Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 201936 CCA

Area Forecast Discussion
National Weather Service Grand Rapids MI
330 PM EDT TUE SEP 20 2016

Synopsis/Short Term/Long Term/Hydro/Marine

Issued at 330 PM EDT Tue Sep 20 2016

After a quiet overnight period, scattered showers and thunderstorms
will become possible on Wednesday and linger through Thursday night.
The most commonplace rainfall will occur over Central Lower, with
less rain as one heads south.  Very little, or even no rain may
occur toward I-94 through Thursday night.

The scattered rain may linger until Friday evening before we finally
dry out for a what looks like a quiet weekend.  Another chance of
rain moves back in for Sunday night.

Wednesday and Thursday will remain warm, with highs in the upper 70s
to lower 80s, but then we will cool down.  Highs will mainly be in
the upper 60s to lower 70s Friday through Tuesday.


.SHORT TERM...(This evening through Thursday night)
Issued at 330 PM EDT Tue Sep 20 2016

Rain chances return early Wednesday and linger into Thursday night
as a surface boundary hangs up over the region.

High pressure will drift off to the east overnight as a slow moving
front sags SE across the U.P.  We will begin to see moisture
advection by daybreak and an increase in mid level clouds.  We may
even see an isolated shower or storm advance toward the lakeshore by
daybreak Wednesday.

The front stalls over Northern or Central Lower Wed and Thu before
finally drifting a bit south Thu night.  Much of the pcpn will be
concentrated near the front.  Upper waves will travel along it, but
they appear to weaken as they head our way, being much stronger over
MN/WI/IA.  Will continue to feature highest POPs across Central
Lower with placement of the front, but a bit more widespread rain
should be seen late Thursday night with the front advancing a bit
south.  Also expect to see an enhanced rain late Wednesday afternoon
into Wednesday night across Central Lower with moderate upper
divergence sliding across from the upper jet.

High temps will be tricky over the next couple of days, largely
depending on the amount of sun that occurs.  Mid 80s are certainly
possible with enough sun, which may occur in the far south.  But
overall expect more upper 70s to around 80 to occur with a fair
amount of clouds around.  Therefore I did lower max temps for Wed in
most places.

.LONG TERM...(Friday through Tuesday)
Issued at 330 PM EDT Tue Sep 20 2016

Plains cyclogenesis may increase mid level warm advection/isentropic
ascent enough to bring showers Friday night into Saturday. This is
followed by shortwave ridging ahead of the western CONUS upper
trough and generally fair weather Saturday into Sunday.

Precip chances increase again Sunday night and Monday as heights
fall and sfc cold front/prefrontal trough moves in. There is still
low confidence here as ensemble spread continues to be large and the
precip may hold off until Monday night and Tuesday as indicated by
the slower solutions.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 204 PM EDT Tue Sep 20 2016

VFR conditions will prevail through this evening. Some shallow fog
may form again tonight with areas of MVFR and isolated IFR
conditions by 12Z. Winds will be light and variable.


Issued at 330 PM EDT Tue Sep 20 2016

Winds will be fairly light through the short term and will become
offshore.  So no headlines are expected.  However 2-3 foot waves
will be possible Wed afternoon north of Grand Haven with a south
flow around 15 knots.


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...


LONG TERM...Ostuno
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