Area Forecast Discussion
Issued by NWS Duluth, MN

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225
FXUS63 KDLH 081159
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
559 AM CST Sun Dec 8 2019

.SHORT TERM...(Today through Monday)
Issued at 425 AM CST Sun Dec 8 2019

The main forecast concern in the short term is the period of snow
expected to begin tonight and continue into early Monday evening.
With this forecast package we added another tier of zones to the
Winter Weather Advisory in Minnesota and upgraded the Winter
Weather Advisory along the south shore of Lake Superior to a
Winter Storm Warning. Snow amounts have increased over much of the
advisory/warning areas, with the biggest change along the South
Shore.

A positively tilted upper-level trough will advance into the
middle of the continent this this afternoon and Monday. It will
become neutrally and eventually negatively tilted. Lee
cyclogenesis will occur over Montana and eastern Wyoming today.
The surface low will slide a bit farther south before making a
turn to the northeast late tonight. The low trajectory will take
it across the middle Mississippi Valley and into northern Lower
Michigan. This system will have far less moisture to work with
than the event last weekend, with mainly Pacific moisture
available. Snow will move into central Minnesota this evening and
spread across the remainder of the Northland by 12Z Monday.
Northwest winds over western Lake Superior may bring a brief
period of lake effect snow this evening before the deeper forcing
and moisture arrive. The northeast winds will lead to lake
enhancement along the South Shore. We have raised snow amounts and
QPF above what the previous forecast indicated as confidence in
the lake enhancement increased. Winds will be strong in the Twin
Ports and east along the South Shore which will lead to blowing
and drifting snow. Snow accumulation will generally range from 3
to 8 inches. Higher snow totals are expected in northern portions
of Douglas, Bayfield, Ashland, and Iron Counties where 8 to 11
inches is likely.

Snow will taper off from west and northwest toward the east on
Monday. Snow will likely end before noon for our Minnesota zones
and by late afternoon for much of northwest Wisconsin. Light lake
effect snow will likely continue through Monday evening in
northern Iron County.

With this forecast package weve added a tier of zones to the
Winter Weather Advisory in northern Minnesota. South Itasca,
central St. Louis, and all of Lake and Cook counties are now
included. In northwest Wisconsin, we have upgraded Douglas,
Bayfield, Ashland, and Iron counties to Winter Storm Warnings for
heavy snow and reduced visibility. Later upgrades are not out of
the question depending on where and when mesoscale bands set up in
the advisory area.

.LONG TERM...(Monday night through Saturday)
Issued at 425 AM CST Sun Dec 8 2019

The upper level long wave trof remains anchored over the region
Monday night. A northwest wind will persist as high pressure
builds through the Dakotas. The wind will combine with cold air
advection over Lake Superior to maintain lake effect snow showers
along the south shore, even inland through much of northwest
Wisconsin. Additional snow accumulation will occur with around 1
inch in northern Iron County. Lighter amounts elsewhere. The wind
turns to a west northwest direction overnight which will change
the location of the lake effect snow, and diminish the
accumulation potential. The upper trof moves slightly to the east
Tuesday. This allows the high pressure to drift into the Upper
Midwest. The wind over Lake Superior becomes westerly, diminishing
the lake effect, but kept some low pops for any lingering
activity.

The upper trof finally exits the area Tuesday night. However, a
potent short wave trof/vorticity maxima crosses the region. Much
of the region is under the influence of the dry airmass courtesy
of the next high pressure dropping into the Dakotas. A west
northwest wind over Lake Superior will lead to some lake effect
snow showers along the higher terrain of the south shore. Any
accumulation will be light with the dry air affecting snow
amounts. The high pressure moves over the area Wednesday.

Model differences begin Wednesday night. The GEM/GFS point toward
some light snow into the southwest portion of the region, but the
GFS is the most aggressive with QPF/accumulation. The ECMWF is
dry with ridging still over the area as the main high drifts to
the eastern Great Lakes. A quiet evening, then small pops
overnight to blend model solutions.

The GFS continues to be the outlier Thursday with a surface low
developing and moving into southern Minnesota with plenty of
QPF/snow, while the GEM/ECMWF are similar with a weaker surface
solution with lower QPF/snow, that moves quickly through the area.
Kept the blend with low chance pops.

An unsettled pattern emerges for Thursday night through Saturday
and the models all offer different solutions in their mass fields,
timing, and QPF. Maintained the blend for this period which
equates to low chance pops.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 559 AM CST Sun Dec 8 2019

A cold front was moving through northwest Wisconsin at the start
of this forecast. MVFR cigs were found along and just behind the
front, IFR cigs well behind the front. Pockets of BR with MVFR
vsbys were found in northeast Minnesota. Some patchy -FZDZ or
flurries will dot the landscape for much of the morning, before
ending. Snow will begin to spread across the Minnesota terminals
tonight from west to east, reaching HYR by midnight. Cigs/vsbys
will be in the MVFR/IFR range with the snow. Heavy snow is
expected from 06Z to 12Z from BRD to HIB and DLH. Gusty winds will
also create BLSN for a time at BRD and DLH.

&&

.MARINE...
Issued at 425 AM CST Sun Dec 8 2019

Gusty southwest winds will continue early this morning, before
subsiding by mid morning. The wind turns to the northeast in the
afternoon at 10 to 20 knots. Waves should remain under 3 feet.
However, the northeast wind increases in speed with some gusts to
30 knots possible tonight. Wave heights will build into the 6 to 8
foot range late tonight, but then subside Monday morning as the
wind speed diminishes and begins to turn to northwest in the late
afternoon. Winds and waves continue to subside Monday night. Will
issue new Small Craft Advisories for tonight and Monday where
winds and waves are highest, especially along the south shore.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  31   9  13  -7 /  10 100 100  10
INL  23   0   7  -7 /  10  60  40  10
BRD  30   7  12  -8 /  10 100 100   0
HYR  34  18  22  -5 /  10 100 100  20
ASX  35  19  22   1 /  30 100 100  30

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory from midnight tonight to 6 PM CST Monday
     for WIZ006>009.

     Winter Storm Warning from midnight tonight to 9 PM CST Monday
     for WIZ004.

     Winter Storm Warning from midnight tonight to 6 PM CST Monday
     for WIZ001>003.

MN...Winter Weather Advisory from midnight tonight to noon CST Monday
     for MNZ012-019>021.

     Winter Weather Advisory from 9 PM this evening to noon CST
     Monday for MNZ025-026-033>038.

LS...Small Craft Advisory from 9 PM this evening to 5 PM CST Monday
     for LSZ146-147.

     Small Craft Advisory from 9 PM this evening to 3 PM CST Monday
     for LSZ144-145.

     Small Craft Advisory from 10 PM this evening to 1 PM CST Monday
     for LSZ142-143.

     Small Craft Advisory from 4 PM this afternoon to 10 PM CST
     Monday for LSZ148.

&&

$$

SHORT TERM...Huyck
LONG TERM...GSF
AVIATION...GSF
MARINE...GSF



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