National Weather Service Raw Text Product

830 
FXUS63 KGRR 220547
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
147 AM EDT Sat Oct 22 2016

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 330 PM EDT Fri Oct 21 2016

A frosty night is expect across much of Southwest Michigan tonight.
Only some areas near the lake shore will escape the frost.  The cool
fall weather will continue into the weekend, but then we will have a
brief warmup on Sunday.  

The lake effect rain showers that have occurred along the lake shore
will slowly diminish overnight, with dry weather by daybreak
Saturday.  A weak system will cross the Great Lakes Sunday and areas
north of I-96 may see a few light rain showers in the afternoon,
otherwise it will be a dry weekend.  The next good chance of rain
should hold off until Tuesday night, lingering through Wednesday
night.

After daytime highs of 60 to 65 on Sunday, much of next week should
feature highs in the 50s.

&&

.UPDATE...
Issued at 1032 PM EDT Fri Oct 21 2016

Did not make much in the way of changes to the forecast for the
evening update. Maintained the Frost Advisory as is, although
there is quite a bit of cloud cover in place at the present time.
Models indicate that between about midnight and 6am we will at
least partially clear inland. The present fog imagery is not real
supportive of this, but given a downsloping northerly flow off of
the high ground of the Northern Lower Peninsula it is plausible.

Essentially thinking we will go partly cloudy for a time overnight
which should allow temps to sink into the lower to middle 30s away
from Lake Michigan. Dew points are in the low to middle 30s so if
we partially clear we should drop the 5 to 10 degrees needed for
frost formation quickly.

Clouds will begin to spread back in late as the flow turns
westerly and we advect lake stratocumulus back inland.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 330 PM EDT Fri Oct 21 2016

Frost is likely tonight, with some concern about the impacts of the
cloud cover.  The lake effect will continue along the lake shore,
but end or diminish to sprinkles by daybreak Saturday.  Then a short
will move through Sunday evening with a few showers possible ahead
of it.

Frost is of most concern tonight and whether the clouds will allow
for temps in the 30s.  Feel we will see a diurnal min in the cloud
cover shortly after midnight making the chances high to see low to
mid 30s across a large portion of the CWA.  Winds also decouple to
less than 5 mph at this time to allow for frost formation.  It does
appear some of the lake effect clouds will move farther inland just
prior to daybreak, along with a bit more mixing.  So many areas near
and west of U.S. 131 will probably see a min temp around 5 AM, with
a slow temp rise thereafter.  Will word these location as areas of
frost.  Better likelihood of a widespread frost east of U.S. 131 and
north of I-96.

As for the lake effect tonight.  The short wave was passing through
late this afternoon, with slowly falling inversion heights
thereafter.  However it looks like the showers do not completely
diminish until close to daybreak when inversion heights drop below
5K feet.  Can not rule out a wet snow flake will mix in toward
Highway 10.  Flow remains north to north northwest, so POPs only hug
the shore.

Quiet weather for Saturday and Saturday night with surface high
pressure moving across to our south.  The flow will go more westerly
so we will see the band of lake effect clouds move inland and erode
in the morning.  Otherwise expect partly cloudy skies.  A turn in
the winds to the southwest will prevent the region from getting as
cold Saturday night, and other than some patchy frost near Highway
10, there should be no risk.

Added POPs to areas north of I-96 for Sunday afternoon as a short
passes through.  This feature also has a surface low that tracks
near I-96 with light pcpn to it's north.  Skies clear out late
Sunday night, so again the risk of frost looks to be low.

.LONG TERM...(Monday through Friday)
Issued at 330 PM EDT Fri Oct 21 2016

To start the period...mid level heights will be on the rise as a
ridge approaches from the west.  Overall the flow will be confluent
which should act to result in dry weather.

Models show a shortwave topping the mid level ridge to our west on
Tuesday before digging and dropping into the Great Lakes region on
Wednesday. This system is looking rather dynamic. The GFS is a
little faster with this feature than the High Res Euro...but the
differences are not substantial. Based on the stronger height falls
and deep saturation...rain is forecasted to be on the increase.  It
looks like the instability remains south of the region so no
thunder...although will need to monitor trends here closely.  

For now the models height rises trying to move in for the end of the
week...although upstream considerable differences exist across the
upper plains for Friday.  The High Res Euro has a broad mid level
trough dropping out of the Canadian Prairies while the GFS feature a
large ridge over the same region.  As a result...considerable
uncertainty exists toward the end of the forecast period.

Without a deeper and stronger southwest flow...the temperatures will
struggle to go much higher than climatology.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 145 AM EDT Sat Oct 22 2016

Latest satellite imagery shows clouds continuing to scatter out
across the cwa. We'll likely see some cu form during the day, but
vfr conditions are expected. As high pressure moves east, north
winds will shift to the west. 

&&

.MARINE...
Issued at 330 PM EDT Fri Oct 21 2016

Will keep the headlines going for areas south of Holland tonight.
Waves should finally subside after midnight.  Much of the weekend
looks quieter on the lake with wind speeds mainly 15 knots or less.
We may need a small craft advisory into Sunday night as north winds
increase behind the passing low pressure.


&&

.HYDROLOGY...
Issued at 1133 AM EDT Fri Oct 21 2016

Recent rainfall did over perform near Jackson on Thursday.
However, it was not by much and hydro response were fairly brief.
All sites remained well within banks and most locations affected
by rainfall are now stabilizing or falling.

The next 5 days includes very little precipitation. It is not
until the middle of next week that Lower Michigan gets into a
wetter pattern. The current forecast plots the heaviest rain well
west of Lake Michigan, which will continue to be reassessed for
any potential changes in coming days.

There are no flooding concerns at this time.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Frost Advisory until 9 AM EDT this morning for MIZ037-043-050-
     056-064.

     Frost Advisory until 10 AM EDT this morning for MIZ038>040-
     044>046-051-052-057>059-065>067-072>074.

LM...Small Craft Advisory until 4 AM EDT early this morning for 
     LMZ844-845.

&&

$$

UPDATE...Duke
SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...MJS
AVIATION...04
HYDROLOGY...JAM
MARINE...JK