Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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372
FXUS63 KGRR 290012
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
812 PM EDT SAT MAY 28 2016

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 256 PM EDT Sat May 28 2016

Isolated severe thunderstorms are possible on Sunday as a cold
front works through the region. The main threats are large hail
and damaging winds. Until then, isolated to scattered
showers/storms will be possible this afternoon into tonight.

Memorial Day looks beautiful with a bit less humidity, plenty of
sunshine, and highs in the lower 80s. Rain chances increase
Wednesday and peak Wednesday night into Thursday.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 256 PM EDT Sat May 28 2016

Isolated strong to severe thunderstorms are possible on Sunday as a
cold front moves through Lower Michigan. The primary threats will be
hail and damaging winds.

The Plains upper trough will weaken as it swings into the Great
Lakes region through Sunday. The H500 vort will provide weak mid-
level support as a cold frontal passage coincides with peak heating.
Showers and thunderstorms are expected to develop along and ahead of
the cold front. Moderate destabilization is expected prior to the
frontal passage. The 12z NAM and GFS diverge a good deal on the
amount of MLCAPE available from late morning into the afternoon, but
it seems reasonable to expect 1000-1500 J/kg. Deep layer shear is
marginal at best around 25 kts. Wind fields in the mid and upper
levels are unimpressive.

However, the cold front will provide better forcing than we`ve had
in the past week in a buoyant atmosphere. A few strong to severe
thunderstorms are possible, with large hail and damaging winds as
the primary threats.

Low level flow goes westerly behind the front Sunday evening, and
mid level height rises begin Sunday night. Surface ridging then
builds into the southern Great Lakes. Memorial Day looks beautiful
with a bit less humidity, mostly sunny skies, and highs in the lower
80s.

.LONG TERM...(Tuesday through Saturday)
Issued at 256 PM EDT Sat May 28 2016

After a break break in the rain chances on Monday, the rain chances
will return at the beginning of the long term portion of the
forecast on Tuesday. These rain chances will not be very high, and
will be more diurnal in nature as increasing moisture will return
ahead of the next system.

The rain chances will increase then on Wednesday and will peak
Wednesday night into Thursday. Showers and thunderstorms will be
supported by the upper low system that is currently centered over
British Columbia. This will gradually drop southeast, and push a
frontal system into the area late Wed into Thu.

We will tend to dry out a bit then for the end of the week and the
beginning of the weekend, but keep a small chance of a few showers
in. The upper low will open up to a trough and move through by Fri
morning. We will see additional short waves coming in on the nw flow
and help to establish a long wave trough over the area. This should
allow for a few diurnal rain showers Fri and Sat afternoon with
cooler temperatures.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 812 PM EDT Sat May 28 2016

VFR conditions prevail at 00z...with only a few isolated showers
drifting north across the region. A stronger line of storms is
noted across portions of central Wisconsin and central Illinois.
VFR conditions should persist through 06z, which is about the time
the line in Wisconsin would get here. A diminishing trend in
instability should occur this evening and the expectation is
anything overnight should be in the form of showers. A few storms
cannot be ruled out. Overnight, mainly expecting VFR as the line
should be washing out. There may be some MVFR haze (3-5SM HZ) late.

On Sunday, a line of showers and storms will likely develop near a
KLAN to KBTL line around 18z and push off to the east in the
afternoon. Have VCTS in the TAFS Sunday afternoon as areal extent
is still a bit uncertain.

Winds will pick up mid morning Sunday reaching the 12-25 knot
range through the midday and afternoon hours from the Southwest.

&&

.MARINE...
Issued at 256 PM EDT Sat May 28 2016

Conditions on Lake Michigan will remain hazardous to smaller craft
and dangerous to swimmers north of Grand Haven through this
evening. Southerly winds will continue to gust to 30 mph this
afternoon and evening before diminishing late tonight. Waves will
subside to 2 to 4 feet tonight and 1 to 3 feet on Sunday.


&&

.HYDROLOGY...
Issued at 109 PM EDT Sat May 28 2016

River levels across the area are near to just above their expected
values for this time of year. Precipitation of up to an inch is
possible over the next week. Convection through the weekend will
produce mainly localized heavy rainfall. Rises will mainly be
confined to smaller creeks and streams and should not reach flood
levels.

&&

.GRR Watches/Warnings/Advisories...
MI...Beach Hazards Statement until 10 PM EDT this evening for MIZ037-
     043-050.

LM...Small Craft Advisory until 10 PM EDT this evening for LMZ847>849.

&&

$$

SYNOPSIS...EBW
SHORT TERM...EBW
LONG TERM...NJJ
AVIATION...Duke
HYDROLOGY...63
MARINE...EBW



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