Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 191117

Area Forecast Discussion
National Weather Service Gaylord MI
617 AM EST Sun Nov 19 2017

.NEAR TERM...(Today through Tonight)
Issued at 351 AM EST Sun Nov 19 2017

High impact weather potential: Accumulating lake effect snow. Some
blowing and drifting and and pretty slick roads where temperatures
have sunk below freezing.

Pattern synopsis and forecast:

Large scale upper troughing is overhead early this morning, with low
pressure and a cold front settled in the eastern conus. A shortwave
seen on satellite is dropping SE into western Lake Superior, working
with fairly little moisture, per Canadian radars which show little
if any synoptic precipitation. That said, the puny NW flow lake
effect snow bands seen over the last several hours have been
increasing in intensity over Lake Superior during the last hour or
so. There was also some increase seen over Lake Michigan, as there
is a connection with Lake Superior in fairly unidirectional low
level winds. On a more gloomy note, widespread stratus stratus was
seen back through much of Wisconsin, but clearing was pushing
through the western part of the state.

As the shortwave presses through the region this morning, gotta
expect the uptick in snowfall intensity to persist. Hi-res guidance
suggesting a dominant band setting up within max convergence from
far western Mackinac county through NW lower, which is likely to
spread snow as far south as Saginaw Bay for a time this morning.
Lake effect bands may prove to be somewhat transient, as 1000-850mb
flow will be backing through the day and night. Nevertheless, am
expecting for a general 1-2 inches this morning with locally higher
amounts, certainly if the dominant band evolves. Heading into the
afternoon, gotta expect these bands to become diurnally disrupted to
some degree, with less than an inch of additional accumulations in
nrn lower, and another inch or so through Chippewa county in eastern
upper as the flow will become more WNW. No stopping the snow into
tonight as winds become more west, but the drier air/clearing from
western Wisconsin will be putting a big dent in the action over
mainly nrn lower. All-in-all, can see a general 1-4 inches in the
favored snowbelts through tonight and gusty winds resulting in some
blowing and drifting. A rather low end snowfall, but roads are slick
already, so will issue a winter weather advisory.


.SHORT TERM...(Monday through Tuesday)
Issued at 351 AM EST Sun Nov 19 2017

...Temperature roller coaster to continue through midweek...

High Impact Weather Potential: Snow accumulations with lake
convection Tuesday night.

Pattern Forecast: Full-latitude short wave trough swinging into the
eastern third of North America early this morning...with flat but
expanding ridging into the western U.S.  Secondary short wave trough
dropping quickly southeast into Minnesota.  Split short wave trough
is over the eastern Pacific...northern branch trough north of 40N
while a substantial (for that latitude) southern branch upper low
spins north of Hawaii (4-5 standard deviations below the mean)...
with additional short wave energy moving east of the dateline.
At the surface...986mb low was tracking northeast across the lower
Great Lakes...with colder air getting pulled across the upper Lakes
in decently strong cyclonic flow.

Strong height rises will spread across the Great Lakes Monday along
with warmer southwesterly low level flow.  Energy associated with
split trough in the eastern Pacific will dig southeast out of the
Prairie provinces Tuesday...with some impressive height falls across
Michigan (potentially on the order of 120m/12h).  An associated cold
front will come along with it...probably in the Tuesday morning time
frame...bringing a comparable or maybe even a bit colder air mass
than the one currently spreading into the region this morning.

Primary Forecast Concerns: Quiet day expected Monday with flat
ridging across the region...with changes coming Tuesday morning with
cold frontal passage across Michigan.  Moisture along the front
itself looks to be pretty sparse...with only some hints of a pre-
frontal rain band sweeping across the forecast area.  Surge of cold
air then follows Tuesday afternoon/night which will allow
temperatures to drop and northwest flow lake bands off Lakes
Superior/Michigan to ramp up.  Bands could be of decent intensity
with inversion height jumping to or above 750mb during the
afternoon/evening.  So a pretty good bet for more accumulating snows
across much of eastern Upper and interior northern Lower Tuesday

.LONG TERM...(Tuesday night through Saturday)
Issued at 351 AM EST Sun Nov 19 2017

High Impact Weather Potential: Minimal.

Big pre-holiday travel day (Wednesday) should continue to see
lingering snow showers coming in off Lake Superior and Lake
Michigan...though with onset of warm advection and backing low level
winds expect intensity to fall off with time.  Some mixed
signals/forecast spread begins creeping into the picture for
Thanksgiving Day itself...forecast will lean toward the idea of a
cold frontal passage which may bring some light precip on Thursday
or some lake effect Thursday night...with a stronger signal for
precipitation with the passage of low pressure Friday and perhaps
more cold air for Saturday.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 609 AM EST Sun Nov 19 2017

Cold air sweeping over the Great Lakes will continue to result in
lake effect snow showers today that will continue to swing up into
mainly PLN and temporarily APN as winds shift more westerly with
time. There will be a brief time or two this morning at PLN when
snowfall rates exceed an inch per hour, but a general light and
wet snow is expected most of the time across NW lower, with snow
ratios around 13:1 initially to near 20:1 later today. Snow
tapers off from south to north through the day as well with only
some scattered light snow and flurries into the evening. Best
snowfall amounts will occur at PLN with 2-3 inches expected. Gusty
winds will result in some blowing snow, helping to limit those
VSBYS at times. MVFR cigs will prevail, going VFR later today and
tonight while winds also start to taper off.


Issued at 351 AM EST Sun Nov 19 2017

Lower end gale force gusts continue across portions of the Great
Lakes, and will persist into the morning hours. No changes to the
current gale warnings and advisories. Winds will gradually weaken
and back more west tonight but remain gusty in solid overlake
instability. Winds turn S/SW Monday and ramp back up heading into
Monday night, out ahead of the next low pressure that will be
crossing Ontario. Solid advisories expected again, with a good
chance for gales over Lake Michigan. Lake effect rain and snow
showers will wane tonight, but kick back in again Tuesday behind the
next cold front.


MI...WINTER WEATHER ADVISORY until 5 PM EST this afternoon for MIZ016-
     WINTER WEATHER ADVISORY until midnight EST tonight for MIZ008.
LH...SMALL CRAFT ADVISORY until 7 PM EST this evening for LHZ345-346.
     GALE WARNING until 7 AM EST this morning for LHZ349.
     GALE WARNING until 11 AM EST this morning for LHZ347-348.
LM...SMALL CRAFT ADVISORY until 7 PM EST this evening for LMZ341.
     GALE WARNING until 7 AM EST this morning for LMZ323-342-344>346.
LS...SMALL CRAFT ADVISORY until 7 PM EST this evening for LSZ321-322.


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