Severe Thunderstorm Warning 162, NWS Duluth, MN

Area Forecast Discussion
National Weather Service Duluth MN
636 AM CDT Fri Sep 22 2017

.SHORT TERM...(Today through Saturday)
Issued at 234 AM CDT Fri Sep 22 2017

Surface low pressure was centered over western Nebraska early
this morning with a quasi-stationary/cool front extending east
then northeast into the Red River Valley. A warm front stretched
from near Grand Forks eastward across the southern portions of the
forecast area. The warm front will continue lifting northward and
move into Ontario this morning. Meanwhile, the surface low will
lift quickly northeast across South Dakota and into northwest
Minnesota by this evening. Thunderstorms ongoing across Minnesota,
Ontario, and South Dakota seem to be aided by a strong south to
southwesterly LLJ. Latest RAP guidance suggests the winds aloft
will begin to weaken over the next few hours. The HRRR agrees with
this solution. If the short-range guidance pans out, storms in
our forecast area may be near their peak intensity. The next few
hours will be quite telling. Many of the other high res models,
including the NCAR ensemble show the South Dakota convection
congealing into an eastward propagating MCS, moving across our
southern CWA later this morning. GOES-16 water vapor imagery
supports the analysis of the RAP and HRRR with the location and
strength of the LLJ, but the trend of the last hour has been for
veering winds without much decrease in intensity. Given the
satellite data and the broad consensus toward continued storm
activity, have leaned more toward the latter solutions and kept
POPs high across my south through late morning.

The other big story will be the very warm temperatures today and
Saturday. With strong warm air advection aloft and efficient
mixing, near-record highs are forecast for most of the Northland
today, with northwest Wisconsin seeing the warmest temperatures.
Highs are forecast in the low to middle 70s along the
International Border to near 90 degrees across central and east-
central Minnesota and northwest Wisconsin. Maximum heat index
values will be near 100 degrees, as well. Another round of
thunderstorms is expected tonight, some may be strong or severe.
Rain chances continue across the northern CWA Saturday with partly
to mostly sunny skies farther south. Temperatures will be warm
once again over east-central Minnesota and northwest Wisconsin.
Cooler temperatures and mainly cloudy skies are likely for the
remainder of the Northland.

.LONG TERM...(Saturday night through Thursday)
Issued at 234 AM CDT Fri Sep 22 2017

The deep upper level trough over the western CONUS/Canada will
only make slow progress toward the east through Monday. A frontal
boundary over the Northland will also only move slowly as a result
of the southerly flow aloft. High PWAT values, around 1.5 inches,
which is quite high for this time of year, will remain in place
across much of the region through Tuesday. There will be a high
chance for showers and storms across much of northern Minnesota
Saturday night into Sunday night. Due to the moisture present,
frontal boundary, and shortwaves in southerly flow aloft, heavy
rain, possibly leading to some flooding, will be a threat over
parts of northern Minnesota. Highs Sunday will be warmest over
northwest Wisconsin where shower/storm coverage will be lowest.
Highs there will be in the upper seventies to lower eighties.
Highs will be in the sixties over far north and west areas of the
Northland where cloud cover and storm/shower coverage will be
greatest.

The upper trough will make some eastward progress later Monday
into Tuesday and a surface low will lift north and the front will
finally make it to our eastern zones or pass just east of there.
More showers and storms will occur Monday through Tuesday with
higher chances across northern Wisconsin as well. Storm total
rainfall today through Tuesday will be from 1 to 4 inches with the
higher amounts most likely over central Minnesota into the far
northeast. There will likely be some locally higher amounts due to
thunderstorms repeatedly affecting the same areas.

The chance for showers/storms will end for most areas by
Wednesday and temperatures will continue to cool with highs in the
mid fifties to around sixty. There will be mainly low chances for
showers Thursday and Friday with cooler temperatures continuing.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 636 AM CDT Fri Sep 22 2017

An area of strong thunderstorms continues to move north and east
across portions of northern Minnesota into far northwest
Wisconsin. This activity will continue to move north and east
through the morning but is expected to weaken by late morning.
IFR/MVFR conditions will occur under the stronger storms.
Conditions will then improve to VFR for most areas. Far northern
Minnesota, including the KINL TAF, will have a better chance at
seeing MVFR ceilings today. An area of low pressure and frontal
boundary will make slow progress into Minnesota this afternoon and
tonight. A low level jet will again form late this
afternoon/early evening and the front, low, and jet will all
combine to form new showers/storms. We were not as confident in
how widespread the storms will be this afternoon and evening and
went with mostly VCTS wording in the TAFs for now. As the day
progresses, timing and coverage will be refined. More fog will be
possible tonight.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  80  67  78  60 /  50  40  40  60
INL  72  60  63  52 /  60  70  40  70
BRD  86  65  73  60 /  60  40  60  80
HYR  89  68  85  65 /  60  30  30  40
ASX  89  69  85  62 /  60  30  20  40

&&

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

SHORT TERM...Huyck
LONG TERM...Melde
AVIATION...Melde

Hazardous Weather Outlook
National Weather Service Duluth MN
330 AM CDT Fri Sep 22 2017

MNZ010>012-018>021-025-026-033>038-WIZ001>004-006>009-231030-
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-
330 AM CDT Fri Sep 22 2017

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

.DAY ONE...Today and Tonight

Strong thunderstorms will continue this morning. Large hail,
damaging wind gusts, frequent cloud-to-ground lightning, and heavy
rainfall are expected. Another round of strong to severe
thunderstorms is expected tonight. The strongest storms are
expected over north-central Minnesota.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Thunderstorms will likely be on-going Saturday morning. A few
storms may remain strong early in the day. Storms are forecast to
redevelop during the afternoon and continue through Saturday
night. Some storms may be strong to severe once again. Heavy
rainfall is possible over much of the Northland and may lead to
localized flooding.

Thunderstorms will continue to be possible through Monday night.
The risk for severe storms is low but there will continue to be a
chance for heavy rainfall, especially over central into northeast
Minnesota into extreme northwest Wisconsin.

.SPOTTER INFORMATION STATEMENT...

SKYWARN Spotters may be needed early this morning and again
tonight. Everyone is encouraged to report hail of any size,
rainfall amounts, wind damage, or flooding to the National Weather
Service.

LSZ121-140>148-231030-
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-
330 AM CDT Fri Sep 22 2017

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

.DAY ONE...Today and Tonight

Thunderstorms will be possible, some could be strong today.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Thunderstorms will continue to be possible Saturday night into
Monday night. The risk for severe storms is low.

Melde/Huyck

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

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Special Weather Statement
National Weather Service Duluth MN
938 AM CDT FRI SEP 22 2017

MNZ020-221515-
Southern Lake/North Shore-
938 AM CDT FRI SEP 22 2017

...A STRONG THUNDERSTORM WILL AFFECT SOUTHERN LAKE COUNTY...

At 938 AM CDT, a strong thunderstorm was near Two Harbors, or 19
miles southwest of Split Rock Lighthouse State Park, moving northeast
at 55 mph.

Wind gusts up to 50 mph, half-inch hail, and occasional cloud to
ground lightning can be expected with this storm.

This storm will be near...
  Castle Danger around 955 AM CDT.
  Split Rock Lighthouse State Park around 1000 AM CDT.
  Beaver Bay around 1005 AM CDT.
  Silver Bay around 1010 AM CDT.

Other locations impacted by this storm include Tettegouche State
Park, Gooseberry Falls State Park, and Alger.

Seek shelter inside a sturdy building and away from windows until
this storm passes.

LAT...LON 4725 9121 4710 9143 4707 9153 4700 9160
      4692 9180 4706 9191 4714 9181 4741 9124
      4731 9116
TIME...MOT...LOC 1438Z 238DEG 48KT 4704 9177

JTS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DULUTH MN
948 AM CDT FRI SEP 22 2017

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

0941 AM     HAIL             10 ENE LITTLE ROUND LAK 46.04N 91.20W
09/22/2017  M0.75 INCH       SAWYER             WI   TRAINED SPOTTER

&&

KC

Special Weather Statement
National Weather Service Duluth MN
950 AM CDT FRI SEP 22 2017

WIZ003-004-221515-
Iron-Ashland-
950 AM CDT FRI SEP 22 2017

...A STRONG THUNDERSTORM WILL AFFECT NORTHWESTERN IRON AND SOUTHERN
ASHLAND COUNTIES...

At 950 AM CDT, a strong thunderstorm was near Mellen, or 29 miles
west of Ironwood, moving northeast at 35 mph.

Wind gusts up to 40 mph, half-inch hail, heavy downpours, and
frequent cloud to ground lightning can be expected with this storm.

This storm will be near...
  Mellen around 955 AM CDT.
  Saxon, Gurney and Upson around 1015 AM CDT.

Other locations impacted by this storm include Morse, High Bridge,
Cedar, Birch Hill, Island Lake Iron County, and Copper Falls State
Park.

Seek shelter inside a sturdy building and away from windows until
this storm passes.

LAT...LON 4613 9082 4634 9093 4643 9092 4656 9046
      4623 9027
TIME...MOT...LOC 1450Z 242DEG 29KT 4632 9074

G2

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DULUTH MN
953 AM CDT FRI SEP 22 2017

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

0941 AM     HAIL             4 WSW NORTHWOODS BEACH  45.89N 91.48W
09/22/2017  M1.25 INCH       SAWYER             WI   PUBLIC

            THE LARGEST HAILSTONES WERE HALF DOLLAR
            SIZED.

&&

WL/KC