Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 050006

Area Forecast Discussion
National Weather Service Marquette MI
706 PM EST Sun Dec 4 2016

.SHORT TERM...(This evening through Monday)
Issued at 405 PM EST SUN DEC 4 2016

12Z raobs/latest wv imagery and RAP analysis show a fairly strong
shrtwv moving e thru srn MN/Iowa toward the the wrn Lower Lks,
accompanied by 12hr h5 hgt falls close to 100m. Although the sharper
dvpa/deep lyr qvector cnvgc/upr dvgc are passing to the s closer to
the shrtwv track, widespread snow has overspread the cwa under the
the colder cld tops expanding into the Upr Lks under the general upr
diffluence/waa ahead of the shrtwv. The pcpn is beginning to
diminish over much of MN/wrn WI as the colder cld tops pass to the
ne of those areas.

Main fcst concerns in the short term focus on pops/sn amounts/going
headlines into tngt associated with shrtwv passing to the s.

Late Today/Tngt...The nrn edge of the sharper forcing wl impact the
se half of the cwa thru this evng, when a steady s wind off the
relatively warm waters of Lk MI under h85 temps remaining as low as
-6 to -7C wl result in some lk enhancement. Thus carried the more
persistent, hier pops in that area. Some of the hier res models
indicate over 0.50 inch of liquid equivalent pcpn wl fall in some
areas under the heavier bands that could impact the cwa e of a line
fm about Escanaba to Munising into Schoolcraft County. Relatively
hi/narrow dgz shown on the fcst sdngs wl result in sn/water ratios
10-15:1, butnot out of the question some places in this area could
see up to 5-6 inches of wet snow. The sly flow off the relatively
warm waters of Lk MI and the Green Bay may result in a mix with rain
at some places along the shore and hold down accums in those areas.
Away fm the area of enhancement, expect up to 2 to 3 inches of wet
sn under axis of 2g/kg of h7 specific humidity in the mid lvl mstr
surge ahead of the shrtwv to the s. Going winter wx advys include
Delta, Alger, Schoolcraft and Luce Counties until 06Z, when the
larger scale forcing wl exit to the e and give way to dnva/deep lyr
qvector dvgc/subsidence/mid lvl drying ahead of trailing shrtwv rdg
axis. There could be some drizzle/freezing drizzle over mainly the
hier terrain fm the Porcupine Mtns thru the Keweenaw as the incrsgly
shallow mstr wl occur under the dgz in the presence of an upslope
wsw wind behind the passing sfc lo pres trof.

Mon...Although some lgt pcpn may linger in the mrng over mainly the
Keweenaw with the upslope wly flow ahead of an aprchg hi pres rdg,
the arrival and passage of this rdg axis should end that pcpn and
allow for at least partial sunshine at many places under the mid lvl
drying associated the passing shrtwv rdg axis. But many of the
models show more waa clds arriving in the aftn as the llvl flow
shifts to the s following the passage of the sfc hi pres to the e.
Some of the models even generate some light pcpn over the wrn cwa
where the sharper isentropic ascent and some pva ahead of a shrtwv
moving thru the nrn Plains results in some deep lyr qvector cnvgc/
greater mid lvl moistening. H85 temps recovering to near 0C wl
support abv normal max temps well into the 30s and perhaps the lo
40s, especially over the w with a downslope s wind.

.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

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

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 705 PM EST SUN DEC 4 2016

As disturbance that has generated -sn shifts e, 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 on Mon will aid the improvement. At KIWD, MVFR
conditions should fall back to IFR for a time overnight, before
improving to VFR Mon morning as low clouds scatter out. At KCMX,
expect LIFR conditions to improve to MVFR by late evening, but will
likely fall back to IFR early in the morning as winds veer to an
upslope westerly direction. Not out of the question that there could
be some -FZDZ under this upslope w wind. Low clouds should scatter
out at KCMX by aftn. At KSAW, IFR conditions this evening will
improve to MVFR overnight. Low clouds will then scatter out in the
morning, leaving VFR conditions for the remainder of the day.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 258 PM EST SUN DEC 4 2016

S to SW winds 20-30 kts through Mon then as low pressure trough
moves in Mon Night then deepens into to a low pressure system on Tue
northwest of Lk Superior, the tightening pressure gradient will
result in SW gales to 35 kts, especially over the west and north
central portions of Lk Superior. NW winds to 30 kts continue Wed
into Fri as colder air moving in increases over water instability.
The colder air and building waves will result in some freezing spray
by late in the week.

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

Lake Superior...
Lake Michigan...


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