338
FXUS63 KGRR 240550
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
150 AM EDT Sat Jun 24 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 PM EDT Fri Jun 23 2017

Colder than normal temperatures can be expected this weekend
through early next week, with widely scattered showers and
thunderstorms. Rainfall will not be excessive.

&&

.UPDATE...
Issued at 850 PM EDT Fri Jun 23 2017

I added a 20 to 30 pct chance of showers to area near and west of
US-131 for this evening as the shortwave currently crossing
central Wisconsin moves over Lake Michigan. A few showers have
developed ahead of the shortwave but there is a lot of dry air at
lower levels for these showers to overcome. I am thinking they
will die off as they move inland this evening.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 330 PM EDT Fri Jun 23 2017

Trough aloft and series of vorticity maxima/shortwaves sliding
through the northwest flow will bring periods of cloudiness and
scattered showers over the weekend.

Best coverage of convection, and the best time for a few tstms,
should generally be in the afternoon and evening hours when the
diurnal contribution/instability is highest. Also,the lake shadow
should tend to focus things inland from lake Michigan.

Lowering freezing heights through the weekend may eventually lead to
a chance of some small hail in some of the low topped convection,
which would be more possible on Sunday than on Saturday.

Scattered/intermittent nature of the convection of the weekend
should lead to total QPFs of generally no more than a quarter
inch, with highest amounts north of I-96.

.LONG TERM...(Monday through Friday)
Issued at 330 PM EDT Fri Jun 23 2017

Monday will see cooler than normal weather with diurnal enhancement
of showers and a few thunderstorms as upper level troughing brings
steep lapse rates. No severe weather is expected although the
storms could bring small hail during the afternoon as freezing
levels are unusually low.

The trough axis moves east by Tuesday with shortwave ridging
returning Wednesday along with warming temperatures. We will also
see moisture return in southwest flow with chances for rain by
Wednesday afternoon. Surface low center tracks north of Lower
Michigan on Thursday and showers and thunderstorms along and ahead
of trailing cold front will persist into Friday as the front sags
south of Lower Michigan and stalls across the Ohio Valley.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 150 AM EDT Sat Jun 24 2017

VFR conditions expected through Saturday night. A brief shower is
possible tomorrow afternoon, but chances too low to include in the
TAFs. Winds will become light overnight and pick back up tomorrow
afternoon out of the west. Gusts to 25 kts expected.

&&

.MARINE...
Issued at 1054 PM EDT Fri Jun 23 2017

Given how cold the air coming in is relative to the Lake Michigan
surface water temperatures, it seems more than reasonable to
believe 3 to 5 foot waves are expected Saturday into Sunday near
and south of Muskegon. So I issued both a SCA and beach hazard
statement from Saturday morning till Sunday evening.

&&

.HYDROLOGY...
Issued at 257 PM EDT Fri Jun 23 2017

Major flooding is expected along the Chippewa River in Isabella
County and sharp rises are also occurring along the Muskegon basin
and will continue the next couple days as the crest moves down
the river. From 3 to 5 inches of rain fell last night combined
with earlier heavy rains.

The good news is that no heavy rain is expected through the
middle of next week which will allow those areas that are flooding
to recover. The next chance for significant rain will be Thursday
of next week.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement from 6 AM EDT this morning through
     Sunday evening for MIZ056-064-071.

LM...Small Craft Advisory from 6 AM this morning to 8 PM EDT Sunday
     for LMZ844>848.

&&

$$

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