Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 111016
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
516 AM EST Mon Dec 11 2017

.SHORT TERM...(Today and tonight)
Issued at 516 AM EST MON DEC 11 2017

Significant lake effect snow impact expected for portions of eastern
Marquette County and western Alger County tonight into Tuesday.
Additionally, lake effect snow and blowing snow will lead to reduced
visibility along Lake Superior tonight into Tuesday. Winter Storm
Warnings were issued for Marquette and Alger Counties and Winter
Weather Advisories have been posted elsewhere along Lake Superior
tonight into Tuesday. In addition a Lakeshore Flood Advisory has
been issued tonight for Alger County.

Water vapor imagery show a vigorous shortwave sliding across the
Northern Plains early this morning with colder cloud tops sliding
across the U.P. ahead of it, shown in IR. Radar shows a band of
light snow sliding into the western U.P., while surface obs indicate
visibilities under the band as low as 1 to 2 miles at times.

Today: The aforementioned shortwave and associated surface low are
progged to slide to Northern Lower Michigan by this evening. As this
happens, forcing and moisture ahead of the system will allow for
light system snow to fall across the U.P. through early afternoon.
The system is moving fast enough that snowfall totals are expected
to only be around 1 to 2 inches for most locations. The main
exception will be over the far eastern U.P., where south to
southwesterly winds off Lake Michigan will lead to some lake
enhancement by mid morning and lingering into the early afternoon
hours. Those locations, mainly eastern Schoolcraft and eastern Luce
Counties may see snowfall totals as high as 2 to 4 inches by mid to
late afternoon. 850mb temperatures (-10C to -12C) are only
marginally cold enough for lake enhancement, so not expecting
anything too drastic out that way through this afternoon. By late
this afternoon, closer to 00Z, a cold front will slide into the west
and central portions of the U.P., leading to a more northerly wind
shift by early evening. This will be the leading edge of much colder
air at the surface and aloft along with fairly gusty winds in the 20
to 30 mph range, especially along Lake Superior. Expect lake effect
snow to begin developing by 00Z as 850mb temperatures are expected
to plummet from -10C this morning to -20C by 00Z/12 over the western
half of the U.P. Only expecting an additional 1 to 2 inches over the
Keweenaw Peninsula when the lake effect snow kicks in late this
afternoon. Winds will be gusty however, and the snow will be powdery
so blowing snow will begin to become an issue over the west during
the late afternoon evening time frame.

Tonight: The aforementioned surface low is progged to become nearly
stationary over Northern Lower Michigan or near Lake Huron through
this time period, allowing for continued north to north-
northwesterly flow into the Upper Peninsula. At the same time,
another strong shortwave is progged to slide form Ontario southward
into the Upper Peninsula tonight. This will help to steepen lapse
rates further as 850mb temperatures fall to around -22C to -23C.
This will be more than enough for lake effect snow all along Lake
Superior. The main are of focus will be over eastern Marquette
County and western Alger County, where the Lake Nipigon connection
is shown in the hi-res model data. This is also the main area
favored for low level convergence. Inversion heights are progged to
jump up to around 10kft or better this evening and lingering around
that height through late tonight. The deeper moisture in place along
with increased fetch and the aforementioned convergence and
inversion heights all point to a heavy snow band across portions of
eastern Marquette County and western Alger County. Current thinking
is that snowfall totals of 5 to 10 inches can be expected from near
Big Bay southeastward to McFarland eastward into the west half of
Alger County. The heaviest totals tonight are expected to be along
the Marquette and Alger county border and will likely include the
City of Marquette. Along with the heavier snowfall, gusty winds
between 20 and 30 mph will allow for blowing and drifting snow
causing visibilities to be reduced below a mile or at times and
could cause some white-out conditions. The combination of heavy
snowfall rates and blowing snow has led to the issuance of the
Winter Storm Warning for Marquette and Alger Counties.  Elsewhere
along Lake Superior, light to moderate lake effect snow and blowing
snow will lead to reduced visibilities at times with light to
moderate accumulations expected. The lower snowfall totals has led
to the issuance of the Winter Weather Advisory for the remaining
counties along Lake Superior. Snow totals outside of the heavy band
in Marquette and Alger County will likely be in the 2 to 5 inch
range with the lowest totals expected inland over the west half.
Gusty winds will also lead to waves as large as 15 ft along the
Alger County shoreline tonight, which will likely lead to minor
lakeshore flooding and minor beach erosion. This has led to the
issuance of a lakeshore flood advisory tonight.

.LONG TERM...(Tuesday through Sunday)
Issued at 516 AM EST MON DEC 11 2017

Overall the focus through the near-term was on the tail-end of the
prolonged LES event on Tuesday. Still looking for the most
significant impacts to linger across eastern Marquette and western
Alger counties on Tuesday, where winter storm warnings for LES have
been issued. Otherwise, the pattern will remain active with multiple
clipper system expected to track across the Upper Great Lakes
bringing chances for area-wide snow with LES lingering behind. There
will be a pattern change out west towards the end of the week
through the weekend which may send a stronger slipper system across
the region, potentially bringing a decent shot of system and
possible lake enhanced snow to portions of Upper Michigan.

Tuesday into Wednesday: Overall not much change in how things are
expected to evolve as light to moderate LES is expected across the
west, and moderate to heavy, LES across the north central and east.
Regardless of the location, wind gusts near 25 to 35 mph are
expected and will likely cause reduced visibilities due to blowing
snow. Across the west, the LES will begin to weaken and gradually
tapper off through the afternoon hours on Tuesday as drier air and
surface ridging works into the region. Further east the LES will
linger through the day on Tuesday. The strongest LES bands are
expected across eastern Marquette county and Alger county through
the day on Tuesday. There may be a couple robust bands, the high-res
and medium range models continue to peg areas across far eastern
Marquette county and western Alger county. In fact, model guidance
all show the robust band expected to impact these areas having a
strong connection to Lake Nipigon, especially with enhanced low-
level convergence due to north-northwest flow and north-northeast
flow bisecting Lake Superior. While SLRs will be around 30:1 across
much of the area given the magnitude of the cold air advection, snow
fall accumulations will largely be a factor of how long stronger
bands sit over certain locations, especially the more robust bands
across the north central portions of Upper Michigan. Therefore,
significant gradients in snowfall are expected when the event is
over, especially across Marquette county. High snowfall rates,
possibly even approaching 2-3`` per hour in the stronger bands will
allow for white-out conditions and extremely difficult travel to
linger through much of the day on Tuesday, especially during the
morning commute. The other hazard will be the bitterly cold
conditions, with wind chills ranging from 5 to 10 below as the cold
air advection continues with lingering gusty winds.

Tuesday night through Wednesday: Lake effect snow will begin to
diminish in intensity and gradually come to an end from west to east
Tuesday night into Wednesday morning. This is due to high pressure
briefly moving across the area, ahead of another clipper system
expected to arrive on Wednesday. This clipper system will bring
chances for widespread snow across Upper Michigan; however, given
how dry the air mass is ahead of this wave do not expect much of an
impact across the area.

Wednesday night through early next week:  Behind the above mentioned
clipper system, LES will kick back in Wednesday night through
Thursday. Another shortwave embedded within the western edge of the
main upper-level trough draped across the region will dig south
Thursday night into Friday, bringing a chance for widespread snow
and the return of LES thereafter. Friday night through the weekend,
upper-level ridging across the west will finally break down as a
strong trough is progged to dig southwest from the Gulf of Alaska.
Given this pattern change expected across the western CONUS, it is
no surprise that there are differences among the medium-range models
with the track and timing of this system. However, it does look like
we will have a chance at seeing some decent system snow across the
area. Depending on the track of the system, some lake enhanced snow
will also be possible in some areas.
&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1235 AM EST MON DEC 11 2017

Synoptic snow moving in late tonight into Mon morning will produce a
period of IFR conditons ahead of a low pressure system. Behind the
low, more lake effect snow kicks in late Mon afternoon/evening
impacting the western TAF sites with more IFR/MVFR conditions. Lake
effect snow and IFR conditions will hold off at KSAW until Mon
evening/night.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 516 AM EST MON DEC 11 2017

Winds will start off between 15 and 25 knots this morning, but as a
clipper system tracks across the Upper Great Lakes this afternoon
and evening winds will come around to the north and increase to
gales of 40 knots. Increasing wave heights during this gale event
combined with colder air pushing south across the lake will allow
for heavy freezing to develop tonight into Tuesday morning across
the north central and eastern portions of the lake. As the gales
subside from west to east across Lake Superior Tuesday morning,
expect winds of 20 to 30 knots to linger through the rest of the
day. Winds will further subside to below 25 knots through the end of
the week.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory from 7 PM this evening to 7 PM EST
     Tuesday for MIZ007-013-085.

  Winter Weather Advisory from 7 PM EST /6 PM CST/ this evening to
     10 AM EST /9 AM CST/ Tuesday for MIZ001>004-009.

  Winter Storm Warning from 7 PM this evening to 7 PM EST Tuesday
     for MIZ005-006.

  Lakeshore Flood Advisory from 10 PM this evening to 10 AM EST
     Tuesday for MIZ006.

Lake Superior...
  Heavy Freezing Spray Warning from 7 PM this evening to 1 PM EST
     Tuesday for LSZ264-266-267.

  Gale Warning from 6 PM this evening to 11 AM EST Tuesday for
     LSZ249>251-266-267.

  Gale Warning from 6 PM this evening to 7 AM EST Tuesday for
     LSZ248-265.

  Gale Warning from 4 PM this afternoon to 5 AM EST Tuesday for
     LSZ243>245-264.

  Gale Warning from 4 PM EST /3 PM CST/ this afternoon to 1 AM EST
     /midnight CST/ Tuesday for LSZ240>242-263.

  Gale Warning from 4 PM EST /3 PM CST/ this afternoon to 11 PM
     EST /10 PM CST/ this evening for LSZ162.

Lake Michigan...
  Gale Warning from 7 PM this evening to 7 AM EST Tuesday for
     LMZ221-248-250.

&&

$$

SHORT TERM...KEC
LONG TERM...Ritzman
AVIATION...Voss
MARINE...Ritzman



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