Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 181725

Area Forecast Discussion
National Weather Service Duluth MN
1225 PM CDT TUE OCT 18 2016

Issued at 1036 AM CDT Tue Oct 18 2016

Updated to adjust cloud coverage due to current obs and trends.
Also, adjusted temps a couple of degrees for cloud cover.

UPDATE Issued at 656 AM CDT Tue Oct 18 2016

Please see the new 12Z Aviation Discussion below.

Cooler air flowing into the area from the northwest along with
some weak subsidence behind the departing shortwave have caused
additional clearing across parts of the forecast area this
morning. Fog has formed in many areas where the skies cleared as
well. Have updated for latest sky, fog and temperature trends. May
need to issue a dense fog advisory, but for now the fog coverage
is somewhat patchy in nature and the specific locations where it
will get down to a quarter mile are uncertain. I will have to
continue to monitor this issue for the next hour or so before
making that call.


.SHORT TERM...(Today through Wednesday)
Issued at 340 AM CDT Tue Oct 18 2016

A strong surface low was over far eastern Lake Superior this
morning, with a cold front draped to it`s southwest across upper
Michigan and Wisconsin to Iowa. Aloft, A shortwave was moving out
of Minnesota and into Wisconsin, driving much of the convection
currently over upper Michigan and northeast Wisconsin. These
storms are also moving along a mid level trough axis/baroclinic
zone which is draped from northern Iowa northeast through
Wisconsin to upper Michigan. These features are keeping all the
current convection to northeast Wisconsin and upper Michigan this
morning, with only some showers over northwest Wisconsin. During
the day today this low pressure system is going to continue to
move east, with diminishing potential for precipitation across the
forecast area this morning. Northwest flow and mostly cloudy skies
in the upper level cyclonic flow aloft will keep our temperatures
cool, with highs only in the 50s to around 60. A weak shortwave
that is currently over northern Montana/southern Saskatchewan and
producing some showers will slowly slide our direction today and
tonight, and should bring a small chance of showers to the
forecast area tonight. With the upper level flow remaining
northwest and cyclonic in nature, expect partly to mostly cloudy
skies to continue. This should also keep our temperatures from
dropping too far tonight, and have lows in the 30s and low 40s.
Some spots may get colder if they clear out. Wednesday will also
be cool as the northwest flow continues, and with enough cold air
aloft to keep even mixing from warming us up very much. Highs
should only get into the mid-upper 40s and 50s.

.LONG TERM...(Wednesday night through Monday)
Issued at 340 AM CDT Tue Oct 18 2016

The main concerns for the long term involve small chances of rain,
possibly mixing with snow, associated with several subtle
disturbances moving through the Northland through the middle of next

A cutoff low is forecast over far northern Ontario and another
trough of low pressure will be found over the Central Plains
Wednesday evening. Quasi-zonal flow is expected in the mid-levels
with northwesterly breezes and cold air advection near the surface.
The southern stream trough and associated vort max will kick the
cutoff low east into Quebec by Thursday afternoon. At the same time
the shortwave trough will amplify the longwave pattern as it moves
into the Mississippi River Valley. Clouds are expected to increase
Wednesday night and Thursday as a ribbon of vorticity rotates
southeastward on the back side of the cutoff low. A few scattered
rain or snow showers are possible along the International Border
late overnight and early Thursday morning. Northwest to northerly
flow over western Lake Superior will raise the potential for lake
effect rain or snow showers for northern Bayfield County Wednesday
night and Thursday. With relatively warm air temperatures, there are
some concerns regarding parcel residence time and the amount of
moisture flux required to generate precipitation. A similar set of
forecast conditions occurred last week with no precipitation. Wind
speeds are somewhat light, as well. Should showers develop, they are
not expected to move inland by more than a few miles. Consensus
blends feature no precipitation, so added some low chance pops
generally north of US-2 in Bayfield County.

Beyond Thursday, confidence in the forecast diminishes. Significant
differences emerge in the GEFS members and in the deterministic
output from the GFS, ECMWF, and GEM. The GEM moves the trough
eastward through Saturday and eventually evolves a cutoff low over
Quebec Saturday night. Meanwhile, the GFS, GEFS members, and ECMWF
all feature a slower eastward progression and an earlier transition
into a cutoff low. Guidance also points to another shortwave trough
moving into the Canadian Prairies on Friday. The intensity of this
feature and timing are split between deterministic solutions, but
GEFS members are similar in their handling. The shortwave is
forecast to move through the Northland Friday night and Saturday
morning. Moisture seems lacking with a persistent west to northwest
flow ahead of the feature. Even so, there is a small chance of a
band of rain developing along and ahead of a warm front lifting
northward as the shortwave passes through. Opted to keep the
consensus blend for POPs Friday night and Saturday.

Model differences are much more pronounced Saturday night and Sunday.
The GFS bringing another potent shortwave and associated vort
max into the region, with a compact surface low advancing out of the
Dakotas and into the Northland by Sunday morning. ECMWF and GEM show
a more subtle feature and GEFS members are split with timing and
amplitude of the feature. Consensus yields a slight chance of rain
or snow showers in far northern Minnesota and a dry forecast
elsewhere Sunday and Sunday night. With poor agreement and overall
low confidence, saw no reason to deviate from consensus.

Sunday night through Monday night should see a ridge building across
the Rockies and into the Northern Plains. This should usher in a
period of quiet weather with zonal flow in the mid-levels and
southwest breezes near the surface.

Temperatures will start out near to slightly below normal for
Wednesday and Thursday, gradually warming to near to slightly above
normal for the remainder of the period.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1225 PM CDT Tue Oct 18 2016

MVFR to VFR conditions through the TAF period. MVFR stratus
across far northern Minnesota will persist through the day and
into tonight, mainly at INL. Elsewhere VFR through the TAF period
with light west to northwest wind. A chance for light rain showers
this evening at INL/BRD and possibly other sites, but given the
uncertainty just introduced VCSH at those two sites.


DLH  57  41  51  33 /   0  20   0   0
INL  51  35  43  32 /   0   0   0  10
BRD  59  40  51  33 /   0  20   0   0
HYR  60  43  56  35 /   0   0   0   0
ASX  60  43  54  36 /  10  10   0   0


.DLH Watches/Warnings/Advisories...
LS...Small Craft Advisory until 4 PM CDT this afternoon for LSZ146-



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