Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 102157
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
357 PM CST Sun Dec 10 2017

.SHORT TERM...(This evening through Monday)
Issued at 356 PM CST Sun Dec 10 2017

The main concern in the short term is the fast moving clipper that
is forecast to move through tonight and early Monday. We can see
this clipper taking shape over northern Saskatchewan on satellite
imagery, producing precipitation there according to the Canadian
radar network. There is a mixture of rain and snow, and where snow
is falling visibilities of less than a mile have been reported.
The surface low is located near La Ronge, well north of Saskatoon
Canada. A warm front extends southeast from the low to eastern
North Dakota before trailing into southwest Minnesota. This front
to ease to the east somewhat tonight, but not enough to bring
temperatures above freezing as the clipper slides southeast across
the forecast area tonight and early Monday. The warm air advection
wing tonight and trailing wrap around precipitation Monday to
bring a short period of snow to the region between midnight
tonight and noon Monday. The heaviest precipitation to fall in
about a 3 hour period mostly tonight ahead of the surface low
where the frontogenesis band is strongest. This is a fairly potent
clipper, but nothing extraordinary and am expecting a quick 1 to 3
inches of snow laid out across the forecast area. The timing of
the snowfall is going to make the Monday morning commute more
difficult. Most of the snow should be on the ground by 6 AM, which
is likely to produce slippery road conditions. Though not
convenient, thresholds are not quite there for a winter weather
advisory and have held off on that for now and am going to beef up
wording in HWO and the weather story, and will be issuing an SPS
for the snowfall to hopefully raise awareness of this clipper.

.LONG TERM...(Monday night through Sunday)
Issued at 356 PM CST Sun Dec 10 2017

Long term forecast remains on track with several periods of light
snow and cool temperatures.

Meridional flow aloft will continue Monday night. Arctic air
advection and clearing skies and fresh snowpack from Monday`s
clipper should yield low temperatures on either side of zero.
Highs on Tuesday will be cool as well with readings in the single
digits northeast to the low 20s southwest. A shortwave trough is
forecast to dive southeastward out of the Canadian Rockies and
into the Central Plains Tuesday night and Wednesday. While that
trough won`t affect the Northland directly, it will change the
upper flow pattern northwesterly. Deterministic guidance is split
in handling the next shortwave which will affect our area
Wednesday. The GFS is a little faster and stronger with the
trough and associated vort max and brings a swath of 1 to 3
inches of snow to northeast Minnesota and northwest Wisconsin.
The GEM and ECMWF are stronger with the western shortwave and
bring lower snow chances to the Northland. A better chance of
light snow arrives Wednesday night into Thursday. All of the long
range models bring some accumulation to the area. GFS brings the
higher amounts once again with several more inches possible.
Another pattern shift to a progressive mode is indicated late
this week into next weekend. While the details differ between
models, the GFS, ECMWF, and GEM all feature a pattern shift. The
GFS and ECMWF bring an Alberta Clipper through the Northland
Friday night and Saturday while the GEM is weaker and farther
north. Given the timing differences, even between the GFS and
ECMWF, continued the earlier trend of chance POPs Friday and
Saturday. The pattern shift late this week will also bring
slightly warmer temperatures to the region. Look for highs on
Friday in the middle teens northeast to the upper 20s southwest.
Highs on Saturday could reach the freezing mark along over our
southern CWA with middle to upper 20s in the north.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1157 AM CST Sun Dec 10 2017

Stratus with a few snow showers loiter across the area this
afternoon. Expect clearing line indicated on GOES-13 satellite
imagery to migrate into INL within the next two hours and progress
farther southeast thereafter. A fast-moving, but strong, clipper
will move through the region tonight and Monday morning bringing a
quick period of snow to the terminals. Visibility of 1 to 2 miles
is likely in the snow, and there is a potential for a period of
visibility as low as 1/4 mile. The timing of visibility less than
1 mile is uncertain with this update, but subsequent forecasts
should be able to further refine the lowest visibility and timing.
Snow tapers off to snow showers Monday morning with MVFR ceilings
continuing into the afternoon.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  15  25  -1  14 / 100  80   0   0
INL  13  19  -6  11 /  90  10   0   0
BRD  23  30   6  21 /  90  50   0  10
HYR  15  29   1  14 / 100  90  10   0
ASX  16  28   7  15 /  90  90  10  20

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...Gale Watch from Monday afternoon through Monday evening for
     LSZ121-146>148.

     Small Craft Advisory from 10 AM Monday to 4 AM CST Tuesday for
     LSZ121-145>148.

     Small Craft Advisory from 4 PM Monday to 4 AM CST Tuesday for
     LSZ140>144.

&&

$$

SHORT TERM...LE
LONG TERM...Huyck
AVIATION...Huyck



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