Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 041927
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
127 PM CST Sun Dec 4 2016

.UPDATE...
Issued at 1052 AM CST Sun Dec 4 2016

Also added a winter weather advisory for the Duluth area.
Observations outside our window, and snowfall reports coming in,
were indicating some dendritic growth was adding to higher
snowfall rates that were previously forecasted.

UPDATE Issued at 840 AM CST Sun Dec 4 2016

The focus of this update was pcpn chances, qpf, and snowfall
through this evening. Considering some of the snowfall amounts we
are already seeing, including here at the office in Duluth, was
concerned the snowfall forecast was too low. Bumped up qpf and
snowfall for some areas, especially along the North Shore after
reviewing the latest high resolution model guidance. Now have a
range of about 3 to 6 inches of snow for much of the North Shore,
so added a winter weather advisory for the North Shore part of
Lake County, and adjusted the range of snowfall for the advisory
for the North Shore part of Cook County. Held off on advisory for
Duluth, even though it now looks like total snowfall will be
higher than forecast at about 3 to 4 inches, since about 1 to 1.5
inches of that snow has already fallen.

UPDATE Issued at 616 AM CST Sun Dec 4 2016

Please see the new 12Z Aviation Discussion below.

&&

.SHORT TERM...(Today through Monday)
Issued at 458 AM CST Sun Dec 4 2016

Light snow has developed over much of northern Minnesota and far
northwest Wisconsin and it will continue to spread east and north
into the rest of northern Wisconsin into the Arrowhead this
morning. The visibility has generally been from 1 to 3 miles. We
have received six tenths of an inch of snow as of 445 am. A trough
of low pressure was still back in the Dakotas and this initial
area of snow was due to a shortwave ahead of the main trough and
in an area of isentropic lift. The models are in pretty good
agreement moving the trough through the region today into this
evening. There will likely be some freezing drizzle or drizzle
that occurs over portions of northern Minnesota this morning,
roughly from west of a line from Pine City to International Falls
as the main area of snow shifts east and before deeper moisture
arrives with the main upper wave. Several observations have
suggested a mix just west of the Brainerd Lakes region. Snowfall
is expected to be from 1 to 3 inches for most areas. Some locally
higher amounts are expected along the North Shore, mainly between
Tofte and Grand Portage due to both lake and terrain enhancement.
We have a Winter Weather Advisory for that area from 9 am to 9 pm.
The precipitation will wind down over western areas later this
afternoon and over the rest of the Northland late this afternoon
into this evening.

A quick moving ridge will pass through the Northland tonight
bringing mainly dry conditions overnight into Monday morning.
However, warm air advection and another shortwave will bring a
chance for light snow or a mix of rain and snow Monday afternoon.
Chances for precipitation will be highest along and north of
Highway 2.

.LONG TERM...(Monday night through Saturday)
Issued at 458 AM CST Sun Dec 4 2016

Not many changes to sensible weather details in the long term
this morning. Forecast of a slow-moving cutoff low loitering in
the area through late week is still on track.

Deterministic and ensemble guidance in relatively good agreement
regarding arrival and placement of stacked low pressure over
northwest Minnesota Monday evening. Precipitation placement and
amounts are more diverse. The GFS and ECMWF are similar while the
NAM is farther north and west and the Canadian to the south. In
any case, the first round of precipitation should bring another
few inches of snow to my northwestern zones Monday night. Higher
elevation areas along the North Shore should pick up another inch
or two of accumulation.

Model differences become more pronounced beginning Tuesday with
the GFS and GEM keeping precipitation over northern Minnesota
through the end of the week. The NAM takes the bulk of the
precipitation into Ontario and the southern Canadian Prairies.
ECMWF straddles the NAM and GFS solutions. Think the GEM is far to
aggressive producing another six-tenths of QPF over my northwest
zones Tuesday afternoon through Wednesday morning. Leaned more
heavily on the consensus approach and nudged toward the GFS. This
yields another 1 to 3 inches of accumulation in my northwest
Tuesday through early Wednesday morning, with lower totals
elsewhere.

With abundant low- and mid-level moisture lingering over the
region Wednesday through Friday, expect periodic light snow
showers for much of the Northland and cooling temperatures.
Several additional inches of snow are possible during that time
for most locales. The northwest flow over western Lake Superior,
antecedent cloud cover, and very warm lake surface temperatures
should yield a prolonged period of lake enhanced snowfall over the
northwest Wisconsin snowbelt areas. There may be periods of heavy
snow during the second half of the week for those areas. Total
accumulation of more than 6 inches seems likely for portions of
Iron, Ashland, and Bayfield Counties from Wednesday night through
Saturday morning.

The cutoff low will eventually move out of the region Friday
night and Saturday and a return to a faster quasi-
zonal/northwesterly flow regime is possible during the weekend and
into next week.

North to northwesterly flow associated with the persistent storm
system this week will bring much colder temperatures into the
Northland. Look for readings by Wednesday much below normal with
highs in the low to upper teens and lows in the upper single
digits to middle teens. The near to much below normal temperature
trend will continue through the remainder of the long term and
into next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 117 PM CST Sun Dec 4 2016

LIFR and IFR ceilings, with some MVFR and isolated IFR vsbys due
to snowfall continues across the TAF sites this afternoon.
Ceilings should continue to be in the 300-1000 foot range. The
main wave causing the snowfall should move out by this evening and
overnight.

Low cigs are expected to continue this evening and
overnight, however, as model soundings are indicating the
development of a low level inversion, which should trap some
moisture in the boundary layer. NAM soundings are looking fairly
dry above 3000 feet or so. Winds are expected to veer more from
the southwest overnight but should stay light. Ceiling heights
should improve Monday morning.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  27  35  25  26 /  40  30  30  30
INL  25  34  22  23 /  50  50  60  50
BRD  25  35  23  23 /  10  30  30  20
HYR  27  37  27  28 /  40  20  30  20
ASX  28  39  29  31 /  40  10  30  20

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Winter Weather Advisory until 6 PM CST this evening for MNZ020-
     037.

     Winter Weather Advisory until 9 PM CST this evening for MNZ021.

LS...Small Craft Advisory until 10 AM CST Monday for LSZ140.

&&

$$

UPDATE...Grochocinski
SHORT TERM...Melde
LONG TERM...Huyck
AVIATION...JTS



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