Area Forecast Discussion
Issued by NWS Marquette, MI

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897
FXUS63 KMQT 050927
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
427 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...(Monday night through Sunday)
Issued at 258 PM EST SUN DEC 4 2016

Late Mon into Mon night the Great Lakes will be within shortwave
ridging btwn the shortwave trough (bringing the snow to Upper
Michigan this aftn) exiting across New England and rather strong
shortwave trough crossing the northern Plains and pivoting north
into southern Manitoba and northwest Ontario. Could see light snow
showers into far west cwa Mon night as h7 moisture/h7-h5 q-vector
convergence pass by mainly to the west. Associated sfc low deepens
blo 1000mb along the SE Mantioba/Ontario border by 12z Tue which
sends a sfc cold front toward western Upper Michigan. Could be light
rain/snow around on Tue over parts of Upper Michigan as the front
crosses especially if the GEM and ECMWF are on track showing
stronger shortwave/h7-h5 q-vector convergence lifting across WI and
Upper Michigan Tue aftn into Tue evening. Temps should be steady or
even fall slightly over the west as colder air works in from the
northern Plains. Could be lake effect on the Keweenaw but should be
light as inversion remains less than 5kft and winds are more SW than
W.

Shortwave trough becomes more of an upper low Tue night into Wed
with sfc low slowly crossing northern Ontario. As this occurs,
another shortwave trough will be tracking across the southwest conus
to the southern Plains with a sfc low crossing vcnty of northern
TX/OK. On Wed, expect lake effect to affect more of the northwest
cwa as colder air moves in with h85 temps down blo -12c and as sfc-
h85 winds veer more W or even NW if the more aggreesive GFS is
correct. Inversion heights around 5kft increase to 6-8kft bringing
dgz into much of lake convective layer so there should be moderate
les. Snow showers over the west could become heavy at times if
stronger low-level convergence develops. Away from the lake effect
the cooldown will be well underway with daytime highs in the 20s
most areas. Could be breezy especially near Lk Superior.

Deep trough aloft with widespread cold air will continue to occupy
much of the eastern half of the Conus late this week with the cold
reaching the deep south and Gulf coast by Fri. Over the Great Lakes,
lake effect snow will be the main story. Areas favored by NW winds
will see the the most snow across Upper Michigan as h85 temps
continue to fall to around -15c by late Thu into Fri. Plenty of deep
moisture to h7/10kft with large scale troughing and low level
cyclonic flow so lake effect may be moderate to even heavy depending
on when shortwaves work through to enhance the snow further. Though
the TX/OK wave and sfc low look to stay south of Upper Lakes
limiting widespread system snow, once that system lifts across New
England late Thu into Thu night it should help a reinforcing cold
front drive across the Upper Great Lakes. GFS continues to be on the
faster side with the fropa (Thu aftn) and ECMWF is slower (Fri
morning into early Fri aftn). As this front moves through winds
could become more NNW or N so lake effect could shift around from
the northwest flow areas to the northerly flow areas for a time.
Unlike the regime we have been in the last week or so with only
marginally cold low-level temps, low-level temps late this week will
be sufficiently cold for snow, so should see snow all areas, even
near the Great Lakes shorelines.

Lake effect will continue at least into Sat morning for NW flow
areas, especially over eastern cwa. Another shortwave works across
north central Conus by next Sun. Sfc low should accompany the
trough. Have to wait on specifics in terms of system snow across
Upper Lakes, but just from a pattern recognition standpoint, should
see lake enhanced snow off Lk Michigan since h85 temps are blo -10c
as the system approaches. Certainly by late next week and next
weekend it will look and feel more like winter across most of Upper
Michigan.
&&

.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.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Gale Warning from 7 AM to 1 PM EST Tuesday for LSZ266-267.

Lake Michigan...
None.
&&

$$

SHORT TERM...07
LONG TERM...JLA
AVIATION...Rolfson
MARINE...07



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