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Area forecast discussion 
National Weather Service Grand Rapids Michigan
150 PM EDT Sat may 30 2015

Latest update...
aviation

Synopsis...
issued at 327 am EDT Sat may 30 2015

A soaking rain is expected over all of southwest lower Michigan
today and over the central and southern sections of lower Michigan
into Sunday morning. A strong cold front comes through the area
during the midday hours of today... meanwhile a low pressure wave
on the front becomes a rather significant system tonight into
Sunday as it tracks northeast along the frontal system. This will
result in a prolonged rain event near and south of Interstate 96
this evening into Sunday morning. Much cooler air also moves into
the area at the same time so we will see falling temperature
across the area this afternoon behind the cold front. It will also
be breezy this afternoon into tonight. Once the system moves out
of the area Sunday afternoon skies will clear but it will remain
cooler than normal into midweek. Frost is possible in central and
norther sections Monday morning.

&&

Short term...(today through monday)
issued at 327 am EDT Sat may 30 2015

As I suspected yesterday... that southern stream wave (mcv) will
not damp out as quickly as the models had forecast it to yesterday.
The result will be rain and plenty of it near and south of
Interstate 96 this afternoon into Sunday morning. Some area near
and south of Interstate 94 could see over 2 inches of rain for a
storm total between 8 am Saturday and 8 am Sunday (wpc 24 hour quantitative precipitation forecast
forecast).

The combination of a digging northern stream polar jet wind maximum
and associated shortwave and a shearing out southern stream wave
(mcv) over OK early this morning will try to phase together by
Sunday afternoon. This is a classic setup with Gulf moisture being
forced over Canadian polar air with a cold conveyor belt easterly
wind on the north side of the system enhancing the rainfall. The
jet entrance region will help to cause significant middle-level fgen
tonight into Sunday morning between I-94 and I-96. There will be a
40 knot low level jet on the front side of the surface wave to
help push the moist Gulf air over the front. Condensation pressure
deficits fall to near 0 mb over the I-94 to I-96 area tonight into
middle morning Sunday as a 30 knot winds lifts the air isentropicallyover
the frontal surface. With precipitable water vales near 150
percent of normal there will be little problem creating bands of
heavy rainfall.

There will be a significant amount of wind this afternoon into
tonight as the cold air comes in and the surface wave deepens.
Temperatures will fall into the 50s across the area this
afternoon.

There will be a few showers and isolated thunderstorm (limited
instability) early to middle morning ahead of the cold front but I
do not expect much out of this expect scattered areas of rainfall.

The system lifts out of the area Sunday night as Canadian high
pressure moves in. We could see frost over the northern and
central sections Monday morning.

Long term...(monday night through friday)
issued at 327 am EDT Sat may 30 2015

High pressure will produce fair weather Monday night through
midweek. Temperatures will undergo a gradual moderating trend
next week as southerly return flow develops on the back side of
the departing high pressure ridge. Dry weather will prevail through
Wednesday and most likely through most of Thursday.

There is potential for some showers and storms to develop late in
the week as continued southerly flow will result in increasing
moisture. This in conjunction with some instability and a frontal
boundary extending into our region late this week will bring the
chance for some showers and storms. Maximum temperatures by Wednesday through
Friday should reach the lower to perhaps middle 80s with gradually
increasing humidity levels by late week.

&&

Aviation...(for the 18z tafs through 18z Sunday afternoon)
issued at 150 PM EDT Sat may 30 2015

IFR conditions will prevail through tonight as rain and low
clouds will be widespread. Conditions will slowly improve Sunday
morning as drier air moves in from the north. Winds will go north
or northeast and increase this afternoon with gusts over 20 knots
continuing through Sunday morning.

&&

Marine...
issued at 327 am EDT Sat may 30 2015

I issued a Small Craft Advisory for today through Sunday for 15 to
25 knots of wind and waves to 6 feet.

&&

Hydrology...
issued at 322 PM EDT Friday may 29 2015

River levels range from above normal in our northern hydrologic
service area to below normal Southeast. Basin-average rainfall
through Saturday evening is likely to be around a half to three-
quarters inch. Per ncrfc ensemble guidance... basin-average totals
of about 2 inches would be necessary to push several of the middle-
Michigan rivers above bankfull.

&&

GRR watches/warnings/advisories...
Michigan...Beach hazards statement through Sunday afternoon for miz037-043-
050-056-064-071.

Lm...Small Craft Advisory until 6 PM EDT Sunday for lmz844>849.

&&

$$

Synopsis...wdm
short term...wdm
long term...Laurens
aviation...ostuno
hydrology...cas
marine...wdm

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