Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 111322 AAA

Area Forecast Discussion...UPDATED
National Weather Service Duluth MN
722 AM CST Wed Jan 11 2017

Issued at 722 AM CST Wed Jan 11 2017

Please read the new 12Z Aviation Discussion below.


.SHORT TERM...(Today through Thursday)
Issued at 411 AM CST Wed Jan 11 2017

Our next wave of snow is spreading into the area this morning,
with snow already as far north as Ely and Hibbing and should begin
very soon at Hayward, having already started at Siren and
Hinckley. This snow is knocking visibilities down into the 1-2
mile range. This band of snow is being generated by frontogenesis
along a very strong baroclinic zone that extends from eastern
South Dakota across Minnesota and northern Wisconsin and upper
Michigan this morning. This frontogenesis is just getting going,
having spread in over the last hour or so and should linger
through approximately 15z before shifting east and out of the
area. A shortwave that moves along the Canadian border this
morning should also help to boost this frontogenesis band this
morning. The shortwave appears slower than the frontogenesis band
though and may only cause a little lingering light snow for
northwest Wisconsin into early afternoon. Higher resolution models
are bringing enough liquid up into the far southeast corner of the
forecast area that have increased snowfall amounts for the morning
into the 2-4 inch range. This is marginal, but considering the
timing overlapping the morning commute and relatively rapid
snowfall rates, have gone with an advisory for this morning for
Price and Sawyer counties. There will be lighter snowfall amounts
farther north and west to contend with, though they may get their
snow in a fairly short period of time.

Attention then turns to the very cold air set to surge into the
area tonight, with 850mb temperatures falling into the -20C degree
range. I expect a certain amount of clearing, especially over the
northern half of the forecast area and with light winds we are
going to have good radiational cooling conditions. Have gone
colder than most guidance tonight, with min temps in the -15F to
-20F range, especially across the Iron Range. Northwest Wisconsin
should hang onto clouds longer and do not get as cold. Expect that
we will need a wind chill advisory for much of northern Minnesota
tonight, but have held off issuing that for now as clearing
trends could have a large effect on where the advisory needs to
be as well as the timing.

Thursday a fast moving shortwave is going to scoot across
Manitoba into northwest Ontario, bringing chances for snow there
that should overlap into the borderlands of northern Minnesota
during the afternoon. Have kept pops relatively low as there is
still a lot of dry air at the low levels, and snowfall amounts to
be pretty minimal. Temperatures on Thursday to also be very cold
as highs to be in the single digits most locations.

.LONG TERM...(Thursday night through Tuesday)
Issued at 411 AM CST Wed Jan 11 2017

The main concerns during the long term are the bitterly cold
temperatures and dangerous wind chills Thursday night.

The axis of a departing trough of low pressure will be located over
northern Ontario, western Lake Superior, and western Wisconsin
Thursday evening and will quickly shuffle eastward through the Great
Lakes overnight. Another shot of bitterly cold Arctic air will follow
the departing trough with deterministic model 850 and 925 mb
temperatures of -25 to -30 degrees Celsius. With winds easing
overnight and clearing skies, think the blends are too warm for much
of the area. Nudged minimum temperatures Thursday night toward a
blend of the bias-corrected versions of the SREF, NAM12, and CONSRAW,
then pulled the bottom end of those values another 1 to 3 degrees
colder. Those changes yield lows from the low teens below zero in
northwest Wisconsin near Lake Superior and along the North Shore,
to the 20s below zero for inland areas of northwest Wisconsin, and
near 30 degrees below zero in north-central Minnesota. Wind Chill
Advisories will likely be needed Friday night and there is
certainly a possibility of needing a Wind Chill Warning from the
Brainerd Lakes northeastward through the Arrowhead, including the
Iron Range. Even with light winds, air temperatures of 25 to 35
below zero would yield wind chills of 40 below zero or colder.
Considered a Wind Chill Watch for a few zones, but with current
winter headlines and the expectation of a Wind Chill Advisory
tonight, opted to hold off for now.

As the trough moves farther eastward on Friday the upper level flow
across the region will shift northwesterly, and eventually into a
quasi-zonal pattern as a longwave trough digs into the Pacific coast
Friday night and Saturday. Temperatures will gradually moderate
heading into the weekend with highs on Friday near zero north and in
the middle single figures above zero for the rest of the Northland.
Saturday and Sunday will both trend warmer as low- and mid-level
winds back southerly.

The western trough kicks eastward by Sunday with a northern stream
shortwave trough moving across the Northern Plains and Canadian
Prairies and into the Northland by Sunday afternoon. The southern
stream system should keep the area cut off from stronger moisture
return. Even with the sharp height falls and differential cyclonic
vorticity advection with the northern shortwave, think we will
notice an increase in cloud cover and a wind shift from the passing
disturbance, but not much else. By the middle of the week
deterministic guidance and ensemble member solutions diverge with
the handling of the trough moving through the CONUS. It seems a
cutoff upper low will drift through the Mississippi River Valley
Tuesday afternoon through Thursday, but the location and strength of
the upper low varies widely. Temperatures will continue to trend
warmer through the first half of the week with above average
readings expected, and even a chance of seeing temperatures nudge
above freezing Tuesday afternoon.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 722 AM CST Wed Jan 11 2017

A fast-moving area of low pressure will bring a round of snow to
northern Minnesota this morning with conditions improving by late
morning or early afternoon. Model soundings from the NAM and RAP
suggest MVFR ice clouds may linger into late afternoon before
skies clear. Upstream observations cast doubt on holding onto
ceilings that long today, but opted to keep a high MVFR broken
deck at most terminals. Cold Arctic air will pour into the region
once again tonight. Winds will veer northwesterly and may become
gusty behind the front tonight. There is also a potential for
low-level wind shear to develop after 10Z, but did not include any
mentions in this forecast.


DLH   6 -11   7 -23 /  80   0  10   0
INL  -1 -16   2 -31 /  10  10  20   0
BRD   6 -12   8 -28 /  60  10   0   0
HYR  11 -10  12 -25 /  90  10  10   0
ASX  10  -6  12 -17 /  80  10  10  10


WI...Winter Weather Advisory until noon CST today for WIZ008-009.

LS...Small Craft Advisory until 10 AM CST this morning for LSZ121-



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