Area Forecast Discussion
Issued by NWS Duluth, MN

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920
FXUS63 KDLH 080006
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
606 PM CST Wed Dec 7 2016

.UPDATE...
Issued at 606 PM CST Wed Dec 7 2016

A surface trof will drop through the forecast area tonight. Snow
showers will persist tonight. Gusty winds and blowing snow will
diminish this evening as the boundary layer decouples. Made some
minor adjustments, especially to the wind.

&&

.SHORT TERM...(This evening through Thursday night)
Issued at 239 PM CST Wed Dec 7 2016

The stacked low north of Lake Superior continues to slowly exit to
the northeast with colder air wrapping in around the low. Widespread
light snow showers and breezy winds continue this afternoon, but as
the low continues to lift away this evening a cold front associated
with the low will push south across northern Minnesota and northwest
Wisconsin leading to winds shifting to become more out of the north
and not as strong. With low level winds turning more northerly and -
10C (now) to -15C (Thurs night) 850mb temps the lake effect snow
machine will roar to life through the rest of the work week. Over a
foot of snow is expected by the end of the week across the the
Gogebic range in northern Iron and Ashland counties, with lesser
amounts across the Bayfield Peninsula. Temperatures will be fairly
steady in the teens to 20s tonight into Thursday, but as high
pressure builds in from the west Thursday night lows will fall to
the single digits in many places.

Lake effect snow advisory and warning continue to be in good shape
with minimal adjustments needed to the prevailing forecast. Per
recent ship reports and GLERL analysis Lake Superior surface water
temps are around 40-44F, or +4 to +7C. With the -10C to -15C air
moving in aloft, thermal conditions will be very conducive for lake-
induced instability on the order 300-500 j/kg. Low level winds will
be great for generating plumes of lake effect snow with little
directional shear in the low levels as winds gradually shift from
northwest this afternoon to nearly due north Thursday morning, then
slightly backing to north-northwest Thursday afternoon into Friday.
Low level moisture will be excellent per model soundings, and with
many open lakes in northern Ontario, upstream seeding may enhance
snowfall further overnight tonight. (In fact, lake effect snow
showers may even develop from open lakes in Northern Minnesota, with
some high-resolution guidance depicting such off of Lake of the
Woods and Leech Lake.)

South shore snow amounts will be 3-5 inches on the Bayfield
Peninsula and 6-12"+ across the Gogebic range, with lesser amounts
around these higher totals as snow showers move inland and gradually
fall apart. Much of this snow will fall tonight into early Thursday,
but continued light snow showers in northern Iron county will
continue well into Friday until high pressure builds in and winds
turn more westerly. Elsewhere across the Northland light snow
showers will continue into tonight, but as moisture aloft decreases
and high pressure builds in snow showers should tapper during the
day Thursday. Up to an inch or two possible through Thursday, with
amounts highest north of the Iron Range.

.LONG TERM...(Friday through Wednesday)
Issued at 239 PM CST Wed Dec 7 2016

Focus for long term will be accumulating snow on Sunday and a
reinforcing shot of cold air next week.

The lake effect snow will continue Friday and Friday night with
additional snow accumulations expected as the winds remain favorable
for shower development.   When the snow showers finally taper off
late Friday night, a total of 12 to 18 inches are possible across
the affected area.  The winds will switch to a more westerly
component ending the snow as the next storm system approaches the
upper midwest.

Models are similar in keeping most of the accumulating south of the
forecast area but are much different in the strength.  The low will
develop in western KS and move northeast to near Chicago by Sunday.
The GFS still shows the low center to be stronger than the ECMWF. As
like the previous shift, the ensembles lean more toward the stronger
GFS.  The area that will receive the most snow will be along Highway
70 and south in NW WI.  Too early to tell on the amounts but a
couple inches could be possible with lower amounts north of highway
70.

Once the low moves NE, a strong high pressure ridge will build into
the region ushering in much colder air.  There could be some lake
effect snow showers on Monday before the winds switch late Monday
ending most of the precipitation.  Temperatures will be 15-20
degrees colder than normal through most of the work week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 606 PM CST Wed Dec 7 2016

A surface trof will drift over the terminals tonight. This will
turn the surface wind to the northwest. Gusty winds will persist
early in the forecast before subsiding. Mainly MVFR is expected
ahead of and behind the trof. There will be some areas of IFR and
VFR. Scattered snow showers with some blowing snow will occur with
the gusty winds. The blowing snow ends when the wind diminishes.
The snow showers will end by late Thursday afternoon.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  19  24   8  12 /  30  20  10  10
INL  20  20   5   9 /  90  30  10  20
BRD  15  20   7  10 /  60  30  10   0
HYR  18  26  12  16 /  70  70  20  10
ASX  20  29  15  16 /  80  90  50  40

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Lake Effect Snow Warning from 9 PM this evening to 6 AM CST
     Saturday for WIZ004.

     Lake Effect Snow Advisory from 9 PM this evening to 3 PM CST
     Friday for WIZ002-003.

MN...None.
LS...Small Craft Advisory until 6 AM CST Friday for LSZ121-143>148.

     Small Craft Advisory until 6 AM CST Friday for LSZ140>142.

&&

$$

UPDATE...GSF
SHORT TERM...JJM
LONG TERM...Stewart
AVIATION...GSF



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