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fxus63 kdlh 141800 aad 
afddlh

Area forecast discussion...updated
National Weather Service Duluth Minnesota
1200 PM CST Sat Dec 14 2019

Update...
issued at 1159 am CST Sat Dec 14 2019

Update for new 18z aviation discussion below.

Update issued at 552 am CST Sat Dec 14 2019

Snow is persisting longer over The Arrowhead this morning as a low
level convergence zone along and east of the inverted trough axis,
and the upper level shortwave moving more slowly across the area
than models have depicted. Some locations are observing
visibilities in the 1 to 3 mile range as far west as Crane Lake
and Hibbing. Snowfall reports from overnight do not support
extending the Winter Storm Warning, but have decided to just
extend the Winter Weather Advisory into both the Lakeshore zones
and until noon today to allow the snow to fully taper off to
flurries.

Update issued at 540 am CST Sat Dec 14 2019

Updated below for 12z aviation discussion.

&&

Short term...(today through sunday)
issued at 351 am CST Sat Dec 14 2019

A weak low pressure system that has moved across the upper
Midwest on Friday and Friday night is now over Eastern Lake
Superior/Upper Michigan. An inverted trough extends west to lie
across the Minnesota arrowhead. Snow is ongoing within the trough
axis, with just enough onshore component for the very tip of The
Arrowhead to detect some lake enhancement to the snowfall. Higher
in the atmosphere there is a shortwave that is in the process of
moving across The Arrowhead as well, and this is all serving to
maintain the snowfall this morning over the area. Over the next 3
to 6 hours the upper level shortwave will begin to move away
again, and the surface inverted trough is expected to weaken,
which should allows the snowfall to rapidly diminish over
northeast Minnesota this morning. For now we have the Winter
Weather Advisory and warning expiring at 12z, which for now
appears reasonable, though we will have to re-evaluate visibility
trends and the latest snowfall reports closer to expiration time
to make any determinations about extending or not. With the
inverted trough sliding southeast, the lake effects shift to the
South Shore this morning, with perhaps some actual banding setting
up by mid morning. These may produce some periods of heavier
snowfall rate along the South Shore, which after they set up
around mid morning, should continue through the day and into this
evening before diminishing/shifting east overnight. In the
meantime, the rest of the area should experience clearing skies
today, and enough cold air advection to keep temperatures from
rising very far today, and then dropping rather dramatically
tonight as a ridge of high pressure builds in. Have made the
overnight min temperature forecast for tonight on the cold end of
guidance, though if we get light enough winds in here, it could be
colder yet than what I have put in. Currently, I have forecast
mins in the teens below zero over much of northern Minnesota, with
single digits near and below zero for most of Wisconsin. The high
pressure ridge will also keep temperatures on the cold side for
Sunday, with highs only in the single digits above zero.

Long term...(sunday night through friday)
issued at 351 am CST Sat Dec 14 2019

Fairly quiet conditions are expected for the extended with no major
system on the horizon. There may be a few chances for light snow,
but a lack of moisture will keep these chances in check.
Temperatures will start the period below normal before warming near
to above normal for late next week and into the weekend.

High pressure will shift to the southeast Sunday night as a
shortwave trough moves into the region and passes through Monday
morning. This may squeeze out a little snow through the borderlands,
but with little in the way of moisture to work with, it appears to
be a dry passage for most. However, there could be some lake effect
snows across the South Shore of Lake Superior with persistent
northwest winds and decent lake effect signals in the
GFS/ECMWF/Gem/NAM. A stronger shortwave and upper low will dive
southeast out of Canada and into the northern Great Lakes for
Tuesday into Wednesday. A lack of moisture again looks to be the
limiting factor for more widespread snowfall and only the GFS bring
measurable quantitative precipitation forecast through the region with the system. A reinforcing
shot of cold air will arrive behind this system for Tuesday night
into Wednesday and will keep below normal temperatures in place
along with chances for lake effect across the South Shore of Lake
Superior.

Another subtle shortwave embedded in the northwest flow aloft will
then pass by the Northland Wednesday night. While it appears there
will be a bit more moisture for this system to work with, the bulk
of the quantitative precipitation forecast looks to pass to our north and east and keep the
Northland mainly dry outside of snow showers across The Arrowhead.
Ridging aloft then starts to build in for Thursday into Friday as
warm air advection brings near to above normal temperatures to the
region. With normal temperatures this time of year in the lower half
of the 20s, temperatures will still be below freezing for both
Thursday and Friday. Overall forecast confidence takes a nose dive
for Friday into the weekend with major model differences in place.
The GFS and Gem move an upper low through the region with that
feature practically non-existent on the European model (ecmwf). Keeping light snow
chances in for this period, but could very well end up dry.

&&

Aviation...(for the 18z tafs through 18z Sunday afternoon)
issued at 1159 am CST Sat Dec 14 2019

High pressure will move southeastward from southern Manitoba to
southern Wisconsin and northern Illinois by 15z Sunday. Lake
effect clouds and snow showers will continue to affect hyr, but
the remaining sites should trend clear through tonight. Winds will
be from the northwest and will back southwesterly Sunday morning.
A few strong gusts to around 25 knots are likely at terminals
along the North Shore, including dlh. Mid-level clouds move in
from the west again late Sunday morning as a weak and moisture
starved shortwave trough moves into the upper Midwest.

&&

Marine...
issued at 1024 am CST Sat Dec 14 2019

Northwest winds are expected through early Sunday morning in
response to low pressure departing to the east and surface high
pressure approaching from the west. The pressure gradient will
tighten for the afternoon and then relax overnight. Wind speeds
will increase to 10 to 20 knots with a few gusts to 25 knots, with
the highest gusts along the South Shore. There may be strong
downslope winds over the waters from Taconite Harbor to Grand
Portage late tonight as cold air drains downhill toward the lake
surface. The wind and resultant waves will create conditions
hazardous to smaller vessels along the South Shore from Port Wing
to Saxon Harbor, except between Bayfield and Chequamegon Bay,
where winds and waves will be lower. A Small Craft Advisory is in
effect for those areas until midnight tonight. Winds will back
southwesterly for Sunday and will generally be in the 10 to 15
knot range for the nearshore waters, with stronger winds possible
over the open waters. No strong storms are expected for the
remainder of the forecast period and wind speeds should remain
below 20 knots.

&&

Preliminary point temps/pops...
dlh 15 -11 4 -3 / 30 0 0 0
inl 6 -16 6 -2 / 10 0 10 10
brd 10 -19 4 -3 / 0 0 0 0
hyr 18 -9 8 -3 / 30 10 0 0
asx 22 1 10 1 / 80 70 10 0

&&

Dlh watches/warnings/advisories...
WI...Winter Weather Advisory until 6 am CST Sunday for wiz004.

Minnesota...none.
Ls...Small Craft Advisory until midnight CST tonight for lsz146>148.

&&

$$

Update...huyck/le

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