Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 141734
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1134 AM CST Tue Nov 14 2017

.UPDATE...
Issued at 611 AM CST Tue Nov 14 2017

Dense fog was expanding across portions of northeast Minnesota and
we added the North Shore zones, central and southern Saint Louis
and Carlton Counties to the Dense Fog Advisory. Areas close to
Lake Superior will have higher visibilities compared to areas in
the higher terrain.

UPDATE Issued at 549 AM CST Tue Nov 14 2017

Updated for the new 12Z Aviation Discussion below.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 333 AM CST Tue Nov 14 2017

Warm air and moisture advection continued this morning across the
region with temperatures and dewpoints rising overnight. Much of the
Northland has seen temperatures rise to or a few degrees above
freezing as of 09Z. This was limiting freezing drizzle with mostly
just fog and drizzle occurring. A shortwave and frontal boundary is
still on track to move toward western portions of the Northland
today. These features will continue east tonight with a surface low
deepening a few MB as it moves over Lake Superior tonight.

Today will be a dreary day with fog and areas of drizzle. Dense fog
will occur in spots with it most widespread over western areas. We
issued a Dense Fog Advisory there for the morning. Highs will range
from 36F to 43F today. The chance for rain will increase over
northwest Wisconsin this afternoon into this evening as forcing
increases. As the low moves over Lake Superior tonight, colder air
will advect in overnight into Wednesday causing the precipitation
to mix with or change over to snow from northwest Minnesota into
northwest Wisconsin. Snow accumulation will be light with a few
tenths of an inch tonight over northern Minnesota. Lows tonight
will drop into the upper twenties over north central Minnesota but
remain in the lower to middle thirties over most of northwest
Wisconsin.

Colder air will continue to move in Wednesday and as mixing
increases, gusty winds will occur. Gusts of 20 to 25 mph with a few
to 30 mph will be possible for most areas by afternoon. Temperatures
will remain nearly steady or drop through the day Wednesday. By
Wednesday mid afternoon, the precipitation will be snow for most
areas. Strong northwest flow over the lowest few thousand feet may
lead to gravity wave enhanced precipitation over northern portions
of Bayfield, Douglas, and eastern Carlton Counties through the
evening. Snow accumulation from a dusting to around a half inch is
expected Wednesday. The Arrowhead and northern Iron County will have
the best chance at seeing a half inch during the afternoon hours
with locally higher amounts also possible under the gravity wave in
in far northwest Wisconsin toward eastern Carlton County.

.LONG TERM...(Wednesday night through Monday)
Issued at 333 AM CST Tue Nov 14 2017

The relatively seasonal weather will continue for until late this
week. A system could bring a sloppy period of rain, freezing rain,
and snow to the Northland Friday. This weekend will turn colder in
the wake of the system.

The Northland will be under cold northerly flow Wednesday evening in
the wake of a passing storm system over the Great Lakes. Gusty winds
are likely in the evening with the strong pressure rises and cold
air advection. Light lake effect snow showers are likely downwind of
Lake Superior in northern Wisconsin, especially along the near the
Gogebic Range. The northerly flow is ideal for lake effect for this
area, but it appears the air will be too dry and not cold enough to
support anything more than a few inches of lake effect snow.

Surface high pressure will move into the Northland early Thursday,
providing a period drier weather. Highs will be in the upper 20s to
lower 30s.

The models continue to indicate a broad area of surface low pressure
will develop up and down the US High Plains into the Canadian higher
plains late Thursday into Thursday night in advance of a deep trough
moving into western US and Canada. This low pressure will advance
east into the Plains and Canadian prairies Thursday night and
Friday, with potentially multiple centers of low pressure. The
upper trough will catch up with the surface low pressure Friday
night into Saturday, and the low pressure will phase into one
strong low somewhere near the Great Lakes by Saturday. A couple
days ago, it looked like the phasing would happen earlier enough
to potentially bring heavy snow to parts of the Northland.
However, over the past couple days, the trend has been to delay
the phasing until much of the low pressure passes the Northland,
so the threat of heavy snow looks lower than it did a couple days
ago. For now, it appears the Northland will see a period of light
snow transitioning to light freezing rain and then freezing rain
from Thursday evening into Friday afternoon. The inland Arrowhead
is still the most likely area to get any significant snow of a few
to up to several inches, as well as some light freezing rain. The
rest of the Northland will probably get light snow and rain.

Northwest flow will bring colder and drier air into the Northland
Friday night and Saturday in the wake of the passing system. There
could be lingering light snow, and light lake effect snow showers
downwind of Lake Superior in northern Wisconsin. The wind direction
over the Lake appears to be too westerly to get significant lake
effect snow in Wisconsin. Blustery winds will develop Saturday
thanks to strong pressure rises, strong cold air advection, and 25
to 30 knots within the low-level mixing layer. Anticipate wind gusts
of 20 to 30 mph. High temperatures will be much colder than the day
before, with highs getting to the lower to middle 20s, and wind
chills will be in the single digits.

There are some model differences in how quickly the cold northwest
flow will relax and switch to warmer southerly flow. The GFS and
Canadian linger cold northerly flow into Sunday, but the European
brings much warmer air into the region Sunday. The warmer air should
make in by at least Monday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1134 AM CST Tue Nov 14 2017

LIFR ceilings and visibilities will persist through this evening
at all sites with a gradual improvement to MVFR ceilings towards
mid-day Wednesday. Light south winds today around 5 to 10 knots
become west-northwesterly Wednesday morning.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  39  32  34  20 /  20  40  30   0
INL  40  30  30  14 /  10  40  50   0
BRD  42  31  32  20 /  20  30  10   0
HYR  41  34  36  22 /  40  60  20  10
ASX  41  36  38  25 /  30  60  40  30

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Dense Fog Advisory until noon CST today for MNZ019-035>037.

LS...Small Craft Advisory until 10 PM CST this evening for LSZ140.

&&

$$

UPDATE...Melde
SHORT TERM...Melde
LONG TERM...Grochocinski
AVIATION...JJM



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