Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 140037
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
637 PM CST Wed Dec 13 2017

.SHORT TERM...(This evening through Thursday)
Issued at 314 PM CST Wed Dec 13 2017

Lake effect snow will linger through tonight across the Twin Ports
east across the south shore. An additional 1 to 3 inches of snow
is expected for the south shore with locally higher amounts
possible. Flurries/light snow possible through the day Thursday
as another (weaker) clipper approaches from the northwest.
Overnight lows in the single digits to low teens. Highs on
Thursday in the teens to low 20s.

Lake effect snow for tonight is the main concern for the short
term. While drier air will move in at mid-levels this evening in
the wake of the clipper today, low levels are expected to remain
saturated overnight. Low level winds support lake effect snow
bands transitioning from the Twin Ports east across the south
shore, with the highest amounts expected across the Bayfield
Peninsula and Gogebic range. Directional shear at low levels may
preclude a wide area of lake effect snow, but given the processes
are already at work over the lake there may be a few narrow bands
of heavier snowfall rates which produce locally higher snowfall.
Thus, we will leave the current Winter Weather Advisory that is
out for the south shore in effect overnight.

.LONG TERM...(Thursday night through Wednesday)
Issued at 314 PM CST Wed Dec 13 2017

The northwest flow pattern will continue through the extended with
several opportunities for snow showers and lake effect snow.

Thursday evening the trough will dig southward from northern
Manitoba reaching Upper Michigan by Friday evening. In addition, a
warm front will lift into western Minnesota/the eastern Dakotas due
to a low developing in northern Alberta late Friday afternoon. This
will bring chances of snow showers to much of the region Thursday
night into early Friday morning. Due to favorable flow aloft, lake
enhancement is expected along the south shore of Lake Superior. The
heaviest snowfall is expected Thursday night into Friday morning,
before drier air moves in due to a weak high nudging in from
Ontario.

Snowfall chances continue on Saturday into early Sunday as the
clipper in Alberta weakens as it moves southeastward reaching
Ontario/Manitoba by Sunday morning. There is potential for freezing
rain/drizzle Saturday afternoon into the evening as warm air advects
in aloft, in addition to drier air eroding ice aloft per the
NAM/GFS/SREF soundings. Added this chance to the forecast from the
Brainerd Lakes to the I-35 corridor, but may need to be refined if
the ice loss aloft is not as robust as current guidance suggests.
The upper level trough associated with the low will dig into the
Dakotas by Sunday morning and lift through the Northland by Sunday
evening. Snow chances will continue through much of northwest
Wisconsin during the morning, while precipitation tapers off during
the afternoon.

Another trough will dig in on Monday, but temperatures will be the
mildest of the extended as 850 hPa flow turns westerly, which will
advect warmer air into the region. The trough moving in will bring
increasing chances of snow to Minnesota and Wisconsin as the day
progresses. Highs range from the upper 20s in the Minnesota
Arrowhead, to the low 30s elsewhere. As the previous trough exits,
flow aloft will become northwesterly and advect cold air back into
the region for Tuesday and Wednesday. There are some hints that sub -
20 degree C 850 hPa temperatures will move in mid to late in the
week, which would bring in some of the coldest air of the winter so
far. There is still a lot of spread between deterministic and
ensemble guidance, so I am uncertain how cold temperatures will
be at this point. However, as highlighted by the Climate
Prediction Centers Day 8-14 Day Outlook, odds are tilted toward
below normal temperatures.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 637 PM CST Wed Dec 13 2017

Surface low pressure was centered along the Indiana and Michigan
border this evening with an inverted trough extending back into
northeast Minnesota. North to northeast low level winds were
occurring and the combination of these features was leading to
areas of MVFR ceilings and snow showers. The snow showers were
most widespread and heaviest from just east of Superior south
through Patzau, Holyoke, and Kingsdale. Drier will gradually move
south and the low level winds will back, especially around 850mb
which will introduce increasing shear. This should cause the snow
showers to diminish after 03Z or at least shift them further east
along the South Shore. Overall, MVFR conditions are expected
through the period. More light snow or flurries will develop late
tonight and through Thursday as yet another shortwave is forecast
to move through the area.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  10  18   5  14 /  20  20  30  10
INL   7  15   1   8 /  20  30  40   0
BRD  14  23  11  21 /  10  20  10  20
HYR  12  20   8  16 /  40  20  30  10
ASX  14  20  10  15 /  80  40  40  20

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory until 6 AM CST Thursday for WIZ002>004.

MN...None.
LS...Small Craft Advisory until 2 AM CST Thursday for LSZ121-145>148.

&&

$$

SHORT TERM...JJM/WM
LONG TERM...WL
AVIATION...Melde



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