Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 080008
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
708 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 night through Wednesday)
Issued at 430 PM EST WED DEC 7 2016

An extended period of LES is expected into Saturday as the first
batch of cold air moves through with n to nw winds. High latitude
blocking near Alaska will favor pattern amplification with an
intrusion of severe arctic cold next week as the mid level low and
core of coldest air drops through cntrl Canada into nrn Ontario.

Thursday night, wind direction in the 340-350 range will favor the
greatest snow accumulations over the west near IWD and n cntrl from
Marquette into the Huron Mountains. However, confidence in the
details about where the heavier or dominant bands will develop (with
the influence of land breezes and upstream bands from Lake Nipigon)
and how long they will persist in any one location is still low.
Instability with 850 mb temps to around -15C resulting in lake
induced CAPE values to 600 J/Kg and DGZ within the convective layer
will favor potential for higher snowfall rates in dominant bands of 1
to 3 inches per hour.

Although there is some spread with the high res models, trend
remains for gradual backing overnight which would shift the greater
snowfall potential in the n cntrl cwa into wrn Alger county.
Snowfall amounts in the 2 to 6 inch range per 12 hours will be
common, especially near IWD and between Big Bay, Negaunee,and
western Alger county. Isolated higher amounts over 8 inches may be
possible. There will be some areas of blsn but overall winds are
expected to remain at or below 30 mph limiting impacts from reduced
vsby or drifting.

Friday, There is higher confidence that wind directons gradually
shifting to 320-300 over the west and to 330-320 over the east will
push the bands into the ern cwa with the greater accumulations in
the 2 to 6 inch range over Alger into nw Schoolcraft counties. In
addition, mid level drying with inversion heights lower to 4k-5k ft
west will limit LES intensity.

Friday night into Saturday, As surface ridging builds toward the area,
winds will gradually back go the nw shifting the heavier LES into
the ern CWA toward Alger county eastward while light to moderate LES
persists over the west.

Sunday, a shortwave trough moving from the nrn plains into the Great
Lakes may bring a widespread few inches of snow to the area.
Significant model differences, especially with the trend toward a
slower stronger system, per ECMWF, keep confidence low. Both
scenarios keep the stronger 700-300 mb qvector conv and moisture
inflow well south of Upper Michigan.

Monday-Wednesday, LES will redevelop behind the trough into Monday
for nw flow locations. The more significant blast of arctic air and
continued w to wnw flow LES is expected to move in with 850 mb temps
dropping toward the -25C to -30c range. Wind chills could also
approach advy criteria -25 by Tuesday night into Wed, per ECMWF,
which brings the core of the coldest air farther south than the GFS.
&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 704 PM EST WED DEC 7 2016

A sfc trough hanging over the tip of the Keweenaw this evening will
continue to bring heavier bands of lake effect snow into CMX this
evening with LIFR conditions (mostly from reduction in vsby due to
heavier snow and blowing snow). Otherwise, at CMX and IWD generally
expect occasional lake effect with IFR vsby and MVFR cigs through
the period. At SAW, expect VFR conditions this evening with a few
flurries then expect widespread lake effect snow showers moving in
around daybreak on Thu with IFR vsby and MVFR cigs 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
waves.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
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 until 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
     LSZ240>244-263-264.

Lake Michigan...
None.
&&

$$

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



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