Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 200522
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
122 AM EDT SAT AUG 20 2016

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 PM EDT Fri Aug 19 2016

A strong cold front will push across Southwest Michigan Saturday
evening.  After a fairly quiet night, all areas will see a high
chance of showers and thunderstorms Saturday and Saturday evening.

Behind the front cooler and less humid air will arrive.  A few
showers may also linger late Saturday night into Sunday.  Areas
north of I-96 and along the lake shore will see the best chance of
showers.  Drier and cool conditions are expected by Sunday night.

Daytime temperatures will be in the 70s Sunday and Monday.
Temperatures are then expected to warm to around 80 Tuesday through
Friday.  The next chance of rain should hold off until Wednesday and
Thursday.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 330 PM EDT Fri Aug 19 2016

The possibility of strong to severe storms will be over the region
Saturday afternoon and evening.  Then we will see a big change in
the weather as cooler and less humid air moves in, along with a
breezy day Sunday.

The cold front is still progged to come through Saturday evening.
Storms will likely proceed the front with the best chance for severe
weather coming mid afternoon into early evening.  This is when the
low level jet and upper jet come across the area.  Actually the LLJ
is progged to be directly over SW MI...leading to the potential for
damaging winds with some of the stronger storms.  Most likely we
will see a fairly solid line of storms with bowing segments.  0-6km
bulk shear values are 25-30 kts, which isn`t off the charts, but
should be enough for a few organized/strong storms.

Behind the front we will see dropping dew points, cooler air and
winds increasing.  H8 temps fall to around 10C, and with water temps
around 25C, we will see lake clouds and a few showers lingering into
late Saturday night and Sunday.  Westerly winds will gust to around
25 mph, which will even bring a chilly feel to the air.  Some areas
across central lower may struggle to reach 70 if enough clouds and
scattered showers persist.

Drier air arrives into Sunday night for a quieter night with lows
in the 50s.

.LONG TERM...(Monday through Friday)
Issued at 330 PM EDT Fri Aug 19 2016

The cool down will be short lived as upper trough quickly lifts out
by Monday and the flow aloft goes zonal. At the sfc, an area of high
pressure centered south of Michigan will drift gradually east-
northeast through midweek. This will lead to predominately dry
weather, along with moderating temperatures within southerly/return
flow on the back side of the high.

The next decent chance of showers and tstms will come later
Wednesday into Thursday as a digging upper trough over the north
central U.S. induces warm advection and a push of higher humidity
into srn lwr MI. The sfc cold front is currently progged to push
through Thursday afternoon or night.

Slightly cooler and dry weather should follow behind this system for
Friday of next week unless the sfc front slows or stalls out.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 119 AM EDT Sat Aug 20 2016

Showers and thunderstorms will increase in coverage this
afternoon as a strong cold front moves through. Confidence is
high that we`ll see storms at/near the taf sites this afternoon
and is reflected in a tempo group. It`s possible that vsbys in
storms could be lower than what is in the tafs. Winds will shift
to the west behind the front.

&&

.MARINE...
Issued at 550 PM EDT Fri Aug 19 2016

Will go ahead and issue a small craft advisory and beach hazards
statement for the entire lakeshore starting 2 PM Saturday
afternoon. Advanced headline being a summer weekend clashing with
an unusual event with high winds and waves seems most prudent.

Southerly winds will approach 25 knots by mid afternoon Saturday.
Waves will build to 3-5 feet by late afternoon. Waves will
increased to 5 to 8 feet by late Saturday night into Sunday as
winds turn to the west behind the cold front.


&&

.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 from this afternoon through late Sunday
     night for MIZ037-043-050-056-064-071.

LM...Small Craft Advisory from 2 PM this afternoon to 1 AM EDT Monday
     for LMZ844>849.

&&

$$

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



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