Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 201151
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
551 AM CST Sat Jan 20 2018

.UPDATE...
Issued at 540 AM CST Sat Jan 20 2018

Updated for the 12z Aviation Discussion below.

&&

.SHORT TERM...(Today through Sunday)
Issued at 341 AM CST Sat Jan 20 2018

The short-term forecast is looking mostly dry through the day
Sunday. This morning, a cold front was draped along the
International Border, which has brought some low clouds over our
northern counties. However, very little, if any, precipitation was
observed on DLH radar. In fact, very little in the way of radar
returns were seen in southwest Ontario Canada. There were some
returns seen up by Dryden, Ontario Canada, but that was about all
that was observed. There may be some flurries near International
Falls and Kabetogama before sunrise this morning. The main highlight
for this morning will be fog, especially from the Brainerd Lakes,
east towards Hibbing and Hayward. As of 09z this morning,
visibilities in these areas have already dropped to as low as 1/4
miles at BRD and 3/4 miles at HYR. Trapped moisture in the boundary
layer due to recent melting snow, underneath a strong inversion,
appears to have led to this morning fog, and the latest high-res
guidance indicates this fog could continue through the morning
hours, and even expand, before temperatures start to increase this
afternoon. Skies will be partly to mostly cloudy as low level clouds
remain in place across the north, and some mid-level clouds will
move across the south. Highs today will range from the lower 30s
over the Arrowhead region to the middle to upper 30s elsewhere. Due
to another day of above freezing temperatures for much of the
Northland today, more fog will be possible tonight.

The most robust potential for precipitation, albeit a small chance,
will come tonight, and through the day Sunday, over northwest
Wisconsin when some 850-700 mb layer warm air advection ahead of the
next winter storm system will bring some light precipitation
chances. Soundings indicate some fairly decent amount of dry air in
the low-levels, so any precipitation that forms will have a tough
time reaching the surface, but the RAP soundings indicate plenty of
ice production aloft, so some ice crystals may melt through the warm
layer on the way down. This could pave the way to snow early,
transitioning to a rain/snow mix by the afternoon. Again, very
little in the way of accumulations are expected. The more impactful
weather will be Monday as the aforementioned winter storm
approaches. More details below.

.LONG TERM...(Sunday night through Friday)
Issued at 341 AM CST Sat Jan 20 2018

The focus in the extended period remains on the winter storm that is
still expected to impact much of northern Wisconsin into adjacent
northeast/east central Minnesota Sunday night into Monday night.

The models are in pretty good agreement on the mass fields but still
differ on some of the details. The ECMWF has made a slight northward
shift in track/QPF compared to the 12Z Friday model run. Surface low
pressure is expected to move roughly from central Kansas Sunday
evening to the eastern Iowa/southern Wisconsin/northern Illinois
vicinity by Monday evening, then into Michigan by 12Z Tuesday.  We
used a blended approach to timing and QPF which mostly keeps the
forecast on track. The precipitation is expected to move in slower
Sunday night so we did delay the start time of the Winter Storm
Watch to midnight Monday. As the low moves northeast Sunday night,
light precipitation is expected to develop over portions of northern
Wisconsin possibly into the Twin Ports and I-35 corridor. Saturation
will be developing Sunday night so there may be a period of freezing
drizzle that occurs before the better lift/deeper saturation
develops late Sunday night into Monday. Snow will increase in
intensity and coverage during the day Monday as the low pressure
system lifts further north and FGEN continues over central/northern
Wisconsin. The differences among the models deals mostly with how
much and where the heaviest precipitation occurs. The GFS is highest
with snow/QPF which is typical and the ECMWF is lighter but also has
trended up some since its last run. As mentioned, we went with a
blended approach and still have a swath of snowfall late Sunday
night through Monday night of 6 to 10 inches from Burnett County
northeast toward Hurley in Iron County. Snowfall tapers off quite
rapidly north and west of a line from Pine City to Bayfield with
the Twin Ports region expected to get 1 to 3 inches. There will
likely be lake enhanced snowfall along much of the South Shore
thanks to east to northeast winds that are expected to back to
north late Monday night. An absence of colder air around 850mb
will keep the lake contribution from becoming too high though. In
addition to the snowfall will be gusty winds, which will cause
some blowing and drifting. The wind will be strongest close to
Lake Superior where gusts over 35 mph will be possible late Sunday
night into Monday evening.

Some adjustments in where the heaviest snow occurs and snow totals
remain likely over the next 24-36 hours. Stay tuned for updates.

The rest of the extended will feature a couple weaker systems that
may bring a chance for precipitation, with the best chance occurring
late in the week toward next weekend. Colder temperatures will move
over the area behind the low Tuesday and Wednesday, with highs in
the teens to lower twenties. Highs will then warm into the upper
twenties to middle thirties by Friday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 551 AM CST Sat Jan 20 2018

A complex aviation forecast on tap for today and tonight, with
flight categories ranging from VFR, down to LIFR in some spots. A
cold front has been draped across the International Border this
morning, supporting MVFR stratus. Across our south, mid- to
upper-level cirrus is building in. Between all of this,
visibilities have plummeted due to fog where skies have cleared.
Vsbys have dropped as low as 1/4 SM at KBRD and KHYR. Moisture
trapped in the boundary layer underneath an inversion has led to
this fog. The high-resolution model guidance has finally started
to resolve this fog, having MVFR/IFR vsbys last through the
morning hours, and generally improving through the afternoon.
However, another night of fog will be possible again tonight, but
some uncertainty does exist for just how low these visibilities
will be. For now, tried to hint at the vsby reductions with some
MVFR values, although some of the high-res guidance goes even
lower than this in some spots. Confidence is just not there yet to
go that low. MVFR cigs will also be possible in spots, especially
overnight tonight.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  35  23  31  21 /   0  10  10  30
INL  34  15  27  13 /   0  10  10   0
BRD  37  22  33  23 /  10  10  10  20
HYR  38  24  37  27 /  10  20  20  60
ASX  39  24  34  25 /  10  10  10  40

&&

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

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

$$

UPDATE...JTS
SHORT TERM...JTS
LONG TERM...Melde
AVIATION...JTS



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