Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 150458

Area Forecast Discussion
National Weather Service Grand Rapids MI
1258 AM EDT Sat Jul 15 2017


Issued at 328 PM EDT Fri Jul 14 2017

The region will be quiet tonight and Saturday.  But then a cold
front will approach and move through the area Saturday night into
Sunday bringing a period of showers and storms.  We return to quiet
weather Sunday night.  Overall, next week looks fairly dry, but we
will have a chance of more showers and storms between Tuesday night
through Thursday.

Temperatures will be cooler Sunday and Monday from 75 to 80,
otherwise we will be in the 80s.


Issued at 1125 PM EDT Fri Jul 14 2017

The waves have fallen to under 4 feet so the hazards were allowed
to expire.

I did add patchy fog to the forecast. There is already some
developing. Looks like the main potential will be west of 131.

UPDATE Issued at 810 PM EDT Fri Jul 14 2017

The wind and waves ended up building over 3 feet. We issued some
headlines for the next few hours to cover the hazardous boating
and swim conditions for mainly south of Grand Haven.


.SHORT TERM...(This evening through Sunday night)
Issued at 328 PM EDT Fri Jul 14 2017

Storms chances return Saturday night and will linger in some spots
into Sunday.  Otherwise the short term looks quiet and slightly
cooler than normal.

The upper wave that put down some light showers this morning has
moved off to the eastern portion of the state.  This will leave us
with a dry northwest flow and surface high pressure that drifts off
to our southwest Saturday morning.

The next upper wave will bring a cold front down across the state
Saturday night and Sunday.  It will be across Central Lower toward
06Z bringing the best chance of showers and storms around midnight
there.  Agree with SPC with the severe threat looking rather
borderline with marginal instability.  There is a weak low level jet
in the order of 25 knots, and the left exit region of the upper jet
seems more well positioned for Northern Lower to see stronger
storms.  So can not rule out isolated severe storms but the window
looks brief (around 06Z Sunday) and mainly along and north of I-96,
and probably west of US-131.

The models suggest a surface low will develop along the front on
Sunday as the upper wave comes in.  This will slow the front down,
causing the chances of rain to linger over the SE portion of the
CWA.  Feel this will mainly impact Ingham and Jackson Counties and
eastward from there.  Instability still looks too marginal to be too
concerned about severe storms on Sunday.  Much of the CWA will be
behind the front into Sunday and temps will only reach the mid to
upper 70s.

Clearing skies into Sunday night and temps dipping into the low and
mid 50s away from the lake.

.LONG TERM...(Monday through Friday)
Issued at 328 PM EDT Fri Jul 14 2017

Flow regime shows little change through next week with the Great
Lakes region remaining in fast west-northwest flow in between a
sprawling subtropical high to our south and upper troughing over
eastern Canada. A series of shortwave troughs continue to move
through while damping out and bringing chances for precip.

The first one comes through Tuesday night into Wednesday morning
with a weak cold front pushing south and possible touching off
scattered showers and thunderstorms. The front hangs up just south
of Lower Michigan then returns as a warm front Wednesday night. A
sfc low follows for Thursday and Thursday night with more widespread
showers and thunderstorms. It is still early but some indications
show severe potential including 12Z operational GFS showing about 50
knots of 0 to 6 km shear Thursday evening.

The sfc low moves off to the east with sfc high building in for
Friday and lingering showers ending by afternoon except across the
southeast zones.


.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1255 AM EDT Sat Jul 15 2017

IR loop shows stratocu thinning across the eastern cwa. We`ll
start the tafs off with clear skies. It`s possible that there
could be a brief period of mvfr fog within a couple of hours of
sunrise so we put in a brief tempo group.

A cold front will move south Saturday evening and a shower or
thunderstorm is possible, but most likely after 06z.


Issued at 328 PM EDT Fri Jul 14 2017

The lake has turned a bit rougher this afternoon, particularly
south of Whitehall with a north wind, and waves that have built to
around 3 feet. The winds will simmer down this evening, also
allowing waves to subside.

A good chance we will need a small craft advisory into Sunday
afternoon and evening.  Another surge of north winds and cold
advection will develop behind a departing cold front.  Waves will
probably build to around 5 feet.


Issued at 1054 AM EDT Thu Jul 13 2017

Rivers and streams have reached their crests or are nearing crest
levels following recent rainfall. Most sites continue to run above
to well above normal through the region with all site remaining well
within banks.

Rain returns to the area on Sunday. However, this moisture will be
of a scattered nature. Soaking rainfall will likely be confined to
locations directly affected by thunderstorms. Therefore, streams and
rivers should continue to see falls through at least Sunday with
little concern for flooding.




LONG TERM...Ostuno
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