Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 200730
AFDGRR

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

LATEST UPDATE...
Synopsis/Short Term/Long Term/Marine

.SYNOPSIS...
Issued at 315 AM EDT Sat Aug 20 2016

Thundestorms with locally heavy rain and gusty winds will preceed
a strong cold front that will come through the area tonight. all
areas will see rain from this system. The storms will be out of
the area by mid evening then a brief clearing is expected. Sunday
will see mostly cloudy and breezy condtions with scattered
showers. Skies will clear by Monday and cooler conditions will
continue. A warm up starts Tuesday.


&&

.SHORT TERM...(Today through Monday)
Issued at 315 AM EDT Sat Aug 20 2016

The main issue is will we see severe storms today? There is no
quesstion about rain, all areas will see the thunderstorm with
this frontal system. The other issue is the extend to which lake
effect rain showers develop Sunday.

All the models do something very similar with this storm system
today. The all show the low level jet getting strongers as the
core of max wind speed moves norhtward from north of ludington to
near the Big Mac bridge by midnight. This puts southwest michigan
in the speed diveregnced area of the low level jet, which is not
good for severe storms. On the other hand the moisture transport
vectors all support storms across the area with the best storms
north of Mugkegon. Some of the storms will have heavy rainfall.

This all clears out this evening, the lake effect rain showers
follow sunday with clearing Sunday night


.LONG TERM...(Monday night through Friday)
Issued at 315 AM EDT Sat Aug 20 2016

We`ll see a couple of dry days as we start the long term period.
High pressure over the eastern Great Lakes will slowly drift east.
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.
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 70s behind the front.

&&

.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 315 AM EDT Sat Aug 20 2016

No changes area expect.

&&

.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 2 PM EDT 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...WDM
SHORT TERM...WDM
LONG TERM...99
AVIATION...04
HYDROLOGY...Hoving
MARINE...WDM



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