craft are expected. Conditions may be close to Gales at times.


Issued at 300 PM EST Sat Nov 26 2016

It continues to look like the basin average rainfall will be 0.50"
to 1.00" Monday into Tuesday. If higher amounts toward 1.00" or
greater occur over numerous locations, it appears the Grand River
would have considerable within bank rises for many locations as well
as potential rises over the banks at a few locations. Smaller rivers
and streams would be prone to within bank, and perhaps out of bank,
rises. Trends will be monitored, but flooding looks localized and
not significant if the heavier rains materialize. At this point, it
appears that the Muskegon and Kalamazoo Rivers would stay well
within banks.




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