Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 182351
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
751 PM EDT Wed Oct 18 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 329 PM EDT Wed Oct 18 2017

Dry conditions are expected with plenty of sunshine to round out
the later portion of the work week. Temperatures will moderate
into the 70s by Friday with mild conditions extending into
Saturday. A cold front will approach the region Sunday, bringing
showers and the possibility for a couple of thunderstorms. Much
cooler air will dive southward into Lower Michigan next week as
the front sweeps to the east.

&&

.SHORT TERM...(This evening through Friday night)
Issued at 329 PM EDT Wed Oct 18 2017

Pleasant weather is expected over the next few days with only minor
topics in the discussion. This includes this afternoon`s gusty
winds, a weakening cold front late tonight/early Thursday and
moderating temperatures late this week.

Surface high pressure and dry air is resulting in plentiful sunshine
across much of the eastern U.S. Active weather remains well north of
the Great Lakes as a vigorous upper trough progresses west to east
over the Hudson Bay through Thursday. The tight pressure gradient
and afternoon mixing will aid in producing wind gusts in the 25-30
mph range inland with some higher gusts possible along the lakeshore.

A weakening cold front will approach the region late tonight into
Thursday morning. A narrow ribbon of mid/upper level moisture will
be aligned with the front and is likely to produce a few clouds.
That`s about as much as we will get out of it. The front pushes east
with plenty of dry air in place Thursday with W to WNW flow behind
the boundary. Otherwise, the boundary goes through unnoticed to many
with any clouds quickly evacuating eastward Thursday morning.

Upper level ridging builds in late Thursday into Friday with
southerly flow redeveloping Friday. Height rises signify a decent
warming trend taking place. Expect sunshine and high temperatures
in the 70s Friday afternoon.

.LONG TERM...(Saturday through Wednesday)
Issued at 329 PM EDT Wed Oct 18 2017

Probably the main weather highlight in the long term is the colder
air which impacts the area next Tuesday and Wednesday. While medium
range guidance differs a bit on the evolution of the upper trough
and it`s duration that it persists over the GrtLks Rgn, there is
decent agreement with the idea that colder air arrives Tuesday and
lingers into Wednesday. Scattered to numerous showers, particularly
west of Hwy 131, should accompany the colder air.

Otherwise models are in good agreement on another warm/dry and
breezy day Saturday, followed by a cold frontal passage on Sunday
afternoon and evening. This does not look like a severe weather or
excessive rain producing system but does offer the potential for
about a quarter to half inch of rain.

An interesting trend developing in the guidance however is to slow
down and stall the Sunday cold front. The Canadian is most
pronounced with this notion and never really pushes it through, and
unlike other models it actually absorbs a srn stream upper low in
with the incoming nrn stream trough. The ECMWF brings the front in
but then stalls it over se lwr mi on Monday which causes rain to
linger south and east of GRR. The colder air mentioned above does
not follow immediately behind the Sunday (Monday?) cold front, but
lags at least 24-48 hours behind it.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 750 PM EDT Wed Oct 18 2017

VFR conditions to continue through tonight and Thursday.
Southwest winds will be gusting over 20 knots at times this
evening near Lake Michigan, otherwise winds will be at or below
10 knots.

&&

.MARINE...
Issued at 329 PM EDT Wed Oct 18 2017

Gusts out of the south-southwest will reach 35 knots this
afternoon/evening in the northern zones (Whitehall to Manistee).
The greater fetch and high winds will allow waves to build above 7
feet through this evening. South of Whitehall, gusts will
generally be around 30 knots or less with waves as high as 9 feet
forecast through mid-lake, tapering down to the 3-5 feet range in
South Haven.

Winds turn out of the west and decrease through Thursday morning.
SCA criteria waves may extent up through 12z Thursday, but will
leave any decisions to extend SCA headlines to later updates. Gale
headlines will remain as is with gales expected gradually decrease
after midnight. Winds drop off dramatically Thursday afternoon
with a lull in wave action through at least Friday morning.


&&

.HYDROLOGY...
Issued at 1050 AM EDT Wed Oct 18 2017

We continue to see river levels slowly recede for the most part
after the heavy rain event last weekend. The trend down will
continue through Saturday with dry weather expected through then.

The next rain event for the area beginning as early as Saturday
night and more likely Sunday will bring measurable rain, however it
appears that rain amounts will be limited to a quarter of an inch or
less. This will not cause any appreciable rises on the rivers and
streams. Additional light rainfall is also expected for the first
half of next week.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Gale Warning until 4 AM EDT Thursday for LMZ848-849.

     Small Craft Advisory until 4 AM EDT Thursday for LMZ844>847.

&&

$$

SYNOPSIS...JAM
SHORT TERM...JAM
LONG TERM...Meade
AVIATION...Ostuno
HYDROLOGY...NJJ
MARINE...JAM



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