Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 092152
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
352 PM CST Sat Dec 9 2017

.UPDATE...
Issued at 351 PM CST Sat Dec 9 2017

Update to add light snow across NE MN north of Highway 2. US and
Canadian radars indicates a shortwave pushing down a quick shot
light snow for late this afternoon and evening hours.
Accumulations should be less than an inch.

&&

.SHORT TERM...(This evening through Sunday)
Issued at 324 PM CST Sat Dec 9 2017

Concern for short term is light snow possible tonight in
the arrowhead.

Current surface analysis indicates mostly cloudy skies across the
forecast region with flurries reported at some sites.  The lake
effect snow showers in northern Ashland and Iron counties have
almost ceased due to the change in wind direction shutting off the
snow.  Only flurries is expected later this afternoon and evening.

The next clipper is weaker than the one on Friday and does not have
much precipitation with it.  The center will pass through the
northern great lakes tonight bringing only a chance for snow
showers for the arrowhead region and in the snow belt areas of NW
WI.

An area of high pressure will give the region a break during the
day on Sunday before another clipper affects the region Sunday
night.

.LONG TERM...(Sunday night through Saturday)
Issued at 324 PM CST Sat Dec 9 2017

Forecast concerns during the long term involve snow chances and
amounts associated with several clippers moving through the
Northland.

Meridional to northwest flow aloft will continue for much of the
upcoming week with a possible pattern change to quasi-zonal
Friday into the weekend. The first clipper system moves
southeastward out of Alberta Sunday afternoon and through the
Dakotas and Minnesota Sunday night and Monday. A surge of Pacific
moisture will accompany the passing shortwave trough along with a
compact and strong vort max. The strongest forcing for ascent
will move across northwest and central Minnesota Sunday night and
early Monday morning. However, a narrow wedge of warmer air aloft
will wrap into the fast-moving system, which may suppress snow
ratios over the southwest corner of the CWA. With higher ratios
in the colder air to the northwest, think the area from
Koochiching and Itasca Counties to northwest Wisconsin is most
likely to see 1 to 3 inches of accumulation. Light to moderate
snow will be falling over much of the Northland during the Monday
morning commute. Considering how quickly the shortwave will move
through the region, the heaviest snow rates should progress
quickly from the northwest to the southeast with any given locale
experiencing the highest rates for only a few hours, with a
prolonged period of light snow afterward. Light snow is expected
to taper off for most locations by late morning or early
afternoon. The exception will be over the Lake Superior snowbelt
areas of Bayfield, Ashland, and Iron Counties where lake effect
snow anticipated. Another 1 to 3 inches of snow is possible
through Monday night.

Light lake effect snow showers will continue Tuesday into Tuesday
night in the persistent northwest flow. Rising heights aloft will
support a ridge of high pressure at the surface Tuesday into
Tuesday night. The GFS is an outlier with the handling of the
next shortwave trough and brings another compact bolus of
vorticity rocketing through the Northern Plains Tuesday night.
The ECMWF/GEM are farther west and slower with this feature. Kept
slight chance POPs in the picture as this trough moves through.
The next disturbance arrives Wednesday afternoon or Thursday.
Deterministic guidance features three different solutions with
the evolution of that trough so we kept a mention of chance POPs
in the forecast. Lake effect snow seems favored once again from
Thursday morning into Friday. Consensus still remains poor
heading into the weekend. A shift toward a quasi-zonal pattern
late in the week seems favored by the models, but the timing and
the progression of an Alberta Clipper through the region is far
from settled. The GEM is the fastest of the guidance and brings a
weak area of low pressure out of northern Alberta through the
Great Lakes as early as Thursday night into Friday. The GFS and
ECMWF are slower and differ in strength. The GFS wraps up an area
of low pressure and brings it eastward across the Canadian
Prairies and into the Northland by Friday afternoon/evening while
the ECMWF is a little slower with the timing, but weaker with an
open wave/FGEN band of precip. Given the poor consensus continued
to broad brush chance POPs across the area Friday afternoon and
night.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1219 PM CST Sat Dec 9 2017

MVFR stratus will linger this afternoon. Low-level moisture is
trapped beneath a temperature inversion aloft. A wedge of drier
air is found above the inversion, but is unable to mix into the
cloud layer. A few holes are possible, but think MVFR ceilings
will continue this afternoon. Scattered snow showers will continue
as well resulting in occasional visibility reductions between 2
and 5 miles. Winds aloft turn westerly by this evening moving a
drier airmass into the area. Look for the low stratus to become
scattered. Snow showers are expected to end with the departure of
the low clouds. Winds aloft turn northerly once again late tonight
pulling another surge of moisture into the region. Look for
ceilings to lower into MVFR range again tonight.


&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  14  24  15  26 /  40   0  80  30
INL  11  20  12  20 /  60  10  80  20
BRD  19  28  22  29 /   0  10  80  20
HYR  13  26  15  29 /  10  10  80  50
ASX  16  25  15  28 /  20  20  80  60

&&

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

$$

UPDATE...Stewart
SHORT TERM...Stewart
LONG TERM...Huyck
AVIATION...Huyck



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