Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 061917

Area Forecast Discussion
National Weather Service Marquette MI
217 PM EST Wed Dec 6 2017

.SHORT TERM...(Today and tonight)
Issued at 515 AM EST WED DEC 6 2017

...Lake effect snow continues but winds gradually diminish...

Amplified upper level trough firmly in place from northern Canada
into eastern Conus, including Great Lakes. Sfc low that brought
strong winds and heavy snow to area on Tue is still at 972mb over
northern Ontario. As the low slides to northern Quebec by this
evening, WSW-W low level winds turn more NW bringing lake effect to
more of northern Upper Michigan. H85 temps of -15c to -17c lead to
delts t/s over 20C into the evening and there is ample deep moisture
with the trough overhead. No strong shortwaves to enhance the snow,
but there is one shortwave sliding through early this morning and
another set to drop over area tonight, first west then affecting
more of the east. Some light snow and flurries could occur even
toward WI border today with the moisture and weak disturbances. Lake
effect snow should overall fall at a moderate clip as inversions
stay more in the 4-7kft AGL range. However when the disturbances
cross, could see heavy snow for a time in the snow belts. Leveraging
higher res QPF from NAM/WRF-ARW/NMM and using SLRs in the 20-25:1
range, expect snow totals through this aftn as high as 5-8 inches
for parts of far western U.P. (Ironwood to Twin Lakes). Otherwise
totals through this aftn should be 3-6 inches. Could see another 2
to 4 inches tonight over far western U.P. vcnty of Ironwood to White
Pine as one of those shortwaves moves through. Also could see a max
of 4 maybe 5 inches for eastern forecast area where convergence snow
band off Lk Nipegon forms. Inversions more in the moderate range of
3-5 kft AGL later tonight should keep snow amounts in check though
with delta t/s over 20c can always end up with localized higher

Significant blowing snow will diminish through the day. Mixed layer
winds into the aftn over Keweenaw and Lk Superior stay around 30-35
kts but relax to less than 30 kts this evening. Given the fluffy
snow that has occurred thus far even a 30 mph wind will lead to
quite a bit of blowing snow. Hazard of blowing snow should diminish
this evening all areas.

For headlines have extended the winter storm warning for the
Keweenaw through this evening. Still some moderate to heavy lake
effect to get through this morning and winds/blowing snow will
remain an issue well into the aftn. Law enforcement report roads
are in hazardous condition due to the snow/drifting and since
cooling temps are leading to icy conditions where roads are not
snow covered. Advisories in the west look good but due to
potential for burst of snow lasting into the evening with the
shortwave mentioned above, extended til midnight tonight. After
midnight the snow over the west should diminish with lowering
inversions and as deep moisture to 15-20kft AGL quickly exits the
area. With the NW wind direction and associated convergence
pattern showing up in QPF, expanded advy to southern Hougton and
Baraga. Advy over the east looked good. Only change there was to
start it earlier as strong convergence band seen on radar over
eastern Lk Superior slides into the Grand Marais and northern Luce
county areas shortly after 12z per HRRR and RAP.

.LONG TERM...(Thursday through Tuesday)
Issued at 507 AM EST WED DEC 6 2017

Models suggest that the high amplitude pattern featuring a mid/upper
level ridge over wrn North America and a trough from far nrn Canada
and Hudson bay through much of the ern CONUS will persist into next
week. This will result in continued below normal temperatures and
LES along with several clipper shortwaves moving through the region.

Thursday, weak sfc and mid level ridging into the nrn Great lakes of
a weak shrtwv will bring backing winds and lowering inversion
heights to around 3k ft even as 850 mb temps remain around -16C.
With nw winds shifting to the west, diminishing LES with additional
accumulations of an inch or two east and an inch or less over the

Thursday night, more favorable 850-700 mb moisture will allow the
LES to increase for the Keweenaw and possibly near the shoreline
around Grand Marais eastward with accumulations in the 1 to 3 inch

Friday into Saturday, Although the models have trended a bit
stronger and farther east with the next shortwave/clipper moving in
late Friday into Friday night there is lower confidence with the
track/timinng/strength of the system. Although there will be limited
moisture available, general accumulations of around an inch will
be possible. In addition, LES will also increase by Fri night
into Saturday with deeper inversion heights/moisture over the
area, especially the west half. Winds should veer more nrly which
will bring the LES into most of the nrn cwa.

Sunday-Tuesday, the LES will again diminish Sunday with ridging
again into the area. A shortwave trough and arctic front will bring
in another round of even colder air by Monday with winds veering
nrly. It is less certain if the bulk of the coldest air (850 mb
temps in the -20C to -26C range)will move into the nrn Great Lakes
or slide just to the northeast.

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1245 PM EST WED DEC 6 2017

Combination of lake effect snow and gusty w winds to around 25kt
producing blsn will result in IFR/LIFR conditions with vis
occasionally near airfield mins thru this aftn at KCMX. Gradual
improvement is expected tonight as winds diminish and somewhat
drier air arrives. At KIWD, gradual veering of winds from w to nw
will result in increasing lake effect shsn this afternoon into
this evening before improvement to MVFR is expected overnight.
At KSAW, downslope nature of the w to nw winds should result in
conditions varying btwn MVFR and VFR with -shsn/flurries at
times, though MVFR conditions will likely become prevailing this
aftn into this evening.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 515 AM EST WED DEC 6 2017

Will stay with gales into much of tonight as deep low over northern
Ontario slowly moves away from the region. Beyond tonight, winds
should stay in the 20-30 kt range into early next week. Freezing
spray is expected into Thu and again late Fri into Fri night. Air
temps staying mainly in the 20s should prohibit heavy freezing spray.

Upper Michigan...
  Winter Weather Advisory until midnight EST /11 PM CST/ tonight
     for MIZ002-004-009-084.

  Winter Weather Advisory until 7 AM EST Thursday for MIZ006-007-

  Winter Storm Warning until midnight EST tonight for MIZ001-003.

Lake Superior...
  Gale Warning until 5 AM EST Thursday for LSZ244-245-248>251-

  Gale Warning until 6 PM EST /5 PM CST/ this evening for LSZ162-

Lake Michigan...


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