Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 041518

Area Forecast Discussion
National Weather Service Marquette MI
1018 AM EST Sun Dec 4 2016

Issued at 1018 AM EST SUN DEC 4 2016

...Delta and Alger Counties added to winter weather advisory...

With some enhancement off Lake MI likely to impact mainly the e half
of Delta and Alger Counties, opted to include those counties in the
winter weather advisory that was issued earlier for Schoolcraft and
Luce Counties.  In fact, many of the hier res models show some
heavier wet snow bands influencing the e half of Delta and Alger
Counties. As is the case for Schoolcraft County, some rain may
mix with the snow near the shore of Delta County.

.SHORT TERM...(Today and tonight)
Issued at 409 AM EST SUN DEC 4 2016

Upper air pattern consists of a 500 mb shortwave over the northern
plains and a closed low over the southern Gulf of California. This
shortwave moves through the area this afternoon and evening. Deeper
moisture and 850-500 mb q-vector convergence moves through the cwa
through this evening, then both move out late tonight.

Made one big change to the forecast. Looks like there will be a Lake
Michigan lake effect snow component to the system for this afternoon
and evening. With Lake Michigan water temperatures around 6C and 850
mb temperatures forecasted to be around -6C, this is enough lake-850
mb delta-t with a south-southwest wind to get some lake enhanced
snowfall across Luce and Schoolcraft Counties. Could see up to 5
inches of snow in those places and issued a winter weather advisory
for snow for that reason. Mesoscale models in particular were
showing a mesoscale band of snow focusing over that area and for
that reason bumped up pops and qpf a bit for that reason in the ern
cwa. Overall though, that was the only big change made to the going
forecast. Did not change temperature much. Forecast hinges a lot on
a mesoscale narrow band of heavier snow affecting the ern cwa.
Otherwise, cwa will see anywhere from 1 to 3 inches of snow. Lesser
amounts will be along the Lake Michigan and bay of Green Bay

.LONG TERM...(Monday through Saturday)
Issued at 429 AM EST SUN DEC 4 2016

Main attention in the long term is Tue night-Fri when LES will occur.

A low pressure system will move across northern Ontario and Quebec
Tue through Fri, bringing 850mb down to -12C and WSW to W winds Tue
night through at least Wed. This will mainly favor the Keweenaw for
moderate LES. The upper trough and secondary SFC trough/cold front
moves through later (Wed night into Thu from the GFS and Thu night
from the ECMWF), turning winds NW and dropping 850mb temps as low as
-17C. With uncertainty in timing of the trough, there is, of course,
uncertainty as to when heaviest snow will fall and exactly where.
Moderate LES will continue to be possible through the end of the
work week. Blowing snow will also be an issue near Lake Superior.

Temperatures will remain favorable for LES through the weekend, but
wind direction is highly uncertain as models handle a shortwave
moving W-E across the CONUS quite differently.

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 611 AM EST SUN DEC 4 2016

An approaching disturbance will spread -sn across Upper MI today.
Conditions will likely fall to IFR at KCMX/KSAW in the aftn. At
KIWD, while prevailing MVFR conditions are expected with the -sn,
there may be some periods of IFR. MVFR conditions are expected in
the evening as the -sn diminishes/ends, though KSAW may remain IFR.
Late tonight, VFR conditions will move into KIWD and KSAW.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 409 AM EST SUN DEC 4 2016

Expect winds to remain 25 kts or less through Mon as the pressure
gradient remains relatively weak. An approaching low pressure trof
will tighten the gradient Mon night/Tue, resulting in sw winds up to
30 kts. There could be some w gales to 35 kts over mainly the
ncentral on Tue night into Wed under the tighter pressure gradient
on the southern flank of the deepening low pressure moving into nw
Ontario and with the arrival of colder air that will increase
overwater instability.

Upper Michigan...
  Winter Weather Advisory until 1 AM EST Monday for MIZ006-007-013-

Lake Superior...
Lake Michigan...


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