Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 151739
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1139 AM CST Fri Dec 15 2017

.SHORT TERM...(Today through Saturday)
Issued at 415 AM CST Fri Dec 15 2017

The main forecast concerns for the short term include a prolonged
period of light snow today through Saturday and a small potential
for a period of light freezing drizzle as snow tapers off
Saturday.

Low stratus and cold air advection continued across the Northland
early this morning resulting in light snow showers and flurries
across the forecast area. A gravity wave developed downwind of the
high terrain along the North Shore and eroded the cloud cover
along MN Highway 61 from Two Harbors to Grand Marais. The
ascending node of the wave produced a band of light snow over
Douglas and Bayfield Counties during the evening. The wave was
still observed on GOES-16 shortwave IR imagery and KDLH
reflectivity, albeit with less intensity than earlier tonight.
Look for light snow showers to continue across much of the area
through mid-morning at least. Accumulation will be light,
generally less than a half-inch, except in the northwest Wisconsin
snowbelt areas where 1 to 3 inches is expected through noon.

Attention then shifts to a band of light snow forecast which will
slowly progress across the Northland from late this morning
through Saturday. A zone of isentropic lift over a warm frontal
zone will move eastward from the Canadian Prairies and North
Dakota into western Minnesota by late morning or early afternoon.
The band of light snow observed on regional radar networks over
southeast Saskatchewan, southern Manitoba, and northern North
Dakota will advance eastward into the forecast area as the forcing
for ascent moves east. The band of snow will slowly drift
eastward bringing snow to most of the area by Saturday morning.
Winds in the boundary layer are forecast to veer southeasterly
overnight which should result in some orographic and lake
enhancement to the precipitation rates along the North Shore. Snow
accumulation of 1 to 3 inches is expected through Saturday
afternoon across the Northland. A few locales may pick up as much
as 4 inches of accumulation. Those areas include much of Cass
County, Crow Win, Aitkin and Pine in addition to locales along the
North Shore from Two Harbors to Grand Marais.

Temperatures will continue to cool for several hours this morning
over northeast Minnesota with afternoon highs in the single
digits northeast and the low 20s in central Minnesota. Lows
tonight will dip into the teens below zero where skies clear in
the BWCA and the middle teens in central Minnesota. Highs on
Saturday trend a bit warmer with readings in the middle teens
northeast to the middle 20s southwest.

.LONG TERM...(Saturday night through Thursday)
Issued at 415 AM CST Fri Dec 15 2017

A positively tilted upper trof will be oriented in an almost
west/east fashion by 12Z Sunday. Embedded impulses with this
feature will be drifting over the region. There will be just
enough lift to wring out some light pcpn along the north shore of
Lake Superior. The higher resolution models are generating too
much QPF/high POPs in this area. Prefer the coarser, more
reasonable deterministic model solutions of lower POPs/lighter QPF
and have followed. There is still an opportunity for some light
freezing rain/drizzle and have left a mention. No ice accumulation
is expected however. Underneath this trof, high pressure at the
surface will be attempting to push across the forecast area
Saturday night and have removed POPs elsewhere. The upper trof
moves very little Sunday and Sunday night, but dry high pressure
remains in charge at the surface. Monday through Tuesday finds the
aforementioned upper trof dissipating as it is overcome by a
closed upper low over northern Manitoba. The surface reflection
from this upper trof is to push a cold front through the region
Monday through Monday night. Much colder air pushes into the
region behind the front. Expect all snow with this frontal
passage. Tuesday and Tuesday night finds a change in the upper
level pattern as the closed upper low opens into a trof and moves
to the East Coast. Some lingering light snow is possible along the
periphery of Lake Superior as well as along the northern third of
the forecast area Tuesday as some elongated vorticity is nearby.
Tuesday night has high pressure over the region, but a west
northwest wind over Lake Superior may create some lake effect snow
showers over the snowbelt area of northwest Wisconsin. This is
not a favorable direction for significant snow and have chance
POPs as a result. A large area of low pressure developing in the
lee of the Rockies Wednesday pulls out into the Plains and moves
to the lower Great Lakes on Thursday. At this juncture, there are
model differences with the location, strength and track of this
system and its affect on the region. Some decent snow totals may
occur with this system, but where and how much will have to wait
until the model differences get worked out and we get closer in
time to this scenario.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1134 AM CST Fri Dec 15 2017

A thin veil of mvfr stratus is causing intermittent mvfr cigs this
morning and likely into the early afternoon. Expect enough breaks
to go VFR for a few hours this afternoon at most sites before the
next system arrives with MVFR cigs and eventually IFR conditions
in snow which should persist through the remainder of the
forecast.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  15   7  21  15 /  90  80  70  10
INL   9  -2  18  12 /  80  30  40  10
BRD  22  15  24  17 /  50  80  40  10
HYR  16  10  22  16 /  80  80  60  10
ASX  16   7  22  17 /  90  60  60  10

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&

$$

SHORT TERM...Huyck
LONG TERM...GSF
AVIATION...Wolfe


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