Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 270547
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
147 AM EDT TUE SEP 27 2016

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 300 PM EDT Mon Sep 26 2016

Seasonably cool weather will continue through the rest of the week
along with a considerable amount of cloud cover and scattered rain
showers. The best chance for rain will come late Tuesday through
Wednesday. High temperatures will reach the 60s through the rest
of the week.

&&

.SHORT TERM...(This evening through Wednesday night)
Issued at 300 PM EDT Mon Sep 26 2016

Windy conditions will continue through late this afternoon into
early evening as deep mixing continues. Wind speeds will diminish
after sunset.

Lake induced stratocu will move into our northern fcst area late
this afternoon through tonight as suggested by 12z nam/gfs low
level rh progs and as h8 temps continue to fall to around 3 to 4
C. Scattered rain showers will also develop over our northern fcst
area tonight as the upper low moves further south and as lake
induced instability increases.

The upper low and associated deep moisture/colder air aloft will
continue to sink further south across our fcst area Tuesday.
Therefore extensive stratocu will continue to develop and move
further south. Showers will increase in coverage from north to
south Tuesday afternoon through Tuesday night.

A few thunderstorms are possible as well tomorrow afternoon and
evening due to instability from daytime heating and as the pool of
colder air aloft tied to the upper low moves in.

The lake component to the pcpn will be lost Wednesday as sfc winds
become northeasterly with the sfc low over Ohio by then. However
it will remain mostly cloudy and cool with numerous showers
through the day with the upper level low overhead.

Several vorticity maxima pinwheeling around the upper low will
enhance showers from time to time through the day. We lowered the
max temp fcst for Wednesday as met/mav numerical guidance is several
degrees too mild given the synoptic pattern and extensive
clouds/showers/ne winds by then.

.LONG TERM...(Thursday through Monday)
Issued at 300 PM EDT Mon Sep 26 2016

The main feature to impact the weather in the long term will be the
mid level low that is currently tracking into the region.  Trends in
the model data suggest that the low will persist longer than
previously forecasted.  Both the GFS and new High Res Euro have this
feature over north central Kentucky to start the period.  The on
Saturday morning the system is shown to be generally in the Indiana
to Ohio region.  With cyclonic flow aloft...relatively low heights
in place and a moist airmass around...there will be some showers in
the Great Lakes Region right into Sunday.  Unseasonably cool
temperatures are for the most part expected.

For now...will feature a dry forecast for Monday.  If models trend
in a similar fashion as they have this week...we may need to add
showers in for Monday as well.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 147 AM EDT Tue Sep 27 2016

The main aviation concern into Tuesday will be brisk WSW winds
that will occasionally gust to 25 knots by daybreak and through
much of the afternoon.

Cloud ceilings will begin to lower from the north by late
afternoon and through the evening hours. This will also come with
scattered rain showers. An isolated thunderstorm will also be
possible, but was not added to the TAFs at this point. Some MVFR,
and possible patchy IFR, is expected to develop toward midnight.

&&

.MARINE...
Issued at 300 PM EDT Mon Sep 26 2016

A small craft advisory remains in effect through early Wednesday
morning. Brisk west winds to 30 kts in conjunction with relatively
cool air moving across unseasonably warm Lake MI waters will
result in wave heights in the 6 to 10 foot range through tonight
and Tuesday. Waterspouts and a few thunderstorms are possible
Tuesday afternoon through Tuesday night as the coldest air aloft
tied to the upper level low moves over the lake.


&&

.HYDROLOGY...
Issued at 300 PM EDT Mon Sep 26 2016

River levels are around normal for this time of year. Lake effect
showers are possible this evening into Wednesday. Rain showers are
possible Thursday into Sunday. With less than a half inch of rain
expected through the end of the week, rivers and streams should
remain below bankfull into the weekend.

&&

.GRR Watches/Warnings/Advisories...
MI...None.
LM...Small Craft Advisory until 8 AM EDT Wednesday for LMZ844>849.

&&

$$

SYNOPSIS...Laurens
SHORT TERM...Laurens
LONG TERM...MJS
AVIATION...JK
HYDROLOGY...63
MARINE...Laurens



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