Area Forecast Discussion
Issued by NWS Duluth, MN

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685
FXUS63 KDLH 110929
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
329 AM CST Sun Dec 11 2016

.SHORT TERM...(Today through Monday)
Issued at 329 AM CST Sun Dec 11 2016

High pressure was located over Ontario at 08Z/2am, while low
pressure was in western Nebraska. An inverted trof extended from the
low into west central Minnesota, while a stationary boundary was
over western Lake Superior. Some very light snow/flurries was
occurring over the far southern tier of zones in the vicinity of the
trof/front. A lake effect band of snow was just offshore of the
north shore of Lake Superior. Some of the snow has moved inland near
BFW. This lake effect band has been waffling along the north shore
since midnight, but remaining primarily offshore. This has been due
in large part to a northwest wind along the shore. The shear has
been enough to keep the snow band from organizing. The primary band
of moderate to heavy snow has been over southern and central
Minnesota. FGEN was maximized in this area. Otherwise, a mainly
clear sky was located over the northern half of the forecast area
and had allowed temps to drop into teens below zero, with an
isolated area of less than 20 below zero near Kabetogama in northern
St. Louis county.

Look for the light snow to gradually spread north through the day as
the surface low drifts east. Meanwhile, a closed upper low moves
into eastern North Dakota by 18Z today, then into northern Minnesota
where it opens into a trof by 00Z Monday. Models have come in with
less QPF than the previous forecast. Even with the arrival of the
trof, snow amounts will be less than previous forecast. Expect a
general swath of 1 to 3 inches of snow across much of the region.
With these lower totals, which are in alignment with the SREF plumes
for mean snow totals, and guidance from the Weather Prediction
Center, have therefore dropped the winter weather advisories. Have
also reduced the snow amounts along the north shore as warm air
advection will occur in the 1000-925mb layer through the day. This
will effectively limit any snow amounts, and is seen in the NAM and
ECMWF.

The surface low and the upper trof will exit the forecast area
tonight. This will bring an end to the snow from west to east. Some
snow will linger over the Arrowhead and northwest Wisconsin. Even
though the flow over Lake Superior will become northwest tonight,
the warm air form earlier in the day is in place along the south
shore which will limit any lake effect potential. Still have pops
regardless.

A brief break into the snow occurs Monday morning as a ridge of high
pressure drifts over the region. By Monday afternoon, snow begins to
spread across much of the area as the next upper level trof moves
into northern Minnesota from Canada. This pushes a cold front across
the region resulting in the light snow. Amounts will be light.

.LONG TERM...(Monday night through Saturday)
Issued at 329 AM CST Sun Dec 11 2016

The focus remains on the very cold, Arctic air that will blast into
the Northland this week, but there is also increasing attention to
the potential for accumulating snow from a potential winter storm
system late this week. The coldest air yet seen this season is
projected to hit the Northland during the middle of the week,
sending temperatures nose-diving to well below seasonal normal. The
latest models in general trended colder for some of the overnight
low temperatures, but generally held steady with daytime high
temperatures, through the middle of the week. While temperatures
will rebound a bit late this week, there are increasing signs a
winter storm system could track across the Central Plains to the
Great Lakes Friday through Saturday, which could bring accumulating
snow and cold, wrap-around flow (and accompanying visibility
reductions with falling and blowing snow) to the North Central US,
including the Northland.

A couple cold front passages, one Monday afternoon & evening and
another Tuesday night & Wednesday morning, will bring blasts of
frigid Arctic air into the Northland. Temperatures will nose-dive to
about 20 degrees below seasonal normal by Wednesday. This will be
the coldest air yet seen this season, with subzero or near zero
degree daytime high temperatures on Wednesday and four successive
nights with overnight low temperatures around -5 to -10 degrees.
There will likely be widespread wind chills reaching -20 to -30
degrees Tuesday, Wednesday, and Thursday mornings. The coldest of
those wind chills, -25 to -30 degrees, would likely be across
northeast Minnesota, possibly prompting the issuance of wind chill
advisories when the time comes.

The cold fronts will be relatively free of any significant snow, but
will likely bring broken/overcast low cloud cover and snow flurries
or very light coating of snow. The first front, late Monday, has the
better potential for snow, even if it`s just a minimal coating, in
part due to better synoptic lift from better falling heights and the
air not being as cold (and being able to hold more moisture) as the
secondary cold front.

The very cold air mass will shift east Thursday, and light southerly
flow Thursday night will begin to bring in warmer air. However, the
passing surface ridge will promote very light wind speeds Thursday
night, and any clearing could easily result in another night of well
below 0 low temperatures.

The models continue to suggest a winter storm system could affect
the Central US late this week. The GFS and ECMWF are in relatively
good agreement in developing a well-organized low in eastern
Colorado Friday, ejecting the low into the Central Plains Friday
afternoon and night, then lifting the low to the Great Lakes region
Saturday. The GFS takes the low through southern and eastern
Wisconsin, followed by northern Lake Michigan (and this track is
close the GFS Ensemble mean). The ECMWF is farther south with a
track through eastern Iowa,the northwest tip of Illinois, followed
by the Milwaukee area and central Lake Michigan. Both models
indicate the potential for widespread accumulating snowfall across
the Northland, combined with frigid north to north-northwest flow of
about 10 to 15 mph, which could significantly reduce visibility. The
greatest impacts in our forecast area would likely be from the
Interstate 35 corridor area in Pine County Minnesota and across
northwest Wisconsin, if the low takes a track similar to these
latest model runs. Despite the relatively good agreement between the
GFS and ECMWF this far out, there is still quite a bit of
uncertainty considering the Canadian has a much less organized-low
(with the upper-level centers of low pressure largely displaced by
the low-level centers of low pressure) and its surface low taking a
track much farther south. The last available frame of the Canadian
model run has the surface low in Oklahoma by Friday evening, whereas
the GFS and ECMWF eject the low through southern Nebraska and
Kansas, respectively. This system is still quite far out, with the
wave still well out in the Pacific Ocean, so it would not be
surprising to see substantial model changes over the coming days.
Nonetheless, we will be keeping a close eye on run-to-run changes on
this system.

There could also be a period of lake effect snow for areas of the
South Shore, downwind of the Arctic flow over western Lake Superior
over the coming weekend in the wake of the passing storm system.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1139 PM CST Sat Dec 10 2016

Light snow has developed over portions of the Northland late this
evening. One area stretched from the Brainerd Lakes region east
through Hayward and Park Falls. A second area was from the Twin
Ports area north along the North Shore. The snow in southern areas
may diminish or end for a bit but will expand again overnight
continuing into Sunday. The snow from the Twin Ports up the North
Shore should continue as low level winds back to east to
southeast. Ceilings were VFR for most areas, with pockets of MVFR.
MVFR ceilings will prevail from near the Twin Ports along much of
the North Shore late this evening lowering late and into Sunday.
Elsewhere, ceilings will be lower through the period to MVFR or
IFR. The visibility will drop to IFR or MVFR in snow for most
areas.

The snow will decrease in area and intensity from west to east
Sunday afternoon into the evening.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  20   7  12  -7 /  80  40  30  20
INL  12   0   6 -12 /  40  10  30  20
BRD  18   4  10  -8 / 100  10  40  10
HYR  21  10  16  -6 /  90  20  20  30
ASX  22  14  18  -1 /  80  40  20  30

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&

$$

SHORT TERM...GSF
LONG TERM...Grochocinski
AVIATION...Melde



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