Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 120543
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
1243 AM EST Tue Dec 12 2017

.UPDATE...
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
snowbelts.

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...(Tuesday night through Monday)
Issued at 426 PM EST MON DEC 11 2017

Models and ensembles suggest that the pattern featuring a mid/upper
level ridge over wrn North America and a trough from nrn Canada into
the ern CONUS will persist through this week but gradually deamplify
into this weekend. Several clipper shortwave troughs will
continue to brush the nrn Great Lakes bringing periods of light
snow followed by additional LES. Temperatures will remain below
seasonal averages until the weekend with temps climbing to around
average.

Tuesday night, the higher res models suggest that as the winds
diminish, the lake induced trough and land breeze will keep the
stronger low level conv and heavier snow bands just to the east of
marquette into wrn Alger county where additional amounts in the 3 to 6
inch range are possible. However, there is still some uncertainty
with the location of this mesoscale feature. Otherwise, LES amounts
in the 1 to 3 inch range are expected. Over the west, sfc ridging
building into the area with winds becoming offshore, and inversion
heights at or below 4k ft should limit accumulations to an inch or
less.

Wednesday, winds becoming light and then southeast as a weak shrtwv
moves toward the area and a stronger shrtwv moves through ern
Nebraska to Missouri will end the lingering LES over most of the
cwa. However, there may still be some very light amounts into the
north central and the Keweenaw.

Wed night-Fri, frequent clipper shrtwvs about 12 hours apart will
bring periods of light snow to the area with the potential for
additional moderate to heavy LES as winds shift to the w and nw-n
in the wake of the weak associated sfc troughs/lows. Confidence in
the timing of these features and potential LES accumulations is
low.

Sat-Mon, Models/ensembles still show a large spread with the
track of the Sat shrtwv and sfc low that could bring a more
significant area of snow, as the ECMWF remains farther south
compared to the GFS/GEFS.
&&

.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.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory until 7 PM EST this evening for MIZ007-
     014-085.

  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-
     013.

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

Lake Superior...
  Heavy Freezing Spray Warning until 1 PM EST this afternoon for
     LSZ264-266-267.

  Gale Warning until 11 AM EST this morning for LSZ249>251-266-267.

  Gale Warning until 10 AM EST this morning for LSZ248-265.

  Gale Warning until 5 AM EST early this morning for LSZ243>245-
     264.

  Gale Warning until 1 AM EST /midnight CST/ early this morning
     for LSZ240>242-263.

Lake Michigan...
  Gale Warning until 7 AM EST this morning for LMZ221-248-250.

&&

$$

UPDATE...Voss
SHORT TERM...Titus
LONG TERM...JLB
AVIATION...Voss
MARINE...BB


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