Severe Thunderstorm Warning 56, NWS Duluth, MN

Area Forecast Discussion
National Weather Service Duluth MN
322 PM CDT Thu Jul 6 2017

.SHORT TERM...(This evening through Friday)
Issued at 322 PM CDT Thu Jul 6 2017

Another night of strong to severe thunderstorms on tap across the
Northland. The mesoscale details near the surface are fairly
complicated. There are two remnant outflow boundaries over the
forecast area this afternoon; one from our northwest into the Twin
Ports to near Hayward, and another arcing clockwise from near
Silver Bay into the Boundary Waters Canoe Area Wilderness. A cool
front was advancing southeastward from near Crane Lake to Grand
Rapids to Leader. Ahead of those boundaries, moderate instability
of 1500-2500 J/kg of MLCAPE has developed with 0-6 km deep layer
shear of 35 to 45 knots. A few thunderstorms have developed ahead
of the cool front, with another area of storms on the eastern
outflow boundary in the Arrowhead. Expect storms to increase in
coverage and intensity during the remainder of the afternoon and
continue into this evening. Large hail, damaging wind, and
torrential rainfall are the main threats. However, with the
quantity of small scale boundaries in place across the Northland,
a small tornado risk cannot be ruled out.

Storms should exit the CWA this evening to the southwest with
quieter conditions expected for much of the night. Lingering
elevated instability over northwest and central Minnesota may
support another round of isolated thunderstorms from around 09Z
Friday morning into the afternoon as a compact and potent
shortwave trough dives out of the Canadian Prairies and across
central Minnesota. Severe storms are not expected, but a few
storms may be strong. Behind the cool front late tonight and
Friday, drier and slightly cooler air will advect into the region,
leading to slightly cooler and more comfortable conditions to
wrap up the work week.

.LONG TERM...(Friday night through Thursday)
Issued at 322 PM CDT Thu Jul 6 2017

A strong mid to upper level ridge across the southern Rockies
into the central and southern Great Plains will persist through
the long- term period, with an upper low approaching Hudson Bay
leading to a northwest flow pattern aloft across the Upper Midwest
this weekend into next week. The mid-level ridging flattens out
towards the middle of next week, with a number of mid-level
shortwave troughs embedded in the northwest to westerly flow
pattern possibly resulting in showers and storms.

Friday night through Sunday skies will be mainly clear with highs
in the 70s to near 80 Saturday and Sunday.

Sunday afternoon into Sunday night a mid-level shortwave trough
embedded in northwesterly flow approaches from the west as a
weakly-defined warm frontal boundary lifts north across central
Minnesota. Showers and storms may fire along the front late Sunday
afternoon into Sunday evening, with the best chance for storms
south of Highway 2. Given the spread in ensemble guidance
regarding placement of the front and thus the best instability,
the possibility for any strong to severe storms is very low.

Early week the subsidence influence from the mid-level ridge
approaching from the west will set in across the Upper Midwest
leading to little to no precipitation chances Monday into Tuesday.
Highs in the 70s to near 80.

Tuesday night into Wednesday another chance for showers and
thunderstorms as a front approaches from the best. Southerly flow
ahead of the front will result in dew points reaching the mid 60s
on Wednesday afternoon resulting in an environment with 1500 to
2500 J/kg MUCAPE. A few strong storms are possible, but deep layer
wind profiles will not be favorable for organized thunderstorms
capable of producing widespread severe weather. Highs in the upper
70s to mid 80s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1234 PM CDT Thu Jul 6 2017

VFR conditions will prevail through the TAF period at all sites
with the exception of HYR where scattered to widespread storms
late today could result in brief MVFR to IFR visibility. Isolated
showers/storms may also impact HIB and DLH, though due to the low
coverage of storms expected kept just a mention of showers in the
TAF for now - will update with a mention of thunderstorms and more
detailed timing if/when confidence is higher that storms will
impact either site. Some mid to high level clouds this afternoon
at most sites, becoming clear overnight. West winds becoming more
northwesterly this afternoon with gusts to 18-22 knots, especially
at BRD and HIB. Winds become light overnight.

Increasing mid-level clouds late Friday morning at all sites,
with ceilings remaining VFR.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  58  73  53  78 /   0  30   0  10
INL  56  73  51  78 /  10   0   0  10
BRD  59  76  54  81 /   0  20   0   0
HYR  58  74  50  78 /  40  40   0  10
ASX  58  72  52  79 /  20  20   0   0

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&

SHORT TERM...Huyck
LONG TERM...JJM
AVIATION...JJM

Hazardous Weather Outlook...UPDATED
National Weather Service Duluth MN
304 PM CDT Thu Jul 6 2017

MNZ010>012-018>021-025-026-033>038-WIZ001>004-006>009-071030-
Koochiching-North St. Louis-Northern Cook/Northern Lake-
North Itasca-Central St. Louis-Southern Lake/North Shore-
Southern Cook/North Shore-North Cass-South Itasca-South Cass-
Crow Wing-Northern Aitkin-South Aitkin-Carlton/South St. Louis-
Pine-Douglas-Bayfield-Ashland-Iron-Burnett-Washburn-Sawyer-Price-
304 PM CDT Thu Jul 6 2017

This Hazardous Weather Outlook is for portions of northeast
Minnesota and northwest Wisconsin.

.DAY ONE...This afternoon and tonight

Thunderstorms are likely this afternoon and tonight from northern
Minnesota southeast across northern Wisconsin. Large hail,
damaging wind gusts, and torrential rainfall are the main threats.
Localized flooding is possible should storms move over the same
location repeatedly tonight. There is a small risk of tornadoes,
especially this afternoon and early this evening, before sunset.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

Several rounds of thunderstorms are possible from Friday morning
through Wednesday. Some of the storms may be strong, but it is too
early to highlight any particular time range or area.

.SPOTTER INFORMATION STATEMENT...

SKYWARN Spotters will be needed this afternoon and this evening.

LSZ121-140>148-071030-
Bayfield to Oak Point WI-Grand Portage to Grand Marais MN-
Grand Marais to Taconite Harbor MN-
Taconite Harbor to Silver Bay Harbor MN-
Silver Bay Harbor to Two Harbors MN-Two Harbors to Duluth MN-
Duluth MN to Port Wing WI-Port Wing to Sand Island WI-
Sand Island to Bayfield WI-Oak Point to Saxon Harbor WI-
304 PM CDT Thu Jul 6 2017

This Hazardous Weather Outlook is for portions of the nearshore
waters of western Lake Superior.

.DAY ONE...This afternoon and tonight

A few thunderstorms are possible across western Lake Superior
this afternoon and this evening. Some of the storms may be strong
or severe with large hail, dangerous wind gusts, and heavy
rainfall which will reduce visibility.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

Thunderstorms are possible across parts of western Lake Superior
late Tuesday night into Wednesday.

JJM/Huyck

More information may be obtained at the following web address:
http://www.weather.gov/duluth (all lower case)

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DULUTH MN
1231 PM CDT THU JUL 06 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0404 AM     TSTM WND DMG     1 NE REMER              47.07N 93.89W
07/06/2017                   CASS               MN   TRAINED SPOTTER

            6 TO 8 INCH DIAMETER TREE DOWNED ON HIGHWAY 6. TIME
            ESTIMATED FROM RADAR.

&&

WL

PRELIMINARY LOCAL STORM REPORT...CORRECTED
NATIONAL WEATHER SERVICE DULUTH MN
115 PM CDT THU JUL 06 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0130 AM     HAIL             3 SSE MCGRATH           46.21N 93.25W
07/06/2017  E1.75 INCH       AITKIN             MN   TRAINED SPOTTER

            CAR TOTALED BY HAIL. TIME ESTIMATED BY RADAR.

&&

WL

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DULUTH MN
126 PM CDT THU JUL 06 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0537 AM     TSTM WND DMG     2 NE DULUTH             46.80N 92.10W
07/06/2017                   ST. LOUIS          MN   PUBLIC

            LARGE TREE LIMB DOWNED ON EAST 6TH STREET. TIME ESTIMATED
            BY RADAR.

&&

WL

Special Weather Statement
National Weather Service Duluth MN
233 PM CDT THU JUL 6 2017

MNZ012-062000-
Northern Cook/Northern Lake-
233 PM CDT THU JUL 6 2017

...SEVERE THUNDERSTORM OVER ONTARIO HEADED FOR THE LAKE
SAGANAGA AND GUNFLINT LAKE AREAS...

At 232 PM CDT, an intense severe thunderstorm was located 15 miles
northwest of Saganaga Lake, moving southeast at 30 mph.

If this storm maintains its current movement and intensity, it will
begin to affect areas around the end of the Gunflint Trail between
245 and 315 PM CDT.

Very large hail, damaging winds and frequent lightning can all be
expected unless this storm weakens significantly.  A severe
thunderstorm warning may be needed.

This storm will affect...
    Saganaga Lake, Gunflint Lake, Sea Gull Lake and Alpine Lake.

Other locations impacted by this storm include Gabimichigami Lake,
Gneis Lake, and Knife Lake.

Seek shelter inside a sturdy building and away from windows until
this storm passes. Anyone on any of the Boundary Waters Lakes should
be prepared to seek shelter immediately.

LAT...LON 4824 9088 4824 9084 4818 9084 4818 9080
      4816 9080 4816 9078 4814 9080 4809 9075
      4810 9064 4812 9061 4810 9057 4799 9098
      4814 9116 4818 9109 4819 9102 4822 9098
      4825 9089
TIME...MOT...LOC 1928Z 311DEG 26KT 4832 9117

 Miller

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