Storms developed along a stationary boundary. One supercell storm produced large hail before a line of storms formed and brought damaging winds and heavy rain.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS DLH wrote it up.
Storms developed along a stationary boundary. One supercell storm produced large hail before a line of storms formed and brought damaging winds and heavy rain.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Duluth, MN wrote its last area forecast discussion before the first event at Sep 13, 11:32 PM CST, 1 hour 39 minutes earlier.
Area Forecast Discussion National Weather Service Duluth MN 1232 AM CDT Fri Sep 14 2018 .SHORT TERM...(This evening through Friday) Issued at 329 PM CDT Thu Sep 13 2018 A weak cold front will slowly track from west to east across the Northland today into tomorrow resulting in increasing clouds and a chance for showers and storms late today into Saturday. It will not be a washout, but locations in northeast Minnesota could see a few rounds of showers and storms. A few storms could be strong to severe, with the best chance for severe storms Saturday afternoon in northern Minnesota. On the synoptic scale a deep longwave trough over the west coast along with a broad ridge across the Lower Missouri River Basin will lead to continued southwest flow aloft across the Upper Midwest. This pattern will bring occasional mid-level disturbances, producing broad-scale lift along a meandering frontal boundary. As of 300 PM this cold front boundary is located along a northeast to southwest long in northwest Minnesota and slowly tracking eastward. Along the frontal boundary a broad area of stratus clouds exist, with strong southerly flow ahead of the front advecting in increasing low level moisture. Dew points are in the low to mid 60s this afternoon ahead of the front with southerly winds gusting to 20-30 mph. Elevated instability on the order of 500 to 100 j/kg MUCAPE along the frontal zone may produce some showers and storms with the low level convergence late today into tonight, thought storms are not expected to severe and precipitation amounts will be light, less than quarter inch. Cloudy skies overnight will cause temperatures to not fall very far, with lows in the low to mid 60s - which is actually what our normal *high* temperature is this time of year! Normal lows are in the mid/upper 40s. On Saturday the cold front stalls out along near the north shore and I-35 in east-central MN, with continued cloudiness through most of the day. A low chance for showers during the day, then better chance for storms in the afternoon across east-central MN and northwest Wisconsin. While greater instability may lead to some strong storms, severe storms are not expected. Highs ranging from the low 70s along the international border behind the front to near 80 ahead of the front. Dew points will approach the 70 degree mark in far east- central MN and most of northwest Wisconsin on Friday afternoon, which will feel almost tropical compared to what it usually feels like in mid-September. .LONG TERM...(Friday night through Thursday) Issued at 329 PM CDT Thu Sep 13 2018 A cold front will stall over the region Friday evening. The front will become stationary and orient itself from a southwest to northeast direction to a west to east direction by early Saturday morning. This will become a warm front and lift northward through Saturday into early Sunday morning. This is in response to a shortwave lifting into Ontario. Severe thunderstorms cannot be ruled out Saturday afternoon into Saturday evening. MLCAPE values range from 1500 to 3000 J/kg from the Brainerd Lakes through northwest Wisconsin. 0-6 km bulk shear values will be around 40 to 50 knots and southerly flow advecting mid to upper 60 degree dewpoints into the region. This is also highlighted by SPCs latest Day 3 outlook. The one crux is that convection from Friday afternoon/evening will impact the evolution of things on Saturday. If it stays cloudy through the day it will inhibit the amount of instability to develop. Due to this am still uncertain about the exact evolution of things, but hope to have this resolved later tomorrow or early on Saturday. Friday night lows range from the mid 60s across the south to the low 50s along the International Border. Highs on Saturday will generally be in the 70s, but a few 80 degree readings are possible across southern locations. Expect a period of dry weather on Sunday as high pressure builds in from the Mid Atlantic. This will be short lived as the shower and thunderstorm chances return Sunday evening into Monday. A trough will lift across the Intermountain West into central portions of Canada. This will slide another cold front through the Upper Mississippi River Valley on Monday. This will bring another round of showers and thunderstorms to the region. Highs on Sunday will generally be in the low 80s. Readings on Monday will be a bit cooler as cold air advects in from the northwest. Highs range from the mid 60s along the International Border to the upper 70s in northwest Wisconsin. After Monday there is a bit of a pattern change as the remnants of Florence get pulled into the upper level flow. The rest of the week will feature more of a progressive pattern as things become zonal aloft. Tuesday could be dry as high pressure builds in, but there are is a lot of discrepancy between the GFS/ECMWF and GEM on a shortwave moving through. Uncertain on the evolution of things at this point in time. Have more confidence in the shower and storm threat Wednesday into Thursday as a trough digs into the Northern Plains from the Intermountain West. Expect readings to return to seasonable temperatures Tuesday and Wednesday with highs in the 60s. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 1232 AM CDT Fri Sep 14 2018 A front moving through the area from northwest to southeast will bring a period of MVFR/IFR ceilings and a band of rain showers across the area through the TAF period. The lowest conditions should be found between 06z and 17z depending on location as the front moves slowly through. Another round of showers and storms should develop after 21z, tapering off to just showers after 03z. Have put in IFR ceilings into the terminals for now, but LIFR conditions are possible. Expect some visibility reduction with fog developing as the lower levels moisten, but have kept them to MVFR now as well. South winds at or less than 10kts should continue overnight, with winds turning northwest after 10z, and increasing to 5-10kts after 15z. && .PRELIMINARY POINT TEMPS/POPS... DLH 66 79 61 69 / 40 40 70 50 INL 59 71 52 70 / 60 10 30 40 BRD 68 78 64 81 / 30 40 50 40 HYR 65 81 65 80 / 30 30 30 40 ASX 65 81 61 74 / 20 40 50 60 && .DLH WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. LS...None. && SHORT TERM...JJM LONG TERM...WL AVIATION...LE
Hazardous Weather Outlook National Weather Service Duluth MN 330 PM CDT Thu Sep 13 2018 MNZ010>012-018>021-025-026-033>038-WIZ001>004-006>009-142030- 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 PM CDT Thu Sep 13 2018 This Hazardous Weather Outlook is for portions of northeast Minnesota and northwest Wisconsin. .DAY ONE...This afternoon and Tonight There is a low chance for a few thunderstorms late today into tonight across northeast Minnesota. Storms are not expected to be severe. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Thunderstorms will be possible on Friday over far northwest Wisconsin and northern Minnesota. Severe storms are not expected. Several rounds of thunderstorms are expected throughout the period. Strong to severe thunderstorms are possible from Friday evening through Saturday night. Large hail, and damaging wind gusts are the primary threats. .SPOTTER INFORMATION STATEMENT... SKYWARN spotters are encouraged to report hail of any size and rainfall amounts to the National Weather Service. LSZ121-140>148-142030- 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 PM CDT Thu Sep 13 2018 This Hazardous Weather Outlook is for portions of the Nearshore waters of western Lake Superior. .DAY ONE...This afternoon and Tonight Thunderstorms are possible late tonight across western Lake Superior. The storms are not expected to be severe. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Several rounds of thunderstorms are expected throughout the period. Strong to severe thunderstorms are possible from Friday evening through Saturday night. Large hail, and damaging wind gusts are the primary threats. JJM/WL More information may be obtained at the following web address: http://www.weather.gov/duluth (all lower case)
The Duluth radar (KDLH), 15 km away, was scanning. The volume nearest the first event began at 07:08 UTC.
10 thunderstorm wind, 7 hail, 1 flash flood. Local standard time, as filed.
Multiple trees were blown down along the Willard Munger State Trail.
A birch tree 25 inches in diameter was blown over.
A tree was blown down across State Highway 47 at mile marker 110.
A downed tree was partially blocking Harney Road.
A tree that was blown down partially blocked Palkie Road.
A 40 foot tall tree was snapped in half. Many smaller trees were also damaged or blown down by the thunderstorm winds.
A tree snapped by the wind landed on a garage while another tree was uprooted in the adjacent yard.
A large pine tree was snapped in half by the thunderstorm winds.
A 12 inch diameter pine tree was snapped off 6 feet above the ground by the thunderstorm winds.
An 18 inch diameter willow tree showing some evidence of decay was snapped off 8 feet above the ground.
Storm sewer manhole covers were flipped over. Standing water was also reported in town.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Minnesota in 2018Every state in 2018This day in weather historyWarnings in Minnesota, September 2018
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 784255, 784247, 784248, 784256, 784250, 784249, 784251, 784257, 784252, 784253, 784258, 784259, 784260, 784261, 784262, 784263, 784264, 784265.