Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 101753

Area Forecast Discussion
National Weather Service Marquette MI
1253 PM EST Sat Dec 10 2016

Issued at 1017 AM EST SAT DEC 10 2016

Dropped warning for Ontonagon and advisory for southern Houghton.
Heavy lake effect continues for portions of Keweenaw Peninsula and
mainly east of Munising along Lk Superior. Westerly convergent flow
set up farther north so have dropped warning for Ontonagon county and
dropped advy for southern Houghton. Big time snow occurred with the
significant lake enhanced setup with amounts in the 1 to 2 feet range
over higher terrain north of Houghton and near a foot around Grand
Marais in Alger county. Models are really doing poorly with pegging
location of dominant bands across Keweenaw but are doing fair job
with the bands over the eastern cwa. Both areas should see several
more inches of accumulation, maybe up to 8 inches, through late this

Expect the heavy lake effect to diminish by the evening, though it
may hang on into the evening over northern Keweenaw. Winds shifting
southerly tonight ahead of low pressure moving into the plains and
high pressure shifting to Quebec should end the lake effect, though
we will have to start looking at lake enhanced snow potential off Lk
Michigan by Sun.

.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 18Z TAFS through 18Z Sunday afternoon)
Issued at 1252 PM EST SAT DEC 10 2016

Lake effect will be in and out of CMX into early this evening. IFR
vsby mainly through brief reduction to VLIFR is possible late this
aftn as heaviest band of snow moves back across. Conditions improve
to VFR late tonight into Sun morning. At IWD expect mainly MVFR to
VFR cigs until system snow with IFR vsby/MVFR cigs moves in on Sun
morning. SAW will remain VFR until midday Sun when system snow moves
in. Expect all sites to drop to LIFR/IFR conditions on Sun aftn as
low pressure system crosses the region.

.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 MIZ003-

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

Lake Superior...
Lake Michigan...


LONG TERM...Beachler
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