Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 211745

Area Forecast Discussion
National Weather Service Grand Rapids MI
145 PM EDT WED SEP 21 2016


Issued at 330 AM EDT Wed Sep 21 2016

A warm front stretches this morning from the Minnesota/Iowa border
southeast into portions of Central Illinois. The warm front will
lift north today into Southern Lower Michigan which will increase
our chances for some showers and thunderstorms. The front will
remain over portions of Lower Michigan through Friday morning when
it will finally slip back south of the state. Chances for showers
and thunderstorms will exist from Today right into Friday. The
highest chances for precipitation will be across Central Lower
Michigan which will be in closer proximity to the front. It will
remain mild both Today and Thursday before we return closer to
normal temperatures for this time of year into the weekend.


Issued at 1046 AM EDT Wed Sep 21 2016

Line of showers and thunderstorms continue to move across the CWA
late this morning and were gradually weakening. Expect all areas,
with the exception of perhaps the far SE will see rain, so
increased POPs to likely for the eastern CWA.

This line was the leading edge of the higher low level moisture
and therefore we will see dew points remain in the 60s the rest of
the day, leading to a humid day. Feel we will slowly clear out,
especially south, helping temps to recover into the lower 80s.
Some mid 80 heat index readings will occur over the southern CWA.

As for additional rain chances later today, it appears we will be
worked over as the line falls apart by early/mid afternoon. Without
much of a trigger over the region, and waiting for the
instability to regenerate, it appears the next cluster of showers
and storms will remain to our west until late evening. So will go
with a dry forecast for the mid afternoon into early evening


.SHORT TERM...(Today through Friday)
Issued at 330 AM EDT Wed Sep 21 2016

Main forecast concerns revolve around precipitation chances and
areal extent of rain the next few days. A secondary concern is cloud
cover and how it will affect temperatures.

MCS in Wisconsin is working our way this morning although
instability is much less over our area as compared to MN/IA/WI.
Convection allowing models have been consistent in showing the
complex continuing to work our way this morning, slowly diminishing
as it does so. Thinking scattered showers and possibly an isolated
thunderstorm or two may work into the area this morning, but in
general a diminishing trend should be noted.

The warm front will remain across Central and Northern portions of
the state from tonight into Thursday night and will continue to  be
a focus for shower and thunderstorm development. The best
instability is actually this afternoon and then it tapers off each
period as we head into Friday. Thinking the current forecast looks
good with highest chances for rain north across Central Lower
Michigan 50-60 pct, diminishing to isolated or dry across the far

The front will drift south of the area on Friday which should take a
lot if not all of the precipitation with it. Regarding temperatures
thinking we will make another run to highs around 80 today and
likely again on Thursday as well, at least in the south. Warm air
advection may be enough to offset some of the mid and high clouds
that may be around.

.LONG TERM...(Friday night through Tuesday)
Issued at 330 AM EDT Wed Sep 21 2016

Forecast concerns deal with a couple of frontal boundaries that will
be moving across the cwa.

The first boundary is the washed-out cold front that will move north
as a weak warm front Friday night. We may see a shower from that but
chances are fairly low. Saturday looks basically dry with seasonable
temps in the lower 70s. Another cold front will approach Sunday
night and linger through Monday. The gfs pushes the front through
but the ecmwf is slower and may be the better solution given the
digging upper trough noted on both models. We`ll keep chc pops in
the grids through Tuesday to account for the slow moving cold front
and the trailing upper low. Highs in the upper 60s to lower 70s
expected Sun-Tue.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 145 PM EDT Wed Sep 21 2016

VFR conditions will prevail through the evening. There could be
areas of MVFR and even some IFR in fog late tonight if skies clear
out. Showers and thunderstorms are possible after 15Z Thursday but
the greater chances will remain north of MKG and GRR.


Issued at 330 AM EDT Wed Sep 21 2016

A southerly gradient that will producing winds of 10 to 15 knots
will likely produce waves of 1 to 3 feet on Lake Michigan from Today
into Thursday. The flow becomes off shore Friday into Saturday which
will also keep waves at a minimum in the nearshore. Not expecting
Small Craft conditions through Friday.


Issued at 330 PM EDT Tue Sep 20 2016

Hydro impacts through this weekend will be limited. Rain and
thunderstorm chances will exist Wednesday and Thursday, mainly north
of I-96. A frontal boundary draped across Central Lower Michigan
will be the focus for diurnally-driven shower/storm activity.

Total rainfall amounts will likely exceed half an inch (0.50 inches)
well to the north of I-96, affecting the Upper Muskegon River basin
and Pere Marquette River basin. Mostly within bank river rises
are expected.


.GRR Watches/Warnings/Advisories...


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