Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 190549
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
149 AM EDT MON SEP 19 2016

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 314 PM EDT Sun Sep 18 2016

A weak cold front will cut across the region Monday night.  A few
showers and storms can be expected late Monday into Monday night as
it comes through.  Otherwise the weather will be quiet through the
first half of the week with temperatures remaining above normal,
mainly in the upper 70s to around 80.

Much of the remainder of the week and into the weekend appears dry.
However we can not rule out a few widely scattered showers or storms
Thursday through Saturday.  Highs are expected to remain in the
upper 70s to lower 80s, but then cool to 70 to 75 by the weekend.

&&

.UPDATE...
Issued at 1019 PM EDT Sun Sep 18 2016

Dewpoints are elevated compared to the overnight low temperatures.
Already some light fog has formed. I ended up putting patchy fog
in the forecast for much of the region. Any fog should dissipated
quickly after sunrise as the wind will be increasing steadily.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 314 PM EDT Sun Sep 18 2016

A weakening cold front will bring a chance of showers and storms
late Monday to the NW CWA, then to the rest of the area Monday night.

The front will weaken as it approaches SW MI Monday night as the
upper trough remains the sharpest near the U.S./Canadian border and
shears out farther south as an upper ridge dominates the southern
half of the U.S.  However still expect scattered showers and storms
will move in late Monday across the NW CWA as moisture pooling holds
together near the front.  But the best moisture never reaches the
southern CWA overnight Monday, so only expect isolated
showers/storms for much of the southern CWA.  Most areas, even in
the north, will see a quarter inch or less from this system.

Severe storm chances look to be isolated, if at all.  The
instability looks marginal late Monday afternoon, and is gradually
lost into the overnight.  Also, the best jet dynamics remains to our
northwest.  I have adjusted the timing of the pcpn to mid afternoon
Monday and later, removing any chance late tonight or through the
first half of Monday.

Otherwise the short term period will be quiet.  The NAM suggests a
shower will still be possible into Tuesday morning over the far SE
CWA, but will keep it dry, and cover it with a 10 POP.  Temps behind
the front for Tuesday will only be a couple degrees cooler.

.LONG TERM...(Wednesday through Sunday)
Issued at 314 PM EDT Sun Sep 18 2016

Flat ridging is in place for much of the period as front stalls over
or near Lower Michigan. Chances for precip may have to be lowered or
dropped for Thursday and Friday, as deep moisture is lacking and
front washes out.

By Saturday, Plains cyclogenesis may increase warm advection enough
to bring higher chances for precip, but shortwave ridging ahead of
the western CONUS upper trough should mean steady rains will hold
off until after the weekend.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 147 AM EDT Mon Sep 19 2016

Patchy fog will bounce between vfr and lifr for the next few hours
up until sunset. VFR expected after mid morning. There is a
possibility of a shower or storm after 00z mainly at MKG as a cold
front moves toward Lower Michigan.

&&

.MARINE...
Issued at 314 PM EDT Sun Sep 18 2016

Will maintain the small craft advisory starting around daybreak
Monday as SW winds stiffen up ahead of an approaching cold front.
Winds and waves will diminish by late Monday evening.  Beyond that,
it appears quiet on the lake for Tuesday and Tuesday night.


&&

.HYDROLOGY...
Issued at 1129 AM EDT Sun Sep 18 2016

The river advisory continues on the Sycamore Creek at Holt this
morning. River obs are reflecting that rises are beginning to
slow, which signals that the site is nearing its peak. The river
should top out around sunset and will begin falling late this
evening. Dry conditions will allow the river to continue to fall
through Monday.

A frontal boundary will bring additional rainfall Monday night.
Overall amounts are expected to be light (around 0.25" or less),
but brief bouts of locally heavy rain cannot be ruled out.
Flooding concerns are low at this time with a side note: Due to
near/above normal river levels, basins affected by any heavy rain
could see quick response times, mainly consisting of within bank
rises.

&&

.GRR Watches/Warnings/Advisories...
MI...None.
LM...Small Craft Advisory from 7 AM this morning to 11 PM EDT this
     evening for LMZ846>849.

     Small Craft Advisory from 11 AM this morning to 11 PM EDT this
     evening for LMZ844-845.

&&

$$

UPDATE...MJS
SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...Ostuno
AVIATION...04
HYDROLOGY...JAM
MARINE...JK



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