Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 172012

Area Forecast Discussion
National Weather Service Marquette MI
312 PM EST Wed Jan 17 2018

.SHORT TERM...(This evening through Thursday)
Issued at 157 PM EST WED JAN 17 2018

Upper air pattern consists of a deep 500 mb trough over the ern U.S.
this morning and a shortwave over Alberta. This shortwave moves to
the east and affects the area late tonight into Thu morning.
Shortwave ridging then begins to build into the area Thu afternoon.
Deeper moisture and dynamics move through Thu morning. Moisture is
limited and will have slight chance to low chance pops as this moves
through with little snow accumulation expected. Overall, did not
make too many changes to the going forecast and looks quiet.

.LONG TERM...(Thursday night through Wednesday)
Issued at 312 PM EST WED JAN 17 2018

...Winter storm remains possible late Sunday into Tuesday morning...

Warm up still a go into the weekend before large storm system takes
aim at Upper Great Lakes by Monday. Temps Friday and Saturday should
reach well above freezing and there may even be some places that
crack 40 degrees over west. With the thaw during the day and temps
below freezing at night will have to watch out for possible black
ice Friday morning and Saturday morning. Northwest flow aloft brings
a couple weaker moisture starved systems across Lk Superior and
northern Ontario. Strongest sfc low expected to track north of Lk
Superior on Friday and there could be a light wintry mix over
northern Upper Michigan. Ptype likely would be sleet or freezing
rain before switching to rain. Precip should be very light, but even
a trace of freezing rain could cause minor issues on untreated
roads. Quiet on Saturday as weak cold front drops through behind the
Friday system. Warmest temps on Saturday will be scntrl but most
areas should be well into the 30s.

Attn by late weekend will be on incoming storm system to the Upper
Great Lakes. Low pressure system will be in the southern stream
upper level trough moving from the Four corners region to the Upper
Great Lakes. Expected track of low will be critical for rain/snow
line with the system. Latest models indicate most precip would start
out as snow later Sunday but could mix with or change to rain over
parts of the east half of forecast area on Monday. Latest ECMWF has
come in slower compared to GFS and most GFS ensembles. GEM is
somewhat slower but GEM ensembles are more like GFS and GFS
ensembles. Also differences in storm total qpf from the system with
the GFS and GEM well over 1.00 inch storm total while ECMWF is more
muted with not even 0.75 inch. GFS ensembles would support the idea
of lesser qpf. System grinding into larger high/dry air with main
shortwave/moisture advection staying east of here supports less qpf
but hint from guidance of stronger deformation axis would support
more qpf. Overall, there are mixed signals with this system. At the
least, will see a moderate to heavy widspread snow for much of Upper
Michigan Sunday night into Monday Night with likely impact on
morning and evening commutes on Monday. Will continue to mention in
the Hazardous Weather Outlook. Further messaging on social media and
in other forms can ramp up next couple days if the storm system
stays on track.

Upper level pattern looks zonal beyind the early week system. Light
lake effect just behind the system but only marginally cold enough.
Perhaps another low pressure system with some system snow late in
the week. Details on that idea are muddled at best so made no
changes to model consensus.

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1153 AM EST WED JAN 17 2018

LLWS will be an issue at KIWD and KSAW into this evening. Could see
some blowing snow at these sites, but not confident that winds will
be strong enough to cause significant reductions in visibilities.

At KCMX, strong winds will lead to blowing snow. Currently have
visibilities bottoming out around 2 miles, but confidence in exact
visibility is limited. The blowing snow will end this evening as
winds diminish.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 157 PM EST WED JAN 17 2018

W to WSW gales will diminish this evening. Next gale event looks to
be late Sun night across western Lake Superior with northeast gales
expected. North to northeast gales across Lake Superior Mon through
Tue are expected as well.

Upper Michigan...
Lake Superior...
  Gale Warning until 7 PM EST this evening for LSZ267.

  Gale Warning until 10 PM EST this evening for LSZ265-266.

  Gale Warning until 1 AM EST /midnight CST/ Thursday for LSZ162-

Lake Michigan...


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