Area Forecast Discussion
Issued by NWS Duluth, MN

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849
FXUS63 KDLH 202137
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
337 PM CST Sat Jan 20 2018

.SHORT TERM...(This evening through Sunday)
Issued at 335 PM CST Sat Jan 20 2018

A weak frontal boundary to our north lingers and trepidatiously
makes its way east while a Hudson Bay high pushes the boundary
south across Lake Superior on Sunday. This will give the slightest
potential for precip mainly near the big lake, but have concerns
that even a hundredth will be hard to come by, so have minimal
PoPs.

The bigger story will likely be the potential for fog as an
approaching weather system surges warm, moist air poleward. The
WAA will ride up and over the cool snowpack and thus am concerned
about fog with likely dense patches tonight and Sunday. Fog should
begin to mix out Sunday afternoon as the larger winter storm
system approaches.

Today was the last warm day before a cool down.

.LONG TERM...(Sunday night through Saturday)
Issued at 335 PM CST Sat Jan 20 2018

The main focus of the extended continues to be on the winter
storm impacting the Northland Monday morning into early Tuesday
morning. Late Sunday night into early Monday a trough will dig
into the Central Plains, while an area of low pressure develops
across the eastern Central Plains/Mid Mississippi River Valley.
The low will deepen on Monday and Monday night, while moving
northeastward into the central Great Lakes by Tuesday morning.
Ahead of the incoming system, there is a period where freezing
drizzle/rain is possible especially along the south shore of Lake
Superior due to ice loss aloft between 00Z and 12Z Monday. The
layer where ice loss is occurring will gradually moisten on Monday
as the low lifts northeastward, this will change any freezing
drizzle/rain to all snow. In general, guidance is in excellent
agreement for this system, however the latest ECMWF/GFS/NAM and
GEM move the low pressure center a bit further to the south and
slower in comparison to the previous runs. So, have delayed the
onset time of precipitation another 6 hours and pushed the winter
storm watch back from midnight to 6 AM. Confidence is still high
that 6 to 12 inches of snowfall will fall across portions of
northwest Wisconsin. Have lowered totals along the I-35 corridor
and into western portions of northwest Wisconsin as the tight
precipitation/snowfall gradient has shifted further southeast due
to the low moving a bit further south. If the system continues to
track southward then precipitation/snowfall totals will need to be
lowered further along the northwest side of the system. Gusty
winds will develop on Monday as the pressure gradient tightens due
to the deepening low. This combined with the snow, will bring
blowing and drifting snow especially along the south shore of Lake
Superior. The low will lift out of the region on Tuesday, but
lake effect snow showers will continue along the south shore of
Lake Superior during the morning hours before drier air moves in
during the afternoon. In wake of low, colder air will advect into
the region. Expect highs on Tuesday in the mid teens and low 20s.

The extended quiets down after this system exits with high pressure
in control for much of the upcoming week. After a cool start to the
week temperatures will be on the rebound. By Friday highs will be in
the mid 30s and low 40s. Precipitation chances return on Friday into
Saturday as a trough digs into the Central and Northern Plains. At
the moment precipitation looks to be a mixture of rain/snow before
becoming all snow on Saturday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1133 AM CST Sat Jan 20 2018

Mostly VFR, but with a frontal zone just to our north could see
some temporary MVFR sneak in from the north. Tonight we transition
into a warm advection regime which should make conditions ripe for
fog formation as the warm air travels over the snow pack, so have
accordingly swamped the TAF sites in IFR fog. Kept this fog
through the remainder of the TAF period with maybe some
improvement as the larger winter system begins to approach the
area Monday.


&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  23  31  21  25 /   0  10  30  50
INL  17  27  13  22 /   0   0   0   0
BRD  22  32  23  28 /  10  10  20  20
HYR  25  37  27  30 /  10  20  60  80
ASX  25  33  25  28 /  10  10  40  80

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Winter Storm Watch from late Sunday night through Monday evening
     for WIZ002>004-006>009.

MN...None.
LS...None.
&&

$$

SHORT TERM...Wolfe
LONG TERM...WL
AVIATION...Wolfe



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