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907
FXUS63 KDLH 111144
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
544 AM CST Wed Dec 11 2019

.UPDATE...
Issued at 544 AM CST Wed Dec 11 2019

Updated for the 12Z Aviation discussion.

&&

.SHORT TERM...(Today through Thursday)
Issued at 502 AM CST Wed Dec 11 2019

Mainly quiet and cold conditions are expected for today before a
system moves through the Northland for tonight into Thursday
bringing a round of accumulating snow.

High pressure was in place across western and southern Minnesota
early this morning. Low pressure over Hudson Bay was keeping a
pressure gradient in place across the Northland allowing west-
northwesterly winds of 5 to 15 mph to persist through the night.
This was leading to wind chills of 25 to 35 degrees below zero under
mainly clear skies. A light plume of light lake-effect snow was also
seen along the South Shore of Lake Superior from northern Douglas
County into the Bayfield Peninsula. Winds will vary a bit through
the day today and may lead to this band shifting from time to time.
Any snowfall accumulations from this bad are expected to be light.
Otherwise, skies will be mostly sunny for much of the day with
clouds starting to increase from the southwest late this afternoon.
Highs will be within a few degrees either side of zero with much of
northeastern Minnesota being on the negative side of zero.

A mid-level shortwave will move from the Northern Plains tonight to
the Central Great Lakes by Thursday evening. This feature will
spread snow showers across the Northland by late evening and
continue overnight and into Thursday morning before tapering off by
midday across northeastern Minnesota and early afternoon in
northwest Wisconsin. While the best isentropic lift and stronger
negative Thaler-QG values will remain south of the Northland, some
of the highest QPF will pass through the southern half of the
forecast area. This will bring a wide swath of around a quarter inch
of QPF to this area with parts of Iron/Ashland/Sawyer/Price Counties
seeing slightly higher amounts. With the cold temperatures in place,
snow ratios will be around 19 to 20:1, leading to a strip of 2 to 5
inch snowfall accumulations from the Brainerd Lakes area to the I-35
corridor and northwest Wisconsin. The highest amounts will be in the
aforementioned Iron/Ashland/Sawyer/Price County area where 3 to 6
inches of accumulation will be possible. Between the snowfall
amounts and the timing of the system impacting the Thursday morning
commute, a Winter Weather Advisory has been issued. Models hint at a
loss of ice aloft as snowfall ends across north-central Wisconsin,
so there may be some light freezing drizzle as snow ends in eastern
Iron and eastern Price Counties Thursday afternoon. Lows tonight
will be in the teens and single digits below zero, but winds are
expected to be lighter and and wind chill headlines are not
currently expected. Highs Thursday will be in the teens above zero.

.LONG TERM...(Thursday night through Tuesday)
Issued at 502 AM CST Wed Dec 11 2019

Thursday night to be relatively quiet with lingering Lake Effect
snow showers along the North Shore.  Our next shortwave moves into
the area for Friday and Friday night, bringing a period of snow to
mainly the northern half of the forecast area. At the surface an
inverted trough slides across the area with this event, but with the
baroclinic zone draped across the Arrowhead, that is where the
better dynamics are with this shortwave, mostly affecting the
afternoon and evening as the upper level feature moves across the
area.  So far, it appears we are looking at a solid 2 to 4 inches
along the Canadian border, with some locally higher amounts in the
higher terrain along Lake Superior.  The clouds and warm air
advection should allow temperatures to rise up into the lower to
middle 20s on Friday. Some lingering lake effect snow continues into
 Saturday along the South Shore before tapering off on Saturday
night as the surface ridge pushes into the area and ridging builds
aloft. This ridge brings another shot of cold air for Saturday
night, with lows probably dipping into the negative double digits
for parts of the area.

Conditions get somewhat quiet for the Sunday through Wednesday time
range, with an upper level trough moving across the area, but it
appears there is very poor agreement between models in the embedded
shortwaves within this trough axis, and the models each bring some
shortwaves across during this time range to affect us with some
light snow, but at different times and affecting different
locations. For now have left the forecast dry, but would not be
surprised to need to add some small pops into this time range at
some point.  It appears temperatures remain below normal for the
first half of the work week, with the upper level trough bringing a
pool of cold air aloft to over the area.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 544 AM CST Wed Dec 11 2019

Cold high pressure has produced predominantly VFR conditions
across the area this morning. These are expected to continue until
approximately 03z tonight when a band of snow will move into the
terminals and bring a period of snow with MVFR ceilings and
MVFR/IFR visibiliities, depending on the location. These
conditions are expected to linger through the end of the TAF
period. Lower conditions are possible, but for now have held off
including these as confidence in timing and placement is low.

&&

.MARINE...
Issued at 502 AM CST Wed Dec 11 2019

West to northwest winds remain in the 15 to 25 knot range overnight,
but should diminish through the day on Wednesday.  This has produced
hazardous conditions for small craft along portions of the South
Shore that lingers into Wednesday.  These winds and waves are also
producing some areas of Heavy Freezing Spray, so we have both Small
Craft Advisories and Freezing Spray warnings for the Port Wing to
Sand Island to Bayfield areas until 10 AM.  Winds continue to
diminish and turn to the southwest Wednesday night, before slowly
turning to the south and then southeast on Thursday.  Waves remain
less than 3 feet Tonight through Thursday.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  -2  -6  15   6 /   0 100  60  20
INL  -1  -8   9   1 /   0  40  10  40
BRD  -2  -3  12   3 /   0 100  30  20
HYR   2  -5  18   5 /   0 100  90  10
ASX   2  -2  19   9 /  10  90  90  10

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Wind Chill Advisory until noon CST today for WIZ001>004-006>009.

     Winter Weather Advisory from 10 PM this evening to noon CST
     Thursday for WIZ001>004-006>009.

MN...Wind Chill Advisory until noon CST today for MNZ010>012-018>021-
     025-026-033>038.

     Winter Weather Advisory from 10 PM this evening to noon CST
     Thursday for MNZ033>038.

LS...Heavy Freezing Spray Warning until 10 AM CST this morning for
     LSZ146-147.

     Small Craft Advisory until 10 AM CST this morning for LSZ146-147.

&&

$$

UPDATE...LE
SHORT TERM...BJH
LONG TERM...LE
AVIATION...LE
MARINE...LE