Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 121720
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1120 AM CST Tue Dec 12 2017

.UPDATE...
Issued at 941 AM CST Tue Dec 12 2017

Radar indicates areas of light snow moving across NE MN. Some of
the snow is reaching the ground as indicated by observations. Have
put in chc pops of light snow across most of NE MN and western
portions of NW WI today.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 317 AM CST Tue Dec 12 2017

After a cold start to the morning and a fairly quiet morning the
next clipper system will affect the region this afternoon into
Wednesday. Light snow should develop this afternoon; however, a
warm tongue of +5 C air at 850 mb will likely cause freezing
drizzle or freezing rain over central/north central Minnesota
where up to a tenth of inch of a glaze can be expected. Most of
the fzra should fall after midnight tonight, so there may be
winter weather headlines for this threat, but confidence is not
quite high enough yet so will pass on concerns to the day shift.
Elsewhere, the low tracks south down the spine of MN which will
cause a favorable fetch for lake effect snow on the north shore,
so snowfall amounts may be enhanced there with 3-5" possible. Most
places should see the typical clipper total of 1-3". A sharp
upper level vort max and short wave are causing this low to deepen
as it moves through the forecast area hence this package has a
little heftier QPF amounts. In fact, 3 out of 10 members of the
NCAR ensemble give >6" to portions along the north shore.

As far as timing, the first wave of precipitation should move
across this afternoon with I-falls being the first to see snow
around 4 pm and then a slow transition across the area with
Duluth seeing snow by 7 pm. The second more aggressive wave should
arrive around 1 am Wednesday and linger through noon on Wednesday
which means the Wednesday morning commute will be another crummy
morning to be out and about. Snow begins to dissipate by Wednesday
afternoon.

.LONG TERM...(Wednesday night through Monday)
Issued at 317 AM CST Tue Dec 12 2017

The upper flow will start out northerly over the region with an
upper ridge over the eastern Pacific into British Columbia but
will transition to more northwest, and at times nearly zonal as
several shortwaves knock down the western ridge. Although no big
storm systems are expected to affect the Northland, several
shortwaves will bring periodic chances for light snow.

Light snow or flurries will continue to be possible over portions of
the Northland Wednesday night into Thursday with a weak trough over
the region. There will be an opportunity for lake effect snow
Wednesday night as winds back to northerly but will become less
favorable Thursday as they become more west to northwest. Mainly
light snow accumulation is expected at this time.

The models forecast a clipper system to move through the Northland
Friday into Saturday, depending on the model. The ECMWF is around 12
hours faster than the GFS bringing in the clipper and ends up being
faster with the track as well. The Canadian is even slower than the
GFS and is further west. Light snow accumulations, mainly from 1 to
3 inches, will be possible with this clipper with some locally
higher amounts possible depending on the track due to off lake winds
around much of Lake Superior for a time, including the North Shore
and Twin Ports areas.

High temperatures will start out below normal Thursday, then slowly
moderate to near or a bit above normal Sunday then warm a couple
more degrees on Monday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1121 AM CST Tue Dec 12 2017

VFR conditions today will gradually diminish to MVFR ceilings and
visibilities this evening through mid-day Wednesday with some
ceilings becoming IFR after midnight tonight. Snow will reduce
visibility to MVFR conditions but periods of IFR visibility will
be possible with the more intense bands of snow. In addition to
the snow, there may be periods of freezing rain/drizzle at BRD,
HIB, and DLH overnight with a light ice accretion (up to a tenth
of an inch) possible. Light northwest winds around 5-10 knots
today will become south-southeasterly overnight tonight, then more
easterly towards Wednesday morning.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  15  11  22  11 /  30  60  70  10
INL  12  11  20   7 /  40  60  60  30
BRD  22  19  27  15 /  30  30  30  10
HYR  13   9  21   9 /  20  60  70  20
ASX  14   9  22  12 /  20  60  70  30

&&

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

$$

UPDATE...Stewart
SHORT TERM...Wolfe
LONG TERM...Melde
AVIATION...JJM



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