Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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462
FXUS63 KGRR 011206
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
706 AM EST Thu Dec 1 2016

LATEST UPDATE...
Update/Aviation

.SYNOPSIS...
Issued at 329 AM EST Thu Dec 1 2016

The trend toward cooler temperatures continues today. Highs will
mostly be in the upper 30s to near 40. Lake enhanced rain
shower, mixed at times with snow inland of Lake Michigan will
continue through the day. Tonight colder air comes in and most
locations should see some snow overnight. Accumulations will be
less than an inch. The showers of mixed rain and snow will
continue into Saturday before finally coming to an end, if only
for a shore time. The next upstream system may bring some snow to
the area Sunday but another strong central plains storm will surge
in warm air early next week before we finally see the arctic air
that has been over Siberia for over a month reach Michigan in the
Thursday time frame.

&&

.UPDATE...
Issued at 705 AM EST Thu Dec 1 2016

I have updated the forecast for colder temperature and more snow
into mid morning. At our office the precipitation changed to all
snow just after 6 am, when the precipitation got a little heavier.
Our air temperature fell to 34 degrees while this happened. It is
apparent the models are struggling with the precipitation type as
they did with the last event on the 19th. This time the air is a
touch warmer so I do believe we will see the showers become all
rain this afternoon only to go back to snow showers later tonight.
However tonight the moisture is not quiet as deep even so there is
enough lift to keep precipitation occuring even so.

There are two shortwaves that have to come through, the first one
is coming through now the next one comes through this evening and
that will enhance the precipitation rates once again.  I also still
believe the temperatures will mostly stay above freezing and the
precipitation rates should not be high enough for significant snow
accumulations.



&&

.SHORT TERM...(Today through Saturday)
Issued at 329 AM EST Thu Dec 1 2016

Little question about the forecast for the next 48 hours... cloudy
temperatures in the 30s and showers mixed at times with snow
likely becoming all snow (except alone the lake shore) Friday
evening before ending Saturday afternoon.

The deep moisture is in the area through late today, then that
moves out but we remain in surface through 850 mb cyclonic flow
continue into Saturday. The coldest air moves in Friday night into
Saturday. There are two periods of good lift, during the mid
morning of today and overnight as the upper level jet moves across
the area. During those times we will see the greatest
precipitation coverage and intensity. However most of the lift is
below the DGZ so I do not expect much in the way of snow.

All of this moves out by late Saturday afternoon. It will however
remain cloudy.

.LONG TERM...(Saturday night through Wednesday)
Issued at 329 AM EST Thu Dec 1 2016

Surface and upper ridging builds into the area Saturday night,
bringing an end to any lake effect snow showers.  However the break
will be short as another system will be close on it`s heels by mid
day Sunday.  The progressive pattern brings a northern stream short
wave into the Western Great lakes by Sunday with favorable warm
advection ahead of a cold front.  This should bring a period of pcpn
to all of SW MI Sunday afternoon and evening.  The forecast
soundings favor mostly snow, which may mix with rain at times.
Surface temps should be in 35 to 40 so it may be hard for the snow
to accumulate other then on grassy areas.  Seems like an inch or
less will be all we can expect.

Temps should warm further into Monday and Tuesday with another ridge
building over SW MI.  Monday appears dry, but then rain should
arrive on Tuesday.  The models are showing the same theme that the
ridge slides to the east and we develop deep SW flow which brings a
Western Gulf surface low into the Great lakes by Tuesday.  The
consensus shows the low staying to our west allowing us to remain all
rain for this event into Tuesday night.  We should be in between
systems on Wed.

Beyond the long term, into late next week, the next system appears
to bring an arctic surge across the Great Lakes with H8 temps
plunging to around -15C by Thursday night.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 705 AM EST Thu Dec 1 2016

With persistent lake effect rain and snow showers into Saturday,
I have to believe MVFR conditions will dominate the taf site
weather observations. When the precipitation becomes all snow
conditions will be IFR, this will mostly be during the mid
morning hours of today and tomorrow. Also the LAN taf site is
mostly out of the rain/snow bands so conditions there will be a
little better for the most part.

&&

.MARINE...
Issued at 329 AM EST Thu Dec 1 2016

Cyclonic flow with colder air moving on mostly westerly to
northwest winds to keep our Small Craft Advisory going into early
Friday morning. It may have to be extended but at this time
marginal enough not to do (extend the end of the SCA).


&&

.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 until 4 AM EST Friday for LMZ844>849.

&&

$$

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



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