Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 290344

Area Forecast Discussion
National Weather Service Grand Rapids MI
1144 PM EDT SAT MAY 28 2016


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.


Issued at 1031 PM EDT Sat May 28 2016

Some instability remains across the Wisconsin, Illinois and
western Lower Michigan. Most unstable CAPE values are around 1000
J/KG. 850mb LI values of around -5C push into our area during the
midnight to 500am time frame. There is a chance that the upstream
convection will survive the lake trip given the fact that it will
likely be elevated. The lake boundary layer is very stable
obviously, but the convection will likely ride up over it as it
will be pushing east on the nose of the LLJ. Also, the upstream
shortwave will be aiding in large scale ascent.

Bottom line, expecting some showers and storms to roll into
western Lower Michigan around 100 am. There should be a gradual
diminishing trend as it moves in though, but some storms are
possible. Not expecting anything strong to severe given marginal
instability and deep layer shear.


.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

.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 06Z TAFS through 06Z Sunday night)
Issued at 1137 PM EDT Sat May 28 2016

Vfr conditions will continue overnight with scattered rain
showers. An isolated thunderstorm cannot be ruled out overnight
but storms over Lake Michigan are weakening with the only
lightning noted between KMKE and KORD. The diminishing trend will
continue and there is not enough potential for a storm to warrant
inclusion in any of the terminal forecasts for the overnight
period given radar/lightning trends.

An approaching cold front will cause scattered showers and
thunderstorms to develop Sunday afternoon and early evening.
Prevailing conditions will remain vfr but brief reductions to
mvfr/ifr flight categories are possible in heavier showers and

Showers and storms will taper off Sunday evening with vfr
conditions expected through 06Z Monday.


Issued at 1031 PM EDT Sat May 28 2016

Have let the Beach Hazards Statement and Small Craft Advisory
expire as winds and waves at the buoys are below criteria. Winds
right along the shore at the beach observation sites are gusty,
but these winds are not making it deep into the marine stable
layer. Therefore winds and waves at the Ludington and Muskegon
buoys are well below what would be considered hazardous.


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


.GRR Watches/Warnings/Advisories...


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