Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 141145

Area Forecast Discussion
National Weather Service Duluth MN
645 AM CDT Fri Jul 14 2017

Issued at 645 AM CDT Fri Jul 14 2017

Updated for the new 12Z Aviation Discussion below.


.SHORT TERM...(Today through Saturday)
Issued at 348 AM CDT Fri Jul 14 2017

After morning fog skies will be sunny today across the Northland
with temperatures reaching near normal values in the mid to upper
70s. This evening into tonight a chance for a few elevated
thunderstorms (or remnants of storms) that may develop along a warm
front building east. Hot and humid Saturday as a warm and moist
airmass builds in - highs reaching 90 in some spots and dew points
in the mid to upper 60s. With ripe low-level moisture and moderately
steep mid-level lapse rates thunderstorms are possible in parts of
northwest Wisconsin Saturday afternoon, mainly east of a line from
Hayward to Ashland. A few strong to severe storms are possible.

On the synoptic scale a mid/upper level longwave ridge will build
across the Rockies into the Great Plains this weekend. As a result,
a large warm surface high pressure will develop across the Canadian
Prairie region and build eastward. A warm front ahead of this high
pressure may result in thunderstorms Friday night then again
Saturday afternoon. While there is a weak shortwave trough axis at
mid to low levels providing some large-scale support both days, the
extremely warm airmass will have such a strong cap that may prove
too difficult for surface heating and weak large-scale lift along
the frontal zone to overcome. Because of this, even at this short
range we`ve kept our POPs around or less than 50 percent Friday
night, and limited to about 30 percent Saturday afternoon. It may
very well end up being dry across the Northland through Saturday,
but should storms move in Friday night or develop Saturday afternoon
they could be strong due to decent mid-level lapse rates supporting
MUCAPE values in the 1000-1500 j/kg range Fri night to nearly 3000
j/kg Sat afternoon. Combined with moderate deep-layer shear (30-45
knots), any storms that can develop, especially Saturday afternoon,
could produce large hail and damaging winds.

.LONG TERM...(Saturday night through Thursday)
Issued at 348 AM CDT Fri Jul 14 2017

Surface high pressure over south-central Canada Saturday evening
will settle over Lake Superior Sunday, while an upper-level ridge
will move into the Northland from the west. This will provide the
Northland with a day of cooler weather because of easterly flow from
the Great Lakes. While the models are generally indicating fairly
sunny skies for Sunday, it`s certainly possible for cooler
conditions and low clouds near Lake Superior if the low-level
humidity is great enough. Sunday`s high temperatures will range from
the upper 60s and low 70s near Lake Superior, to the middle and
upper 70s well inland.

The high pressure and upper-level ridge will shift east Sunday night
and Monday. Low-level southerly return flow will develop Monday,
bringing warm and humid weather to the Northland. Highs should reach
the lower 80s. Showers and storms are possible late in the day and
into Saturday night with a cold front passage from the northwest.
There may be modest large-scale forcing for ascent from the
associated short-wave trough to help trigger storm development. If
storms do develop, there may an environment capable of developing
discreet supercells and storms that could bring severe weather. The
GFS is indicating 1000 to 3000 most unstable CAPE and 35 to 40 knots
of 0-6 km deep layer wind shear, and 1.5 to 2 inches precipitable
water values. The best chances of severe weather will be across the
northern and western forecast area.

High pressure will likely bring a period of cooler and drier weather
for the middle of the week after Monday night`s cold front passage.
Highs will likely return to the lower and middle 70s for Wednesday
and Thursday. While the Canadian and GFS keep the Northland fairly
dry through Thursday, the European has a warm front lifting into
southern or central Minnesota and central Wisconsin during the
middle of the week, so the forecast has low chances of showers and
storms to account for the European.


.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 645 AM CDT Fri Jul 14 2017

Surface high pressure was over Minnesota early this morning, with
fog across parts of northeast Minnesota and northwest Wisconsin. Once
the morning fog across northeast Minnesota and northwest
Wisconsin dissipates, expect VFR conditions for the day. A cool
front will pass through the region tonight. There are low chances
of showers and storms with its passage overnight.


DLH  75  57  84  55 /   0  40  10   0
INL  78  57  78  50 /   0  40  10   0
BRD  77  60  86  58 /   0  20  10   0
HYR  75  55  85  55 /  10  20  20  10
ASX  76  55  85  55 /   0  20  20  10




LONG TERM...Grochocinski
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