Area Forecast Discussion
Issued by NWS Duluth, MN

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243
FXUS63 KDLH 210942
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
342 AM CST Sun Jan 21 2018

.SHORT TERM...(Today through Monday)
Issued at 334 AM CST Sun Jan 21 2018

The main story for the short-term forecast period is the upcoming
heavy snow potential over our northwest Wisconsin counties. For
this morning, fog, with some locally dense, looks to be the main
concern. Moisture trapped underneath a strong inversion due to
melting snow these past few days will support the fog this
morning, especially from Itasca and Koochiching counties east to
Ely and south to Hibbing. Doesn`t look like the visibilities will
warrant a Dense Fog Advisory, but will monitor throughout the
morning. Fog should mix out, and visibilities improve, by this
afternoon.

For tonight and Monday, the well-advertised winter storm,
currently over the Intermountain West states, will make its way
into the region. A deep, longwave trough will translate eastward,
supporting a surface low that is expected to develop out of the
Colorado/OK Panhandle region due to lee cyclogenesis. The 21.00z
model runs have trended the path of the surface low to the
southeast, over eastern Iowa and southern Wisconsin. This has also
shifted the axis of the heaviest snow over northwest Wisconsin to
the southeast. The bulk of the heaviest snowfall now could fall
over our eastern northwest Wisconsin counties, including Price,
Sawyer, Ashland, and Iron counties. Due to the trend to delay the
onset of the snowfall, and shift the heaviest snow axis to the
southeast, decided to keep the Winter Storm Watch as is for
now. The high-resolution models, such as the NAMNest, ARW, and
NMM, are still indicating that some freezing drizzle/light snow
will be possible at the head of Lake Superior tonight and early
Monday morning, due to a prolonged northeast fetch ahead of the
winter storm. Soundings indicate that ice aloft is somewhat
lacking at times, and a layer of dry air does exist above 900 mb,
so decided to maintain the freezing drizzle.

Through the rest of the day Monday, the winter storm arrives,
with the strongest lift translating over northwest Wisconsin. More
ice production will lead to a transition to mostly snow over this
area, with perhaps some light snow falling over the Twin Ports.
The bulk of the snow will fall Monday morning after daybreak,
through Monday evening. In total, snowfall amounts between 5 to
10 inches, with some locally higher amounts, will be possible,
especially over Price, Iron, Sawyer, and Ashland counties. In
addition to the snow, northeast winds will also be gusting between
20 to 30 mph, so some blowing and drifting snow will also be
possible. The freezing drizzle over the head of Lake Superior
Monday could lead to accumulations up to one-tenth of an inch, so
some icing downstream of Lake Superior will also be possible.

.LONG TERM...(Monday night through Saturday)
Issued at 334 AM CST Sun Jan 21 2018

Snow will continue over portions of northwest Wisconsin into Monday
night as the surface cyclone moves northeast through Michigan toward
Lake Huron by 12Z Tuesday. There will be lake enhanced snow possible
along portions of the south shore of Lake Superior due to northeast
low level winds and 850mb temperatures initially around -8C dropping
to around -10C by 12Z Tuesday. Inversion levels are low and drier
air moves across western Lake Superior through the night. These
factors should limit the lakes contribution to snow accumulation
some. The bulk of the snow will fall Monday evening with 1 to 3
inches possible from near Siren into the Bayfield Peninsula and
points east. An additional inch or so will be possible in the
snowbelt of Ashland/Iron Counties after 06Z Tuesday. The snow
showers along portions of the South Shore will end Tuesday as drier
air moves in. An area of high pressure will move through Ontario
late Tuesday into Tuesday night causing low level winds to veer to
the east, then southeast. Colder temperatures will be moving over
the region Tuesday/Tuesday night, and this may lead to lake
effect snow showers along portions of the North Shore Tuesday
night into Wednesday. We increased chances and have some light
snow accumulations during that time.

An upper level ridge will move over the central CONUS into
Saskatchewan/Alberta by 12Z Thursday and it will continue east
passing through the Northland Thursday night. Other than a few
chances for light lake effect snow, dry conditions are expected for
the rest of the Northland Tuesday into Thursday night. Warm air
advection will strengthen Thursday into Thursday night. An area of
low pressure will move into the Northern Plains/Canadian Prairies
Thursday then head over Minnesota late Friday into Friday night.
High temperatures will warm from the teens to lower twenties Tuesday
to the lower thirties to lower forties by Friday. There will be a
chance for light snow or rain with the low pressure system Friday
with mainly snow Friday night into Saturday. At this point, a few
inches of snow looks to be possible in spots but heavy snow looks
unlikely.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1148 PM CST Sat Jan 20 2018

High pressure is nearby at the start of the forecast with mainly
VFR. However, with light winds and the snowmelt from Saturday,
areas of BR/FG are expected with conditions dropping into the
MVFR, IFR, LIFR and some pockets of VLIFR. The cigs and vsbys will
improve around 18Z and approach the VFR range. After sunset, a
transition back down into the IFR/LIFR range with BR is expected.


&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  31  21  25   8 /  20  30  30  20
INL  28  11  21   0 /   0   0   0   0
BRD  31  22  29  11 /  10  10  10  10
HYR  36  25  30  14 /  10  50  80  60
ASX  34  24  28  15 /  20  40  70  60

&&

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

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

$$

SHORT TERM...JTS
LONG TERM...Melde
AVIATION...GSF



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