Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 180921

Area Forecast Discussion
National Weather Service Duluth MN
421 AM CDT Fri Aug 18 2017

.SHORT TERM...(Today through Saturday)
Issued at 421 AM CDT Fri Aug 18 2017

A chance for isolated/scattered showers/storms today across northern
Minnesota and parts of northwest Wisconsin under partly sunny skies
today, then warmer and mostly sunny on Saturday.

On the synoptic scale a mid-level shortwave will subtly deepen as it
moves from southern Manitoba southeast across the Upper Midwest
today. With clearing skies today, diurnal heating will lead to cu
developing across the region today, and with the wave coming across
leading to broad-scale lift (or at least a lack of strong
subsidence) there will be at least isolated showers developing this
afternoon. Instability on the order of around 1000 j/kg SBCAPE may
lead to some brief thunderstorms, though weak winds through the
column (nothing stronger than about 25 knots) will lead to short-
duration storms. Otherwise northwest winds today with highs in the

Tonight the afternoon cu clears out and another round of fog is
expected to develop away from Lake Superior. Lows upper 50s to low

Warmer Saturday as a mid-level ridge building across the Great
Plains leads to broad-scale subsidence, though scattered diurnally
driven afternoon "fair weather" cu expected. Highs around 80.

.LONG TERM...(Saturday night through Thursday)
Issued at 421 AM CDT Fri Aug 18 2017

Main concerns for the long-term involve cloud cover and
precipitation chances Sunday evening through Tuesday morning.

Surface high pressure is forecast over the Midwest Saturday
evening as the mid-level pattern transitions to quasi-zonal flow.
Surface low pressure over northern Manitoba will advance eastward
ahead of a shortwave trough over the western Canadian Prairies. A
cool front will trail south into the Northern Plains and Upper
Midwest and move eastward as well. Convergence along the frontal
boundary may be sufficient to generate a few showers or
thunderstorms Saturday night and Sunday morning. Held onto mainly
slight chance POPs, with a few pockets of low-end chance POPs.
There are several differences between deterministic models with
the 00Z packages, and confidence is not especially high in any
particular location receiving rain. The frontal boundary will
stall out to our south and eventually move northward as a warm
front Sunday night and Monday.

A southern stream shortwave trough will move through the Four
Corners region and into the western Plains with lee cyclogenesis
over southeast Colorado Sunday and Sunday night. The low pressure
at the surface and aloft will bring clouds and rain showers north
into the region. There are some convective elements in the GFS
and NAM solutions which result in lower confidence. There is a
potential for an MCS to develop Sunday afternoon/evening in
Nebraska or South Dakota, which would then ride east near the
warm front and into Minnesota and eventually Wisconsin.
Considering the difficulty in resolving storm-scale features 3.5
days before the event support sticking with a consensus approach
to POPs and precip at this time. Have lowered max temps a few
degrees below the consensus blends Monday as a 3-hour window of
the upcoming solar eclipse will have its greatest affects during
peak heating. Further nudges cooler may be needed with the next
several forecast cycles. Several deterministic models point to a
potential for brief clearing during the early afternoon Monday,
which would permit viewing some of the eclipse for portions of
the Northland.

A progressive northern stream shortwave trough will move through
the northern Rockies and into region Monday night. Rain chances
increase once again Monday night and Tuesday morning as that
trough moves through. For the remainder of the week, an omega
blocking pattern evolves with anchoring low pressure over eastern
and western Canada and a high amplitude ridge over the center of
the continent. The Northland will be on the edge of the
northwesterly flow aloft and the ridge to the west. Precipitation
chances will be low and temperatures will trend near normal.


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1253 AM CDT Fri Aug 18 2017

Periods of MVFR/IFR overnight, improving to VFR by later this
morning. Areas fog are expected where winds diminish ahead of
approaching cirrus from the southwest. HYR will start with MVFR
CIGS, but improve to VFR by 07Z. Areas most likely to experience
fog include DLH, INL, HIB, and BRD. As a shortwave trough
approaches in the afternoon, some thunderstorms are possible near
BRD by 22Z. Timing is difficult and will have a VCTS mention.


DLH  76  55  80  60 /  20  20   0  20
INL  77  51  81  60 /  30  10   0  30
BRD  73  54  81  61 /  40  10   0  20
HYR  75  53  81  58 /  20  20  10  10
ASX  76  57  84  61 /  10  10   0  10




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