Area Forecast Discussion
Issued by NWS Duluth, MN

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131
FXUS63 KDLH 231729
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1229 PM CDT Mon Oct 23 2017

.UPDATE...
Issued at 1221 PM CDT Mon Oct 23 2017

Updated for the 18z Aviation Discussion below.

&&

.SHORT TERM...(Today through Tuesday)
Issued at 350 AM CDT Mon Oct 23 2017

An area of low pressure was located on the northern end of the
Red River Valley of the North, on the Canadian side of the
international border at 0730Z. A cold front extended south
southwest from the low through eastern North Dakota. This surface
low was being pushed along by an upper level trof that was also
moving through the Valley. Some showers were developing along and
ahead of the front and were affecting northwest Minnesota. A few
sprinkles were also dotting the landscape in the area of strong
warm air advection ahead of this system. After this initial surge
of showers, some drier air will follow behind the cold front as
the front and area of low pressure move across the region.
Meanwhile, the upper trof also moves overhead and ushers much
colder air into the region. Some patches of moisture will
encounter this trof and the cold front and generate some showers
for much of the day. The prime location for showers will be along
the northern third of the forecast area in the vicinity of the
surface low and collocated with a vigorous embedded impulse.

By this evening, the aforementioned low will be absorbed into a
stronger surface low over Michigan. Meanwhile, the upper trof
evolves into a closed low that gradually attempts to become
vertically stacked. This leads to the surface low
intensifying/deepening as it lifts toward Upper Michigan by 12Z
Tuesday. The upper flow becomes northerly and continues to pull
even colder air into the region tonight. Embedded impulses will
rotate through the eastern portion of the forecast area and generate
more showers. Some light snow will begin to mix in with the rain
late tonight over the higher terrain areas. Not expecting any
accumulation as the cold air is not deep enough and the ground is
warm. The pressure gradient tightens up over the region, along with
the cold air advecting into the Northland, look for windy conditions
to develop and have raised wind speeds.

This system will remain fairly stationary on Tuesday. Expecting the
wind to stay up for most of the day. The pressure gradient begins to
relax in the late afternoon and the wind speeds will diminish. Drier
air will also begin to be pulled into the region through the day.
This will bring an end to the precipitation for much of the area.
The exception being along the Gogebic Range into northern Price
county where some lake induced rain or snow showers will persist.
Any snow accumulations will be less than one half inch.

.LONG TERM...(Tuesday night through Sunday)
Issued at 350 AM CDT Mon Oct 23 2017

Sharp upper trough slowly translates eastward shedding weak
clipper systems over the region which will bring little in the way
of precip, but still have on/off nuisance PoPs until a larger
system arrives Thursday night.

This Thursday-Friday system has been threatening the region with
a large snowfall, however, latest GFS and Canadian models have
continued the trend of moving the heaviest snowfall northward into
Canada leaving our area with much lighter snowfall accumulations
than prior runs. Based on current ensemble thinking, snowfall in
the 1 to 3" range for the area seems plausible except near the
Canadian border where 4-8" seems reasonable. If the Canadian model
is correct, areas south of Grand Marais would just see a dusting.
So there still is some uncertainty here, but overall the models
are beginning to converge on a solution. One other issue with the
more northerly track is warmer air makes its way northward which
could wrap a melting layer around the warm conveyor belt of the
developing low leading to a tongue of mixed precip in the heart of
the precip shield thus decreasing snowfall accumulation
potential. Either way, continue to monitor this system as the
forecast progresses.

The low shifts eastward Friday afternoon with yet another backside
upper trough situated over the area for more weak clipper systems
sliding through the region into early next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1221 PM CDT Mon Oct 23 2017

VFR to high-end IFR conditions were observed across the Northland
this early afternoon as a cold front boundary makes its way
through the region. Behind the front, cigs will decrease from west
to east into the MVFR categories, with heights between 1.5 to 3.0
kft. Some light rain showers will be possible this afternoon and
evening as cold air advection becomes enhanced behind the front.
Also, north to northwesterly winds will be gusty this afternoon
through tonight as the surface pressure gradient tightens, so
winds will likely gust up to 30 knots in some locations. These
wind gusts will likely persist through the day Tuesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  55  35  43  32 /  30  40  20  20
INL  51  29  43  31 /  70  40  10  20
BRD  53  35  46  35 /  20   0   0  10
HYR  57  38  44  30 /  40  70  60  10
ASX  59  40  45  32 /  40  90  70  20

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...Gale Warning from 1 AM to 8 PM CDT Tuesday for LSZ121-140>143-
     146>148.

     Gale Warning from 3 AM to 1 PM CDT Tuesday for LSZ144-145.

     Small Craft Advisory until 4 PM CDT this afternoon for LSZ140.

&&

$$

UPDATE...JTS
SHORT TERM...GSF
LONG TERM...Wolfe
AVIATION...JTS



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