Increasing moisture and instability ahead of cold front approaching from the Northern Plains aided the development of strong to severe thunderstorms over portions of western Upper Michigan from the afternoon of the 9th into the morning of the 10th.
Every event with a place to put it. Tap one for its entry below.
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.
Increasing moisture and instability ahead of cold front approaching from the Northern Plains aided the development of strong to severe thunderstorms over portions of western Upper Michigan from the afternoon of the 9th into the morning of the 10th.
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, 2:42 PM EST, 1 hour 3 minutes earlier.
Area Forecast Discussion National Weather Service Marquette MI 342 PM EDT Sun Aug 9 2020 .SHORT TERM...(This evening through Monday) Issued at 240 PM EDT SUN AUG 9 2020 Upper air pattern consists of a 500 mb trough across the northern Rockies and northern plains with a MCV in MN this morning. The upper trough will continue to move east into the upper Great Lakes tonight into Mon. Some deeper moisture and 850-500 mb q-vector convergence moves through tonight and moves out of the eastern cwa Mon afternoon. Tough forecast for this period as there are numerous mcv's off to the west of the area and also a lot of old outflow boundaries around the area as well. Thinking is that there will be a line that moves in late this afternoon across the far west, then this gradually moves eastward with time tonight and then exits slowly out of the cwa with the passage of the cold front across the area on Mon. Followed close to the conshort for pops for this time period as this model seemed to have the best handle on the ongoing convection off to the west and was the slowest to bring in pops into the far west late this afternoon. Could be some severe weather with this line with large hail and damaging wind gusts the primary threat. There could also be some heavy rain with the high dew points in the area as well. Confidence is low with this forecast however, especially later in the time period as it all hinges on the evolution of the convection this evening. .LONG TERM...(Monday night through Sunday) Issued at 342 PM EDT SUN AUG 9 2020 With the cold front clear through the UP and any remaining thunderstorms exiting over the far eastern CWA, Monday night begins a long period of tranquil weather over our area. By Tuesday, models show a closed upper low over Hudson Bay and a second short wave moving into the Canadian Rockies. The northern tier of the CONUS remains in low-amplitude quasi-zonal mid-level flow. A packet of mid- level dry air on Tuesday will keep skies completely clear but could lead to deep mixing and drying out of the PBL. This could drop afternoon RH to around 20-25% which, in combination with a breezy SW gradient wind gusting to 20-25 mph at times, may lead to a concern for fire weather. However most of the area having seen copious rainfall over the weekend into early Monday should limit the fire weather potential overall. Ridging builds in for Wednesday through at least Friday leading to continued warm and rain-free weather. GEFS mean 850 mb temps continue hover right around 16-17 C each of those three days, pretty much in line with what the deterministic EC and UKMET, among other guidance. Light synoptic/background flow will allow Lake Superior lakebreezes to develop on Wednesday keeping those shorelines cooler in the upper 70s, but elsewhere highs should easily reach the mid 80s. Thursday and Friday look equally as warm, with less relief along the Lake Superior shoreline as strengthening SSE flow will keep the lakebreeze mostly offshore those days. Given the run-to-run and model-to-model consistency in 850 mb temps, and given that the NBM seems to be running a bit cool, added about a couple degrees to afternoon highs each of these three days, except along the Lake Superior shoreline on Wednesday. By the weekend the pattern becomes more unsettled again. The GFS and EC both show a strong short wave digging into the Northern Plains late Friday and then lifting northeastward through northern Ontario Saturday into Sunday. As the ridge overhead begins to break down and shift east, there may be one or two ridge-roller type MCSs Friday night or Saturday, depending on the exact strength and orientation of the height gradient. Then the system's cold front moves through around Saturday or Sunday leading to additional thunderstorm chances. Given the agreement in the models, could have gone higher with POPs, but for now was content to just keep the NBM's broad chance POPs through much of the weekend until the fine scale details come into focus. && .AVIATION...(For the 18Z TAFS through 18Z Monday afternoon) Issued at 148 PM EDT SUN AUG 9 2020 Conditions at each TAF site will move to VFR conditions for a short time, before convection fires up to our west and moves into our area late this afternoon/early evening. KIWD should receive thunderstorms first, then KCMX, and finally KSAW in the nighttime hours. Storms could bring locally higher and erratic wind gusts, as high winds, particularly west near KIWD, are possible. These storms may bring some LLWS to KIWD and KCMX as they move past each of these respective TAF sites. MVFR conditions look to occur as these storms pass, particularly at KIWD and KCMX. VFR conditions look to return for a short time tonight after the convection moves through, before MVFR cigs move back into each of the TAF sites in the morning. KCMX and KIWD should see returns to VFR conditions by late morning/early afternoon tomorrow. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 240 PM EDT SUN AUG 9 2020 The winds will shift from the E/SE to W/SW at 10 to 20 knots as a cold front moves through tonight. Thunderstorms could briefly produce much stronger winds, as well as possibly some hail overnight. Once the cold front clears the lake on Monday, winds look to remain 10-20 knots with gusts up to 25 knots, particularly in the western lake between Isle Royale and the Keweenaw Peninsula due to funneling. Winds will subside slightly Monday night before picking back up again in western Superior between Isle Royale and the Keweenaw Peninsula; look for winds to pick up to 15-20 knots with gusts up to 25 knots again due to the funneling of the winds in this area. Winds will decrease to around or less than 20 knots Tuesday night and should remain that way through the rest of the mid-week. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && SHORT TERM...07 LONG TERM...RJC AVIATION...TAP MARINE...TAP
Hazardous Weather Outlook National Weather Service Marquette MI 357 PM EDT Sun Aug 9 2020 MIZ001>007-009>014-084-085-102000- Keweenaw-Ontonagon-Northern Houghton-Baraga-Marquette-Alger-Luce- Gogebic-Iron-Dickinson-Menominee-Delta-Southern Schoolcraft- Southern Houghton-Northern Schoolcraft- 357 PM EDT Sun Aug 9 2020 /257 PM CDT Sun Aug 9 2020/ This Hazardous Weather Outlook is for portions of western Upper Michigan and central Upper Michigan. .DAY ONE...Tonight Thunderstorms are likely through the overnight hours. Some of the storms could produce large hail, damaging winds, and heavy rain. .DAYS TWO THROUGH SEVEN...Monday through Saturday Thunderstorms are possible again on Monday, mainly over south- central and eastern Upper Michigan. There is a moderate swim risk for the Lake Michigan beaches of Schoolcraft County on Monday. .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 using #906wx. LSZ162-240>251-263>267-102000- 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- 357 PM EDT Sun Aug 9 2020 /257 PM CDT Sun Aug 9 2020/ This Hazardous Weather Outlook is for portions of Eastern Lake Superior...Central Lake Superior and Western Lake Superior. .DAY ONE...Tonight Areas of dense fog will remain possible today and tonight. Thunderstorms are likely through the overnight hours. Some of the storms could produce large hail, damaging winds, and heavy rain. Areas of fog are expected tonight and could be locally dense. .DAYS TWO THROUGH SEVEN...Monday through Saturday Thunderstorms are possible again on Monday, mainly over far eastern Lake Superior. Areas of fog are expected on Monday and could be locally dense. .SPOTTER INFORMATION STATEMENT... The need for weather spotter reports is not anticipated at this time. LMZ221-248-250-102000- 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- 357 PM EDT Sun Aug 9 2020 This Hazardous Weather Outlook is for portions of Northern Lake Michigan. .DAY ONE...Tonight Thunderstorms are likely tonight. Some of the storms could produce large hail, damaging winds, and heavy rain. .DAYS TWO THROUGH SEVEN...Monday through Saturday Thunderstorms are possible again on Monday. .SPOTTER INFORMATION STATEMENT... The need for weather spotter reports is not anticipated at this time. RJC
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MARQUETTE MI
1115 AM EDT SUN AUG 9 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0800 AM HEAVY RAIN THREE LAKES 46.56N 88.21W
08/09/2020 M1.21 INCH BARAGA MI COCORAHS
COCORAHS STATION MI-BG-3 LANSE 17.8 SE.
RAINFALL STRADDLED OBSERVATION TIME BUT
MOSTLY FELL IN A 6-12 HOUR PERIOD.
&&
RJCPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MARQUETTE MI
1116 AM EDT SUN AUG 9 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0800 AM HEAVY RAIN 9 S KENTON 46.36N 88.91W
08/09/2020 M1.14 INCH IRON MI COCORAHS
COCORAHS STATION MI-IR-1 TROUT CREEK 9.6
SSE. RAINFALL STRADDLED OBSERVATION TIME BUT
MOSTLY FELL IN A 6-12 HOUR PERIOD.
&&
RJCPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MARQUETTE MI
1117 AM EDT SUN AUG 9 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0800 AM HEAVY RAIN 6 NNE WAY DAM 46.24N 88.19W
08/09/2020 M1.09 INCH IRON MI COCORAHS
COCORAHS STATION MI-IR-2 CRYSTAL FALLS 11.7
NE. RAINFALL STRADDLED OBSERVATION TIME BUT
MOSTLY FELL IN A 6-12 HOUR PERIOD.
&&
RJCPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MARQUETTE MI
1119 AM EDT SUN AUG 9 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0900 AM HEAVY RAIN 4 NW MENOMINEE 45.16N 87.69W
08/09/2020 M1.45 INCH MENOMINEE MI COCORAHS
COCORAHS STATION MI-MM-8 MENOMINEE 4.1 NW.
RAINFALL STRADDLED OBSERVATION TIME BUT
MOSTLY FELL IN A 6-12 HOUR PERIOD.
&&
RJCPRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE MARQUETTE MI
1123 AM EDT SUN AUG 9 2020
...SUMMARY OF RAINFALL TOTALS FROM MORNING OF AUGUST 8, 2020...
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1256 PM HEAVY RAIN 3 W ECHO LAKE 46.61N 88.91W
08/08/2020 M3.00 INCH HOUGHTON MI MESONET
MESONET STATION KTNM4 8 N KENTON.
1000 AM HEAVY RAIN 4 NNE WATTON 46.58N 88.58W
08/08/2020 M2.38 INCH BARAGA MI CO-OP OBSERVER
CO-OP OBSERVER STATION SNWM4 3.5 NE WATTON.
0800 AM HEAVY RAIN 1 ESE BERGLAND 46.59N 89.55W
08/08/2020 M1.75 INCH ONTONAGON MI CO-OP OBSERVER
CO-OP OBSERVER STATION BERM4 BERGLAND DAM.
0824 AM HEAVY RAIN 6 ENE ROCK OF AGES 47.91N 89.14W
08/08/2020 M1.68 INCH KEWEENAW MI MESONET
MESONET STATION WINM4 WINDIGO - ISLE ROYALE.
0856 AM HEAVY RAIN 1 W IRONWOOD 46.46N 90.16W
08/08/2020 M1.52 INCH GOGEBIC MI PUBLIC
RAIN FROM 3AM TO 7AM TODAY FOR EVENT.
0900 AM HEAVY RAIN 4 NW MENOMINEE 45.16N 87.69W
08/09/2020 M1.45 INCH MENOMINEE MI COCORAHS
COCORAHS STATION MI-MM-8 MENOMINEE 4.1 NW.
RAINFALL STRADDLED OBSERVATION TIME BUT
MOSTLY FELL IN A 6-12 HOUR PERIOD.
0100 PM HEAVY RAIN ISHPEMING 7.2 SW 46.41N 87.75W
08/08/2020 M1.35 INCH MARQUETTE MI NWS EMPLOYEE
COCORAHS MI-MQ-19.
0700 AM HEAVY RAIN 2 SE CHAMPION 46.50N 87.94W
08/09/2020 M1.35 INCH MARQUETTE MI COCORAHS
COCORAHS STATION MI-MQ-24 WOBIC 0.5 ESE.
0700 AM HEAVY RAIN 6 E CHAMPION 46.50N 87.84W
08/09/2020 M1.32 INCH MARQUETTE MI CO-OP OBSERVER
CO-OP OBSERVER STATION CLKM4 5.7 E CHAMPION.
1045 PM HEAVY RAIN 4 ESE CHAMPION 46.50N 87.89W
08/08/2020 M1.28 INCH MARQUETTE MI MESONET
MESONET STATION HUMM4 3.8 E CHAMPION.
0800 AM HEAVY RAIN 2 WSW WATTON 46.53N 88.64W
08/09/2020 M1.24 INCH BARAGA MI CO-OP OBSERVER
CO-OP OBSERVER STATION WTNM4 WATTON 2 WSW.
RAINFALL STRADDLED OBSERVATION TIME BUT
MOSTLY FELL IN A 6-12 HOUR PERIOD.
0800 AM HEAVY RAIN 1 NE IRONWOOD 46.47N 90.14W
08/08/2020 M1.23 INCH GOGEBIC MI CO-OP OBSERVER
CO-OP OBSERVER STATION IWOM4 IRONWOOD.
0800 AM HEAVY RAIN 1 ESE THREE LAKES 46.55N 88.18W
08/09/2020 M1.23 INCH BARAGA MI CO-OP OBSERVER
CO-OP OBSERVER STATION MIEM4 MICHIGAMME
3WNW. RAINFALL STRADDLED OBSERVATION TIME
BUT MOSTLY FELL IN A 6-12 HOUR PERIOD.
0800 AM HEAVY RAIN THREE LAKES 46.56N 88.21W
08/09/2020 M1.21 INCH BARAGA MI COCORAHS
COCORAHS STATION MI-BG-3 LANSE 17.8 SE.
RAINFALL STRADDLED OBSERVATION TIME BUT
MOSTLY FELL IN A 6-12 HOUR PERIOD.
0930 AM HEAVY RAIN 2 SW BAGLEY 45.53N 87.62W
08/09/2020 M1.20 INCH MENOMINEE MI COCORAHS
COCORAHS STATION MI-MM-5 DAGGETT 4.8 N.
0800 AM HEAVY RAIN 2 SE HERMAN 46.65N 88.33W
08/09/2020 M1.20 INCH BARAGA MI CO-OP OBSERVER
CO-OP OBSERVER STATION HERM4 2.0 SE HERMAN.
RAINFALL STRADDLED OBSERVATION TIME BUT
MOSTLY FELL IN A 6-12 HOUR PERIOD.
1124 AM HEAVY RAIN 34 ENE ROCK OF AGES 48.11N 88.61W
08/08/2020 M1.19 INCH KEWEENAW MI MESONET
MESONET STATION OJIM4 OJIBWAY - ISLE ROYALE.
0900 AM HEAVY RAIN 1 SE IRONWOOD 46.44N 90.13W
08/08/2020 M1.17 INCH GOGEBIC MI COCORAHS
COCORAHS STATION MI-GG-5 IRONWOOD 1.4 SE.
0800 AM HEAVY RAIN 2 WNW IRONWOOD 46.47N 90.18W
08/08/2020 M1.17 INCH GOGEBIC MI CO-OP OBSERVER
CO-OP OBSERVER STATION IRMM4 IRONWOOD WWTP.
0615 AM HEAVY RAIN 3 S BETSY LAKE 46.58N 85.27W
08/09/2020 M1.16 INCH LUCE MI MESONET
MESONET STATION TAPM4 3.4 S BETSY LAKE.
0800 AM HEAVY RAIN 9 S KENTON 46.36N 88.91W
08/09/2020 M1.14 INCH IRON MI COCORAHS
COCORAHS STATION MI-IR-1 TROUT CREEK 9.6
SSE. RAINFALL STRADDLED OBSERVATION TIME BUT
MOSTLY FELL IN A 6-12 HOUR PERIOD.
0800 AM HEAVY RAIN 6 NNE WAY DAM 46.24N 88.19W
08/09/2020 M1.09 INCH IRON MI COCORAHS
COCORAHS STATION MI-IR-2 CRYSTAL FALLS 11.7
NE. RAINFALL STRADDLED OBSERVATION TIME BUT
MOSTLY FELL IN A 6-12 HOUR PERIOD.
0240 PM HEAVY RAIN HARVEY 46.49N 87.35W
08/08/2020 M1.03 INCH MARQUETTE MI MESONET
MESONET STATION FW7853 MARQUETTE.
1100 AM HEAVY RAIN 3 S SWANSON 45.43N 87.71W
08/08/2020 E1.00 INCH MENOMINEE MI TRAINED SPOTTER
FROM EMAIL. FROM 8AM TO 11AM EDT.
&&
RJCPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MARQUETTE MI
210 PM EDT SUN AUG 9 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0900 AM HEAVY RAIN 1 SE MENOMINEE 45.11N 87.61W
08/09/2020 M1.00 INCH MENOMINEE MI CO-OP OBSERVER
CO-OP OBSERVER STATION MENM4 MENOMINEE.
&&
TAPThe Marquette radar (KMQT), 93 km away, was scanning. The volume nearest the first event began at 20:45 UTC.
16 thunderstorm wind, 3 flash flood, 2 tornado, 1 hail. Local standard time, as filed.
The spotter near Alston observed hail up to penny-sized which lasted for about ten minutes.
Gogebic County Sheriff's department reported that a portion of Highway US-2 was flooded with stranded vehicles. Highway US-2 was closed from Douglas Boulevard to Lowell Street. Law enforcement also reported a downed power line nearby in Ironwood. Nearly an inch and a half of rainfall from thunderstorms over a three-hour period caused the flooding.
The NWS storm survey found widespread extensive tree damage on both sides of Golden Lake in Iron County. At least a hundred healthy softwood and hardwood trees were snapped and uprooted, some causing minor damage to homes in the area. One camper had to be rescued after being trapped by falling trees but was uninjured. Time of the report was estimated from radar.
The Iron County Road Commission reported clearing numerous trees fallen on power lines along Gold Mine Road for about four miles northeast of the intersection with Basswood Road. The time of the report was estimated from radar.
There was a picture posted on social media from one of the local TV stations of a large portion of a tree downed on power lines south of Sidnaw.
Tornado damage was confirmed by NWS storm survey team with numerous hardwood and softwood trees snapped off or uprooted on its path along and north of the Brule River in Iron County. Time of the damage was estimated from radar.
There was a photo submitted to local media of numerous trees down near Golden Lake in Iron County. The time of the report was estimated from radar.
Two fresh pine trees about a foot in diameter were uprooted on the side of Highway M-95 northeast of Republic. The time of the report was estimated from radar.
Photos received through social media indicated at least a dozen trees were snapped or uprooted from thunderstorm winds near Peavy Falls Dam.
Two trees at least a foot in diameter were uprooted by thunderstorm winds in Champion.
There was a photo submitted to local media of two trees at least a foot in diameter uprooted in Champion. The time of the report was estimated by radar.
At least 50 to 100 healthy softwood and hardwood trees were snapped and uprooted on both sides of the road where NWS personnel has access to the path. The tornado, with estimated wind speed of 105 mph, started at Peavy Pond Road and took a path over the northern end of Peavy Pond. Damage could be seen where the tornado moved back onshore and across a small island.
There was a report and video received on social media of water flowing over the roads near the intersection of Massie Road and US-Highway 41 in Chassell. There was also a video received of a business in Chassell surrounded by about a foot of standing water. Three to four inches of rainfall over a couple hours time caused the localized flooding over the area.
There were multiple shoulder washouts along Pike Lake Road. There were also some docks on local lakes underwater. The time of the report was estimated from radar.
Numerous softwood trees were snapped and uprooted near Clarksburg. The time of the report was estimated from radar.
There was a report of half a tree down and a power outage near Ishpeming from thunderstorm winds. Time of the report was estimated from radar.
There was a damage report via social media of a brand new trampoline bent and torn along with a shattered planter on a deck.
Law enforcement reported downed power lines on Highway US-41 near Heritage Drive causing power outages. The NWS Marquette also took a power hit and was on generator power for a period.
Law enforcement reported multiple power lines down along County Roads CJ and 496 in Ely Township.
Law enforcement dispatch reported downed power lines across a driveway on County Road CD southwest of Ishpeming.
Law enforcement reported a tree down from thunderstorm winds across Miller Road in New Buffalo location near Negaunee.
There were photos received through social media of at least a dozen trees snapped or uprooted near Peavy Pond Road. The time of the report was estimated from radar.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Michigan in 2020Every state in 2020This day in weather historyThe tornado archive for Michigan, 2020Warnings 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: 910981, 910998, 915465, 915252, 914962, 915257, 914963, 915254, 911021, 911022, 914964, 914976, 914955, 914969, 915255, 911010, 911006, 910999, 914974, 911000, 911002, 914966.