Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 142128

Area Forecast Discussion
National Weather Service Duluth MN
328 PM CST Thu Dec 14 2017

.SHORT TERM...(This evening through Friday)
Issued at 328 PM CST Thu Dec 14 2017

Our wintry pattern continues tonight as another clipper system moves
through the Northland. The best chances of precipitation should
persist over our northeastern forecast area, including the Arrowhead
and northwest Wisconsin, as a lobe of positive vorticity advection
associated with a mid-level shortwave moves through the region this
evening and overnight. Northwest flow, with some low-level moisture,
should support a period of a standing gravity wave over the Bayfield
Peninsula area late tonight, peaking around midnight. There should
be a period of light to moderate snowfall, with total amounts
through Friday morning between 1 to 3 inches. The timing of the
precipitation, per the latest convective-allowing models, looks to
be between 04z and 11z before drier air from aloft eliminates the
saturation. Also, downstream from the gravity wave, some lake effect
snow is also expected over Iron and Ashland counties. The heaviest
amounts should fall along the Gogebic Range, with expected amounts
between 1 to 3 inches. Generally, since much of this snow will fall
during the overnight hours, not expecting much in the way of
impacts, but there could be some periods of light to moderate snow
with the lake effect. Temperatures tonight will drop down into the
single digits below zero north to the single digits above zero
south. Wind chill values tonight should drop into the single digits
below zero for nearly all of the Northland, with some negative teens
over the Minnesota Arrowhead.

There should be a brief respite from light snow across most of the
Northland Friday morning, except for lingering lake effect along the
Lake Superior snowbelt. Then, chances of snow will increase from the
west, especially over central Minnesota in the late morning and
through the afternoon as a band of 850-700 mb layer warm air
advection and frontogenetical forcing will move in. Snow amounts
north and west of Brainerd could be up to 1 inch Friday afternoon.

.LONG TERM...(Friday night through Thursday)
Issued at 328 PM CST Thu Dec 14 2017

The band of snow will continue to move into the Northland on
Friday evening, as a clipper moves southeastward through
Minnesota. Have raised POP`s considerably for the band of snow
that is expected to take on a northwest to southeast orientation
Friday night and early Saturday. The models are in fairly good
agreement that we should see snow accumulation, starting Friday
afternoon, and continuing into Saturday morning. The mid level WAA
and FGEN should help to bring snow accumulation to much of the
region. Snowfall amounts are expected to range from an inch or
less in the Ely area, to 2 to 4 inches in Walker, Brainerd,
Duluth, Superior and most of northwest Wisconsin. The north shore
of Lake Superior could also see some higher amounts as easterly
winds and orographic lift contribute to better forcing.

The clipper will gradually exit the region on Saturday, although
it will linger across the southeast and the north shore into
Saturday night. Sunday looks to be dry at this point, as high
pressure builds into the region.

Another shortwave will move across the Northland on Monday,
bringing a small chance of precipitation, with a cold front
dropping southward across the area on Monday night. Arctic high
pressure will build in behind the cold front, with high
temperatures gradually dropping from the lower 30s on Monday, to
the teens and 20s during the remainder of the work week.

The big discrepancy at this point is with regard to the potential
for a storm from Wednesday into Thursday. The models have some
fairly big differences at this point, with ECMWF more aggressive
in bringing the potential for heavy snow into our region.
Definitely one we will want to be keeping a close eye on,
especially so close to the holidays.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1200 PM CST Thu Dec 14 2017

A weak upper level system will drop southeast across the northern
Great Lakes today and tonight, as a cold front drops southward
across the region as well. The system will bring continued snow
showers to the area throughout the day and into tonight, before
high pressure attempts to bring dry weather for the remainder of
the night and into Friday morning for most locations. The sky
cover will be chaotic, with highly variable conditions during the
afternoon and evening. This makes applying one condition tough, as
we will likely see conditions alternate between IFR/MVFR to VFR as
snow showers move through locations. Snow will already move back
into the Northland on Friday, with snow spreading eastward into
the KBRD area later in the morning.


DLH   2  13   5  20 /  30  30  30  30
INL  -1   7  -3  19 /  50  20  20  30
BRD   8  19  13  24 /  10  40  40  20
HYR   4  14   7  22 /  30  30  30  20
ASX   9  14   6  22 /  50  30  20  20




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