Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 200712
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
312 AM EDT Fri Oct 20 2017

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

.SYNOPSIS...
Issued at 312 AM EDT Fri Oct 20 2017

Dry conditions are expected into Saturday night. High temperatures
will be 10 to 15 degrees above normal Friday and Saturday with highs
in the lower to mid 70s. Sunday into next week will be unsettled
with frequent rain showers. Much of next week will also be
considerably cooler with highs in the 50s.

&&

.SHORT TERM...(Today through Saturday night)
Issued at 312 AM EDT Fri Oct 20 2017

No impact weather expected. Only change of note was to bump up
Friday and Saturday high temperatures to the mid 70s for much of the
area. This is a bit greater than model guidance and was done in
coordination with the Detroit and Gaylord offices.

Rainshowers are expected to have spread eastward into our waters and
western zones by early Sunday morning. Timing with this has been
quite consistent with successive model runs. Therefore, confidence
with timing the onset of this precipitation is currently good.

.LONG TERM...(Sunday through Thursday)
Issued at 312 AM EDT Fri Oct 20 2017

Confidence is high that we`ll see rain Sunday as a cold front moves
across the state. The gfs and ecmwf haven`t changed much in their
solutions. The gfs is still a bit quicker and the ecmwf continues to
develop a wave on the front over the souther U.S. before moving it
north along the frontal boundary. The change from yesterday is that
the bulk of the rain from this wave is not depicted over southeast
Lower MI. Thus the chances for significant rainfall...over an
inch...is lower than yesterday. Still think we could see a third of
an inch or so from this system Sunday.

Chances for thunderstorms aren`t zero Sunday, but aren`t high
either. LI`s fall to around 1c as the front passes through. There
may be a better chance at seeing convection along the lake shore
Tuesday when LI`s fall to around -2c. Lapse rates will steepen quite
a bit (~8c/km) when the colder air aloft moves over the warm lake
water. Opted to include a isolated mention of storms Tuesday
afternoon along the lake shore.

An impressive upper low will develop over the Great Lakes Mon-Wed
resulting in more showers and much cooler temperatures. This cool
down has also been well advertised by the models for several days
and highs in the 50s are expected Tue-Thu. We`re likely to see
temperatures fall into the 30s Tue night and Wed night.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1248 AM EDT Fri Oct 20 2017

Clear skies and south winds around 10 knots are expected through
the period.

&&

.MARINE...
Issued at 312 AM EDT Fri Oct 20 2017

We have made some adjustments to the Small Craft Advisory. First,
it`s been expanded southward to Grand Haven based on WW3 guidance.
Second, we have made the beginning time earlier based on WW3
guidance and also on the Ludington buoy, which already has reported
4 foot waves north of Pentwater.

&&

.HYDROLOGY...
Issued at 320 PM EDT Thu Oct 19 2017

River levels continue to fall as dry conditions prevail following
heavy rain last weekend. Dry weather will continue through Saturday.

The next chance for rain will be on Sunday and Monday as a weak low
pressure system and cold front track through the area. Most forecast
guidance continues to show rainfall amounts of about one-quarter of
an inch, which would not cause flooding or much of a rise in rivers,
creeks, or streams. A lower-potential scenario is for the system to
stall over the area and bring heavier amounts of rain that lasts
into Tuesday. While this scenario is not likely at this time, it is
one we will continue to watch for in forecast models.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 8 PM EDT Saturday for LMZ849.

     Small Craft Advisory from noon today to 8 PM EDT Saturday for
     LMZ847-848.

&&

$$

SYNOPSIS...TJT
SHORT TERM...TJT
LONG TERM...04
AVIATION...04
HYDROLOGY...HLO
MARINE...TJT



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