Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 230551
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
151 AM EDT FRI SEP 23 2016

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 305 PM EDT Thu Sep 22 2016

A nearly stationary frontal boundary over the Great Lakes region
will move slowly south Friday and bring scattered rain showers
and perhaps a few thunderstorms through Friday. A few showers may
linger into Saturday before fair weather briefly returns. However
a cold front will bring potential for more showers Sunday night
through Monday and will be followed by the arrival of a cooler
airmass for the middle of next week.

&&

.SHORT TERM...(This evening through Saturday night)
Issued at 305 PM EDT Thu Sep 22 2016

A quasi stationary frontal boundary over central lower Michigan
will focus development of scattered rain showers and perhaps a few
thunderstorms late this afternoon and tonight mainly north of
Interstate 96.

Convective potential is mitigated significantly by several
factors including weak instability and lack of stronger forcing.
Greater low level moisture remains focused well to the west of our
area across eastern Iowa/southern WI.

The boundary will sink slowly south Friday and bring continued
potential for scattered showers and perhaps an isolated storm.
Once again convective potential tomorrow remains low given weak
instability and lack of stronger forcing as winds will switch the
ne once the front moves through.

A few showers may linger on Saturday as suggested by short range
guidance trends and the 12Z ecmwf. However only low pops are
warranted and most of the day should be dry.

.LONG TERM...(Sunday through Thursday)
Issued at 305 PM EDT Thu Sep 22 2016

Heights begin falling late Sunday as shortwave upper ridging moves
east of Lower Michigan to eventually be replaced by a trough or
closed upper low later next week. There is a slight chance of
showers Sunday afternoon and night but the bulk of the showers may
hold of until Monday.

There continues to be a lot of model spread on how the upper
trough/low evolves and this meant spreading POPs out over much of
the period, as the model blend accounts for the wide range of
solutions. With the way the operational runs have flip flopped
between yesterday and today this seems that way to go until a more
coherent picture develops.

If the more blocky solutions verify, such as the 12Z GFS, max temps
would have to be lowered Wednesday and Thursday as the upper low
spins across Lower Michigan. Waterspouts on Lake Michigan would also
be likely in that scenario.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 151 AM EDT Fri Sep 23 2016

Our main focus in the 06z fcsts is on the lower conditions
expected this morning. Mid and high clouds are moving out with the
front passing through the area. The temporary clearing and light
winds are allowing for some fog to form from NW to SE. We are
expecting lower clouds to move in from the north in the next few
hours. This should stabilize the fog a bit, but bring MVFR to
possibly IFR cigs.

Once the low clouds move in, they will be around most of the day.
They will tend to slowly and gradually lift through the day,
becoming VFR toward 00z this evening. Winds will generally be
from the NE through today. Wind speeds should remain at or below
12 knots.

&&

.MARINE...
Issued at 305 PM EDT Thu Sep 22 2016

Fairly minimal wave heights of around 1 to 3 feet are anticipated
tonight through Friday with relatively higher wave heights within
that range well offshore Friday as winds become easterly at around
5 to 15 kts.


&&

.HYDROLOGY...
Issued at 305 PM EDT Thu Sep 22 2016

Hydro concerns are minimal through the weekend, as heavy rain is not
expected. The potential for thunderstorms is low, limiting the
threat for localized heavy rainfall. Rivers and streams will remain
below bankfull.

&&

.GRR Watches/Warnings/Advisories...
MI...None.
LM...None.
&&

$$

SYNOPSIS...Laurens
SHORT TERM...Laurens
LONG TERM...Ostuno
AVIATION...NJJ
HYDROLOGY...EBW
MARINE...Laurens



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