Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 162338

Area Forecast Discussion
National Weather Service Marquette MI
638 PM EST Tue Jan 16 2018

.SHORT TERM...(This evening through Wednesday)
Issued at 342 PM EST TUE JAN 16 2018

...Lake effect snow diminishes this evening, gusty winds overnight
through Wednesday...

The layout of lake effect snow has been quite complicated today as a
weak surface trough lingers across the eastern CWA and ridging
slowly builds across the western CWA. Moreover, LES activity became
increasingly cellular this afternoon in response to sheared low-
level flow and insolation. The wind shift ahead of the ridge was
located along a line from approximately Negaunee to Iron Mountain at
20UTC. Behind this line, light W to NW-wind lake effect will
continue into the evening. Ahead of this line, pockets of moderate
to heavy LES continue near Lake Superior. Given low visibility to
1/4mi and quick 1/2" to 1" accumulations under these showers, will
hold on to ongoing advisories for Marquette and Alger counties. As
WSW winds take hold later this evening, LES should shift northward
over Lake Superior. However, it would not be surprising to see a LES
band hug the shore of Keweenaw County or even possibly linger on
shore into the early overnight.

A weak trough embedded in larger mid-level troughing over northern
Quebec will brush NE Lake Superior overnight. Fairly dry low-levels
will prevent any precip, so only some mid-level clouds are expected.

Gusty winds and blowing snow will then be of some concern overnight
through Wednesday. W to WSW will increase overnight and remain gusty
through the day as Upper MI sits between a 1002hPa low over southern
Hudson Bay and a 1042hPa high over OK/AR. Though there will be a
substantial inversion around 2kft in response to robust WAA aloft,
dry conditions and 45-55kt winds on the inversion should translate
to very gusty conditions at the surface, especially with mostly
sunny skies during the day. With plenty of fresh, loose snow from
the past couple days, sharp reductions in visibility are expected
generally north of M-28 between Wakefield and Marquette, where gusts
of 30 to 35mph will be possible mid morning into the afternoon.
However, gusts to 40mph will be possible for westward facing slopes
of the Keweenaw Peninsula. Given this potential impact of briefly
very poor visibility during peak travel times Wednesday, have issued
an SPS for the aforementioned locations.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 342 PM EST TUE JAN 16 2018

...Storm system still on track Sunday night into Monday...

Late this week focus is on warm up that will boost daytime temps
above the freezing mark. Upper level flow will be west to northwest
so there could be a couple weaker shortwaves coming through.
Strongest sfc low expected to track north of Lk Superior on Friday.
Lift with the system and sufficient moisture could lead to light
wintry mix over northern Upper Michigan on Friday. Ptype likely
would be snow or sleet before switching to rain. Precip would be
very light. May be enough clearing on Friday aftn behind the system
for temps to warm well into the 30s and maybe even reach lower 40s,
especially west with more sunshine and no flow off chilly waters of
northern Lake Michigan. Weak cold front could drop temps back some
on Saturday but still should see most areas above freezing.

Attn by late weekend will be on incoming storm system to the Upper
Great Lakes. Low pressure system will be forced by southern stream
upper level trough. Expected track of low will be critical for
rain/snow line with the system. As it stands now, looks like most of
the area away from Lk Michigan will see widespread snow, possibly
heavy. May also have blowing snow issues too near Lake Superior. The
primary time that precip would occur would be Sunday evening through
Monday afternoon. Monday morning commute to work/school would
certainly be impacted. Forecast ensembles from the GFS, ECMWF and
GEM also point to a sfc low track that would favor mostly snow for
all but south and east forecast area. Energy that eventually forms
the southern stream system is still well offshore the Pacific
Northwest coast. A lot of time for track to shift around but attm
models/ensembles are locked into strong storm affecting Upper
Michigan which what could be first widespread moderate to heavy snow
this cold season. Latest WPC experimental guidance is also showing
high probabilities for seeing at least moderate snow amounts Sunday
into Monday. Will continue to mention in Hazardous Weather Outlook.

Broad upper level troughing persists beyond this early week system.
Could see another shortwave/wave of low pressure produce some snow,
then some indication gradually colder air could arrive mid to late
next week.

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 637 PM EST TUE JAN 16 2018

The main aviation concerns later tonight through the day on
Wednesday will be the low-level wind shear, and gusty winds at all
terminals resulting in areas of blowing snow, especially at KCMX
where reduced visibilities are expected. Even though gusty winds
will mix down to the surface, still maintained low-level wind shear
within the TAFs as there will still be a significant vertical
gradient in wind speeds as we approach 45 to 55 knots around 2kft.
Otherwise, ceilings have begun to improve across all terminals this
evening with lingering lake effect snow showers diminishing. This
trend will continue over the next few hours giving way to VFR
ceilings through the rest of this TAF period.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 342 PM EST TUE JAN 16 2018

W to WSW gales to 40 knots are expected to develop across western
Lake Superior overnight and eastern Lake Superior on Wednesday, then
diminish Wednesday evening. Heavy freezing spray is also expected
across the western lake during this time. Otherwise, no gales are
expected through the upcoming weekend.

Upper Michigan...
  Winter Weather Advisory until 7 PM EST this evening for MIZ006.

Lake Superior...
  Gale Warning from 7 AM to 7 PM EST Wednesday for LSZ267.

  Gale Warning from 1 AM to 10 PM EST Wednesday for LSZ265-266.

  Heavy Freezing Spray Warning from 10 PM EST /9 PM CST/ this
     evening to 11 AM EST /10 AM CST/ Wednesday for LSZ162-263-

  Gale Warning from 10 PM EST /9 PM CST/ this evening to 1 AM EST
     /midnight CST/ Thursday for LSZ162-263-264.

Lake Michigan...


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