Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 152352

Area Forecast Discussion
National Weather Service Duluth MN
552 PM CST Fri Dec 15 2017

.SHORT TERM...(This evening through Saturday)
Issued at 326 PM CST Fri Dec 15 2017

Another round of widespread light snow is expected to increase from
the west late this afternoon and evening, persisting for much of the
Northland through Saturday morning. A rather complex synoptic setup
has developed over the Upper Midwest region, with a surface low
pressure system currently situated over northwest Lake Huron, with
surface high pressure over northwest Ontario Canada. Increasing
clouds from the west were observed this afternoon due to an
approaching corridor of enhanced isentropic upglide, 850-700 mb
layer warm air advection, and weak frontogenetical forcing. This
corridor of lift will support the increased chances of snow. High-
res and synoptic models both indicate a rather sluggish band of
light to moderate snow that will slowly advance eastward through the
region through Saturday morning. We maintained at least likely PoPs
along the band for most of Saturday morning, with widespread 1 to 3
inches of snowfall possible. The heaviest amounts will primarily be
over the southwestern one-half of our forecast area, including the
Brainerd Lakes and Grand Rapids. Some slick roads may result from
the light snow on untreated roadways.

As the surface low pressure over Lake Huron departs eastward, the
high pressure will dive southeastward over southern Ontario, which
will cause winds over Lake Superior to veer to a more westerly
direction. Due to this on-shore flow along the North Shore, the
concern then shifts to along the Highway 61 corridor for heavier
snow amounts. The enhanced lift over the higher terrain of the North
Shore, along with favorable 850 mb/lake temperature delta-Ts between
18 to 20 degrees below zero should support some lake effect snow.
There are some questions regarding the robustness of the environment
as there is some low-level wind shear, which may inhibit the lake
effect. Most of the model guidance is still in good agreement with
bringing this heavier snow along the North Shore. Given the stronger
on-shore flow, and favorable delta-Ts, will maintain higher PoPs
along the North Shore. Winds will slowly shift to a northwesterly
direction, which will transition higher chances of snow from Lake to
Cook counties in the Minnesota Arrowhead. By late Saturday
afternoon, drier and slightly warmer air will move into the
Arrowhead region, which should bring the lake effect to an end as
the soundings indicate a loss of ice crystals aloft. Upstream over
the Brainerd Lakes region late Saturday morning and early afternoon,
there may be a period of light freezing drizzle. Soundings indicate
that aforementioned loss of ice crystals, but there`s still shallow
saturation below the ice-producing layer, indicating this period of
freezing drizzle. Significant ice accretion is not expected with

.LONG TERM...(Saturday night through Friday)
Issued at 326 PM CST Fri Dec 15 2017

Nothing too significant expected through Monday. A bit of a
change in the weather pattern with systems becoming increasingly
more zonal rather than nwly/nly which increases the threat for a
larger system. One such system may pass near the region Friday;
however, latest model guidance has backed off a tad on the
potential for any significant snowfall for our area taking the
system on a much more southerly track. That system is fueled by a
180 kt jet maxima and there still is quite a bit of time between
now and when it`s projected to pass by to our south, so it
definitely bears watching.

After that system passes to our east, a frigid blob of arctic air
makes its way into the region with -30 C at 850 mb on the


.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 547 PM CST Fri Dec 15 2017

A wave of -sn is moving into the terminals as of issuance time. It
will bring several hours of MVFR to IFR ceilings and visibilities,
mainly to KBRD, KDLH, KHYR and possibly also KHIB as this initial
wave moves through the area through 12z. A secondary wave will
bring IFR/MVFR ceilings with VFR visibilities and flurries in the
15z-21z time range. Conditions likely to be variable for KINL,


DLH   8  21  16  28 /  70  70  10   0
INL   2  18  14  27 /  50  50  10   0
BRD  18  25  17  30 / 100  30   0   0
HYR  10  23  16  29 /  70  60  10  10
ASX  11  23  17  30 /  40  40  10  10




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