Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 200940

Area Forecast Discussion
National Weather Service Duluth MN
440 AM CDT Thu Oct 20 2016

.SHORT TERM...(Today through Friday)
Issued at 440 AM CDT Thu Oct 20 2016

A cutoff upper low was centered over far northeast Ontario early
this morning. A ribbon of vorticity and a weak shortwave trough
were found over the southern Canadian Prairies and northern North
Dakota. Weak subsidence located ahead of the shortwave resulted in
a wedge of clear skies from southern and southwest Minnesota into
the Arrowhead, while much of northwest Wisconsin was still mainly
cloudy. Temperatures over portions of north-central Minnesota have
fallen into the upper 20s where clear skies and light winds have
been present much of the night, leading to efficient radiational
cooling, and the upper 30s and low 40s under the clouds.

The shortwave trough will continue to rotate southeastward into
Minnesota by late morning/early afternoon. Skies will briefly
clear over much of northwest Wisconsin this morning, except for
areas downstream from Lake Superior. Clouds will spread
southeastward with the approaching shortwave, beginning in far
northern Minnesota around sunrise. Cold advection and cyclonic
flow aloft should wring some precipitation out of those clouds in
the form of scattered light rain or snow showers. Snow
accumulation is not anticipated at this time. The clouds and
scattered showers will spread toward the Twin Ports by early
afternoon, and into northwest Wisconsin late today. Temperatures
will trend cooler than yesterday with readings near 40 degrees in
the high terrain of northeast Minnesota and the upper 40s in
southern Pine County, about 5 to 8 degrees below normal.

Scattered rain or snow showers should linger into this evening in
northeast Minnesota and northern portions of Bayfield and Iron
Counties. The shortwave trough will quickly move out of the area
tonight with ridging building in from the west. Skies are expected
to clear tonight as heights rise and broad subsidence returns.
Look for low temperatures in the upper 20s and low 30s.

Friday should start out generally mostly sunny across the
Northland. A warm front will lift northeastward into western
Minnesota by early afternoon. Isentropic upslope flow to the east
of the boundary, along with warm air advection and associated
frontogenetic forcing for ascent, will bring an area of clouds and
a few rain showers into the area. Deterministic guidance differs
slightly with the potential precipitation placement. The GFS and
ECMWF are a bit faster, while the NAM and GEM are a bit slower.
The GEM has a much more robust precipitation signal and features
rain as far south as central Minnesota. Trended toward the faster
solution and precipitation location of the GFS/ECMWF blend, with a
band of rain showers moving across my northern zones during the
afternoon. Winds will turn southerly during the morning allowing
warmer air to lift into the area. Highs will trend close to
normal, in the low 40s along the high terrain of northeast
Minnesota to around 50 degrees in my southwest.

.LONG TERM...(Friday night through Wednesday)
Issued at 440 AM CDT Thu Oct 20 2016

The models have trended to a weaker upper level trof clipping the
International Border area Friday night. The best forcing will be
be found along the border and this is where QPF signals have come
into better agreement. Lowered POPs/QPF as a result with best
chance of rain now north of the Iron Range. On Saturday, upper
level and surface ridging moves across the region. Model
differences continue on Saturday night with the arrival of a
positively tilted upper trof and its associated surface low. By
12Z/7am Sunday, the NAM is the deepest and places the low center
near INL. The GFS is weaker and near CKN, the ECMWF is way south
with the low center near southeast Minnesota, the GEM is in
southwest Minnesota. Used a blended approach to POPs which kept
the evening dry and small POPs over northwest Koochiching county
overnight. This is where the best forcing will be from the upper
trof. All models agree on moving the surface low center quickly to
the east on Sunday as the upper trof moves into Ontario. Have POPs
aligned over northeast Minnesota Sunday nearest the best upward
vertical motion from some embedded pieces of energy moving through
this area. Upper level and surface ridging move into the region
Sunday night. There is a small opportunity for some showers in
north central Wisconsin Sunday evening as the last bit of energy
clips this area. Model differences return Monday night. The
GEM/ECMWF are in better agreement than the GFS which has a rather
quick developing area of precipitation. The evening is dry, then
bring in some low POPs as a compromise. These differences continue
Tuesday through Wednesday. The GFS suffers from some large
gridscale feedback Tuesday night. Will lean more toward the ECMWF.
Removed the mention of thunder as the best instability will be
well south of the region.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1254 AM CDT Thu Oct 20 2016

A trough axis will dig southeastward from southern Saskatchewan
into western Upper Michigan by the end of the forecast period per
the latest guidance. This will generally keep MVFR/VFR ceilings
through the forecast. All terminals, except for INL, will see
ceilings flirt with MVFR with ceilings around or just above 3000
ft. Still uncertain how widespread shower activity will be
tomorrow, but think the latest GFS/ECMWF have the best handle on
the situation. Used this guidance for VCSH mention at INL/HIB.
May need to expand VCSH to DLH in future updates if guidance
trends towards the GFS/ECWMF. Winds will remain less than 10 kts
through the forecast.


DLH  44  32  47  37 /  20  20  10  10
INL  42  29  47  37 /  40  30  30  20
BRD  46  32  51  37 /   0   0   0   0
HYR  46  31  49  36 /   0   0   0  10
ASX  47  34  48  37 /  20  20   0  10




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