Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 181928

Area Forecast Discussion National Weather Service Grand Rapids MI
328 PM EDT Sun Jun 18 2017

Synopsis/Short Term/Long Term/Marine

Issued at 328 PM EDT Sun Jun 18 2017

High pressure at the surface is building into the Great Lakes and a
few days of cooler and drier air is on the way. However, an upper
trough will now move over the state and that may result in a few
showers and/or storms during the afternoons Monday and Tuesday.


.SHORT TERM...(This evening through Tuesday night)
Issued at 328 PM EDT Sun Jun 18 2017

Forecast concerns deal with precipitation trends.

Sfc high pressure is moving into the cwa attm but cooler air aloft
is resulting in quite a bit of cu. This will dissipate this evening
leaving partly cloudy skies.

The next few nights will see lows in the 50s and afternoons will see
temperatures climb into the 70s. For the most part the mornings will
be dry. However, much cooler air aloft will move over Michigan early
this week. Lapse rates will steepen during the afternoon as the
temperatures warm and h8 temps fall to near -20c. This instability
will result in isolated to scattered showers. The coldest air aloft
will arrive Tuesday. With sfc dewpoints in the mid 50s and h5 air
near -20c, it`s not out of the question that some small hail may
develop in the stronger showers/storms.

.LONG TERM...(Wednesday through Sunday)
Issued at 328 PM EDT Sun Jun 18 2017

Strong signal in the guidance that an active summertime MCS pattern
will be present over the Great Lakes Region during the middle to
late part of the week.  Warm/humid air returns from the southwest
with high PWATs near 2 inches and a fast zonal flow aloft.

Potential exists for ocnl rounds/clusters of storms to impact the
area, particularly at night when the low level jet will be active.
Deep layer shear values are progged to be greater than 35 knots with
strong belt of westerlies over the northern US.

Currently it looks like a decent potential for MCSs on both
Wednesday and Thursday night. in addition to strong storms, heavy
rainfall may also be a concern considering the recent heavy rains.

Low confidence forecast for next weekend, but it appears the active
warm front/baroclinic zone may settle south of the state Friday into
Saturday. very unclear if it will lift back north Saturday night
into Sunday.


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 150 PM EDT Sun Jun 18 2017

Gusty sfc winds of 15 to 30 kt from the west-southwest are
expected for the rest of the afternoon, then the winds will
diminish to 5 to 10 kts after sunset.

Conditions will be mostly VFR with sct-bkn clouds with bases of
3000-5000 ft. The shower threat has pretty much ended for today,
but more scattered showers will return Monday, with an isolated
tstm even possible after 15Z.

Can`t rule out some fog developing tonight given recent heavy
rains. However since the winds look to stay up above 5kts, will
keep fog out of the TAFs for now.


Issued at 328 PM EDT Sun Jun 18 2017

Looking at marine obs shows that waves are below sca criteria,
however the Ludington buoy is close at 3.7 ft. Given that mixing has
begun to diminish the waves will continue to decrease and we`re
going to cancel the marine and beach headlines.


Issued at 1138 AM EDT Sun Jun 18 2017

Rainfall amounts over the last 48 hours have ranged from less than
a quarter inch from Battle Creek to Marshall and 3
to 5 inches from Grand Haven to Mount Pleasant and Saginaw Bay.
Many of the smaller rivers across the region have shown strong
rises overnight...with the Flat River at Smyrna expected to rise
above bankfull later Monday. Other rivers in the area of greatest
runoff...the Rogue River at Rockford...the Chippewa at Mount
Pleasant...and the Looking Glass at Eagle to name a few...have
also risen overnight but are not expected to reach bankfull stage
at this time.

Dry weather is expected for the rest of today through Tuesday...
when a fast moving system is depicted to move through southern
Michigan. If the forecast track verifies...the heaviest rain will
fall in areas that did not see much rain over the past few days.
Therefore...little if any impact expected on area river levels as
a result of this system. Expect the smaller tributaries in the
Grand and Muskegon river basins to return to normal...with sub
bankfull rises developing on the main stem rivers as the runoff
moves downstream.






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