Area Forecast Discussion


239 
FXUS63 KDLH 102320
AFDDLH
Area Forecast Discussion
National Weather Service Duluth MN
520 PM CST Sun Dec 10 2017
.UPDATE...
Issued at 520 PM CST Sun Dec 10 2017
The system due to affect the forecast area tonight is still in
Canada as of 5pm. A warm front was approaching the Red River
Valley with plenty of mid and high clouds ahead of this system. 
Best forcing is still off in the western Dakotas and have delayed 
the onset of the snow by a few hours. Rest of the forecast is on 
track.
&&
.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 00Z TAFS through 00Z Monday evening)
Issued at 520 PM CST Sun Dec 10 2017
A mix of MVFR and VFR cigs at the start of the forecast. Expect
more clouds in the MVFR range as the system gets closer. Have
delayed the onset of the snow by a few hours as the system is a
bit slower. Once the snow gets going, IFR conditions are expected,
with pockets of VLIFR in the more intense bands of snow. As the
system departs Monday morning, will see an improvement to VFR at
all locations but HYR, which may have MVFR cigs linger until the
end of the forecast. Gusty winds will also follow behind the
system.
&&
.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 / 100  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.
&&
$$
UPDATE...GSF
SHORT TERM...LE
LONG TERM...Huyck
AVIATION...GSF