Winter Storm Warning 6, NWS Marquette, MI

Area Forecast Discussion
National Weather Service Marquette MI
453 AM EST Wed Dec 14 2016

.SHORT TERM...(Today and tonight)
Issued at 424 AM EST WED DEC 14 2016

...Blizzard conditions continue across the Keweenaw Peninsula
through this evening...

Early this morning winds have begun to turn more southwesterly to
westerly along the Keweenaw Peninsula and allowed the LES bands to
move inland. This is translating into conditions deteriorating
quickly. Expect the obs across the Keweenaw to frequently drop to
near zero for visibilities, with moderate and at times heavy
snowfall. Tight pressure gradient will produce gusty winds as well,
and with the low-density recent snowfall along with current snow,
considerable blowing/drifting will occur. LES setup becomes optimal
with surface flow and considerable lake induced instability
approaching 1000 j/kg; however, the strength of the surface flow
could result in more cellular like structure rather than dominant
bands. Nonetheless, continued heavy snow/white-out
conditions/blowing/drifting snow will persist for the Keweenaw. So
will leave current blizzard warning in place for these locations.
Elsewhere for Ontonagon/Houghton/Baraga, while lake effect bands
will be shifting into these counties, they don't appear to be as
potent. But with the combination of still gusty winds/blowing and
drifting of fresh snow will continue to create hazardous conditions.
At times vsbys will approach white-out conditions; however, the
frequency will be less and thus will hold onto the current winter
weather advisory handling the multiple elements.

By this afternoon another meso-low is progged to develop along the
eastern portions of Lake Superior, which will help to tighten the
pressure gradient over the marine areas and build waves considerably
along the shoreline for eastern Alger and Luce counties. This
appears to simultaneously enhance the moisture feed and LES band
into those counties and points east. Expect snow-liquid ratios to
generally be around 20:1 to 22:1, should easily see a few areas
receive upwards of 12-14 inches within the next 24hrs. But with the
blowing/drifting snow along with wind chill values hovering around -
15 to -20, have opted to go with a winter storm warning for Luce and
a winter wx adv Alger and Schoolcraft.

Lastly, the combination of winds and temps will continue produce
wind chills of -25 to -30 this evening to daybreak Thursday for
Gogebic/Iron/Dickinson/Menominee counties and have issued a wind
chill advisory for tonight in those counties. Elsewhere wind chill
values will not be as potent but close to around -20 to -25
deg.

.LONG TERM...(Thursday through Tuesday)
Issued at 452 AM EST WED DEC 14 2016

Main impacts during the extended will be the continued lake effect
snow and dangerous wind chills to begin the period and then
attention turns to moderate/widespread snow accumulation potential
Friday night through Sunday. Lake enhancement is also expected
Saturday into the day Sunday for north to northeast wind favored
snow belts.

Arctic air will remain in place through Friday before moderating
over the weekend ahead of an approaching low pressure system.
Overnight lows will be cold Thursday night with many areas of the
western U.P. dropping into the teens below zero to around 20 below
zero. The positive note is that the winds will begin to lighten up
as a brief ridge slides across the Upper Great Lakes region. Winds
speeds and gusts should remain under 10 mph. Of course, even a light
wind with these cold temperatures will feel very cold, but will
likely remain below advisory criteria due to the lighter winds. Wind
chills Thursday night will be around 20 below zero and 25 below
zero, mainly over the inland west U.P. Highs Thursday and Friday
will be in the single digits above zero to teens above zero
producing daytime wind chills around 5 below to 15 below zero.

Lake effect snow chances will continue over northwest to west-
northwest wind favored snow belts Thursday and Thursday evening
before winds begin to shift to the southwest overnight Thursday
through Friday. The more dominate northwest wind Thursday into
Thursday evening would place the heavier snow band over the far
eastern U.P. due largely to the increased fetch across Lake Superior
and more than sufficient temperature differentials between the Lake
Surface temp and 850mb temperatures.

Beyond the lake effect time period, Friday night through Saturday
night a broad low pressure system is set to slide from the Central
Plains northeastward into the Lower Great Lakes and then into
Southern Quebec. Ahead of this system, widespread snow is expected
to develop on isentropic asent on WAA ahead of the system Friday
night into Saturday morning. As the low slides across Lower MI on
through the day Saturday into Saturday evening, system forcing will
increase across the area and a north to nortwest wind lake enhanced
component will also increase. This would lead to a widespread
moderate snowfall across most of the U.P. with perhaps the higher
totals falling where the north to northwest wind enhancements occur.
Current model trends would indicate a widespread 4 to 8 inches of
snow across the U.P. from Friday night through Saturday evening.
Again, locally higher totals would be possible for the favored lake
effect snow belts, which currently seems to be the north wind
locations. Some uncertainty still exists, but current and previous
model runs are beginning to align a bit better. The big question
will be where the lake enhanced bands will set up based on the final
track of the surface low; however, it does look like significan
accumulations will be possible with this system.
&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 642 PM EST TUE DEC 13 2016

At KCMX, tt is becoming more evident that the bulk of the snow may
shift just north of the terminal late this evening, so a period of
MVFR and potentially briefly IFR conditions may exist overnight.
However, a trough tracking SE over Lake Superior early Wednesday
morning will shift the bands back across the terminal.

At SAW and IWD, non-favorable wind directions for LES will keep
conditions VFR through tonight, albeit with gusty westerly winds.
LES may begin to shift into both sites by late Wednesday morning.

AMD NOT SKED at KIWD, KCMX and KSAW due to national FAA data outage.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 452 AM EST WED DEC 14 2016

West-northwest to northwest gales of 35 to 40 knots will continue
across Lake Superior through Thursday. Gale warnings are in effect
across all of Lake Superior. The combination of waves building as
high as 12-17 feet at the end of the fetch and the very cold air
will result in periods of heavy freezing spray through Thursday,
leading to the continuation of a heavy freezing spray warning for
all of Lake Superior. Gales will end from west to east by Thursday
night. Expect soutwest to northwest winds of up to 20 knots Thursday
night through Friday. Increasing north to northeast winds to 30
knots late Friday night through Saturday are expected as a low
pressure system passes south of the region. West winds to 30 knots
will follow for Sunday.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory until midnight EST tonight for MIZ004-
     084.

  Winter Weather Advisory from noon today to 7 PM EST Thursday for
     MIZ006-085.

  Blizzard Warning until 7 AM EST Thursday for MIZ001-003.

  Wind Chill Advisory from 6 PM this evening to 11 AM CST Thursday
     for MIZ009>012.

  Winter Storm Warning from noon today to 7 PM EST Thursday for
     MIZ007.

  Winter Weather Advisory until 7 AM EST Thursday for MIZ002.

Lake Superior...
  Heavy Freezing Spray Warning until 7 AM EST /6 AM CST/ Thursday
     for LSZ162-240>244-263>267.

  Gale Warning until 1 PM EST Thursday for LSZ264>267.

  Heavy Freezing Spray Warning until 7 AM EST Thursday for
     LSZ248>251.

  Gale Warning until 1 PM EST Thursday for LSZ248>251.

  Gale Warning until 7 AM EST /6 AM CST/ Thursday for LSZ162-
     240>247-263.

Lake Michigan...
  Gale Warning until 7 PM EST this evening for LMZ221-248-250.

&&

SHORT TERM...Beachler
LONG TERM...KEC
AVIATION...Titus
MARINE...KEC

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