Area Forecast Discussion
Issued by NWS Marquette, MI

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029
FXUS63 KMQT 080918
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
418 AM EST Fri Dec 8 2017

.SHORT TERM...(This evening through Friday)
Issued at 355 PM EST THU DEC 7 2017

...Lake effect snow ramping up again late today and tonight over the
northwest and late tonight into Friday over the eastern counties...

Radar and visible satellite imagery show lake effect snow bands
pushing east of Alger and northern Schoolcraft this afternoon. They
will continue to move east of Luce County by evening with backing
wind flow.

Convergent westerly wind flow noted over western and south central
Lake Superior along lake-induced trough will likely focus a dominant
les band into the Keweenaw Peninsula late this afternoon into the
evening hours. Enhancement of this developing band will be provided
by a clipper shortwave descending through northern Ontario as noted
on water vapor imagery. Would not be surprised to see localized
snowfall rates of 1 to 2 inches this evening wherever this
developing dominant band sets up, likely between Twin Falls and
Hancock as steep lapse rates and deep moisture to 8-10 kft noted on
fcst soundings along with very favorable dendrtic snow growth.

Shortwave moving across the Upper Lakes will push lake induced
trough onshore late tonight into Friday morning. At that time
dominant snow bands will push south of the Keweenaw and into
Ontonagon, Baraga and southern Houghton counties of west and into
Alger, Luce and northern Schoolcraft counties.

For headlines...have winter wx advisories starting into northwest
counties this afternoon and those will be extended into Saturday to
capture next round of lake snows Fri night into Sat with next
clipper system moving through area. Started advisories for Alger,
Luce and northern Schoolcraft 09Z tonight and those will also be
extended into early Sat to include snow for next clipper system.
Started Gogebic and Marquette County advisories late Fri afternoon
and will continue those headlines into Sat morning as flow veers
from northwest to north with clipper system. With SLRs expected from
25-30/1 expect storm total snow amounts to generally range from 4 to
9 inches across the advisory areas with localized amounts closer to
a foot over higher terrain of eastern and north central counties and
probably from 14 to 18 inches over a few higher terrain locations of
the west where dominant band this evening boosts snow amounts.

.LONG TERM...(Saturday through Thursday)
Issued at 418 AM EST FRI DEC 8 2017

The extended forecast will continue the trend of near to below
normal temperatures along with a very active lake effect snow
pattern through the entire period.

Generally expecting northwesterly flow aloft into the Upper Great
Lakes region, bringing the continued cold air into the area. 850mb
temperatures are expected to be in the -12C to -18C range through
much of the extended, which will be plenty cold enough for continued
lake effect snow downwind of Lake Superior. For the most part, north
to northwest wind favored snow belts will be the favored lake effect
areas; however, there are a couple clipper systems that will drop
850mb temperatures to around -20C and allow winds to shift.

Saturday: A strong and fairly quick moving clipper systems will
slide through during this time period. This will allow 850mb temps
to drop down near -20C, helping to steepen the overwater
instability. The surface pressure pattern would favor the north to
north-northeast wind favored snowbelts as a surface low shifts off
to the south and east of the U.P. This would give most locations
along Lake Superior a good shot at at least moderate lake effect
snow. Snow ratios look to be a little better during the late Friday
night into Saturday time period as the wave slides through with
fairly light winds through and below the snow growth layer. Good
forcing and instability in the snow growth layer along with
inversion heights reaching close to 10 kft also point to an uptick
in the snowfall intensity into at least Saturday morning. At this
point, blending some hi-res qpf guidance gives several inches of
snow from Friday night into Saturday morning especially for north
wind favored snow belts. The heaviest snowfall totals are expected
over the high terrain of the west and over the high terrain of the
north central U.P. Current thinking is that 4 to 8 inches of fluffy
snow may fall in the aforementioned areas with locally higher totals
possible by early Saturday afternoon. Elsewhere along Lake Superior
will likely see totals around 3 to 6 inches. Again these totals
include the Friday night accumulation. The upslope flow into the
higher terrain of Marquette county, could help to increase totals,
but a lot of this will depened on how much of a northeasterly
direction the wind shifts and where/if a more dominant bands sets up.

Sunday into Sunday night: Another quick moving, very weak, clipper-
type system is progged to slide through the Upper Peninsula. This
will again act to steepen the lapse rates enough to enhance the lake
effect snow downwind of Lake Superior. This will be a similar type
setup as the Friday night into Saturday setup, except not quiet as
strong and much quicker. Initially the lake effect snow would be
confined to the west wind favored snowbelts Sunday morning; however,
as the low shifts to the east of the U.P., winds are expected to
once again shift to the north and northwest, giving most areas
mainly light to possibly moderate lake effect snowfall along Lake
Superior.

Monday into Tuesday: Yet another strong shortwave, in the active
weather pattern, will slide through the Upper Peninsula Monday
through Tuesday morning. Winds look to be east to northeast Monday
before shifting to the north Monday night into Tuesday, allowing for
yet another period of enhanced lake effect snowfall downwind of Lake
Superior. Again, moderate to heavy lake effect snow is possible for
the north to north-northwest wind favored snow belts and as is
typical, the greatest totals are expected over the higher terrain of
the north central U.P. and over the higher terrain of the west.
Depending on the final wind direction, some location could again see
several inches of snow for this time period. At this point, it looks
like the north to north-northwest wind favored locations would see
the heaviest snowfall totals.

Rest of the Extended: Active cold weather pattern is expected to
continue with another strong shortwave progged to slide through the
area Wednesday night into Thursday. At this point, will stick with a
consensus of the models, giving good chances of lake effect snowfall
along Lake Superior, especially in the north to northwest wind
favored snowbelts.
&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1156 PM EST THU DEC 7 2017

In the wake of a passing disturbance, arrival of drier air will
cause lake effect shsn, affecting mainly KCMX, to diminish thru the
morning hrs. At KCMX, expect prevailing IFR conditions to improve to
MVFR early this morning. MVFR conditions should prevail at KIWD
while VFR conditions at KSAW should fall back to prevailing MVFR
toward daybreak. Late this aftn/evening, another approaching
disturbance will cause snow to increase, dropping conditions to IFR
at all terminals for at least a time. LIFR conditions will be
possible, especially at KIWD as winds shift to an upslope direction
off Lake Superior.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 355 PM EST THU DEC 7 2017

Winds are expected to remain in the 20-30 kt range into early next
week as an active weather pattern keeps a fairly tight gradient
across Lake Superior. Freezing spray is expected through Friday
night and again late Monday into MOnday night. Air temps staying
mainly in the 20s should prohibit heavy freezing spray through this
time period.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory until 5 PM EST Saturday for MIZ006-007-
     085.

  Winter Weather Advisory until 1 PM EST Saturday for MIZ001>004-
     084.

  Winter Weather Advisory from 10 PM this evening to 1 PM EST
     Saturday for MIZ005.

  Winter Weather Advisory from 3 PM this afternoon to noon CST
     Saturday for MIZ009.

Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...Voss
LONG TERM...KEC
AVIATION...Rolfson
MARINE...BB



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