Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 121636
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1236 PM EDT Thu Oct 12 2017

LATEST UPDATE...
Hydro

.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 12Z TAFS through 12Z Friday morning)
Issued at 728 AM EDT Thu Oct 12 2017

Ceilings in the 1000 to 2500 feet AGL range will persist this
morning then conditions will gradually improve this afternoon
before becoming primarily VFR this afternoon. Lowering clouds late
tonight will again bring widespread MVFR and IFR conditions. Winds
will be 5 to 10 knots from the east this morning then going
southeast and south overnight.


&&

.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 1236 PM EDT Thu Oct 12 2017

We are monitoring the potential for heavier rains and possible
flooding for this weekend. A frontal system settling over the area
beginning Friday night and lasting into Sunday will bring multiple
periods of rain.

Precipitable water values will be about as high as possible by
mid-October standards with values over 1.5 inches expected. This
will bring the potential to see locally heavier downpours, and
some narrow bands of heavier accumulations through the period.
The axis of the heaviest rain for now looks to occur generally
north of a line from South Haven to Saginaw Bay. This is still
subject to change depending on where exactly the front sets up.
Right now, heaviest amounts looks to be over 2 inches, with some
areas possibly seeing locally up to 4 inches.

Thankfully this is displaced a little north from the heavier
rains earlier this week. We still could be looking at some minor
flooding.

&&

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

$$

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



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