Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 120820

Area Forecast Discussion
National Weather Service Marquette MI
320 AM EST Tue Dec 12 2017

Issued at 1034 PM EST MON DEC 11 2017

Just a quick update to the discussion regarding headlines. High-res
models in fairly good agreement that a dominant band will set up
along the Marquette-Alger County line in strongly convergent north-
northwest wind flow and moist unstable environment to 8 kft
resulting in lake induced CAPEs exceeding 800 j/kg and lake
equilibrium levels exceeding 11 kft per NAM soundings. This band
is fcst to reach well into northern Delta County given the strong
nnw winds and will impact travel with whiteout conditions tonight
along Highways M-35 and US-41 from Marquette-Harvey heading
south. So have elected to include Delta in a warning. Expect to
see storm total accumulations exceeding a foot over portions of
northern Delta County.

Also included southern Schoolcraft in a winter wx advisory as strong
nnw winds will push les bands far enough south to impact locations
along Highways M-94 and M-77 with occasional whiteout conditions.

All other headlines appear to be on track.

.SHORT TERM...(This evening through Tuesday)
Issued at 356 PM EST MON DEC 11 2017

Heavy lake effect snow and blowing snow are the primary hazards in
the short term, but lakeshore flooding/beach erosion is expected E
of Marquette as well.

Gusty NW winds and lake effect snow have already begun in the
Keweenaw this afternoon behind a compact SFC low over NE Lake
Superior. The low will shift to the SE of the CWA tonight, leading
to strong NNW winds over and near mainly central and eastern Lake
Superior. Models trended stronger with winds, so now expecting gusts
to 50mph tonight near and E of Marquette. That combined with
moderate to heavy LES will lead to blowing snow, especially along
the shoreline tonight into Tue morning. Winds and blowing snow
will then diminish Tue afternoon and evening.

Outside of the N-central U.P. LES will be light to moderate, with
generally 2-5 inches expected through Tue. Main show is over the N-
central, where a more dominant type LES band originating from Lake
Nipigon is expected. Exactly where the band hangs out is more
uncertain, but the majority of high-res models keep it near and just
E of Marquette. Depending on placement and residence time of the
stronger band, could see somewhere around 17 inches of snow through
Tuesday in far eastern Marquette and far western Alger Counties.
Elsewhere across the N-central, expect 6-10 inches in the NNW wind

Large waves up to 16 feet will result in beach erosion and lakeshore
flooding tonight into Tue morning in Alger County.

No changes were made to hazards and forecast thinking has changed
little from the previous shift.

.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 06Z TAFS through 06Z Tuesday night)
Issued at 1242 AM EST TUE DEC 12 2017

NNW lake effect snow and blowing snow will impact all the TAF sites
late tonight into Tuesday. As is typical with lake effect,
conditions will likely vary more than shown in the forecast but will
typically range from IFR to MVFR. A large, dominant lake effect snow
band setting up over eastern Lake Superior should stay mostly E of
KSAW, but may occasionally move into the TAF area with visibilities
below 1/4SM. Although conditions will improve Tue afternoon with
decreasing wind, some lake effect could continue mainly at KSAW into
Tuesday evening.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 356 PM EST MON DEC 11 2017

Northwesterly gales of 35 to 45 knots will develop this evening with
the highest gusts expected across the central and eastern zones.
Combined with increasing waves and low temperatures in the lower
teens, heavy freezing spray is likely tonight through early Tuesday.
Winds will decrease to 20 to 30 knots late Tuesday 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 Weather Advisory until 7 PM EST this evening for MIZ007-

  Winter Weather Advisory until 10 AM EST /9 AM CST/ this morning
     for MIZ001>004-009.

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

  Lakeshore Flood Advisory until 10 AM EST this morning for MIZ006.

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

  Gale Warning until 11 AM EST this morning for LSZ248>251-265>267.

  Gale Warning until 5 AM EST early this morning for LSZ243>245-

Lake Michigan...
  Gale Warning until 11 AM EST this morning for LMZ221-248-250.



LONG TERM...Ritzman
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