Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 180625
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
225 AM EDT THU AUG 18 2016

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 PM EDT Wed Aug 17 2016

Areas of fog will develop tonight as the atmosphere remains moist.
The warm and humid conditions will continue through Saturday when a
strong cold front comes through.  Prior to the front arriving, the
next chance of showers and storms will move in on Friday and could
linger into Saturday night.  Some of these storm could be strong to
severe, mainly Saturday and Saturday night.

Cooler and less humid air will push into the region for the first
part of next week.  Daytime temperatures should be in the 70s Sunday
through Tuesday, then we may return into the 80s by Wednesday.
Another chance of showers may cross the area Monday night.

&&

.SHORT TERM...(This evening through Friday night)
Issued at 330 PM EDT Wed Aug 17 2016

The cold front continues to march across the CWA this afternoon,
exiting around 00Z.  Somewhat unclear how quickly the low clouds
exit.  If we do clear, it seems like an ideal set up for fog with
minimal winds and high moisture in the boundary layer.  Will have
areas of fog for all areas except I-94.  There are better chances I-
94 will hang on to some clouds, so will just have patchy fog there.
The best chance for dense fog should be across central lower where
clearing is most likely.

The front will sag south, but stall over northern IN as another wave
moves along it.  Much of the CWA will lose the deeper moisture, so
will go with a dry Thursday, but areas along I-94 may see an
isolated shower/thunderstorm where the deeper moisture will yet to
scour out.  This chance of pcpn may linger into the evening too.

Attention then turns to the front and short wave approaching from
the northwest Friday and Friday night.  This will be a slow moving
front that will only gradually increase moisture and lift over SW
MI.  It will move from NW WI Friday morning to the northwest
portion of the GRR CWA by daybreak Saturday.  Will have 30 POPs for
most of the CWA for Friday, rising to 40 POPs Friday night.  The
best jet dynamics remains to our north and west, so not expecting
anything strong or overly concentrated.  Instead expect scattered and
non-severe storms.

.LONG TERM...(Saturday through Wednesday)
Issued at 330 PM EDT Wed Aug 17 2016

An early fall like storm system will move through Southwest Michigan
in the Saturday into Sunday time frame.  This will mean a strong
surge of warm air ahead of the system which will lead to
thunderstorms later in the day Saturday into early Sunday. Much
cooler temperatures will follow for a good part of next week behind
the system.

The models continue to be in very good agreement on taking the
latest system from the Gulf of Alaska forcing it over the mean upper
ridge over the west coast, then it digs strongly into the central
United States this coming weekend. While this is a progressive it is
large enough to impact on southwest Michigan weather for nearly a
week. So we get the warm up in front of it Saturday then a cool
temperatures follow for next week.

There is strong dynamic forcing with this system so we get a decent
low level jet, deep layer shear, significant SB cape ahead of the
system. So strong storms are possible late Saturday ahead of the
cold front.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 225 AM EDT Thu Aug 18 2016

Fog is expected to form overnight with areas of IFR and patchy
LIFR across parts of Lower Michigan. The fog should dissipate
after sunrise with VFR conditions by 16Z. Winds will be west to
southwest on Thursday AOB 10 knots.

&&

.MARINE...
Issued at 330 PM EDT Wed Aug 17 2016

Rather quiet on the lake, with the next threat coming Friday in the
form of thunderstorms.  WSW winds will be dropping off nicely this
evening, and remaining light through Thursday night.  Southerly
winds will increase Friday, but these shouldn`t last long enough to
build waves any higher than 1-3 feet.


&&

.HYDROLOGY...
Issued at 541 PM EDT Wed Aug 17 2016

Flood warnings continue for Sycamore Creek at Holt in Ingham County
and for the Portage River near Vicksburg in Kalamazoo County. Rivers
have crested or are expected to crest soon. Widespread heavy rain is
not expected this week but, there will be periods of showers and
thunderstorms. Basin average precipitation will not be significant
given the more scattered nature of the rains. Rivers will likely
begin falling after crests over the next few days. Additional
precipitation for the weekend will need to be monitored given very
saturated soils that will not be able to absorb much rain.

&&

.GRR Watches/Warnings/Advisories...
MI...None.
LM...None.
&&

$$

SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...WDM
AVIATION...Ostuno
HYDROLOGY...63
MARINE...JK



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