Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 120730
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
330 AM EDT Thu Oct 12 2017

LATEST UPDATE...
Synopsis/Short Term/Long Term/Marine

.SYNOPSIS...
Issued at 330 AM EDT Thu Oct 12 2017

There will be scattered showers tonight but widespread rain
is not expected until later on Saturday when low pressure
approaches Lower Michigan from the west.

&&

.SHORT TERM...(Today through Saturday)
Issued at 328 AM EDT Thu Oct 12 2017

Hemispheric wave train of strong lows will be featured across
North America the next week or so with one of the storms
affecting lower Michigan this weekend with another one to two inch
rain event expected.

Showers tonight should not amount to much as shortwave upper
ridging is in place and best isentropic ascent is north of the
forecast area. Stronger area of warm advection forms on Friday
night and Saturday along and north of wavy front draped across
Lower Michigan. Elevated instability increases Friday night and
may be surface based in Saturday if there are breaks in overcast.
Severe threat appears low due to marginal instability although
forecast profiles show 35 to 40 knots of 0 to 6 km shear.

.LONG TERM...(Saturday night through Wednesday)
Issued at 314 AM EDT Thu Oct 12 2017

Surface low pressure is expected to track NE across WI and toward
the Eastern U.P. Saturday night, then pulling a cold front through
the CWA early Sunday.  This system will give the region another
solid soaking rain, particularly for areas closer to the surface
low, north and west of Fremont where upwards of two inches of rain
will be possible. The heavier rains will taper off to the SE.  The
system has potential for a narrow frontal rain band, but given the
timing of the front, this seems somewhat unlikely.  Even so, will
carry thunder with favorable jet dynamics in the lower and upper
levels.

There are some timing differences with the front, so we may see
falling temps Sunday, or certainly by late day, as H8 temps are
shown to drop from +15C Saturday night to around 0C by Sunday night
and Monday. Monday`s highs should only be in the mid and upper 50s.
But this appears to be a quick shot of chilly air as temps already
should moderate by Tuesday.  By then high pressure will be in
control of the eastern third of the nation and return flow will
bring warm advection.  Expect dry weather for mid week with temps
back to near normal Tuesday and perhaps a bit above normal by
Wednesday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 115 AM EDT Thu Oct 12 2017

Much of the region was blanketed by MVFR ceilings, with some
patchy IFR. This trend should continue much of the next 24 hours.
However expect more IFR as we see a nocturnal lowering of the
ceilings through the early morning.

Then ceilings should trend upward a bit mid/late morning to mostly
MVFR. However due to the lessening winds and strengthening
inversion, these clouds/ceilings should remain over the region
through the day and into the evening.


&&

.MARINE...
Issued at 330 AM EDT Thu Oct 12 2017

Winds and waves will be below SCA criteria through Friday night
but could ramp up Saturday and Sunday as sfc low moves through.

&&

.HYDROLOGY...
Issued at 329 PM EDT Wed Oct 11 2017

Widespread rainfall of one half to inch fell across West
Michigan overnight into this morning...with isolated amounts in
excess of two inches west of US-131. Even with the recent dry
weather...runoff was sufficient to produce rises on area
rivers..but we do not expect any of the area rivers to reach
action stage.

While the latest model data suggests scattered showers will be
possible Thursday...coverage and amounts are not expected to
produce impactful rises on area rivers. Precipitation associated
with a cold front this weekend has a greater potential to produce
significant runoff...which could produce stronger rises on area
rivers. This situation will need to be watched closely.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&

$$

SYNOPSIS...Ostuno
SHORT TERM...Ostuno
LONG TERM...JK
AVIATION...JK
HYDROLOGY...MWS
MARINE...Ostuno



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