Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 120451

Area Forecast Discussion
National Weather Service Gaylord MI
1151 PM EST Sat Nov 11 2017

Issued at 1052 PM EST Sat Nov 11 2017

Sault Ontario reporting a snow/freezing rain mix at this hour,
indicative of mid level moisture getting stripped away. Beaver
Isl is meanwhile claiming rain at 34f (which is reasonable, though
with the AWOSs you can never be quite sure). Have accelerated the
mention of freezing/liquid precip in nw sections.

UPDATE Issued at 903 PM EST Sat Nov 11 2017

Lake effect banding was still poking into far western Mack Co a
couple of hours ago, but with mid level moisture stripping out
that has further weakened. The long marine fetch is also pushing
temps above freezing, 36f in Naubinway presently. Have cancelled
the wint wx advis in Mack Co a bit early.

Synoptic light snow is thinning out across ne lower MI, as forcing
shortwave becomes more sheared. Deeper moisture will exit in the
next couple of hours, but low clouds are abundant. Cigs are
lowering in northern sections, in weak 1000-850mb convergence
ahead of a decaying cold front. That will be favorable for some
DZ/FZDZ tonight, especially after midnight, with FZDZ more likely
away from the immediate Great Lakes coastlines.


.NEAR TERM...(Tonight through Sunday)
Issued at 346 PM EST Sat Nov 11 2017

High impact weather potential: Continued accumulating snows into
western Mackinac county, and to some degree Chippewa county through
this evening. Blowing snow at times, with difficult driving
conditions along portions of US-2.

Pattern synopsis and forecast:

Nice compact shortwave is working eastward into Lake Superior this
afternoon, resulting in generally light synoptic snowfall across nrn
Michigan. Low level southerly winds are starting to undergo added
convergence with the approach of the wave, while overlake
instability remained sufficient for enhanced lake effect snows into
primarily western Chip/Mack counties of eastern upper (Delta T`s of
17C or so). Snowfall has recently tapered off across NW lower around
the GTV Bay region, with overlake instability in WAA approaching
more marginal levels. Further upstream there was another mid level
trough with an associated cold front working through MN.

The initial compact shortwave crosses late in the afternoon through
evening with convergence tightening even further in the low levels,
but deeper moisture will be starting to strip out aloft early in the
evening (can already see it in latest IR imagery) across eastern
upper. Winds will also be veering slightly more westerly, which will
shove that band a bit more into Chip/Mack counties, but will be
weakening. Thus, most of the greater impact of the better snows
ought to be completed over the next handful of hours. Will keep the
current winter weather advisory going until this process completes
later this evening. Total snowfall not to change, ranging from 2-4
with locally higher amounts in western Mack county, decreasing
rapidly to the east. Chances for snow drop off through the night as
moisture strips out aloft even further from W to E, leaving most of
nrn Michigan in more of a drizzle/freezing drizzle scenario. After
further inspection, best chances for seeing drizzle, may not only be
in the interior highlands of nrn lower due to upslope, but also
along the aforementioned upstream cold front that trickles in the NW
lower coastline nearing daybreak. Some semblance of weak low level
troughing lingers over the area through Sunday, with deep low level
moisture also hanging around, so cannot rule out drizzle at any
point during the day tomorrow.

Lows tonight in cloudy skies, in the upper half of the 20s to lower
30s. Highs tomorrow in cloudy skies, in the upper half of the 30s
most areas.


.SHORT TERM...(Sunday night through Tuesday)
Issued at 346 PM EST Sat Nov 11 2017

...Cloudy, foggy, and damp conditions...

High Impact Weather Potential...Additional freezing drizzle possible
Sunday night into Monday morning, particularly near Lakes Michigan
and Superior. Areas of fog both Sunday and Monday nights.

Pattern Synopsis/Forecast...Slightly colder air at 850mb will
continue to spill into the region Sunday night into Monday as
surface high pressure upstream allows for continued weak cold air
advection. The high will slide overhead on Monday before pushing
east of the area by Tuesday, leading to a switch to warm air
advection and some moderation in temperatures.

Primary Forecast Concerns...Continued drizzle/freezing drizzle
potential Sunday night into Monday morning as well as fog concerns
through much of the period.

Forecast soundings across northern Michigan Sunday night into Monday
continue to show a shallow, nearly saturated layer from the surface
up through about 1 to 1.5 km but below -10C, so no ice in the
clouds. This suggests a continued potential for drizzle/freezing
drizzle, especially near Lakes Michigan and Superior where lake-
induced troughing will yield an axis of weak convergence, which is
resulting in models continuing to spit out some light QPF in those
areas. Low level wind field continues to look anemic, however, so
lift from any convergence or upsloping will be weak. Not expecting
any significant impacts from patchy freezing drizzle Sunday night as
QPF and icing amounts are expected to be very light, but suppose
exposed surfaces could become a little slippery in spots.

Do expect plenty of low stratus in the area through Monday night.
The surface high drifting overhead will also yield a good chance for
fog both Sunday and Monday nights, thanks to all that moisture
trapped in the low levels beneath a strong inversion above 850mb.
Additional moisture from any snowmelt that occurs on Monday as
temperatures climb above freezing will further enhance fog potential
for Monday night. The SREF continues to show decent potential for
reduced visibilities both nights, but especially Monday night. The
only question at this point is how widespread and thick will the fog
be. For now have gone with areas of fog, but wouldn`t rule out
possibility of locally dense fog. Will continue to monitor. Low
levels begin to dry out a little bit through the day on Tuesday with
some peeks of sunshine possible.

.LONG TERM...(Tuesday night through Saturday)
Issued at 346 PM EST Sat Nov 11 2017

High Impact Weather Potential...Minimal.

Temperatures will continue to moderate heading into midweek with
warm air advection ongoing across the region. Low pressure trekking
across Ontario into the James Bay area will drag a cold front
through the Upper Great Lakes on Wednesday. Still looking like
plenty of moisture will accompany this front, mostly in liquid form.
However, some wet snow may mix with rain in the higher elevations
Tuesday night as isentropic lift develops out ahead of this system.
Some colder air wraps in behind this system Wednesday night, with
lake processes likely kicking in for a brief period in the resultant
northwest flow. High pressure then quickly slides through the region
on Thursday providing a brief break from precipitation before the
next developing system sets its sights on the region for the end of
the week, bringing with it another surge of colder air and
widespread precipitation.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1151 PM EST Sat Nov 11 2017

Cigs lowering with dz/fzdz at times.

Decaying cold front over eastern Superior and central upper MI
will stall as it approaches nw lower MI overnight. That will
contribute to lowering cigs (MVFR) and some patchy drizzle/fzdz
developing. Fzdz is most likely at PLN/APN, with TVC/MBL being a
smidge warmer. MVFR cigs will persist thru most of the forecast.

Light s to sw winds.


Issued at 346 PM EST Sat Nov 11 2017

Still getting gale force gusts out there over Lake Michigan and
Whitefish Bay, and advisory level gusts elsewhere. Headlines to
remain as is through all this afternoon. Winds will drop off heading
through tonight and Sunday as weaker gradient along a decaying cold
front arrive. Winds remain light into Tuesday morning with higher
pressure lingering over the Great Lakes.


LH...SMALL CRAFT ADVISORY until 5 AM EST Sunday for LHZ345>349.
LM...SMALL CRAFT ADVISORY until 5 AM EST Sunday for LMZ323-341-342-
LS...SMALL CRAFT ADVISORY until 5 AM EST Sunday for LSZ321-322.


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