A deep low pressure system moving through northwest Ontario pushed a warm front across the Upper Great Lakes region on the morning of the 19th. This warm front produced strong to severe thunderstorms over western Lake Superior.
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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 deep low pressure system moving through northwest Ontario pushed a warm front across the Upper Great Lakes region on the morning of the 19th. This warm front produced strong to severe thunderstorms over western Lake Superior.
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 19, 12:12 AM EST, 3 hours 58 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 112 AM EDT FRI AUG 19 2011 UPDATED FOR THE 06Z TAF ISSUANCE .SHORT TERM /TONIGHT AND FRIDAY/... YET ANOTHER DAY OF ABOVE NORMAL TEMPS AND LOWER RH VALUES. WINDS FOR MOST PART HAVE REMAINED LIGHT...BUT HAVE GUSTED TO AROUND 20 MPH FM KEWEENAW INTO NCNTRL CWA...JUST AHEAD OF THE LK SUPERIOR BREEZE. SCT-BKN CU DEVELOPED DESPITE DRY LOW-MID LEVELS SEEN ON 12Z GRB SOUNDING. WEAK SHORTWAVE/H925-H7 MOISTURE ADVECTION HAS RESULTED IN BAND OF SHRA/ISOLD TSRA OVR MN AND THESE ARE NOW PUSHING INTO NW LK SUPERIOR AND ISLE ROYALE. PRIMARY SHORTWAVE TROUGH STILL WELL UPSTREAM OVR MANITOBA AND WILL NOT REALLY IMPACT WX HERE TONIGHT. THETA-E ADVECTION MAINLY AT H85 AND INCREASING SW WINDS AT H85 PULL SOME MOISTURE INTO THE AREA AND THAT COULD TRIGGER ISOLD SHRA/TSRA AS SI/S DIP TO JUST BLO ZERO. BEST CHANCE FOR ANY RAIN WILL BE OVR FAR W UPR MI TOWARD THE KEWEENAW PENINUSLA. JUST SLIGHT CHANCE POPS THOUGH. ASSOCIATED SFC LOW AND SFC TROUGH IS CURRENTLY ORIENTED FM SOUTHERN MANITOBA INTO ND. HEIGHT FALLS/LARGE SCALE DYNAMICS WITH THE TROUGH DO NOT MAKE IT INTO UPR MI TIL LATE FRIDAY AFTN. SFC TROUGH FCST TO REACH A LINE ROUGHLY FM P53 TO ESC BY THAT SAME TIME. 1000-850MB WIND/MOISTURE CONVERGENCE WITH THE TROUGH AND 925-850MB THETA-E ADVECTION AND AFTN BUILD-UP OF INSTABILITY ARE THE MAIN INSTIGATORS FOR SHRA/TSRA OVR UPR MI ON FRIDAY. SINCE HEIGHT FALLS ARE MINIMAL AND UPR MI IS MORE IN THE RIGHT FRONT QUADRANT OF JET STREAK OVR SOUTHERN MANITOBA AND INSTABILITY IS NOT THAT ROBUST (MLCAPES UP TO 1000 J/KG)...COVERAGE OF PCPN SEEMS LIKE IT WILL BE SCT AT BEST. HAVE HELD ONTO THE LOW CHANCE POPS...HIGHEST OVR ROUGHLY THE EAST 2/3 OF THE CWA IN THE AFTN. DEEP LAYER SHEAR BLO 30 KTS POINTS TO LOW RISK OF ORGANIZED STORMS INITIALLY...HOWEVER SHEAR BECOMES MORE FAVORABLE BY LATE AFTN AS TROUGH AND JET STREAK ARE CLOSER TO THE AREA. SEEMS THERE IS AT LEAST A REMOTE POSSIBILY OF SVR INTO THE SCNTRL AND EASTERN CWA AS FRONT WILL BE ARRIVING THERE BY LATE AFTN. MAIN THREAT WOULD BE GUSTY WINDS WITH HIGHER SFC-THETA-E VALUES AND MID LEVEL DRYING PUNCHING IN FM THE WEST. AHEAD OF THE TROUGH... EXPECT MAX TEMPS TO PUSH ABOVE NORMAL YET AGAIN WITH READINGS INTO THE LOW-MIDDLE 80S. SIDED WITH LOWER SIDE OF GUIDANCE FOR DWPNTS BASED ON PERSISTENT DRY PATTERN WE ARE IN. .LONG TERM...FRIDAY NIGHT THROUGH THURSDAY FRIDAY NIGHT...SCT SHRA/TSRA MAY LINGER...MAINLY OVER THE SE PORTION OF THE CWA EARLY (BTWN 00Z-03Z) AS THE FRONT AND THE TAIL OF THE NRN ONTARIO SHORTWAVE MORES THROUGH. ALTHOUGH THE GFS/ECMWF HINT AT POSSIBILITY OF ADDITIONAL PCPN WITH A BAND OF 700-300 MB QVECTOR CONV SOUTH OF THE MAIN SHRTWV MOVING THROUGH NRN ONTARIO...AGGRESSIVE LOW LEVEL DRYING BEHIND EVENING COLD FRONTAL PASSAGE SHOULD END PCPN POTENTIAL EVEN THOUGH SOME MID/HIGH CLOUDS MIGHT LINGER. SATURDAY...THE GFS AND ESPECIALLY THE ECMWF SUGGEST THAT 850-600 MB FGEN MAY PRODUCE SOME PCPN...SINCE THE MODELS KEEP QPF MAINLY OVER NRN WI...DID NOT INCLUDE POPS AS HIGH AS SLIGHT CATEGORY. 850 MB TEMPS DROPPING INTO THE 8C TO 10C RANGE WILL RESULT IN COOLER READINGS MAINLY IN THE LOWER TO MID 70S. SATURDAY NIGHT NIGHT AND SUNDAY...THE MODELS WERE SIMILAR WITH PATTERN AMPLIFICATION ALLOWING A STRONGER SHORTWAVE TO DIVE INTO THE NRN GREAT LAKES. MODERATE TO STRONG FORCING WITH 700-300 MB QVECTOR CONV AND THE NOSE OF THE 250-300 MB JET STREAK SHOULD BE ENOUGH TO SUPPORT SCT SHRA INTO THE CWA EVEN WITH THE LIMITED MOISTURE AVAILABLE. FCST INSTABILITY...ONLY TO NEAR 500 J/KG WAS MARGINAL FOR TSRA...BUT SOME TSRA MAY BE POSSIBLE DURING PERIOD OF PEAK HEATING. MONDAY THROUGH THURSDAY...FGEN MAY LEAD TO A BAND OF PCPN ALONG THE 850-700 MB FRONTAL BNDRY TO THE SOUTH AND WEST. MODELS HAVE KEPT PCPN WITH THIS FEATURE MAINLY OVER WI. ANOTHER WEAK FRONTAL BNDRY OR SHORTWAVE MAY MOVE INTO THE NRN GREAT LAKES TUE NIGHT INTO WED...PER GFS/GEM...BUT SINCE THE ECMWF MAINTAINS MORE ZONAL PATTERN...REDUCED POPS TO SLIGHT. OTHERWISE...TEMPS WILL AGAIN CLIMB ABOVE NORMAL WITH MAX READINGS INTO THE LOWER TO MID 80S BY WED/THU WITH 850 MB TEMPS INTO THE 16C TO 18C RANGE...PER ECMWF. && .AVIATION /FOR THE 06Z TAF ISSUANCE/... HIGH PRESSURE OVER THE UPR LAKES WILL GIVE WAY TO A SFC TROUGH APPROACHING LATE TONIGHT/FRIDAY MORNING. EXPECT INCREASING MID CLOUDS OVERNIGHT AHEAD OF THE SFC TROUGH WITH EVEN SOME LIGHT SHOWERS POSSIBLE AT KCMX. TROUGH MOVES THROUGH KCMX BY MIDDAY FRIDAY WITH A GUSTY WEST WIND DEVELOPING. DAYTIME HEATING AHEAD OF THE TROUGH COULD TRIGGER SCATTERED SHRA/TSRA FRIDAY AFTN AT KSAW. DESPITE THE RAIN CHANCES...LACK OF LOW-LEVEL MOISTURE SHOULD ALLOW FOR CONDITIONS TO REMAIN VFR THROUGH THE PERIOD AT BOTH SITES. IF A HEAVIER SHOWER OR STORM DIRECTLY IMPACTS EITHER TERMINAL THEN CONDITIONS MAY BRIEFLY DROP TO MVFR. CONFIDENCE IS LOW ENOUGH NOT TO PUT SHOWERS AT BOTH SITES FOR NOW AS SHOWERS WILL BE WIDELY SCATTERED. && .MARINE /FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE/... LOW PRESSURE TROUGH MOVES THROUGH ON FRIDAY. EXPECT WINDS OF 15-25 KTS THROUGH SATURDAY JUST AHEAD OF AND BEHIND THE TROUGH...WITH A FEW GUSTS NEARING 30 KTS BETWEEN ISLE ROYALE AND THE KEWEENAW PENINSULA ON FRIDAY. PRESSURE GRADIENT BECOMING LIGHT BY LATER IN THE WEEKEND AND INTO NEXT WEEK RESULTS IN WINDS STAYING BLO 20 KTS. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... NONE. LAKE SUPERIOR... NONE. LAKE MICHIGAN... NONE. && SHORT TERM...JLA LONG TERM...JLB AVIATION...07 MARINE...JLA
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE MARQUETTE MI 433 PM EDT THU AUG 18 2011 MIZ001>007-009>014-084-085-191300- KEWEENAW-ONTONAGON-NORTHERN HOUGHTON-BARAGA-MARQUETTE-ALGER-LUCE- GOGEBIC-IRON-DICKINSON-MENOMINEE-DELTA-SOUTHERN SCHOOLCRAFT- SOUTHERN HOUGHTON-NORTHERN SCHOOLCRAFT- 433 PM EDT THU AUG 18 2011 /333 PM CDT THU AUG 18 2011/ THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF WESTERN UPPER MICHIGAN AND CENTRAL UPPER MICHIGAN. .DAY ONE...TONIGHT THERE IS A SLIGHT CHANCE OF THUNDERSTORMS LATE TONIGHT OVER FAR WESTERN UPPER MICHIGAN. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY THUNDERSTORMS ARE POSSIBLE FRIDAY OVER ALL OF WEST AND CENTRAL UPPER MICHIGAN...THEN ON FRIDAY EVENING OVER CENTRAL UPPER MICHIGAN. WIND GUSTS TO 40 MPH AND SMALL HAIL MAY ACCOMPANY ANY STRONGER STORMS. THERE IS A CHANCE OF THUNDERSTORMS SUNDAY AFTERNOON AND EVENING. .SPOTTER INFORMATION STATEMENT... THE NEED FOR WEATHER SPOTTER REPORTS IS NOT ANTICIPATED AT THIS TIME. LSZ162-240>251-263>267-191300- 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- 433 PM EDT THU AUG 18 2011 /333 PM CDT THU AUG 18 2011/ 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 OVER WESTERN LAKE SUPERIOR. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY THUNDERSTORMS ARE POSSIBLE FRIDAY OVER ALL OF LAKE SUPERIOR AND THEN OVER FAR EASTERN LAKE SUPERIOR ON FRIDAY NIGHT. THERE IS A CHANCE OF THUNDERSTORMS SUNDAY AFTERNOON AND EVENING. .SPOTTER INFORMATION STATEMENT... THE NEED FOR WEATHER SPOTTER REPORTS IS NOT ANTICIPATED AT THIS TIME. LMZ221-248-250-191300- 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- 433 PM EDT THU AUG 18 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHERN LAKE MICHIGAN. .DAY ONE...TONIGHT NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY THERE IS CHANCE OF THUNDERSTORMS FRIDAY AFTERNOON AND EVENING. WIND GUSTS TO 40 MPH AND SMALL HAIL MAY ACCOMPANY ANY STRONGER STORMS. THERE IS A CHANCE OF THUNDERSTORMS SUNDAY AFTERNOON AND EVENING. .SPOTTER INFORMATION STATEMENT... THE NEED FOR WEATHER SPOTTER REPORTS IS NOT ANTICIPATED AT THIS TIME. JLB
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE MARQUETTE MI 441 AM EDT FRI AUG 19 2011 MIZ001-003-084-191000- HOUGHTON-KEWEENAW-SOUTHERN HOUGHTON- 441 AM EDT FRI AUG 19 2011 ...SIGNIFICANT WEATHER ALERT FOR HOUGHTON AND KEWEENAW COUNTIES UNTIL 600 AM EDT... AT 440 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM 13 MILES NORTH OF REDRIDGE...OR 18 MILES WEST OF CALUMET. THIS STORM WAS MOVING EAST AT 20 MPH. NICKEL SIZE HAIL AND WINDS UP TO 50 MPH ARE EXPECTED WITH THIS STORM. * LOCATIONS IN OR NEAR THE PATH OF THIS STORM INCLUDE... FREDA... REDRIDGE... MCLAIN STATE PARK... SOUTH RANGE... HANCOCK... CALUMET... STAY TUNED TO NOAA WEATHER RADIO...COMMERCIAL RADIO...OR YOUR LOCAL TELEVISION STATIONS FOR LATER STATEMENTS AND POSSIBLE WARNINGS CONCERNING THIS WEATHER SITUATION. KF
The Marquette radar (KMQT), 111 km away, was scanning. The volume nearest the first event began at 09:09 UTC.
9 marine thunderstorm wind. Local standard time, as filed.
Wind gust measured at the Portage Canal GLOS Station.
Wind gust measured at the Portage Canal GLOS Station.
Wind gust measured at the Portage Canal GLOS Station.
Wind gust measured at the Portage Canal GLOS Station.
The spotter at the headquarters of Porcupine Mountains State Park reported severe downdrafts, trees falling and dime-sized hail.
Numerous trees uprooted and power poles snapped from confirmed weak tornado in the village of Ontonagon.
Numerous trees uprooted and power poles snapped from confirmed weak tornado in the village of Ontonagon.
Wind gust measured at buoy 45025 near the Lower Entrance of Portage Canal.
Wind gust measured at buoy 45025 near the Lower Entrance of Portage Canal.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Lake Superior in 2011Every state in 2011This day in weather history
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: 343642, 343643, 343644, 343645, 343681, 343689, 343702, 343714, 343716.