Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 121842
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
242 PM EDT Sat Aug 12 2017

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

.SYNOPSIS...
Issued at 242 PM EDT Sat Aug 12 2017

Showers will continue to end by early this evening, leaving a nice
and cool night. Dry weather will continue through Sunday night with
comfortable conditions expected.

A small chance of rain will develop on Monday and Monday night as a
system moves through. Most of the time will not be raining. Rain
chances will increase mid-week as warm and humid conditions move in
ahead of the next frontal system. Rain will move out by the end of
the week, and somewhat cooler conditions will move back in.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 242 PM EDT Sat Aug 12 2017

Showers this afternoon have been migrating to the east, and will
continue to move away and diminish by early evening. This occurs as
the upper trough axis continues to shift to the east and we become
under increasing control of upper ridging to our west. Clouds will
clear out, and a cool and comfortable night can be expected.

No worries for Sun through Sun night as the upper ridging remains in
control. Mainly sunny skies and temps around 80 with lower
humidities will make for a great second half of the weekend.

We have added in a small chance for some showers for Mon and Mon
night. We will see better dew points start to move in Mon in the
lower levels, while the upper trough to our NW approaches the area.
Models are hinting at some convergence inland with a weak flow and
lake breezes from Lakes Huron and Michigan possibly colliding. There
is somewhat of a cap around H850, so thinking most areas will stay
dry on Mon.

The best chance of showers Mon and Mon night will come Mon night as
the upper trough moves across Central and Northern Lower. There may
be enough deep moisture with the wave to produce some pcpn.

.LONG TERM...(Tuesday through Saturday)
Issued at 242 PM EDT Sat Aug 12 2017

High pressure will bring dry weather and seasonable temperatures to
West Michigan Tuesday.  Warm air advection ahead of next system to
affect region will result in warm and muggy conditions Wednesday
with apparent temperatures approaching 90 south of I-96. Rain
chances increase Wednesday into early Thursday. Drier air moves in
for later Thursday and Friday before the next system brings a chance
of rain on Saturday.

Highs will reach the lower 80s on Tuesday...rise into the middle 80s
Wednesday...before cooling back into the lower 80s for Thursday and
near 80 for Friday and Saturday. Lows around 60 Wednesday morning
will increase into the middle 60s Thursday before cooling to around
60 by Saturday morning.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 110 PM EDT Sat Aug 12 2017

Mid level trough moving south through Lower Michigan at this
time...producing extensive cloud cover and scattered showers.
KLAN/KJXN would have the best chance of seeing precipitation this
afternoon as they are ahead of the trough axis. Will keep other
sites dry.

Ceilings have been quite variable again today. Expect ceiling
heights to remain VFR at KMKG/KGRR/KAZO/KBTL while KLAN/KJXN
retain MVFR ceilings through late afternoon. Model soundings
indicate drier conditions moving in from the northwest this
evening...so will clear the ceilings accordingly.

VFR weather will then persist through 18Z Sunday. High clouds
will then increase ahead of system moving in from the west for
Monday.


&&

.MARINE...
Issued at 242 PM EDT Sat Aug 12 2017

The worst conditions seem to have migrated down the shoreline today,
with the worst conditions south of Grand Haven now with almost 5
foot waves at the Port Sheldon and South Haven buoys. Conditions
have not quite come down enough to drop headlines up north this
afternoon. The 8 pm expiration up north should work out well, and
the later expiration down south should also work.

Conditions should then calm down for Sunday, and last through
Tuesday with lighter winds expected.

&&

.HYDROLOGY...
Issued at 1112 AM EDT Sat Aug 12 2017

There are no hydro concerns at this time.

Rivers are running well within their banks. Limited chances for
rain exist today. Mainly dry conditions are anticipated up through
midweek, when our next chance for any measurable rain moves in.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement until 2 AM EDT Sunday for MIZ056-064-
071.

     Beach Hazards Statement until 8 PM EDT this evening for MIZ037-
     043-050.

LM...Small Craft Advisory until 8 PM EDT this evening for LMZ847>849.

     Small Craft Advisory until 2 AM EDT Sunday for LMZ844>846.

&&

$$

SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...MWS
AVIATION...MWS
HYDROLOGY...JAM
MARINE...NJJ



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