Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 301900
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
200 PM EST Wed Nov 30 2016

LATEST UPDATE...
Hydro

.SYNOPSIS...
Issued at 329 AM EST Wed Nov 30 2016

Expect a trend toward cooler weather over the next few days.
Today should see considerable clouds but still mild for this time
of year. Tonight the colder air really starts to move in on west
winds so we will see lake effect rain showers over western
sections into Friday morning. The rain may mix with wet snow at
time during the night time hours both tonight and tomorrow night.

A system moving through the area Sunday may bring a little snow
to the area but accumulations will be limited. A much stronger
system will move through the Great Lakes early next week. That
will bring another warm surge Monday into Tuesday with the threat
of more rain by Tuesday. Much colder weather is expected by late
next week.

&&

.SHORT TERM...(Today through Friday)
Issued at 329 AM EST Wed Nov 30 2016

The main issue with this forecast is the treat for precipitation
that is lake enhanced tonight into Friday morning. One has to
wonder if we will see any snow from this event.

That large slow moving storm system to our west and northwest has
finally moved far enough east to bring the cold air to our door
step (so to say). We will see what will be like a dry surge behind
an occluded front today. An isolated shower or two (seen on the
HRRR) may be possible over eastern sections late morning or early
afternoon as the leading edge of the cold air slowly moves east.

Tonight we finally get into the cold air and this will bring deep
moisture and lift to the area. Given the deep moisture and strong
lift, there is no question in my mind, there will be rain showers
after 10 pm that will continue through most Thursday into Thursday
night. This time, unlike on the 19th, will not be nearly as cold,
so the threat for snow will be marginal at best. There is good
lift but it well below the DGZ, so that means mostly rain in this
area. Surface temperatures will have a hard time getting below 35
degrees (needed to really see any snow). The deep moisture is
east of the area by Friday but we still have cold air on a west
wind with nearly saturated air through 5000 ft or so. Thus showers
will continue.

.LONG TERM...(Friday night through Tuesday)
Issued at 329 AM EST Wed Nov 30 2016

With cyclonic flow continuing into the first part of the weekend,
the light lake effect snow showers should also continue.  However
any accums appears to be light, and mainly confined to areas north
of a Whitehall to Clare line.  The flow gradually goes more
anticyclonic by Saturday afternoon when most of the snow showers
should end.

The models are in much better agreement into early next week, no
longer showing any significant storm. A short wave and cold front
should approach the western Great Lakes by Sunday/Sunday night.  We
should begin to see a warm advection snow move into area through the
day. This appears to become mixed with rain across southern Lower,
but may stay snow across Central Lower.  Then as the front comes
through the pcpn should end late Sunday night.  This should be a
quick hitter that may put down a couple inches of snow for areas
that remain all snow.

Good agreement remains through Monday/Monday night as the models
show upper ridging moving in behind the Sunday system.  This will
bring us warmer temps for Monday and Tuesday.  A similar looking
system as Sunday`s should arrive on Tuesday but this time rain looks
more likely, with some snow possible across Central Lower.

.WEEK TWO...(Wednesday through Tuesday)

A change toward a more persistently colder than normal
temperatures is expected during this time frame. This pattern
change should last into the new year.

The mostly warmer than normal temperatures we have been seeing
over southwest Michigan since last September (2015) is about to
come to an end. This change has been consistently shown by the
GFS and ECMWF over the past few days and in fact the latest long
range ECMWF (28th of November) shows the colder temperatures
(highs below freezing) continuing into mid January. Part of the
reason for this change is the significant changes in the sea
surface temperature anomalies over the northern Pacific Ocean. For
the most part most of the northern Pacific Ocean, even north to
Alaska has been warmer than normal through the summer into mid
fall. Since October, most of northern Asia has been 10 to 20
degrees below normal with unusably large amounts snow cover, which
as persisted through November. That cold air over Northern Asia
has resulted in a significant cooling over the North Pacific Ocean
north of 35N, from the Asian coast nearly to the west cost of
North America. This cooling coupled with the developing weak La
Nina will result the upper level wave pattern change that will
favor a trough over eastern North America from mid December into
at least early January (as seen on the ECMWF ensemble mean
forecast for 500 height and 850 temperatures). It is that pattern
change that will bring us the colder than normal temperatures.

Both models have suggested a significant storm event during the
late next week ( Thu- Fri). It is way to early to suggest impacts
from this storm but it is typical to have a major storm ahead of a
major upper level wave pattern change. It would seem to me if this
colder than normal pattern change does occur we will be seeing
lake effect snows once the cold air arrives. The ECMWF ensemble
mean has highs below freezing starting on the Thursday and
continuing through the following Wednesday.

We will continue to watch to see how this pattern change evolves
over the next week or so.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 119 PM EST Wed Nov 30 2016

A variety of conditions are occurring across Southwest Lower
Michigan at 18z. An area of IFR ceilings has just lifted towards
KLAN and KJXN. Much of the area is seeing clouds fill back in, in
a dry slot with ceilings that are mainly in the 2000-3000ft layer.
This should continue to be the trend of more and more in the way
of MVFR clouds. A much more widespread overcast will then spread
in this evening between 21z and 01z.

The widespread overcast will be MVFR and is associated with colder
air filtering in from the west. The colder air will develop rain
showers off of Lake Michigan. These rain showers may mix with a
bit of snow late tonight into Thursday morning, but did not
include yet as the dominant precip type should be rain. The
outlook for Thursday is more MVFR ceilings with lake effect rain
showers continuing.


&&

.MARINE...
Issued at 329 AM EST Wed Nov 30 2016

I issued a small craft advisory for tonight through Thursday night
since west winds of 15 to 25 knots with cold advection mean 4 to 6
foot waves. There is little question about this so I figured I
may as well put the headline out.


&&

.HYDROLOGY...
Issued at 200 PM EST Wed Nov 30 2016

Sycamore Creek at Holt has crested a few inches above bankfull and
is now receding. Maple River at Maple Rapids continues its slow
rise toward bankfull. Only light lake enhanced precipitation is
expected this week, but it will not affect river levels. There
will be chances for more substantial precipitation next week.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory from 7 PM this evening to 4 AM EST Friday
     for LMZ844>849.

&&

$$

SYNOPSIS...WDM
SHORT TERM...WDM
LONG TERM...JK
AVIATION...Duke
HYDROLOGY...CAS
MARINE...WDM



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