Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 050930

Area Forecast Discussion
National Weather Service Marquette MI
430 AM EST Mon Dec 5 2016

.SHORT TERM...(Today and tonight)
Issued at 427 AM EST MON DEC 5 2016

Upper air pattern consists of a 500 mb trough over the upper Great
Lakes this morning and another shortwave over the northern Rockies.
There is also a closed 500 mb low over northern Saskatchewan. The
shortwave over the northern Rockies heads east and moves through the
northern plains tonight. This shortwave brings in some 850-500 mb q-
vector convergence along with some deeper moisture overnight.
Overall, did not make too many changes to the going forecast. Pcpn
pulls out this morning with sfc ridging quickly moving through. Have
some pcpn with the next shortwave and warm air advection moving into
the west late today with slight chance pops late in the afternoon
across the west. Put in some chance pops across the far west tonight
as warm air advection pcpn moves through and slight chance pops
elsewhere as the warm air advection moves through. Still looks like
there will be a rain/snow mix as this moves through overnight, but
amounts will be low.

.LONG TERM...(Tuesday through Sunday)
Issued at 430 AM EST MON DEC 5 2016

Main attention continues to be Wed through at least Fri night as
significant LES kicks in.

A low pressure system will gradually move from northern MN Tue
through Ontario and into Quebec by Thu. Cold air moving in with the
system will lead to WSW wind LES on Tue night will probably impact
the Keweenaw, accumulations should be on the light side as 850mb
temps will only be around -9C. Winds will gradually turn W on Wed as
the system moves E, with light LES continuing.

Most attention is on Wed night into Fri along and behind a shortwave
and SFC trough/cold front that moves through. 850mb temps fall to
around -15C on Thu, which when combined with the other forcing
mechanisms leads to potential for moderate to heavy snow in the NW
wind snowbelts, and briefly along all of the north shores of the
U.P. as the trough passes. Only have snowfall amounts through Thu
right now, but an early prediction of up to around a foot of snow
just Wed night through Thu for the W and NW, and around 6 inches E
near Lake Superior. Additional persistent snowfall into Fri will add
to those totals. Exactly how long the LES continues is uncertain as
models differ on when to switch flow around to the south. The ECMWF
if faster in doing so on Fri, while the GFS doesn`t switch winds the
southerly until Saturday morning. Blowing snow will also be an issue
along Lake Superior Wed through Fri. Plenty of uncertainty for the
weekend and early next week, so just let the blends handle that.

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1153 PM EST SUN DEC 4 2016

In the wake of departing disturbance, expect slowly improving
conditions at KIWD/KCMX/KSAW as -sn ends and drier air eventually
spreads into the area. Arrival of high pres ridge and anticyclonic
flow today will further aid the improvement. Before -sn ends, the
pcpn may change to -FZDZ, which may linger into the mid morning hrs
at KCMX. Otherwise, expect prevailing MVFR conditions at KIWD to
improve to VFR mid morning as low clouds scatter out. Conditions at
KCMX will likely vary btwn MVFR and IFR with IFR more likely during
the early morning hrs when winds veer to an upslope westerly
direction. Low clouds should scatter out at KCMX by early aftn. At
KSAW, expect prevailing MVFR conditions to improve to VFR during the
mid morning hrs as low clouds scatter out.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 427 AM EST MON DEC 5 2016

Active period on the upper Great Lakes as several gale events will
occur. First gale event will be Tue morning with south gales to 35
knots on the eastern lake as a trough moves through the area. Next
event will occur with cold air advection Tue night and Wed with SW
to W gales to 35 knots. A tight pressure gradient will be across the
area along with colder air moving across the warmer waters.  NW
winds to 30 kts will continue Wed night into Fri as colder air
moving in increases over water instability.

Upper Michigan...
Lake Superior...
  Gale Warning from 7 AM to 1 PM EST Tuesday for LSZ266-267.

Lake Michigan...


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