Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 251153
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
753 AM EDT THU AUG 25 2016

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 329 AM EDT Thu Aug 25 2016

A cold front dropping south through the state will bring showers and
storms from early this morning into the afternoon hours. The front
will push towards I-94 this afternoon and south of the state this
evening. A few storms may become strong today along and south of
Interstate 96. Dry weather settles in for tonight through Friday
night as high pressure slides east through the Great Lakes region.
Much less humid air will filter in for Friday. Another round of
showers and storms are expected this weekend as a low pressure
system moves through our area. Highs will be close to normals for
this time of year the next couple days.

&&

.SHORT TERM...(Today through Saturday)
Issued at 329 AM EDT Thu Aug 25 2016

Precipitation chances today and again on Saturday are the primary
concerns in the short term. Also, the chances for any severe weather
need to be addressed for today.

Starting with today, the SPC has placed southeast sections of the
forecast area in a Marginal Risk for severe weather. Feel we are
looking at two distinct periods of storms, tied to the low level
jet. The first is beginning now around 330am which will last to
around 15z. A low level jet is currently nosing in from the
southwest which is touching off showers and storms from near Grand
Rapids MI west across the lake towards Milwaukee. Feeling is that
these storms will continue to fill in as the nocturnal low level jet
increases. The cold front sagging south through the area will add to
low level convergence. CAPE values are already on the order of 1000
j/kg even at this early hour. Not expecting severe through 15z, but
there is roughly 30 knots of deep layer shear. We will be watching
storms for organization this morning.

The next time frame will be in the 18z to 22z time frame in the far
southeast CWA as the low level jet increases once again. Issue with
convection this afternoon will be the extensive cloud cover that may
be around limiting solar insolation. Even so, with the low level dew
points in the 70s and convergence along the cold front, storms will
refire. The storms may just be on the edge of our area though
towards Jackson. Deep layer shear this afternoon ramps up to around
40 knots, so storms will likely acquire rotation and organization.
Main storm threats look to be wind and locally heavy rains today.

A period of quiet weather will come tonight through Friday night
with dry air in place. The quiet period does not last long through
as the front comes back as a warm front on Saturday. Have showers
and storms in the forecast with the highest chances across our
northwest towards Ludington.

.LONG TERM...(Saturday night through Wednesday)
Issued at 329 AM EDT Thu Aug 25 2016

We will see a continuation of the likely rain chances on Saturday in
the short term, into Saturday night and early Sunday. The short wave
responsible for the rainfall will move across Lake Superior Sat
night, and will not move east of the area until Sunday. We will see
some moisture from the Gulf be advected in via a 30 knot low level
jet. The rain chances will linger through much of Sunday, before the
cold front passes through and ends the rain threat.

Much of the remainder of the long term looks rather quiet with
seasonable temperatures. The upper jet will remain north of the
border, keeping most systems north of the area. The other factor to
play an indirect factor in our weather will be the tropical system
that will likely be impacting the Florida and/or Gulf Coast. This
will induce higher heights to the north of it, in our vicinity. Max
temps should be in the 80s, with lows in the 50s/60s.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 753 AM EDT Thu Aug 25 2016

A band showers and embedded thunderstorms were lifting north of
the TAF sites at 1130z. Additional showers and storms are expected
today, especially for KAZO, KBTL, KLAN and KJXN. These locations
can expect periodic storms this morning and afternoon. Rain should
come to an end by 22z at KJXN. The MVFR/IFR has moved through the
TAF sites and lifted. Cannot rule out more MVFR/IFR especially in
the heavier showers and storms that develop today. VFR conditions
are expected tonight.


&&

.MARINE...
Issued at 329 AM EDT Thu Aug 25 2016

Wave heights through the next couple days should remain below
advisory criteria. Expecting fairly tame waves today on the order of
a foot or two. Tonight, waves ramp up some in cold air advection,
most likely reaching the 2 to 4 foot range. High pressure should
then provide light winds and limited wave action Friday into Friday
night.

The next time frame of concern on the big lake will be on Saturday
in strengthening southerly flow.


&&

.HYDROLOGY...
Issued at 121 PM EDT Wed Aug 24 2016

A Flood Warning remains in effect for the Portage River near
Vicksburg into the weekend. More rain is expected for this area and
river levels will be slow to fall. River levels are above normal
across the area but falling. Additional rainfall may bring levels
near bankfull, but new river flooding is not expected through the
weekend.

&&

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

$$

SYNOPSIS...Duke
SHORT TERM...Duke
LONG TERM...NJJ
AVIATION...Duke
HYDROLOGY...63
MARINE...Duke



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