Area Forecast Discussion
Issued by NWS Duluth, MN

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814
FXUS63 KDLH 190857
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
357 AM CDT Tue Sep 19 2017

.SHORT TERM...(Today through Wednesday)
Issued at 349 AM CDT Tue Sep 19 2017

High pressure was over Quebec at 08Z with a ridge axis into the
forecast area. A light easterly flow off of Lake Superior was
helping to produce some patchy drizzle and fog from the Twin
Ports/Cloquet area and along the North Shore. Some patchy fog was
noted elsewhere. This ridge axis should affect the forecast area
through the day. Meanwhile, a surface low center was located in
southeast Montana at 08Z. A warm front extended in a easterly
direction from this low and into southwest Minnesota. The surface
low will become elongated through the day with the main low center
appearing to be in western Nebraska by 00Z Wednesday. Another low
was located over eastern Saskatchewan. An occluded frontal boundary
connected these two lows and will be the focus for storm
development. The warm front appears to remain over southern
Minnesota through the day. With the forecast area ahead of these
lows and the departing ridging, will see plenty of moisture advect
into the region with warm air advection. Showers and storms should
hold off through the day, but see plenty of clouds.

A pair of vigorous short waves will eject eastward from a closed low
over the Canadian Rockies tonight. The first one, which is weaker
than the second, reaches the western edge of the forecast area by
06Z Wednesday. Not expecting any storms into the western portion of
the area prior to 03Z. However, there are some models that bring
some into this area during this time. Have small pops to account for
these differences. This is supported by the ARW/NMM/NAM/NAMNest
and the NSSL WRF. The storms begin to move across the western tier
through 06Z and possibly into Pine county. There is potential for
some severe storms with MUCAPE values rising into the 1500-2500
J/kg range over the Brainerd Lakes region east into Pine county.
40-50kt of shear will accompany these CAPE values. Better
opportunity for severe will be with the second stronger short
wave. The first short wave lifts north into Canada by 12Z as the
second arrives in western Minnesota. It is with this second wave
and an approaching cold front that the stronger storms will
arrive. Will hold off on the mention of severe for now as there
are timing differences, as well as storm strength advertised by
the various short term hires models. Cloud over will also affect
amount of destabilization/severe potential.

A broken line of storms will continue to march east through the rest
of the forecast area Wednesday morning, diminishing by afternoon.
This activity will be aligned with the second wave and the cold
front. The cold front should reach the eastern edge of the forecast
area late Wednesday afternoon as the short wave lifts northeast into
Canada. Dry high pressure will follow behind the cold front.

.LONG TERM...(Wednesday night through Monday)
Issued at 349 AM CDT Tue Sep 19 2017

An active weather pattern will continue through the long term.
Very warm temperatures are expected for the remainder of the
week. Cooler air will gradually invade the Northland from the
northwest, but areas in northwest Wisconsin will see much above
normal temperatures continue through Sunday. There will be
several opportunities for strong to severe thunderstorms and
heavy rainfall.

The eastern arm of an Omega Block over the eastern Pacific will
loiter over the western half of the continent for much of the
extended. The mid- and upper-level trough will be quite broad
Wednesday evening stretching from Ontario westward into the
eastern Pacific. Surface high pressure and subsidence can be
expected over the Upper Midwest in the wake of a departing
shortwave trough and cold front. Winds aloft will turn southerly
once again by mid-morning Thursday as a warm front lifts
northward into northwest Ontario. That boundary will become quasi-
stationary with areas to the south, including the Northland,
experiencing unseasonable warmth with near record temperatures
forecast. The chance of rain and thunderstorms increases Thursday
night and continues through early next week as the front slowly
migrates eastward each day. The latent baroclinic zone and broad
swath of isentropic ascent in the warm sector should provide
ample chances for strong thunderstorms and heavy rainfall. The
potential for strong to severe thunderstorms will include the
entire CWA Thursday night and Friday morning thanks to moderate
instability and strong deep layer shear of 30 to 45 knots. The
atmosphere will recharge during the day with another round of
strong to potentially severe storms possible Friday afternoon and
evening. That period also holds the best potential for excessive
rainfall with surface low pressure lifting through northern
Minnesota along the stationary front. The thunderstorm risk will
shift farther southeast for Saturday and Sunday, mainly focused
over northwest Wisconisn. Another shortwave trough will move
through the Upper Midwest along the baroclinic zone, which may
lead to a heightened risk of excessive rainfall again on Sunday.
By Sunday night the deep trough will begin moving eastward,
taking on a slightly more progressive character. Rain and
thunderstorm chances remain high Monday before high pressure
moves through the Canadian Prairies and grazes the region
bringing quieter conditions Monday night.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1245 AM CDT Tue Sep 19 2017

Conditions will be mainly MVFR/IFR through the night with CIGS
below ovc010 from KHIB to KDLH and KBRD. CIGS will be higher to
the far north at KINL and the far south at KHYR. Clouds will have
a hard time breaking up tomorrow, so CIGS will likely rise to MVFR
by afternoon. Winds will get very strong tomorrow afternoon with
gusts to 30 kts. There will be wind shear in the evening with
strong winds 1500 to 2000 off the surface of at least 40 kts.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  65  58  69  49 /  10 100  50  10
INL  67  58  68  45 /   0 100  50  10
BRD  72  60  70  50 /   0  80  20   0
HYR  72  62  74  47 /   0  60  50  10
ASX  72  59  75  47 /   0  60  40  10

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement through this evening for WIZ001.

MN...Beach Hazards Statement through this evening for MNZ037.

LS...None.
&&

$$

SHORT TERM...GSF
LONG TERM...Huyck
AVIATION...CLC



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