Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 200513
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
113 AM EDT TUE SEP 20 2016

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 329 PM EDT Mon Sep 19 2016

A weak cold front will bring scattered showers and thunderstorms to
areas north of I-96 tonight, and only isolated precipitation to
areas along and south of I-96.  Some of these storms could be strong
toward Highway 10.  The rain chances will diminish by late tonight.
Another chance of showers and storms will move in Wednesday and
Wednesday night.  Again, this rain appears most likely for areas
north of I-96.

Showers and storms should remain widely scattered into Thursday and
Friday, then the weekend looks to be dry.  Another chance of rain
returns Sunday night.

The temperatures will remain well above normal through Thursday with
highs in the upper 70s to mid 80s.  Then we expect a cool down, with
highs closer to normal, mainly 70 to 75 Friday through Monday.

&&

.UPDATE...
Issued at 935 PM EDT Mon Sep 19 2016

Showers were moving in from the west...even a few thunderstorms.
There is still some instability around...but it has been
diminishing steadily. Will feature slightly higher POPs for the
evening with the update given the amount of shower activity
moving in. The cloud cover was also bumped up.

&&

.SHORT TERM...(This evening through Wednesday night)
Issued at 329 PM EDT Mon Sep 19 2016

Some strong to marginally severe storms will be possible over
Central Lower through about 10 PM, otherwise a dying front will have
little impact.  More showers and storms by Wed and Wed night.

A ribbon of increased instability extends from roughly Sheboygan WI
to Rogers City MI, and convective activity was blooming as I write
this.  This instability will sag south with the front into this
evening, reaching about a Grand Haven to Mt. Pleasant line by mid
evening, then the instability and the storms will diminish as the
heat of the day is lost.  Can`t rule out an isolated severe storm
in this area prior to 10 PM.

Farther south, drier air and less instability will result in most of
the showers and storms remaining north of I-96, but isolated pcpn
could reach as far south as I-94 before it dries up.  Feel up pcpn
will be dried up by 08Z, and added this timing to the grids.

Quiet weather for Tuesday and Tuesday night with high pressure
replacing the washed out front.  Then on the backside of the high
another front will form and looks to become nearly stationary over
Northern or Central Lower.  Moisture depth gradually increases late
Tuesday through Wednesday night and pcpn chances will increase with
time, especially across Central Lower.  Again, much of the showers
and storms will remain north of I-96 with the placement of the
front.  still expect most areas with tonight`s and the mid week
system will see a half inch or less of pcpn.

.LONG TERM...(Thursday through Monday)
Issued at 329 PM EDT Mon Sep 19 2016

Flat ridging is in place for much of the period as front stalls over
or near Lower Michigan. Some sfc convergence along the front could
bring scattered showers Thursday into Friday. Then Plains
cyclogenesis may increase mid level warm advection/isentropic ascent
enough to bring showers Friday night into Saturday. This is followed
by shortwave ridging ahead of the western CONUS upper trough and
generally fair weather Saturday into Sunday.

Precip chances increase again Sunday night and Monday as heights
fall and sfc cold front/prefrontal trough moves in.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 112 AM EDT Tue Sep 20 2016

A brief shower is possible for the next couple of hours at GRR and
MKG, otherwise sct-bkn clouds around 10k feet are expected through
the period.

&&

.MARINE...
Issued at 329 PM EDT Mon Sep 19 2016

Will keep the marine headlines going through much of tonight.
Southwest winds will diminish nicely late tonight and waves will
subside toward daybreak.  Choppy waves of 2-4 feet may linger much
of the Tuesday however, especially south.  Tuesday night through
Wednesday night look quiet on the lake, with the exception of hit and
miss storms north of Grand Haven Wed and Wed night.


&&

.HYDROLOGY...
Issued at 329 PM EDT Mon Sep 19 2016

The hydro concerns with tonight`s cold front are limited. Any
heavier rainfall this afternoon and evening is expected to be
localized, and widespread rainfall amounts should remain less than
0.50 inches. Most of this rain will fall north of Interstate 96,
with the Ludington area seeing the most. A few smaller streams could
see brief rises, but widespread river rises are not likely.

&&

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

$$

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



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