Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 130315
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
915 PM CST Tue Dec 12 2017

.UPDATE...
Issued at 901 PM CST Tue Dec 12 2017

Latest water vapor imagery showed a strong shortwave diving
southeast through southern Saskatchewan this evening. This
feature is expected to move southeast through the Northern Plains
toward the South Dakota/Minnesota/Iowa border region by 12Z
Wednesday. A surface low was in southern Manitoba and will move
into southeast Minnesota by 12Z Wednesday then continue southeast
through the day. Light snow was falling from near Crane Lake
southeast into northern Wisconsin. Another area of precipitation
was over southern Manitoba/Saskatchewan/northwest North Dakota and
was moving southeast. The latest NAM has a narrow ribbon of 0.20
to 0.35 inches of precipitation after 06Z from southern Cass
County southeast through southern Sawyer Counties. However,
several of the higher resolution models including the latest HRRR,
NMM, ARW, and RAP all have this band either further south or
lower amounts of precipitation. We did make some adjustments up
to the depth of the saturation, temperatures aloft, and QPF. What
this did was lower the icing a bit and increase snowfall some from
Walker southeast through Hinckley and points south. We`ve tossed
around the need for an advisory but decided not to issue there
yet. We will continue to highlight in an SPS.

Further north, the Winter Weather Advisory for the Arrowhead still
looks on track. Lake enhancement will occur there and 3 to 6
inches looks likely, with some locally higher amounts in the
higher terrain. The Twin Ports may get into some lake enhancement
late tonight into Wednesday morning as winds veer to east then
northeast as the low departs through the day.

&&

.SHORT TERM...(This evening through Wednesday)
Issued at 328 PM CST Tue Dec 12 2017

At 3 PM, light snow was falling across much of northeast
Minnesota. Snowfall amounts up to this point have been light based
on reports and a survey of web cams across the area. Much of the
moisture at this point has gone into saturating the drier low
levels of the atmosphere. Temperatures ranged from the single
digits in the Minnesota Arrowhead to the teens elsewhere.

The focus for tonight and Wednesday will be the evolution of the
incoming clipper system. While the models are generally in decent
agreement, there are some differences in synoptic and mesoscale
handling of the system. The initial band of light snow will
continue to move eastward across the region late this afternoon
and evening, helping to saturate the low level environment. The
question is with regard to where the main axis of precipitation
will pivot across the region. The HRRR supports more of an
opportunity for snow accumulation than the NAM for the
Duluth/Superior area. Nearly all of the deterministic models
support a solid advisory across the Minnesota Arrowhead, so we did
issue an advisory for the entire Arrowhead starting at 9 pm
tonight and ending at 4 pm Wednesday. Easterly winds will likely
contribute to locally higher amounts, up to 6 inches in spots.

Based on current thinking, we should see a widespread swath of 2
to 4 inch snow accumulation from north central Minnesota, near the
International Border, down through the Twin Ports and into
northern Wisconsin. The greatest amounts are expected further
east. Duluth is still a bit of a tricky one, as some of the models
only support about an inch of snow, while others would indicate
the 2 to 4 inches. So we should fall somewhere in that range.
Generally expecting a couple here. The least snow accumulation is
expected in the Brainerd Lakes, although they are the ones that
may see a bit more mixed precipitation, and possible freezing
drizzle overnight and early Wednesday.

Will issue an SPS for areas outside of the advisory, and would not
be surprised to see some modifications to the current advisory for
the overnight hours into Wednesday due to the possibility of mixed
precipitation and some west to east convective banding. We may
need to expand the advisory beyond it`s current area, but will
start with the most likely scenario at this point.

The precipitation focus will then shift southward on Wednesday, as
the low slides southeast, and brings the main area of wrap around
precipitation southward with it.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 328 PM CST Tue Dec 12 2017

The persistent northwest flow of the past seven days will finally
give way to a small pattern change late-week into the weekend
leading to slightly warmer temperatures this weekend into early next
week. A continued chance for snow showers most days through the long
term period, with the best chance for accumulating snow Friday night
into Saturday when around an inch or so is possible. Highs in the
teens to 20s through the rest of the week and into the weekend, then
warmer Monday with highs in the 30s across much of the Northland.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 543 PM CST Tue Dec 12 2017

Light snow was moving through central portions of the Northland
toward the east. Low pressure will move from southwest Manitoba
this evening toward southeast Minnesota by 12Z Wednesday, then
continue to move away from the region on Wednesday. Warmer air
will move into portions of the area this evening, especially the
Walker, Brainerd Lakes, Aitkin, and Hinckley areas. Precipitation
will redevelop tonight after the band of snow moves through and
may be a wintry mix in southwest/southern areas including freezing
drizzle. Steady snow is expected across the Arrowhead into
Wednesday morning and an enhanced band of lake enhanced snow will
be possible further south to the Twin Ports area and along the
South Shore late tonight into Wednesday morning as low level
winds back. Ceilings will lower tonight to low MVFR or IFR for
most areas with some LIFR possible. As the low pulls away from the
area Wednesday, the precipitation will end for most areas, except
along the South Shore, and ceilings will gradually lift.


&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  11  22   9  19 /  80  80  20  10
INL  12  20   5  15 /  80  70  10  20
BRD  19  27  13  22 /  40  30  10  10
HYR  11  21  10  20 /  70  80  40  20
ASX   8  22  13  20 /  80  90  70  30

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Winter Weather Advisory until 4 PM CST Wednesday for MNZ012-020-
     021.

LS...None.
&&

$$

UPDATE...Melde
SHORT TERM...DAP
LONG TERM...JJM
AVIATION...Melde



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