Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 181148
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
748 AM EDT Sun Jun 18 2017

LATEST UPDATE...
Aviation/Marine

.SYNOPSIS...
Issued at 313 AM EDT Sun Jun 18 2017

After numerous rounds of thunderstorms over the last couple days
for many locations, conditions dry out this afternoon. Monday and
Tuesday will feature some scattered showers and perhaps a few
thunderstorms, but much of the time will be dry. Active weather
returns for the second half of the week with more rounds of
thunderstorms possible.

&&

.SHORT TERM...(Today through Tuesday)
Issued at 313 AM EDT Sun Jun 18 2017

Showers and thunderstorms will be winding down this morning, but
locally heavy rainfall is still a threat through about 14z. Some
areas picked up 1 to 2 inches of rain during the early morning hours
and an additional 1 inch or more of rain is possible in the heaviest
storms through mid morning. Most areas will stay dry this afternoon
aside from a widely scattered light shower. There will be almost
zero instability and the GFS is showing a very dry sounding. Daytime
mixing will yield wind gusts to around 25 mph, so a breezy afternoon
looks likely.

There may be a few hundred J/kg of CAPE on Monday along with
increasing deep layer RH to afford some scattered showers and
isolated storms outside of the lake shadow with west winds at H850
and the surface. POPs aren`t zero at the lakeshore but the
precipitation will likely be focused inland. Tuesday features a 40-
50 kt mid level jet core over the region (especially southern Lower)
but even MUCAPE will struggle to get over a few hundred J/kg. The
soundings also look drier. If there are any storms that manage to
pop, some gusty winds may occur given the mid level jet and dry
adiabatic lapse rates to 5k ft.

.LONG TERM...(Tuesday night through Saturday)
Issued at 313 AM EDT Sun Jun 18 2017

We continue to expect a fairly unsettled weather pattern in the long
term with multiple chances of rain through the period.

Rain chances early in the week should end Tue evening for the area,
with the area likely staying dry through most of Wed. The upper
troughing expected to be in place early in the week will slip east
of the area. This will bring anti-cyclonic flow aloft back over the
area by Wed.

The break in the rain chances looks to be short in nature, with rain
chances returning as early as Wed evening. This results from the
upper ridge to our west building in over the area and it dampens a
bit. The heat and humidity will push in via a healthy low level jet,
and spark some showers and storms. The rain chances will continue
into Fri when the associated cold front extending from a low across
Ontario pushes through the area.

Sat was looking like it would be another dry day, and we will keep
it that way for now. We are expecting some ridging to build in the
wake of the front that comes through Friday. Some of the models are
holding up the front a bit, possibly accounting for a tropical
system lifting north and holding the front up from sinking too far
south. Way too much uncertainty with the multiple ingredients to do
anything drastic for now, so we will hold on to the dry Sat
forecast. Cooler temps look likely behind the Fri cold front.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 744 AM EDT Sun Jun 18 2017

Low cigs this morning will give way to improving conditions this
afternoon. Expect wind gusts to continue holding around 25 knots
or higher at times. Best risk for IFR will be MKG and GRR through
the mid morning hours due to low cigs. RAP model RH at 975mb is
showing an eroding of the lower cigs as we progress through the
morning.

&&

.MARINE...
Issued at 744 AM EDT Sun Jun 18 2017

SCA was hoisted after reviewing marine obs that were over
achieving on wind speed and wave height. Most locations should
reach wave heights of 3 to 5 feet, starting with southern Lake
Michigan and progressing northward. These waves will subside after
00z or so.

&&

.HYDROLOGY...
Issued at 313 AM EDT Sun Jun 18 2017

Dual pol radar along with observer and station reports have
indicated the hardest hit region over the last 48 hours is across
west central Lower MI, particularly from Ottawa and Kent Counties
to the northeast toward Gratiot and Isabella Counties. Ribbons of
heavy rain also occurred near a line from South Haven to Lansing.
Much of this region received 1" to 4" of rain. Main stem rivers
are handling this fine given how dry this month has been, though
small rivers and streams are exhibiting considerable within bank
rises. No flooding is anticipated at this time.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 8 PM EDT this evening for LMZ844>849.

&&

$$

SYNOPSIS...Hoving
SHORT TERM...Hoving
LONG TERM...NJJ
AVIATION...Hoving
HYDROLOGY...Hoving
MARINE...Hoving



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