Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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263
FXUS63 KGRR 270540
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
140 AM EDT SAT AUG 27 2016

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 328 PM EDT Fri Aug 26 2016

Low pressure will move toward northern Lower Michigan Saturday.
Showers and thunderstorms are possible and a few could be strong.
After the low moves by, a cold front will sweep through and Sunday
will be mainly dry. More showers and storms will be possible Tuesday
as the next cold front moves through.

&&

.UPDATE...
Issued at 957 PM EDT Fri Aug 26 2016

Have updated to adjust pops a bit for late tonight. First, an
area of showers across nrn IN will approach the I-94 corridor
after midnight. Second, and more significantly, numerous showers
and tstms which are expected to develop across nrn IL and srn WI
with the low level jet after midnight should be moving into the
area after 5 or 6 am from the southwest. Highest pops with this
activity expected to be west of hwy U.S. 131, and especially along
the lakeshore north of Holland.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 328 PM EDT Fri Aug 26 2016

We`ll see increasing clouds tonight as mid/high clouds stream
northeastward ahead of the next front. Short range models are fairly
consistent in showing showers/storms developing Saturday morning and
continuing through the afternoon. Much of the upper energy moves
across Wisconsin and northern Lower. In fact, shear increases to 40-
45kts Saturday morning as the llj begins to increase. However,
instability will be highest over the southern cwa Saturday
afternoon. Shear values are progd to be around 35 knots during the
afternoon as instability increases. So, the strongest storms, should
they form, will be south of I-96 tomorrow afternoon.

Heavy rain appears to be a possibility too as pwats increase to
around 2 inches across the southern cwa Saturday afternoon.

Mainly dry weather is expected Sunday and Sunday night.

.LONG TERM...(Monday through Friday)
Issued at 328 PM EDT Fri Aug 26 2016

A few showers and thunderstorms may linger across the far southern
zones early Monday before sfc high builds south bringing a break in
the chance for rain. This is short lived as an area of warm
advection/isentropic ascent begins Monday night with at least
isolated showers and storms moving in from the southwest.

A higher chance of rain follows for Tuesday as a shortwave trough
amplifies with sfc cyclone moving across Canada and trailing cold
front across the Great Lakes. The trough axis shifts east with sfc
and upper ridging bringing generally fair weather Wednesday through
Friday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 140 AM EDT Sat Aug 27 2016

A round of showers will be moving into the TAF sites early this
morning. These should be relatively light, with VFR continuing.
However thunderstorms will also gradually move/form over the area
after sunrise, perhaps impacting all the TAF sites by 15Z as we
become increasingly unstable. These storms will continue over the
region until somewhat drier air arrives by late afternoon/early
evening.

Ceilings and vsbys should lower with the rain. Expect some MVFR
will be around by late morning, most likely over far Western
Lower, including MKG and GRR, where the steadiest rains can be
expected. This too is expected to improve toward late afternoon
as the bulk of the rain moves out.

&&

.MARINE...
Issued at 328 PM EDT Fri Aug 26 2016

Fairly tame conditions on the lake tonight and Saturday.
Thunderstorms though will create a marine hazard. Strongest south
winds will be found over the northern portion of the lake.


&&

.HYDROLOGY...
Issued at 328 PM EDT Fri Aug 26 2016

The Portage River is slowly falling and is expected to fall below
flood stage tonight or tomorrow. The only fly in the ointment is
likely rainfall on Saturday. Any thunderstorms will be rather
efficient rainfall producers as humidity increases through the depth
of the troposphere. Locally over an inch of rain is possible.

&&

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

$$

UPDATE...Meade
SYNOPSIS...04
SHORT TERM...04
LONG TERM...Ostuno
AVIATION...JK
HYDROLOGY...63
MARINE...04



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