Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 050450

Area Forecast Discussion
National Weather Service Gaylord MI
1150 PM EST Sun Dec 4 2016

Issued at 957 PM EST Sun Dec 4 2016

Snow continues to fall across much of the forecast area this
evening...with some rain along the southeast Upper Michigan
shoreline as well as along the Lake Huron shore south of Alpena.
Back edge of the synoptic snow is approaching western Lake
Michigan...with the widespread precipitation expected to taper off
from west to east after midnight.  Bit of an interesting scenario
sets up for overnight...with enough cool air still in place to
allow for some lake convection to develop...aided by a well-
defined vorticity center in water vapor imagery tracking across
northern Wisconsin which should help stir things up. Meanwhile...
drying mid levels will lower probabilities of cloud ice particularly
from Grand Traverse Bay south. This brings in the possibility of
some drizzle/freezing drizzle across the interior where
temperatures are below freezing...though winds becoming more
westerly expected to allow some warming overnight as marine layer
gets advected inland.

So current plan is to allow for a transition to more of a lake
effect look especially across the tip of the mitt counties
overnight...while drying across across eastern Upper. Will leave
the Winter Weather Advisory in effect for eastern Upper...probably
could have had it for more areas given 2-4 inch snow amounts
having already fallen through mid evening across the area but with
snow winding down over the next several hours will let it go.


.NEAR TERM...(Tonight and Monday)
Issued at 356 PM EST Sun Dec 4 2016

High impact weather potential: Light to moderate snowfall through
tonight. Slippery roads.

Pattern synopsis and forecast:

Upper trough continues to become more negatively tilted as it works
into the western Great Lakes, with the associated sfc low crossing
nrn MN and a sfc trough pressing through the Mississippi. Forcing is
increasing via left front exit region jet dynamics and strong DPVA,
while deeper Gulf moisture feeds into the system. PWATS have
increased a little higher than thought yesterday, to near 0.60". The
strong deep layer forcing is evident in expanding >24 dbz echoes
along and south of M-72. This is also the region where there were
hints of strong lift in the DGZ, for bigger flakes/higher snow
ratios and better accumulations. The onset of the precipitation has
primarily been snow, as wet bulb effects/evap cooling quickly
brought middle 30s temperatures down into the lower 30s.

The upper trough lifts through nrn Michigan tonight with mid level
ridging settling in Monday. Snowfall will spread across all of nrn
Michigan over the next few hours, with a continuation of feeding two
areas of lake effect snow showers that have been going on since this
morning. One area in across western Mackinac county, and the other
in eastern sections of Chip/Mack, up the St. Mary`s. The signals for
strong lift in the DGZ continues in the evening as the upper
divergence and DPVA continue. Did increase snowfall amounts to 2-4"
with potentially higher amounts in those lake enhanced areas of
eastern upper. Still tough with some melting going on into evening,
and since snowfall rates are not expected to reach an inch per hour
for very long periods of time, getting a quick couple inches on the
ground to help will not be the rule. Roads will gradually become
snow-covered and slippery.

Snow will end late this evening across the GTV Bay region, and the
remainder of the region overnight, from SW to NE as the deeper
moisture aloft strips out, and the top of the moisture sinking below
-10c. Could see precipitation ending as a little drizzle/freezing
drizzle, especially in the higher terrain due to orographic lift in
developing westerly flow. There is also the increasing likelihood of
weak westerly flow lake effect into Monday morning, impacting far
nrn lower. Things try and dry out heading through Monday, maybe some
sun, but stratus and incoming higher cloud from the next shortwave
will already be moving in in the afternoon.


.SHORT TERM...(Monday night through Wednesday)
Issued at 356 PM EST Sun Dec 4 2016

...Colder air begins to ooze in later Tuesday into Wednesday...

It looks like it will take a couple of days but a change in the
pattern is shaping up for the middle and end of next week. This will
be in the form of a trough across the Great Lakes, along with colder
air and lake effect snow. The main short term forecast concern
revolves around when the lake effect machine will be turned back on.

Monday night into Tuesday...Northern Michigan will be squarely
between a northern stream wave moving by to our northwest and low
pressure moving by to our southeast. Meanwhile, warm advection
should put an end to any lingering southwest flow lake effect off of
Lake Michigan Monday evening (which would mainly effect eastern
upper). Low chance pops on Tuesday (for rain or snow showers) from
the combination of the two systems but not much if any actual
precipitation is expected at this point. Cold advection will begin
late in the day as the low pressure system moves by to our

Tuesday night into Wednesday...Steady cold air advection as the
incoming upper trough drops heights. It will turn cold enough for
chances for what looks like west southwest flow lake effect
Wednesday. However, models vary on the timing of the cold air as
well as the exact flow and amount of moisture (which looks limited
initially). Better moisture/over lake instability arrive Wednesday
night and especially on Thursday (see below). Temperatures will
remain well above normal through Wednesday.

.LONG TERM...(Wednesday night through Sunday)
Issued at 356 PM EST Sun Dec 4 2016

High Impact Weather Potential...Accumulating lake effect.

Primary concern through the extended remains the prolonged lake
effect snow possibilities. Cold H8 air will move overhead behind a
mid-week system, getting progressively colder going into the
weekend. Winds continue to remain NW for a couple of days before
backing to SW by Sunday. This will increase accumulations for NW flow
snow belts. Also seeing further enhancements in the form of
shortwaves moving through the flow that could increase accumulations
for some. This push of cold air will also bring below normal
temperatures, something we haven`t seen much of so far this year.


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1147 PM EST Sun Dec 4 2016

Snow is pulling away from northern Michigan...and with it
conditions should generally improve to MVFR flight category.
Expecting MVFR ceilings to persist into Monday morning...with an
improvement to VFR conditions during the afternoon.


Issued at 356 PM EST Sun Dec 4 2016

Rain and snow will continue into the evening, ending from SW to NE
late this evening through daybreak Monday morning. Southerly
winds will turn westerly by Monday with sporadic low end advisory
level speeds. Winds turn back southerly later Monday and Monday
night as low pressure lifts into srn Canada. Additional advisories
likely for Lake Michigan and Whitefish Bay, and again Tuesday and
through much of the remainder of the work week, in cold advection
and unstable conditions.


MI...WINTER WEATHER ADVISORY until 4 AM EST Monday for MIZ008-015.
LM...SMALL CRAFT ADVISORY until 1 PM EST Monday for LMZ323-341-342-


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