Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 270002

Area Forecast Discussion
National Weather Service Grand Rapids MI
802 PM EDT FRI AUG 26 2016


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.


.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


.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 802 PM EDT Fri Aug 26 2016

Confidence is somewhat low regarding the timing and coverage of
convection over the next 24 hours. Consensus of short range
guidance indicates that numerous showers and tstms should develop
after midnight on the nose of the low level jet over nrn IL/srn
WI, then spread into sw lwr MI by daybreak. The convection should
tend to dissipate toward noon as the low level jet departs to the
northeast, but then another batch of storms may refire later in
the day - particularly southeast of GRR - on a leftover
boundary/outflow from earlier convection. Again confidence in this
scenario is somewhat low at this time.

Will have VFR weather in the TAFs for much of tonight... then showers
and tstms after roughly 09z may produce MVFR or lower conditions
with the possibility of heavy rainfall. Also there will be higher
sfc dew pts and a pseudo-warm front approaching from the south on
saturday, which may support some lower MVFR cigs developing as


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.


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...


LONG TERM...Ostuno
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