Area Forecast Discussion
Issued by NWS Grand Rapids, MI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KGRR 300940 CCA
AFDGRR

Area Forecast Discussion...CORRECTED
National Weather Service Grand Rapids MI
440 AM EST Wed Nov 30 2016

LATEST UPDATE...
Synopsis/Short Term/Long Term/Marine

.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 Octobver, 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 signficant 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 seeinglake
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 06Z TAFS through 06Z Wednesday night)
Issued at 1243 AM EST Wed Nov 30 2016

The region was VFR early this morning, with some very patchy MVFR
ceilings. Expect any MVFR ceilings will be lifting out of the
area by 07-08Z. VFR will prevail through the rest of the morning
and into the afternoon. A few showers may develop over the eastern
half of Lower MI toward mid day. These could impact LAN and JXN,
but should be rather light and scattered.  Southwest winds will
come up to around 10 knots into the afternoon and continue this
evening.

Ceilings are expected to lower by late afternoon and through the
evening hours as a trough approaches SW MI. MVFR ceilings are
expected to return after 22Z in the west and move across the
region by 03Z. Rain showers will also move in, but mainly across
the I-96 TAF sites. The lowering trend should continue and ceiling
may move into the IFR range after 04Z, especially west. Some snow
should mix in after 06Z.


&&

.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 232 PM EST Tue Nov 29 2016

Rainfall amounts ranged from roughly a half inch in the greater
Lansing area to over 2 inches in Oceana county. The only rivers
making a run toward bankfull are Sycamore Creek at Holt (cresting
Wed morning) and Maple River at Maple Rapids (cresting this
weekend). Very minor flooding in low lying areas adjacent to the
rivers is expected. Heavy precipitation is not anticipated until
at least 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...JK
HYDROLOGY...CAS
MARINE...WDM



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.