Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 072119

Area Forecast Discussion
National Weather Service Marquette MI
419 PM EST Wed Dec 7 2016

.SHORT TERM...(This evening through Thursday)
Issued at 418 PM EST WED DEC 7 2016

Upper low north of Lk Superior reaches Quebec on Thu allowing cold
air to advect across the Great Lakes with h85 temps at or blo -15c
slowly settling across the Upper Great Lakes. Sfc low is north of Lk
Superior with sharp cold front extending west toward southern
Mantioba. Winds in wake of front are shifting north to northeast over
northern Ontario. WSW winds to the south of the sfc low have brought
occasional heavy bands of lake effect snow to northwest Keweenaw
peninsula through the day. 12z INL sounding indicated h85 temps near
-13c with inversions to 8kft. Plenty of deep moisture is poised to
swing across Lk Superior/Upper Michigan late tonight into Thu as the
reinforcing cold front moves in. Game plan remains same and no
changes were made to the going lake effect warnings and advisories at
this point. Heavy lake effect on the Keweenaw this evening gradually
shifts across much of western Upper Michigan late this evening into
the overnight hours as h85 winds veer more northwest. In addition to
the snow that already occurred today, could see additional
accumulations on the Keweenaw reach 3 to 5 inches late this aftn into
tonight. Meanwhile...decent signal from consensus of higher
resolution models that front/convergence zone of heavy lake effect
will remain just north of Marquette to Munising to Grand Marais much
of the night.

Late tonight though, after 10-11z Thu/5-6 am ET, expect the
front/convergence band to sink across northern Upper Michigan
including over far west cwa near IWD and over ncntrl cwa on Thu
morning. Additionally shortwave causing the snow over northern
Dakotas this aftn arrives late tonight into Thu morning further
enhancing the snow wherever the convergence is maximized. Seems
there will be a quick burst of heavier snow late tonight and
possibly for the morning commute. Expect some blowing snow/drifting
snow in these areas as well but that will not really increase until
after some snow begins to accumulate with minimal snow on the ground
to start with late tonight. Once the convergence band moves through
will take time for NW-NNW flow lake effect to become established
though deeper moisture and flow becoming pretty quickly alligned
with little shear in the sfc-h85 layer should help the orginization
occur steadily. Total snow accumulations tonight into Thu will top
out in the 5 to 10 inch range in the higher terrain areas near Lk
Superior with fairly sharp cutoff to just a few inches farther
inland. Expect the west cwa will have greatest chances of seeing the
highest amounts since the heavier snow moves in there earlier
tonight. On into Thu, could see more persistent snow showers also
making it into northern Delta and southern Schoolcraft later on
Thursday morning into Thursday aftn but accums at this point of only
a few inches did not seem to justify advisory with winds/gusts
staying blo 20 mph in those areas into Thu aftn.

.LONG TERM...(Thursday through Tuesday)
Issued at 300 AM EST WED DEC 7 2016

Nam shows a 500 mb trough over the upper Great Lakes 12z Thu.
Troughing remains through 12z Sat over the area. Prolonged lake
effect scenario in NNW lake effect snow belts will continue this
forecast period. This was covered in the previous forecast and used
that as the basis for this forecast. Will have numerous advisories
up for the NNW lake effect snow belts continuing. Did not make too
many changes to the going temperatures. Snow ratios look to be
between 20 to 25 to 1 for this event.

In the extended, GFS and ECMWF show a zonal 500 mb pattern across
most of the U.S. with a broad trough across most of the country 12z
Sat. 850 mb temperatures across Lake Superior at 12z Sat are from -
17C to -19C. A shortwave digs into the upper Great Lakes 12z Sun.
Troughing continues over the area Mon into Tue with cold air
remaining over the area through then. Temperatures will continue to
be below normal and lake effect snow showers will continue through
this forecast period as well. Get system snow in for Sat night
through Sun morning and then lake effect gets going in earnest again
Sun night through Wed with even colder air arriving in. The lake
effect event will be in WNW lake effect snow belts. Could see some
below zero temperatures for lows Tue night and Wed night.

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1252 PM EST WED DEC 7 2016

A sfc trough will bring a heavy band of lake effect snow into CMX
this aftn into this evening with LIFR conditions (mostly from
reduction in vsby due to heavier snow and blowing snow). Otherwise,
at CMX and IWD expect occasional lake effect with IFR vsby and MVFR
cigs through the period. At SAW, light snow with MVFR conditions
early this aftn (due to lower ceilings) could diminish most of tonight
with widespread lake effect snow showers moving in around daybreak on
Thu with IFR vsby and MVFR cigs persisting through most of Thu.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 418 PM EST WED DEC 7 2016

Southwest gales of 35-40kt will continue across much of Lk Superior
this evening. Winds will shift northwest later tonight staying up to
30 kts through Fri. Winds should diminish to less than 25 kts
through the weekend as pressure gradient weakens. Some freezing
spray is possible later tonight into Thu night with the higher

Upper Michigan...
  Lake Effect Snow Advisory from 1 AM Thursday to 7 AM EST
     Saturday for MIZ006-007-084-085.

  Lake Effect Snow Warning until 7 AM EST Saturday for MIZ001-003.

  Lake Effect Snow Warning from 10 PM EST /9 PM CST/ this evening
     to 7 AM EST /6 AM CST/ Saturday for MIZ002-009.

  Lake Effect Snow Warning from 1 AM Thursday to 7 PM EST Friday
     for MIZ004-005.

Lake Superior...
  Gale Warning until 5 AM EST Thursday for LSZ245>247-265>267.

  Gale Warning until midnight EST /11 PM CST/ tonight for

  Gale Warning until 7 PM EST /6 PM CST/ this evening for LSZ162.

Lake Michigan...


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