Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 171810
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1210 PM CST Sat Feb 17 2018

.UPDATE...
Issued at 1209 PM CST Sat Feb 17 2018

Snow has ended in north central Wisconsin and have removed. Some
cloud streets have formed over northeast Minnesota and have bumped
up the cloud cover. Prior max temp forecast has been exceeded in
some spots and have raised a few degrees. Rest of the forecast in
the ballpark.

UPDATE Issued at 1137 AM CST Sat Feb 17 2018

Please see the 18Z Aviation Discussion below.

UPDATE Issued at 925 AM CST Sat Feb 17 2018

Snow is winding down in northwest Wisconsin. The only area to
still see some snow this morning is Sawyer and Price counties. The
snow should end/move off by noon. Elsewhere, a clearing trend is
ongoing. The exception is a patch of mid clouds working through
north central Minnesota. The mid clouds should erode by
afternoon. Made some changes based on these trends.

&&

.SHORT TERM...(Today through Sunday)
Issued at 332 AM CST Sat Feb 17 2018

A weak mid-level shortwave and associated cold front will eventually
move through the region this morning. Some light returns were
observed on radar, but very little appears to be reaching the
ground. Some chances of light snow will linger over northwest
Wisconsin late this morning before tapering off. New snowfall
accumulations should remain light...only up to one inch over
northwest Wisconsin through this morning.

Once the front moves out, high pressure will build across the
Northland, leading to a chilly night with lows in the single digits,
approaching the negative single digits along the International
Border region. Skies should clear out for a time overnight, allowing
for good radiational cooling as winds weaken.

The main focus for the short-term period will be Sunday when a
more potent band of snow makes its way across the region. A potent
mid-level shortwave will move across the Northland, with the
strongest lift expected either over or near the region. A band of
frontogenetical forcing and low-level warm air advection will
move through during the day Sunday, but there is still some
uncertainty as to where this band will set up. Right now, the
forecast models are split on whether we can get some dendrites out
of this system, or if the thermal profiles will be a smidge too
warm, like what the 17.00z NAM is showing. The SREF and GEFS
ensemble plumes are generally showing between 3 to 6" of snow
across the Northland. There could be amounts up to 7" possible
along the North Shore due to an on-shore component of the wind,
leading to orographic enhancement. The NAM model is bringing the
FGEN band about 100 miles north compared to the GFS, with the
ECMWF kind of in between these solutions. Due to the uncertainty,
decided not to issue any advisory headlines at this time, and
instead will handle the snow with a Special Weather Statement.
However, we did decide to issue a Winter Storm Watch for our North
Shore zones as confidence in heavier amounts of snow is higher in
these areas. Will let the day shift have a second look before
proceeding any further on headlines. There may be a small warm
nose that could bring temperatures near or even slightly above
freezing, particularly over our southern row of northwest
Wisconsin counties. The thermal profiles in these areas indicate
that there could be a wintry mix of drizzle/freezing drizzle
possible along with the snow. There doesn`t appear to be a layer
above freezing aloft, so thinking more of drizzle than rain should
fall. Due to the freezing drizzle, there could be some small ice
accretion over our southern forecast area.

.LONG TERM...(Sunday night through Friday)
Issued at 332 AM CST Sat Feb 17 2018

The low pressure system that will bring the accumulating snow to the
Northland on Sunday will gradually pull off to the east Sunday
night, with little additional snow accumulation overnight. The
next wave of precipitation is expected to start impacting the
region on Monday, with snow lingering into Monday night and
Tuesday morning. ECMWF has surface low pressure reaching southwest
Wisconsin by 00Z Tuesday, with GFS bringing an elongated area of
low pressure into northern Illinois. The GFS/ECMWF/NAM and GEM
show a great deal of disagreement concerning the evolution of this
system, and confidence is not particularly high regarding
QPF/snow. A compromise solution indicates little snow
accumulation along the international border, with advisory-range
snow across east central Minnesota and northern Wisconsin. Have a
feeling that convection closer to the surface low/front could have
an impact on snowfall amounts this far north. None of the models
appear to phase the energy from the upper level shortwave and the
precipitation associated with the front/surface low. High pressure
will then take over for Wednesday and Thursday, with generally
dry weather expected across the Northland. The next chance of
light snow after that will be on Friday and Saturday, but the
snowfall at this point looks fairly minimal. Highs from Monday
into Wednesday are expected to be in the teens and 20s, with highs
on Thursday in the 20s to around 30. On Friday and Saturday, we
should generally see highs in the upper 20s to middle 30s. Some
below zero low temperatures are still possible from the early to
middle part of next week, but moderation in overnight lows is
expected later in the week as well.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1137 AM CST Sat Feb 17 2018

Fair weather cumulus has developed across parts of northeast
Minnesota early this afternoon per observations. This has been
well handled by the latest RAP/HRRR guidance, so have leaned
heavily on this data for the next 6 to 12 hours. Ceilings are
right around 2000-2500 feet, so there may be periods of MVFR
ceilings. In addition, winds will be gusty as the mixed layer has
developed in the wake of a departing cold front.

Expect a return to VFR conditions this evening as the cumulus
layer dissipates once the sun sets. Gusty winds will also subside
as the mixed layer decouples. Snow will gradually spread in from
west to east Sunday morning and into the afternoon as a warm
front lifts across northern Minnesota. This will gradually lower
ceilings to MVFR levels with MVFR/IFR visibility. Most confident
in visibilities at HIB/INL, less certain at DLH/HYR and BRD as the
latest high resolution guidance keeps these sites on the southern
periphery of the precipitation shield.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  30   5  22   7 /  20  30  90  20
INL  21   0  15  -7 /  10  20  70  10
BRD  28   6  26   7 /   0  70  80  20
HYR  33   4  32  14 /  70  20  70  30
ASX  33   8  28  14 /  60  10  80  40

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Winter Storm Watch from Sunday morning through Sunday afternoon
     for MNZ020-021.

LS...None.
&&

$$

UPDATE...GSF
SHORT TERM...JTS
LONG TERM...DAP
AVIATION...WL



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