Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 280523
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
123 AM EDT Sun May 28 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 303 PM EDT Sat May 27 2017

Most of the night will be dry, but a few areas could pick up an
isolated shower or storm.  However Sunday will become wet for most
areas by afternoon into the evening.  Most areas will pick up a
quarter to half inch of rain in this time period.  The rains will
end toward midnight Sunday night.  Another round of showers and
storms are expected for Monday afternoon, but these could begin
across Central Lower during the morning hours.  Then we will dry out
Monday night.

The rest of next week appears drier, but a few lingering widely
scattered showers could occur Tuesday and Wednesday.

After temperatures in the 70s through Memorial Day, we will cool
into the 60s Tuesday and Wednesday.  Then we should return to 70 to
75 for the latter portion of the week.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 303 PM EDT Sat May 27 2017

We will see a couple of wet periods during the short term.  These
will be Sunday afternoon and evening, as well as Monday afternoon. A
few hit and miss showers may occur outside of these periods as well.

We will be transitioning into a wetter period.  However the
overnight period looks mainly dry, with an upper ridge sliding off
to the east, and a cold front crossing WI.  I did reduce the POPs
tonight, but can`t rule out a shower or storm skimming across the
Highway 10 region overnight, but this will be the exception.

The cold front will arrive through the afternoon into the evening on
Sunday, likely bring showers and storms.  This is a bit slower than
the previous forecast package.  The best jet dynamics also arrives
later in the day. Therefore I have adjusted the POPs to be focused
on Western CWA in the afternoon, and over the Southeast CWA into the
evening. Agree with the severe weather outlook that includes the
marginal chance for severe storms over the SE CWA, where the
instability maxes as the jet dynamics come overhead.  Best chance
for this appears to be late afternoon/early evening.

Behind the front, an upper low develops over the Superior region and
several spokes, or troughs come through during the late Sunday
night through Monday night periods. Highest chance of additional
showers and storms will come Monday afternoon, as we build
instability, along with series of troughs.

.LONG TERM...(Tuesday through Saturday)
Issued at 303 PM EDT Sat May 27 2017

Some gradual improvement will occur in the extended period as an
upper low slowly moves east. After some diurnally enhanced showers
on Tuesday and to a lesser extent Wednesday, there should be a dry
period as sfc high builds in and heights rise Wednesday night into
Thursday.

There is low confidence in the forecast by end of the week as
ensemble spread increases. Canadian sfc high may hold on for Friday
and Saturday or there could be an area of warm advection and
isentropic ascent bringing scattered showers as a sfc low tracks
across southern Canada.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 113 AM EDT Sun May 28 2017

Dry weather is expected overnight. VFR conditions expected through
the period. Showers and thunderstorms are most likely from 18-02z.


&&

.MARINE...
Issued at 303 PM EDT Sat May 27 2017

Thunderstorms will be the main threat for mariners on Sunday
afternoon.  WSW winds will increase by Memorial Day when rougher
conditions can be expected.  Waves should build to 2-3 feet, still
below small advisory criteria, but a bit rough for the less seasoned
boater.


&&

.HYDROLOGY...
Issued at 210 PM EDT Sat May 27 2017

River levels in the upper Grand and the Kalamazoo basins are running
above normal for late May while elsewhere the levels are closer to
normal. Rain totals around a half inch on Sunday will likely not be
enough to produce flooding. Occasional showers over the upcoming
week will be rather light.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&

$$

SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...Ostuno
AVIATION...04
HYDROLOGY...CAS
MARINE...JK



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