The interaction of a warm front and a lake breeze off Lake Superior generated an isolated severe thunderstorms near Trenary on the afternoon of the 9th.
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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 MQT wrote it up.
The interaction of a warm front and a lake breeze off Lake Superior generated an isolated severe thunderstorms near Trenary on the afternoon of the 9th.
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 Marquette, MI wrote its last area forecast discussion before the first event at Aug 9, 2:38 PM EST, 47 minutes earlier.
Area Forecast Discussion National Weather Service Marquette MI 338 PM EDT Wed Aug 9 2017 .SHORT TERM...(This evening through Thursday) Issued at 230 PM EDT WED AUG 9 2017 The main forecast concerns are the chances for pulse type thunderstorms this afternoon, then the attention turns towards the low pressure system expected to move into the area tonight and continues to track across Upper Michigan during the day on Thursday with additional chances for showers and thunderstorms. Afternoon visible satellite and radar imagery shows scattered showers with some isolated thunderstorms developing across the interior of Upper Michigan, and then along the Lake Superior breeze. Expect this trend to continue, with additional developing through the afternoon hours. Given the weak shear and instability, expect updrafts to struggle a bit; however, a few stronger storms are possible especially where boundary interactions take place. Coverage wise, given the weak shear in place it is very difficult to pinpoint what locations will have the best chance at seeing thunderstorm activity. The main hazards with stronger activity will be primarily gusty winds and small hail as updrafts collapse given the inverted-v profile through the boundary layer. Tonight, shortwave energy will begin to dig southeast across the Upper Mississippi Valley allowing surface low pressure to become better organized as it tracks across central Minnesota. Ahead of this surface low, across Minnesota and west-central Wisconsin, a broad area of warm air advection and 700mb moisture will continue to push northeast towards the area. Therefore, expect a fairly widespread area of showers and perhaps a few rumbles of thunder to lift northeast across Upper Michigan late tonight through the first part of the day on Thursday. There is still some uncertainty across the models in regards to the track of this low through the day on Thursday, which will directly impact how things play out. Given the track of the shortwave trough, leaning towards a slow solution which would push the warm sector at least across central portions of the area Thursday afternoon, with north-central sitting around the triple point. With at least 1500-2000 J/kg of MUCAPE across the warm sector, the combination of lift along the surface features and upper- level troughing across the area should be enough to initiation additional showers and storms as the cold front pushes across central, and especially the south-central, portions of Upper Michigan in the afternoon hours. With shear still looking very marginal, 20 to 30 knots at best, we may see another day with pulse type thunderstorms, a few of which could be strong to possibly severe. .LONG TERM...(Thursday night through Wednesday) Issued at 331 PM EDT WED AUG 9 2017 Most active weather in the long term occurs Thu night into Fri as low pressure system crosses the Upper Great Lakes. Looks quiet for the weekend into early next week as high pressure settles over the region. Compared to 24hr ago the sfc low at 1010-1013mb is forecast to track farther northwest late Thu into Thu evening. Could be enough instability in the warm sector of the low with MUCAPES up to 2000j/kg for stronger storms late Thu afternoon into early Thu evening, especially over west and central Upper Michigan through 03z/11 pm EDT. Even with the sufficient instability for storms, the effective shear stays 30 kts or less so like we have seen most of this week, probably looking at mainly pulse type storms with a small chance of seeing isolated severe storm. Enough elevated instability to keep some thunder in over east half into the early overnight hours Thu night. As sfc low tracks to somewhere vcnty of eastern U.P. to northern lower Michigan by daybreak Fri, expect lingering showers over eastern forecast area to become more focused over north central Upper Michigan with upslope northerly cyclonic flow developing. May also see fog overnight into Fri morning, especiallly near Lk Superior. For Fri, showers over the north central will gradually diminish late morning into the early afternoon but some showers and even isolated thunder may linger into the afternoon over the eastern forecast area. Clouds will probably try to stick around for most areas on Fri with cool and moist northerly flow off Lk Superior. Increased north winds over the blends for Fri which resulted in 15 to 20 mph winds with gusts to 25 mph first on Lk Superior then later on Mon on Lk Michigan. Probably will need small craft advisories for marine areas on both Lk Superior and Lk Michigan and waves could end up high enough for an elevated swim risk for the Lk Superior beaches in Alger and Marquette county. Cooler condtions expected for all areas with readings staying in the mid 60s closer to Lk Superior. High pressure moves overhead for the weekend into early next week. After below normal temps on Sat should see warming trend through rest of the extended. Since the high is in the vcnty though the nights will be seasonably cool inland. Could be some pop up shra and tsra Sun through Tue due to daytime heating and upper level trough and cool air aloft still close by. Some hint at stronger shortwave moving through on back side of trough Tue so could see a bit better chances at that time. && .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) Issued at 106 PM EDT WED AUG 9 2017 Given the pulse type storms expected this afternoon, it is difficult to discern whether other not certain terminals will see thunderstorm activity this afternoon. KSAW looks the most likely right now, so have included a TEMPO for this activity; however, at KIWD/KCMX there is a more uncertainty so have only included mentions of VCTS for now. Tonight into Thursday as low pressure swings through the region low ceilings and additional chances for showers, and perhaps thunderstorms will be possible. Lower ceilings may also develop; however, confidence is not high in how low ceilings will get. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 230 PM EDT WED AUG 9 2017 As low pressure moves east across Upper Michigan, northeast winds will increase to around 20 to 25 knots tonight through a good portion of the day on Thursday. Thursday night through Friday, winds will subside to 15 to 20 knots as the system exits the region. Friday through the first half of next week, the winds will be less than 15 knots as high pressure takes over across the region. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && SHORT TERM...Ritzman LONG TERM...JLA AVIATION...Ritzman MARINE...Ritzman
Hazardous Weather Outlook National Weather Service Marquette MI 427 AM EDT Wed Aug 9 2017 MIZ001>007-009>014-084-085-101200- Keweenaw-Ontonagon-Northern Houghton-Baraga-Marquette-Alger-Luce- Gogebic-Iron-Dickinson-Menominee-Delta-Southern Schoolcraft- Southern Houghton-Northern Schoolcraft- 427 AM EDT Wed Aug 9 2017 /327 AM CDT Wed Aug 9 2017/ This Hazardous Weather Outlook is for portions of western Upper Michigan and central Upper Michigan. .DAY ONE...Today and Tonight Thunderstorms are possible through tonight. A few storms could be severe this afternoon into this evening and contain gusty winds and large hail. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday Thunderstorms are possible Thursday through Friday. .SPOTTER INFORMATION STATEMENT... Spotters are encouraged to report any observed hail or wind damage from thunderstorms to the National Weather Service in Marquette. The public may also submit reports to the National Weather Service via phone, on our website, or through Facebook or Twitter. LSZ162-240>251-263>267-101200- Lake Superior west of a line from Saxon Harbor WI to Grand Portage MN beyond 5NM-Saxon Harbor WI to Black River MI- Black River to Ontonagon MI- Ontonagon to Upper Entrance of Portage Canal MI- Upper Entrance of Portage Canal to Eagle River MI- Eagle River to Manitou Island MI- Manitou Island to Point Isabelle MI- Point Isabelle to Lower Entrance of Portage Canal MI- Lower Entrance of Portage Canal To Huron Islands MI Including Keweenaw and Huron Bays-Huron Islands to Marquette MI- Marquette to Munising MI-Munising to Grand Marais MI- Grand Marais to Whitefish Point MI- Lake Superior from Saxon Harbor WI to Upper Entrance to Portage Canal MI 5NM off shore to the US/Canadian border including Isle Royale National Park- Lake Superior from Upper Entrance to Portage Canal to Manitou Island MI 5NM off shore to the US/Canadian Border- Lake Superior West of Line from Manitou Island to Marquette MI Beyond 5NM from shore- Lake Superior East of a line from Manitou Island to Marquette MI and West of a line from Grand Marais MI to the US/Canadian Border Beyond 5NM from shore- Lake Superior from Grand Marais MI to Whitefish Point MI 5NM off shore to the US/Canadian border- 427 AM EDT Wed Aug 9 2017 /327 AM CDT Wed Aug 9 2017/ This Hazardous Weather Outlook is for portions of Eastern Lake Superior...Central Lake Superior and Western Lake Superior. .DAY ONE...Today and Tonight Thunderstorms are possible through tonight across the south half of Lake Superior. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... The need for weather spotter reports is not anticipated at this time. LMZ221-248-250-101200- Green Bay North of line from Cedar River MI to Rock Island Passage-Seul Choix Point to Point Detour MI- 5NM East of a line from Fairport MI to Rock Island Passage- 427 AM EDT Wed Aug 9 2017 This Hazardous Weather Outlook is for portions of Northern Lake Michigan. .DAY ONE...Today and Tonight Thunderstorms are possible this evening. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday Thunderstorms are possible Thursday afternoon through Friday. .SPOTTER INFORMATION STATEMENT... The need for weather spotter reports is not anticipated at this time. 07
Special Weather Statement National Weather Service Marquette MI 400 PM EDT WED AUG 9 2017 MIZ002>004-084-092045- Ontonagon MI-Baraga MI-Houghton MI-Southern Houghton MI- 400 PM EDT WED AUG 9 2017 ...SPECIAL WEATHER STATEMENT... At 359 PM EDT, Doppler radar was tracking strong thunderstorms along a line extending from Ontonagon to near Nisula. Movement was northeast at 20 mph. Half inch hail and winds in excess of 30 mph will be possible with these storms. Locations impacted include... Ontonagon, Mass City, Nisula, Keweenaw Bay, Greenland, Twin Lakes, Toivola, Fourteen Mile Point, Pelkie and Winona. LAT...LON 4710 8896 4689 8842 4666 8890 4688 8939 TIME...MOT...LOC 1959Z 239DEG 18KT 4688 8928 4672 8888 Kluber
Special Weather Statement
National Weather Service Marquette MI
403 PM EDT WED AUG 9 2017
MIZ006-013-092045-
Delta MI-Alger MI-
403 PM EDT WED AUG 9 2017
...SPECIAL WEATHER STATEMENT...
At 402 PM EDT, Doppler radar was tracking a cluster of strong
thunderstorms near Trenary, or 24 miles southwest of Munising,
moving east at 10 mph.
Half inch hail and winds in excess of 30 mph will be possible with
these storms.
Locations impacted include...
U.S. 41 between Trenary and Rapid River, Trenary, Diffin and Round
Lake.
LAT...LON 4617 8712 4620 8711 4627 8668 4610 8670
4609 8711
TIME...MOT...LOC 2002Z 266DEG 5KT 4615 8702
KluberSpecial Weather Statement National Weather Service Marquette MI 419 PM EDT WED AUG 9 2017 MIZ006-085-092100- Northern Schoolcraft MI-Alger MI- 419 PM EDT WED AUG 9 2017 ...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN SCHOOLCRAFT AND CENTRAL ALGER COUNTIES UNTIL 500 PM EDT... At 419 PM EDT, Doppler radar was tracking a strong thunderstorm 7 miles south of Munising, moving east at 25 mph. Dime size hail and winds in excess of 40 mph will be possible with this storm. Locations impacted include... Shingleton, Van Meer and Wetmore. PRECAUTIONARY/PREPAREDNESS ACTIONS... Torrential rainfall is also occurring with this storm, and may lead to localized flooding. Do not drive your vehicle through flooded roadways. && LAT...LON 4627 8669 4637 8671 4646 8633 4627 8632 TIME...MOT...LOC 2019Z 259DEG 22KT 4632 8663 Kluber
The Marquette radar (KMQT), 58 km away, was scanning. The volume nearest the first event began at 20:23 UTC.
2 hail. Local standard time, as filed.
There was a picture of near golf ball sized hail near Trenary via social media. The hail fell for about twenty minutes. Strong winds were also observed.
There was a public report of one and a half inch diameter hail near Trenary.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Michigan in 2017Every state in 2017This day in weather historyWarnings in Michigan, August 2017
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: 714522, 714521.