Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 172341
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
641 PM CDT WED AUG 17 2016

.SHORT TERM...(This evening through Thursday)
Issued at 340 PM CDT Wed Aug 17 2016

As of this afternoon, the Northland had surface high pressure over
the region with light westerly flow. There were some showers and
weak storms along and near a lake breeze (and/or some sort of
subtle boundary) extending across northwest Wisconsin into east
central Minnesota. These showers and storms may drift south and
east through early this evening. Showers and storms are also
possible along and near the lake breeze along the North Shore.

The high pressure will shift to the east tonight. Clear skies,
humid conditions, and light winds speeds are a recipe for some
fog. The modeled surface condensation pressure deficits,
particularly of the NAM, suggest northwest Wisconsin and nearby
areas of Minnesota have the best chance of fog, but added patchy
fog to much of the Northland for late tonight.

Warm southerly flow will develop Thursday ahead of an approach
cold front from the west and northwest. Morning sunshine should
send temperatures quickly into the upper 70s and low 80s, but
there will be increasing chances of showers and storms from the
west in the afternoon. The approaching cold front will be
associated with a deep low over northern Canada and linked to
another area of low pressure in South Dakota. The GFS, NAM,
Regional Canadian, and ECMWF are suggesting a complex of storms
could develop near or north of the triple point, somewhere near
the SD/ND/MN border area, during the afternoon, aided by a passing
shortwave trough to provide some better overall lift to initiate
thunderstorms. That complex might move east or southeast during
the afternoon and evening with the east-moving shortwave trough,
and the complex (if it develops) could affect the southern
forecast area. It might depend on where the warm front sets up,
with the complex likely wanting to graze on the
warm/humid/unstable air near the warm front. The latest model runs
suggest the warm front may set up south of the forecast area, so
perhaps the complex would only affect far southern parts of the
forecast area, mainly the southwest forecast area. If the complex
develops, there ought to be enough instability and shear to pose
a damaging wind threat. Heavy rain is not out of the question
considering the precipitable water values of 1.5 to 1.75 inches.
Otherwise, the coming cold front will also bring increasing
chances of showers and storms to the western forecast area during
the middle to late afternoon onwards.

.LONG TERM...(Thursday night through Wednesday)
Issued at 340 PM CDT Wed Aug 17 2016

The main concern for the extended is the potential for strong to
severe storms Thursday evening into Friday. On the synoptic scale,
a trough will dig and deepen as it moves from western Canada into
the Northern Plains late Thursday night/early Friday. Well ahead
of the trough, a cold front will slide southeastward from eastern
North Dakota into Minnesota and into NW Wisconsin by early Friday
morning. Still somewhat uncertain on strong to severe storm
potential as convection ahead of the cold front will be impacted
if a complex of thunderstorms develop late Thursday
afternoon/early Thursday evening as indicated by
NAM/GFS/ECMWF/GEM. The main impact being the amount of instability
developing along and ahead of the cold front. 0-6 km bulk shear
values will increase to around 40 kts Thursday night into early
Friday with dew points in the mid to upper 60s. PWAT values will
be around 1.70 inches, which is around 150-200% higher than normal
for this time of year. If the instability is present, strong to
severe storms will be possible. If storms develop the main threats
would be damaging wind gusts, large hail and heavy rainfall.
Additional strong to severe storms will be possible across far
eastern WI zones on Friday as the cold front stalls just to the
south and east. If skies can clear and instability develops, there
will be 40-50 kts of 0-6 km bulk shear to work with, so strong to
severe storms cannot be ruled as highlighted in SPCs latest day 3
outlook.

The front will move out of the area once the upper trough moves
through late Saturday afternoon/evening. Increased POPS across NE
MN Saturday afternoon as the cool northwesterly flow combined with
day time heating and trough axis nearby will result in scattered
shower activity and perhaps a few isolated thunderstorms.
Temperatures will be a bit cooler through the weekend with highs
in the 60s.

High pressure will build into the region late on Sunday into
Monday. This will bring drier weather with a return to seasonable
temperatures across the Northland. Shower and thunderstorm chances
return for Tuesday/Wednesday as a trough digs into the Northern
Plains from Western Canada.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 640 PM CDT Wed Aug 17 2016

Mainly VFR conditions are expected throughout the TAF period. The
exception will be overnight, where there could be some patchy fog.
The result of the fog could be some MVFR/IFR CIG`s and VSBY`s.
Spotty showers and a few thunderstorms will be possible late in
the period, especially in the western TAF sites.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  61  83  62  73 /  10  30  60  50
INL  56  80  58  75 /   0  60  40  10
BRD  60  82  62  73 /   0  70  70  40
HYR  57  84  63  76 /  20  10  60  70
ASX  61  84  65  76 /  10  10  60  60

&&

.DLH Watches/Warnings/Advisories...
WI...None.
MN...None.
LS...None.
&&

$$

SHORT TERM...Grochocinski
LONG TERM...WL
AVIATION...DAP



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