Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 121755

Area Forecast Discussion
National Weather Service Marquette MI
1255 PM EST Tue Dec 12 2017

.SHORT TERM...(Today and tonight)
Issued at 516 AM EST TUE DEC 12 2017

Significant lake effect snow impact continues for portions of
eastern Marquette County and western Alger County today.
Additionally, continued lake effect snow and blowing snow will lead
to reduced visibility, especially near Lake Superior this
morning. Winter Storm Warnings continue for Marquette, Alger and
Delta Counties and Winter Weather Advisories continue elsewhere
along Lake Superior, ending this morning over the west and
lingering through this afternoon over the eastern U.P.

Water vapor imagery shows a deep shortwave sliding across the the
Upper Great Lakes early this morning with colder cloud tops sliding
across the U.P. under the wave, shown in IR. Radar has shown a
dominant lake effect snow band over eastern Marquette County and
western Alger County early this morning, with radar estimates of 1
to 2 inch per hour snowfall rates. Additional lake effect bands are
showing up as well from near Marquette through much of the eastern
U.P. Surface observations show wind gusts around 20 to 30 mph out of
the north early this morning, allowing for blowing and drifting snow
along with reduced visibility at a mile or less at times.

Today: The aforementioned deep shortwave is progged to slide from
the Upper Great Lakes eastward into southern Ontario by 00Z/13. At
the same time, the associated surface low over Lake Huron this
morning will shift into the northeastern CONUS through the same time
period. This will keep continued north to north-northwesterly flow
across eastern half of the U.P. The combination of this flow along
with 850mb temperatures as low as -22C will continue to create
favorable lake effect snow conditions for north to north-northwest
snow belts through late this afternoon. Low level convergence is
shown to be maximized over portions of the north-central U.P., which
will help continue the dominant lake effect snow band centered
around the Marquette/Alger County line. Inversion heights are
expected to continue to be in the 6kft to 8kft range through much of
the day as well, indicating the potential for heavier snow. As is
typical with these stronger bands, there may be some movement, but
this should remain localized to the aforementioned county border,
and may at times impact the city of Marquette. Radar estimates have
shown that upwards of 10 inches have already fallen in those areas
late last night into early this morning. With that said, it is not
out of the question to see up to an additional 10 inches of snow
along that border. There will be a gradually diminishing trend this
afternoon as the aforementioned shortwave axis slides east of the
area and a surface ridge/anticyclonic flow begins to slide into the
U.P. from the west. This will also help to slowly shift the winds
more northwesterly this afternoon over the west and central portions
of the U.P. At this point, have kept the warnings in place for
blowing snow and additional heavy snowfall accumulations through
late this afternoon. The advisories will drop over the west this
morning as drier air moves in and the surface high pressure ridge
begins to build into the area. The east half will continue the
advisory through this afternoon as lake effect snow will continue
and gusty winds will cause reduced visibility through late morning
or early afternoon.

Tonight: The trough axis continues to shift eastward as the surface
low departs the area. This will allow the surface ridge to move into
the U.P. and warmer air to shift in aloft. This will the lake effect
snow to diminish across much of the U.P. by late evening, with only
a couple additional inches expected over the north-central U.P. by
late this evening. The next low pressure system will begin
approaching the Upper Great Lakes from the Plains. This will allow
winds to shift more easterly by late tonight as a warm front begins
to lift northeastward toward the U.P. At this point, there may be
some light snow that lifts into locations near the Upper Mi/WI
border; however, this should remain fairly light with only minor
impacts expected.

.LONG TERM...(Wednesday through Monday)
Issued at 319 AM EST TUE DEC 12 2017

The active weather pattern across the central CONUS will linger
through the end of the week as multiple embedded shortwaves dig
southeast across the region on the western edge of the main upper-
level trough. As a result, expect a couple of clipper systems to
impact the region, with lingering lake effect snow in between
systems. This weekend through early next week, a pattern change is
in store across the western CONUS with the upper-level ridge
breaking down as a trough digs southeast across the west.
Temperatures will fluctuate through the end of the week with various
stints of cold air advection, but overall below normal temperatures
are expected with a warming trend towards normal early next week.

Wednesday through Friday: The first clipper system is expected to
track just south of Upper Michigan across Wisconsin. This should
keep the higher QPF and accumulating snow around or south of the
Michigan/Wisconsin border. The main concern is the upslope flow and
developing lake effect on the back side of this system initially
across the Keweenaw and then transitioning to the northeast wind
snow belts during the afternoon hours on Wednesday. Forecast
soundings across the north central portions of Upper Michigan look
sufficient for accumulating lake effect snow with inversions lifting
to around 8k feet at times with enhanced lift through the DGZ due to
the upslope northeast flow. Wednesday night through Thursday the
lake effect snow will transitions from the northeast to the west
wind snow belts as the flow backs in response to a developing low
pressure system across Lake Superior. Thursday night through Friday,
there are chances for snow across much of the area again as the
above mentioned surface low strengthens with as a potent shortwave
digs south across the Upper Great Lakes. The orientation with this
system and Upper Michigan will also bring the potential for some
lake enhanced snow across the northeast to north wind snow belts.

This weekend into early next week: As aforementioned upper-level
ridge finally begin to break down across the west, a pattern change
is expected towards early next week. In fact, it looks like we may
get out of northwest by at some point late next week. Behind the
exiting clipper system discussed above we could see lake effect snow
showers linger, but as surface ridging moves overhead this should
help diminish some of these showers Saturday into Sunday. Towards
the end of the weekend/early next week, a shortwave will dig across
the Upper Great Lakes region and bring another chance for widespread
snow and lingering lake effect behind.

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1254 PM EST TUE DEC 12 2017

Although conditions will improve this afternoon with decreasing
wind, some light lake effect will continue at KIWD/KCMX through mid
afternoon and at KSAW into early this evening. Otherwise, mainly
MVFR conditions will improve to VFR this evening at KSAW/KIWD and
toward midnight at KCMX. MVFR conditions are expected to return late
tonight into Wednesday morning at KIWD with light snow from a
clipper system moving through the region.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 516 AM EST TUE DEC 12 2017

Northwesterly gales to 35 will possible over the central and eastern
zones thorough late this morning. Combined with increasing waves and
low temperatures in the lower teens, heavy freezing spray is likely
through this morning. Winds will decrease to 20 to 30 knots late
this morning and then below 20 knots by Wednesday morning. Winds
will then increase to 15 to 25 knots late Thursday and into Friday
as the next system approaches from the west.

Upper Michigan...
  Winter Storm Warning until 7 PM EST this evening for MIZ005-006-

  Winter Weather Advisory until 7 PM EST this evening for MIZ007-

Lake Superior...
  Heavy Freezing Spray Warning until 1 PM EST this afternoon for

  Gale Watch until 7 PM EST /6 PM CST/ this evening for LSZ162-263.

Lake Michigan...


LONG TERM...Ritzman
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