Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 091959

Area Forecast Discussion
National Weather Service Marquette MI
259 PM EST Sat Dec 9 2017

.SHORT TERM...(Today and tonight)
Issued at 422 AM EST SAT DEC 9 2017

A clipper system charged across the region during the overnight
hours and is currently centered over southeast Wisconsin this
morning, with an inverted surface trough draped across central and
eastern portions of the area. With enhanced convergence along this
inverted surface trough, and fairly weak synoptic flow a few
mesolows have developed - one over the northern half of the Bay of
Green Bay and a couple across the southern shore of Lake Superior.
Otherwise, unidirectional flow out of the north continues to push
eastward across the area, as evident on IR satellite imagery showing
colder cloud tops becoming more prevalent across Lake Superior this
morning. Lake effect snow has already begun impacting the west this

Today: We`re still looking at accumulating lake effect snow this
morning across the north wind snow belts as flow behind the exiting
surface low becomes northerly across the region. There are multiple
different aspects to this lake effect snow event, including mesolows
coming on shore this morning across the north central and east,
followed by more numerous and widespread lake effect snow expected.
As these mesolows come on shore, primarily looking at Marquette
County early this morning and then Alger/Luce counties later this
morning, expect a quick burst of snow where snowfall rates may
approach 1 to 2 inches an hour. Then, behind these leading mesolows,
an additional 3 to 6 inches is expected through the rest of the day;
however, as we progress into the afternoon hours the focus for
additional lake effect snow will transition to the northwest,
and west wind snow belts.

Across the west, the lake effect snow has already begun and will
continue through the morning hours. As we progress through the
afternoon hours surface ridging will begin to build in the western
half of Upper Michigan. This will allow flow to transition from north
to west-northwest, as well as the lingering lake effect snow.

Tonight: With yet another wave digging south across the region,
another surface trough is progged to develop across Lake Superior.
This trough will enhance low-level convergence across the ongoing
lake effect snow in the west to northwest wind snow belts.
Therefore, have opted to extend the winter weather advisory into
Sunday for the northwest and eastern portions of Upper Michigan.
Given the enhanced lift along the surface trough, forecast soundings
show strong lift through the DGZ and inversions deepening to around
10k feet. Therefore, like the current thinking of the high-res
models with higher QPF tonight into Sunday morning mainly across the
Keweenaw and around/east of Munising. Have increased QPF and snow
ratios over those areas as the snow should be highly efficient. It
is possible that snowfall accumulations during this time period may
top 8 inches in some locations, so the ongoing advisory may need to
upgraded to a warning.

.LONG TERM...(Sunday night through Saturday)
Issued at 259 PM EST SAT DEC 9 2017

The continued northwest flow will persist through much of the
extended periods, as the 500mb trough carved over the Great Lakes
region will slowly begin to weaken. Upstream amplified ridging will
begin to weaken; however, the ridging remains and will continue to
send weak lobes of vorticity southeast towards the Upper
Midwest/Great Lakes region.

Sun ngt thru Tue will feature a clipper moving south across Central
Wisconsin, which will allow winds to turn easterly/northeasterly.
This will likely setup ideal conditions for LES bands to push inland
towards Marquette County during the day Mon. Guidance differs on how
much QPF will accompany the system; however, it does appear SLR will
be hovering in the 25:1 to 30:1 range. Have nudged QPF down to
around .25 to .50" from 00Z Sun thru 00Z Wed, with the bulk falling
midday Mon thru late Mon ngt. Snowfall totals could exceed 6" for
portions of Marquette County, mainly closer to Lake Superior and
Alger County. As the clipper slides southeast, winds will turn
northerly and then northwesterly. Weak surface ridging is progged to
push into the upper midwest Tue; however, it does not arrive over
the Upper Peninsula. Which indicates we will continue a northwest
flow and likely periodic LES.

Temps Mon/Tue will be well below normal, with highs likely
struggling to warm beyond the low/mid-teens.

Another shortwave will dive southeast Wed/Thur, with increased
chances for periodic snow showers and continued temps in the 20s
with overnight lows in the single digits above zero.

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 117 PM EST SAT DEC 9 2017

Lake effect will generally taper off through this evening, though
probably not completely end at KCMX. Lake effect will ramp back up
tonight mainly at KCMX, but also at KIWD to some degree. KSAW may
see some lake effect nearby Sun morning.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 422 AM EST SAT DEC 9 2017

Wind gusts will primarily remain between 20 and 30 knots through the
weekend before a brief decreased to less than 15 knots Sunday night
into Monday. However, late Monday into Tuesday gales of 35 to 40
knots look possible, especially across the central and eastern half
of the lake. Winds will drop below 30 knots by Tuesday night, and
further decrease to around or below 15 knots on Wednesday.
Occasional freezing spray is likely into the middle of next week. We
could see heavy freezing spray develop Monday night into Tuesday,
especially across the north central portions of the lake.

Upper Michigan...
  Winter Weather Advisory until 2 PM EST Sunday for MIZ006-007-085.

  Winter Weather Advisory until 11 AM EST Sunday for MIZ001>004-

  Winter Weather Advisory until 4 PM EST /3 PM CST/ this afternoon
     for MIZ005-009.

Lake Superior...
Lake Michigan...


SHORT TERM...Ritzman
LONG TERM...Beachler
MARINE...Ritzman is the U.S. government's official web portal to all federal, state and local government web resources and services.