Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 210520
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
120 AM EDT SUN AUG 21 2016

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 309 PM EDT Sat Aug 20 2016

A cold front will continue to slide east across the CWA this
evening bringing an end to the storms. Showery cooler and breezy
weather will continue into Sunday. Then a quieter period is
expected for Sunday night through Monday night as high pressure
arrives.

The next chance of rain should hold off until Wednesday night
through Thursday night. It will be slightly warmer for the mid and
end of the week with daytime highs mainly in the upper 70 to lower
80s.

&&

.UPDATE...
Issued at 934 PM EDT Sat Aug 20 2016

Storms have exited the cwa, but we have a few residual showers
moving east attm. Upstream radars also show scattered showers so
we`ll keep a few in the grids overnight.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 309 PM EDT Sat Aug 20 2016

Severe storms seem most likely to continue through about 21Z. Then
a diminishing trend is expected.

The front will clear the CWA toward midnight and bring an end to
the storms, as well as the warm and humid air. Some lake
enhancement into Sunday will lead to showery weather. Strong
winds behind this system will lead to marine issues tonight into
Sunday evening.

Storms will end by about 03Z with the exit of the cold front. Dew
points will lower and winds will increase through the night,
making for more comfortable conditions.

With H8 temps of 10C coming across the lake, and water temps
around 25C, we will see lake clouds and scattered showers much of
Sunday. Drier air moves in later in the day and we should see
these diminish and perhaps some sunshine late in the day. Highs
only low to mid 70s.

The drier air continues to filter in Sunday night as surface and
upper ridging moves in. We should remain dry through Monday night
as the ridge slides over the region. Slightly warmer Monday with
return flow coming in.

.LONG TERM...(Tuesday through Saturday)
Issued at 756 PM EDT Sat Aug 20 2016

The first part of the long term period looks dry as high pressure
over the eastern Great Lakes will slowly drift east, but still have
a grip on Lower Michigan. The cooler temperatures realized during
Sunday and Monday will warm to 80 by Tuesday as south flow develops.

An approaching cold front will generate more showers and storms
Wednesday through Thursday with high probabilities Wednesday night
and Thursday. The mid week system looks similar to the current one
in that the low pressure driving the cold front will be well north
of the cwa. Temps will fall into the mid 70s behind the front
Friday and Saturday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 118 AM EDT Sun Aug 21 2016

Cooler temperatures aloft today will create unstable conditions
and showers will develop after 13z. It`s possible we could see a
thunderstorm as well. Look for pcpn to end by sunset.

Cigs will begin near mvfr and rise to low vfr this afternoon.

&&

.MARINE...
Issued at 309 PM EDT Sat Aug 20 2016

Will keep headlines as is. We still make approach gales mainly
north of Muskegon late tonight, but this looks marginal enough to
stay the course with the current headlines.

A very rough day is expected on the lake Sunday with WNW flow to
30 knots. Beach hazards will also be high for anyone hoping for
a beach day. Swimming is highly discouraged. Certainly an
unusually strong synoptic storm that impacts weekend plans.

Slow improvement is expected Sunday night. It still appears Monday
and Monday night will be better as winds lessen and turn to the
southwest.


&&

.HYDROLOGY...
Issued at 100 PM EDT Fri Aug 19 2016

Most rivers have crested or will very soon. The rivers within the Grand,
Kalamazoo, and St. Joseph river basins are flowing at or above the 90th
percentile for this time of year compared to historical readings. Any
added rainfall will continue to keep the rivers elevated. 24 hour rainfall
ending Saturday morning is not expected to cause additional rises. Locally
heavy rains Saturday afternoon and evening may need to be watched for
excessive runoff into elevated rivers given saturated soils in place.
In general, basin average amounts are expected to be 0.50"-1.00" through
Saturday night. This may, at the least, slow some of the receding flows
but could cause new rises into the weekend.

&&

.GRR Watches/Warnings/Advisories...
MI...Beach Hazards Statement through late tonight for MIZ037-043-050-
     056-064-071.

LM...Small Craft Advisory until 1 AM EDT Monday for LMZ844>849.

&&

$$

UPDATE...04
SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...Meade
AVIATION...04
HYDROLOGY...Hoving
MARINE...JK



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