Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 080912
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
412 AM EST Thu Dec 8 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...(Friday through Wednesday)
Issued at 412 AM EST THU DEC 8 2016

Nam shows a broad 500 mb trough over most of the U.S. 12z Fri with a
shortwave moving into the northern plains 00z Sun and into the upper
Great Lakes late Sat night. Nam brings in some deeper moisture and
strong 850-500 mb q-vector convergence Sat night across the area.
Went with persistence for the lake effect and made very few changes
to the going forecast. One change though is the system for Sat night
looks to be a bit further south now and lowered pops a bit for this.

In the extended, GFS and ECMWF show a 500 mb trough with 850 mb
temperatures from -15C to -19C over Lake Superior 12z Sun. There is
also a sfc low pressure system passing by to the south near Dubuque,
IA. The upper level trough at 500 mb broadens and deepens across the
U.S. on Mon with colder air poised to come down over the northern
plains and northern Rockies. This colder air sweeps across the upper
Great Lakes on Tue with a sfc cold front moving through the area.
850 mb temperatures drop down to -23C to -28C by then over Lake
Superior at 12z Wed with the core of the coldest air over the area
then. Slow modification takes places on Thu as the cold core moves
over the New England. Prolonged lake effect snow event during this
forecast period with temperatures well below normal.
&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1225 AM EST THU DEC 8 2016

A sfc trough/cold front will push south across the northwest half of
Upper Mi overnight and across the rest of the forecast area Thu
morning. IWD could see a brief burst of heavier snow overnight
with LIFR vsbys as this trough moves through. Otherwise, at CMX and
IWD generally expect occasional lake effect with IFR vsby and MVFR
cigs through the period. At SAW, expect mainly VFR conditions
into the overnight hours and then widespread lake effect snow showers
moving in around or just after daybreak on Thu with IFR vsby and MVFR
cigs through most of Thu. Conditions could improve at SAW Thu
evening as winds back more nw and push heavier lake effect bands
east.
&&

.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
waves.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Lake Effect Snow Warning until 7 PM EST Friday for MIZ004-005.

  Lake Effect Snow Warning until 7 AM EST /6 AM CST/ Saturday for
     MIZ001>003-009.

  Lake Effect Snow Advisory until 7 PM EST Friday for MIZ013.

  Lake Effect Snow Advisory until 7 AM EST Saturday for MIZ006-007-
     084-085.

Lake Superior...
  Gale Warning until 5 AM EST early this morning for LSZ265>267.

Lake Michigan...
None.
&&

$$

SHORT TERM...JLA
LONG TERM...07
AVIATION...Voss
MARINE...JLA


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