A warm front lifting through a moist and unstable airmass generated several strong thunderstorms over southeast Upper Michigan on the morning of the 26th.
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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.
A warm front lifting through a moist and unstable airmass generated several strong thunderstorms over southeast Upper Michigan on the morning of the 26th.
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 26, 2:40 AM EST, 1 hour 3 minutes earlier.
Area Forecast Discussion National Weather Service Marquette MI 340 AM EDT Wed Aug 26 2020 .SHORT TERM...(Today and tonight) Issued at 340 AM EDT WED AUG 26 2020 As the advertised warm front is currently pushing into Upper Michigan this morning, isentropic ascent ahead of an increasing LLJ is helping kick off the late night thunderstorms popping up across the UP. This WAA along the warm front has attributed to an increasing inversion as instability becomes elevated. CAMs suggest these thunderstorms to increase spatially over the next couple hours as the warm front continues pushing NE into Upper Michigan. Now that there are some echos for KMQT to play with, the VAD shows good shear throughout the column, with 50kt winds to work with at 18kft. There is good directional shear in the the 4kft, but since these storms are more elevated, we're not tapping into to much of that, which is probably a good thing looking at sfc-1km helicity values and NW flow is typically where the UP can get some of it's stronger storm set ups. In terms of what to expect the next few hours, SPC mesoanalysis suggests CAPE increasing in excess of 2000J/kg over the next few hours. As KMQT VAD suggests sufficient shear to play with for the elevated updrafts to tap into, strong to severe storms will be possible now through the next 6 to 8 hours. Primary threats with elevated cells like this would be large hail, which a few cells have been shown on radar upwards of 1.5 inch hail signatures. Heading into today, a few shrtwv embedded in the dampening central CONUS ridge will serve as the next add'l kickers for precipitation and thunderstorm chances today. As the shrtwv moves through late this morning into the afternoon, CAMs suggest add'l developing across the west as ongoing storms continue into the east. As before, confidence is highest for the ongoing convection to continue into eastern UP, with chc PoPs remaining back across the west. Bulk shear remains impressive and low-level helicity values are concerning, but model soundings suggest storms will remain elevated throughout the event. Should some clearing occur and low-level diabatic heating occur to break down some of the inversion, a stronger wind threat could develop, with an isolated tornado even possible...but really not looking like much of a chance at this. As another wave and weak associated sfc cold front move through tonight, another bout of showers and thunderstorms will develop. Models and CAMs suggest the best chance for these are along the WI border and across south-central Upper Michigan. These storms should behave them selves a bit more with less instability, and the best shear off the east. With bulk shear values up to around 40kts though, day time trends today should be monitored for potential changes in the fcst. .LONG TERM...(Thursday through Tuesday) Issued at 317 AM EDT WED AUG 26 2020 Pattern remains fairly progressive across the northern CONUS and Upper Great Lakes through much of the extended period as mainly Pacific-based shortwaves will bring periods of showers to the area most likely from Fri into Sat and then again for the early part of next week. Temps through much of the extended will trend slightly cooler than normal for late summer. Thursday, rising heights behind Wednesday's shortwave and sfc high pressure/subsidence building in from the west should result in a mostly dry day. Mixing through 850 mb temps of 13-15C in a northerly flow ahead of the building sfc high should yield highs from the low to mid 70s north to around 80F south. A couple of shortwaves will impact the weather for the Friday to Saturday time frame. The first shortwave emerging from the CA coast will spin up a sfc low which eventually will track across the Central/Northern Plains and into the Upper Midwest on Fri. Models differ on exact track of the sfc low and coverage and northward extent of developing pcpn over the area on Fri along/ahead its associated warm front. The 00Z NAM and GFS appear to be trending farther south with sfc low track and associated pcpn while the Canadian and ECMWF remain a bit farther north. Model blend of sfc low track would probably favor south central and eastern U.P. for better pcpn chances on Fri. A second and stronger shortwave tracking through south central is progged to deepen as it digs toward the Upper Great Lakes Fri night and Sat. The cold front extending south from the associated sfc low tracking into northern Ontario could bring a cluster of showers into the western U.P. and maybe far north central portions of the cwa Fri night. Models indicate that the sfc low with this second system will track across northern Lake Superior Sat morning and eventually merge with Friday's weaker system to form a stronger low over eastern Ontario Sat afternoon. A secondary and stronger cold front associated with this deeper system is projected to move through the area late Sat and could support some scattered lake enhanced showers over northern and eastern sections of the U.P late Sat afternoon into Sat evening as 850 mb temps lower to 5-6C as lake sfc-850 mb delta-t approaches 10C. With associated CAA and mixing with cold fropa and tightening of gradient behind strengthening system nw winds could get blustery Sat afternoon into early evening with gusts to 30-35 mph across the area, strongest east half. Would also not be surprised to see gale force gusts to 35 knots over at least the higher platforms of eastern Lake Superior. After the wave on Saturday, an amplified ridge is progged to traverse the central CONUS and build over the UP on Sunday. As associated sfc high pressure builds over the area, Sunday looks dry...but then another sharp Pacific trough advances in from the west late Sun night and Mon. Looks like another widespread rain event on Mon perhaps into Mon night as the associated cold front marches west to east across the area. Models and ensembles appear to trend drier and cooler for Tue as sfc high pres builds in behind Mon's fropa. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 128 AM EDT WED AUG 26 2020 VFR conditions will prevail at IWD/SAW terminals overnight and at IWD through the whole forecast period. Conditions will deteriorate to MVFR early this morning at CMX and SAW as a warm front moves through. Over the next few hours, showers and thunderstorms will develop associated with a warm front that moves through. There will be some categorical improvement in the afternoon, but showers and thunderstorms will linger through much of the day today. Cigs at CMX should fall close to MVFR near the end of TAF period and SAW should see cigs drop close to IFR but not confident to include in TAF at this time. && .MARINE...(For the 4 AM Lake Superior forecast issuance) Issued at 340 AM EDT WED AUG 26 2020 This morning, a warm front lifts north over the area allowing winds become more southerly. Stable low-level conditions over the lake will prevail, but winds will increase to 20-25 knots over the east half of the lake after sunrise. Some stronger storms may impact parts of the lake on today. Tonight winds become northwest at 15-20 knots after a weak cold front moves through. Behind the exiting system and cold front, northwest winds of 15-20 knots will linger on Thursday. High pressure takes over for Friday bringing light winds around or less than 15 knots, but as a surface low drops over the lake this weekend winds up of 25-30 knots continue to appear possible. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && SHORT TERM...JAW LONG TERM...Voss AVIATION...07/JAW MARINE...Ritzman/JAW
Hazardous Weather Outlook National Weather Service Marquette MI 444 PM EDT Tue Aug 25 2020 MIZ001>007-009>014-084-085-262045- Keweenaw-Ontonagon-Northern Houghton-Baraga-Marquette-Alger-Luce- Gogebic-Iron-Dickinson-Menominee-Delta-Southern Schoolcraft- Southern Houghton-Northern Schoolcraft- 444 PM EDT Tue Aug 25 2020 /344 PM CDT Tue Aug 25 2020/ This Hazardous Weather Outlook is for portions of western Upper Michigan and central Upper Michigan. .DAY ONE...Tonight A few strong to severe thunderstorms are possible late tonight, mainly around and after midnight along and north of the Wisconsin/Michigan border. Large hail and heavy rain will be the primary concerns. .DAYS TWO THROUGH SEVEN...Wednesday through Monday Thunderstorms are expected on Wednesday into Wednesday evening. Some storms could be strong to severe with all hazards being possible. Heavy rain will also be a concern and may lead to localized flooding where thunderstorm activity trains throughout the day. There will be periodic chances for thunderstorms continuing into early Saturday. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to submit reports to the National Weather Service in Marquette. The public may also submit reports on our webpage, Facebook page, or on Twitter using #906wx. LSZ162-240>251-263>267-262045- 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- 444 PM EDT Tue Aug 25 2020 /344 PM CDT Tue Aug 25 2020/ This Hazardous Weather Outlook is for portions of Eastern Lake Superior...Central Lake Superior and Western Lake Superior. .DAY ONE...Tonight There is a chance of thunderstorms late tonight, mainly across the western portions of Lake Superior. Some storms could become strong to severe late tonight with large hail. .DAYS TWO THROUGH SEVEN...Wednesday through Monday Some storms may be strong to severe on Wednesday into Wednesday evening, with gusty winds and hail possible. There will be periodic chances for thunderstorms continuing into early Saturday. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to submit reports to the National Weather Service in Marquette. The public may also submit reports on our webpage, Facebook page, or on Twitter using #906wx. LMZ221-248-250-262045- 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- 444 PM EDT Tue Aug 25 2020 This Hazardous Weather Outlook is for portions of Northern Lake Michigan. .DAY ONE...Tonight Thunderstorms are expected late tonight. Some could become strong to potentially severe with hail being the primary concern. .DAYS TWO THROUGH SEVEN...Wednesday through Monday Thunderstorms are expected on Wednesday into Wednesday evening. Some storms may be strong to severe with gusty winds and hail possible. There will be periodic chances for thunderstorms continuing into early Saturday. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to submit reports to the National Weather Service in Marquette. The public may also submit reports on our webpage, Facebook page, or on Twitter using #906wx. Ritzman/lg
Special Weather Statement National Weather Service Marquette MI 204 AM EDT Wed Aug 26 2020 MIZ002-003-084-260630- Ontonagon MI-Houghton MI-Southern Houghton MI- 204 AM EDT Wed Aug 26 2020 ...SIGNIFICANT WEATHER ADVISORY FOR WEST CENTRAL HOUGHTON AND EAST CENTRAL ONTONAGON COUNTIES UNTIL 230 AM EDT... At 204 AM EDT, Doppler radar was tracking a strong thunderstorm over Mass City, or 12 miles southeast of Ontonagon, moving east at 30 mph. Nickle size hail and winds in excess of 30 mph will be possible with this storm. Locations impacted include... Rockland, Mass City, Greenland, Bob Lake and Winona. PRECAUTIONARY/PREPAREDNESS ACTIONS... Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. This storm may intensify, so be certain to monitor local radio stations and available television stations for additional information and possible warnings from the National Weather Service. && LAT...LON 4671 8924 4687 8918 4688 8882 4663 8891 TIME...MOT...LOC 0604Z 282DEG 26KT 4677 8908 JAW
Special Weather Statement National Weather Service Marquette MI 254 AM EDT Wed Aug 26 2020 MIZ005-011-260730- Marquette MI-Dickinson MI- 254 AM EDT Wed Aug 26 2020 ...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN DICKINSON AND SOUTHWESTERN MARQUETTE COUNTIES UNTIL 330 AM EDT/230 AM CDT/... At 254 AM EDT/154 AM CDT/, Doppler radar was tracking a strong thunderstorm 8 miles northeast of Witch Lake, or 13 miles southwest of Ishpeming, moving east at 50 mph. Nickel size hail and winds in excess of 30 mph will be possible with this storm. Locations impacted include... Republic and Big Bass Lake. PRECAUTIONARY/PREPAREDNESS ACTIONS... Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. This storm may intensify, so be certain to monitor local radio stations and available television stations for additional information and possible warnings from the National Weather Service. && LAT...LON 4631 8805 4646 8797 4636 8744 4617 8754 TIME...MOT...LOC 0654Z 289DEG 42KT 4636 8789 JAW
Special Weather Statement National Weather Service Marquette MI 406 AM EDT Wed Aug 26 2020 MIZ005-011-260830- Marquette MI-Dickinson MI- 406 AM EDT Wed Aug 26 2020 ...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN DICKINSON AND SOUTH CENTRAL MARQUETTE COUNTIES UNTIL 430 AM EDT/330 AM CDT/... At 405 AM EDT/305 AM CDT/, Doppler radar was tracking a strong thunderstorm 11 miles southwest of Gwinn, or 20 miles south of Ishpeming, moving east southeast at 35 mph. Nickel size hail and winds in excess of 30 mph will be possible with this storm. Locations impacted include... Watson, Northland and Arnold. PRECAUTIONARY/PREPAREDNESS ACTIONS... This storm may intensify, so be certain to monitor local radio stations and available television stations for additional information and possible warnings from the National Weather Service. && LAT...LON 4619 8779 4626 8772 4612 8729 4598 8746 TIME...MOT...LOC 0805Z 303DEG 30KT 4619 8765 JAW
The Marquette radar (KMQT), 86 km away, was scanning. The volume nearest the first event began at 08:45 UTC.
1 lightning, 1 hail. Local standard time, as filed.
A barn near Hyde in Delta County was struck by lightning during a thunderstorm and set on fire. The fire caused extensive damage to the second story.
There was a public report of nickel-sized hail in Manistique.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Michigan in 2020Every state in 2020This day in weather historyWarnings in Michigan, August 2020
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: 915473, 915474.