Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 222331
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
731 PM EDT THU SEP 22 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 00Z TAFS through 00Z Friday evening)
Issued at 731 PM EDT Thu Sep 22 2016

Currently VFR conditions prevail across the CWA and it would seem
this should be true most of the night too. However toward morning
and cold front will slip south from northern lower Michigan
bringing low clouds and maybe some drizzle and fog too. So, the
latest TAFs are not all that different from the previous version,
around 12z or so I bring in IFR/MVFR cigs to most of the TAF
sites. The models suggest the low clouds will mix out by mid to
late afternoon, I am not sure about that but did put it in the
TAFS.

&&

.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...WDM
HYDROLOGY...EBW
MARINE...Laurens



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