Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 101031

Area Forecast Discussion
National Weather Service Marquette MI
531 AM EST Sat Dec 10 2016

.SHORT TERM...(Today and tonight)
Issued at 524 AM EST SAT DEC 10 2016

Main threat in the short term is the heavy LES band moving over
Grand Marais and northern Luce County this morning. A meso-low can
be seen in radar data N of Marquette County that will cause the band
to be enhanced this morning. Up to another foot of snow is possible
today near Grand Marais and northwest Luce County. Up to 6 inches of
snow is possible today in a couple spots over northern Ontonagon and
central Houghton County. LES will push offshore this evening into
tonight ahead of a low pressure system. May see some LES off Lake
Michigan starting late tonight. Made no changes to winter headlines.

.LONG TERM...(Sunday through Friday)
Issued at 441 AM EST SAT DEC 10 2016

Main theme for the extended periods will continue to be on the
arctic air that will arrive early in the week and linger through the
bulk of the extended. Prior to the much colder air arriving, the
late weekend shortwave will be lifting northeast across Chicago late
Sun evening, but the effects will be overspreading the U.P. in the
late afternoon hours and continue through Monday, as strong
isentropic ascent through a moist column will likely push
accumulating snow to the area. Winds will be southeasterly, and
there could be enough cold air to see some minor enhancement off of
Lake Michigan to the snow. Operational solutions then lift the
shortwave northeast towards Toronto by daybreak Mon, with the
surface flow turning northeasterly then northerly Mon afternoon.

Surface ridge will slide southeast across the Missouri Valley, which
will place the Upper Midwest/Northern Great Lakes in a Northwest
flow in the lower-levels Mon in the wake of the departing surface
low. Upstream 500mb robust vort max will be starting to bleed south
from the Canadian Rockies, helping to sharpen the baroclinic zone
across the Northern Plains Mon aftn/eve.

Ensembles continue to show minimal spread amongst members in the
medium term with respect to the arctic frontal boundary approaching
the Upper Midwest late Mon ngt, then reaching the U.P. by early Tue.
An elongated surface trough will have a couple weak surface lows
from Wisconsin to just west of Hudson Bay, but expect these to
consolidate over Ontario early Tue. Much colder air will quickly
advect south/southeast from Canada towards the Great Lakes region,
with a potent 850mb thermal trough of -20 to -25 deg c air. This
will likely set the stage for high temps struggling to warm beyond
the single digits above zero, with the exception possibly being
areas immediately downwind of Lake Superior. As for LES, expect
several periods of light accumulating snow to occur in the extended;
however, the favored dendritic growth zone will be crashing towards
the surface and could limit flake size or accumulations but on the
flip-side visibilities could be impacted due to the abundance of
snow crystals. But again the main theme of the extended will be the
bitter cold temperatures in the single digits for highs and sub-zero
overnight lows.

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1255 AM EST SAT DEC 10 2016

Lake effect will continue at CMX through the TAF period with IFR to
MVFR vsby and MVFR cigs. Lake effect will move out of IWD by Saturday
morning but bkn cigs will stay MVFR. SAW should stay out of the lake
effect for the most part through the rest of the TAF period with
mainly VFR cigs.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 524 AM EST SAT DEC 10 2016

Expect NW winds up to 25 kts to diminish under 20 kts Sat night
through Mon as a weak high pressure ridge moves over the area. A
steady WNW wind to 30 kts will redevelop on Mon night into Thu
following a strong cold frontal passage that will introduce arctic
air into the Upper Lakes. Expect some heavy freezing spray over at
least portions of the Lake on Tue night/Wed as this arctic air moves
into the area and waves at the end of fetch build to at least 10

Upper Michigan...
  Lake Effect Snow Warning until 7 PM EST this evening for MIZ002-

  Lake Effect Snow Advisory until 7 PM EST this evening for MIZ001-

  Lake Effect Snow Advisory until 1 PM EST this afternoon for

Lake Superior...
Lake Michigan...


LONG TERM...Beachler
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