The passage of a cold front through a very warm and unstable air mass generated scattered severe thunderstorms across portions of west and central Upper Michigan on the afternoon of the 21st.
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.
The passage of a cold front through a very warm and unstable air mass generated scattered severe thunderstorms across portions of west and central Upper Michigan on the afternoon of the 21st.
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 21, 2:41 PM EST, 13 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 341 PM EDT WED AUG 21 2013 .SHORT TERM...(THIS EVENING THROUGH THURSDAY) ISSUED AT 340 PM EDT WED AUG 21 2013 MAIN FOCUS OF THE FORECAST FOR TODAY IS THE DEVELOPING THUNDERSTORMS ASSOCIATED WITH A COLD FRONT JUST STARTING TO MOVE INTO WESTERN UPPER MICHIGAN. THE COLD FRONT HAS BEEN MAKING IT/S WAY ACROSS WESTERN LAKE SUPERIOR AND NORTHWEST WISCONSIN OVER THE LAST FEW HOURS AND THERE WAS SOME CONCERN THAT THE STRATUS DECK THAT DEVELOPED FROM THE FOG NEAR DULUTH WOULD LIMIT COME OF THE CONVECTION. BUT THE FORCING FROM THE COLD FRONT COMBINED WITH DIURNAL HEATING HAS BEGAN TO PRODUCE THUNDERSTORMS ALONG THE COLD FRONT WITH SOME BECOMING FAIRLY STRONG AT THIS WRITTING. WITH A VERY UNSTABLE ATMOSPHERE (MLCAPE VALUES ANALYZED FROM 2000-3000 J/KG DUE TO SFC DEWPOINTS IN THE UPPER 60S AND LOWER 70S)...THEY SHOULDN/T HAVE MUCH DIFFICULTY CONTINUING THROUGH THE EARLY EVENING. AS HAS BEEN MENTIONED OVER THE LAST COUPLE OF DAYS...0-6KM SHEAR VALUES ARE A LITTLE MARGINAL...BUT LATEST RAP TRENDS SHOW VALUES APPROACHING 30-35KTS RIGHT ALONG THE COLD FRONT. THIS SHOULD HELP THE THUNDERSTORMS BECOME A LITTLE MORE TILTED AND BETTER ORGANIZED OVER THE NEXT FEW HOURS. THINKING THAT THERE IS A DECENT CHANCE OF THIS CONVECTION BECOMING LINEAR AND MOVING ACROSS MUCH OF UPPER MICHIGAN LATE THIS AFTERNOON AND INTO THE EVENING. DAMAGING WIND IS A DECENT THREAT WITH DCAPE VALUES AHEAD OF THE FRONT OF 800-1100 J/KG. WHERE THERE ARE STRONGER STORMS...HAIL IS ALSO A THREAT...BUT IT WILL LIKELY BE MORE ISOLATED DUE TO THE HIGHER FREEZING LEVELS. WITH THE BOUNDARIES OVER THE WEST AND LOWER LCL HEIGHTS FROM THE LEFT OVER STRATUS...THERE COULD BE A ISOLATED TORNADO THREAT...BUT SHOULD BE CONFINED TO THE LATE AFTERNOON. IN ADDITION...ANOTHER BOUNDARY (AIDED BY EARLIER CLOUDS/SHOWERS THAT MOVED ACROSS NORTHERN LAKE SUPERIOR) HAS SETUP FROM WEST TO EAST FROM ONTONAGON THROUGH MARQUETTE COUNTY. SHOWERS/THUNDERSTORMS HAVE ALSO STARTED TO DEVELOP ALONG THIS AND ARE SLIDING EAST. SPC HAS JUST ISSUED A SEVERE THUNDERSTORM WATCH FOR MUCH OF UPPER MICHIGAN THROUGH 4Z. THE COLD FRONT AND THUNDERSTORMS ARE EXPECTED TO EXIT INTO LAKE MICHIGAN AROUND 06Z. PREVIOUS FORECAST HAD A GOOD HANDLE ON TIMING...SO ONLY MADE MINOR ADJUSTMENTS. THE REST OF THE NIGHT SHOULD BE DRY (DUE TO DRIER AIR SURGING IN BEHIND THE COLD FRONT)...EVENTHOUGH A FAIRLY POTENT SHORTWAVE WILL BE SLIDING SOUTHEAST ACROSS THE AREA FROM LAKE WINNIPEG. THIS SHOULD LEAD TO MOSTLY CLEAR SKIES AND MUCH COOLER TEMPERATURES THAN LAST NIGHT. COOLER NORTHERLY FLOW WILL BE IN STORE FOR UPPER MICHIGAN ON THURSDAY...AS HIGH PRESSURE APPROACHES THE AREA FROM THE UPPER MISSISSIPPI VALLEY. 850MB TEMPS WILL BE AROUND 10C COOLER THAN TODAY AND EXPECT A SIMILAR RESPONSE WITH THE HIGHS (IN THE 70S). COOLEST TEMPERATURES WILL BE NEAR LAKE SUPERIOR...WHERE THE NORTHERLY WINDS OFF THE LAKE WILL KEEP TEMPS RIGHT AROUND 70. A SUNNY TO MOSTLY SUNNY SKY IS EXPECTED. .LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY) ISSUED AT 340 PM EDT WED AUG 21 2013 NAM SHOWS A 500 MB RIDGE ACROSS THE ROCKIES AND CENTRAL PLAINS WITH A TROUGH OVER THE ERN U.S. 00Z FRI. THE 500 MB RIDGE BUILDS INTO THE CENTRAL PLAINS THIS FORECAST PERIOD WITH THE EDGE OF THE WESTERLIES OVER THE AREA THIS FORECAST PERIOD. DID PUT IN SLIGHT CHANCE TO CHANCE POPS IN THE FORECAST FOR THE WEST HALF FOR SAT AFTERNOON AS A WARM FRONT HEADS TOWARDS THE AREA AND MOISTURE STARTS TO INCREASE. OTHERWISE...DID NOT MAKE TOO MANY CHANGES TO THE GOING FORECAST FOR TEMPERATURES. LOOKS TO STAY WARM THROUGH THIS PERIOD. IN THE EXTENDED...GFS AND ECMWF SHOW A 500 MB RIDGE OVER THE CENTRAL U.S. SAT NIGHT INTO SUN. THE RIDGE REMAINS STATIONARY THROUGH THE PERIOD WITH THE U.P. IN THE PERIPHERY OF THE RIDGE IN THE RING OF FIRE SCENARIO WHERE ANY SHORTWAVE CAN SET OFF A ROUND OF THUNDERSTORMS. WILL BE HARD TO TIME THESE SHORTWAVES AND EASIEST WAY TO FORECAST THIS WOULD BE TO BROADBRUSH THIS FORECAST PERIOD WITH CHANCE POPS EVEN THOUGH IT WILL NOT BE A TOTAL WASHOUT. TEMPERATURES WILL STAY ABOVE NORMAL FOR THIS FORECAST PERIOD ALONG WITH INCREASING HUMIDITY. ONLY PERIOD THAT LOOKS DRY IS WED WITH A FRONT MOVING OUT OF THE AREA. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON) ISSUED AT 146 PM EDT WED AUG 21 2013 VERY TRICKY AVIATION FORECAST FOR KIWD/KSAW THIS AFTERNOON DUE TO SOME UNCERTAINTY ON TIMING/LOCATION OF THE CONVECTION THIS AFTERNOON/EVENING. A COLD FRONT CURRENTLY APPROACHING WESTERN UPPER MICHIGAN AND POTENTIALLY THROUGH KCMX WILL BRING A POTENTIAL FOR SHOWERS AND THUNDERSTORMS. BUT HAVE SOME CONCERN THAT THE MVFR DECK NOW MOVING INTO KIWD WILL LIMIT COVERAGE SOME. THE LAST HOUR HAS SEEN SOME INCREASE IN CU AND SHOWERS WITHIN THE AREA OF STRATUS...SO OPTED TO LEAVE IN A TS/VCTS MENTION FOR A PERIOD THIS AFTERNOON AT KIWD. ONCE THE FRONT MOVES THROUGH AROUND 21-22Z...THUNDER POTENTIAL SHOULD END ALONG WITH THE MVFR CEILINGS. AS THE SHOWERS/THUNDERSTORMS DEVELOP OVER WESTERN UPPER MICHIGAN THIS AFTERNOON...MAIN QUESTION FOR KSAW IS IF THEY WILL DEVELOP FAR ENOUGH NORTH TO INFLUENCE THE SITE. THINKING THEY WILL WITH THE CU FIELD GOING UP FROM THE CITY OF ONTONAGON TO BARAGA AND THE EASTWARD MOVEMENT WOULD SLIDE IT THROUGH KSAW AFTER 21Z. BEHIND THE FRONT TONIGHT INTO THURSDAY...VFR CONDITIONS WILL PREVAIL AS HIGH PRESSURE BUILDS OVER THE AREA. THERE MAY BE A BRIEF PERIOD OF SCT100 CLOUDS MOVING IN FROM NORTHWEST MN...BUT WILL NOT EFFECT OPERATIONS. && .MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE) ISSUED AT 340 PM EDT WED AUG 21 2013 A COLD FRONT CURRENTLY MOVING ACROSS CENTRAL LAKE SUPERIOR WILL CONTINUE SOUTHEAST THIS EVENING AND LEAD TO NORTHERLY FLOW (GENERALLY BELOW 15KTS) OVER THE LAKE FOR THE REST OF TONIGHT AND INTO THURSDAY EVENING. HIGH PRESSURE THAT IS PRODUCING THE LIGHTER WINDS WILL THEN SHIFT SOUTHEAST INTO THE LOWER GREAT LAKES AND ALLOW WINDS TO SLOWLY INCREASE FROM THE SOUTH-SOUTHWEST FRIDAY INTO THE WEEKEND. AT THIS POINT...WOULD EXPECT LAKE STABILITY FACTORS TO KEEP WINDS AT OR BELOW 20KTS. ONE FINAL ITEM TO MENTION IS IF THE SHOWERS/THUNDERSTORMS AFFECT ENOUGH OF EASTERN LAKE SUPERIOR TO DEVELOP FOG. LEFT OUT AT THIS POINT SINCE VISIBLE SATELLITE INDICATED THE FOG OVER NORTHERN LAKE SUPERIOR HAS DISSIPATED AND THERE IS SOME UNCERTAINTY ON HOW FAR THE RAIN WILL GET INTO EASTERN LAKE SUPERIOR. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... NONE. LAKE SUPERIOR... NONE. LAKE MICHIGAN... NONE. && SHORT TERM...SRF LONG TERM...07 AVIATION...SRF MARINE...SRF
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE MARQUETTE MI 314 PM EDT WED AUG 21 2013 MIZ001>007-009>014-084-085-221200- KEWEENAW-ONTONAGON-NORTHERN HOUGHTON-BARAGA-MARQUETTE-ALGER-LUCE- GOGEBIC-IRON-DICKINSON-MENOMINEE-DELTA-SOUTHERN SCHOOLCRAFT- SOUTHERN HOUGHTON-NORTHERN SCHOOLCRAFT- 314 PM EDT WED AUG 21 2013 /214 PM CDT WED AUG 21 2013/ THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF WESTERN UPPER MICHIGAN AND CENTRAL UPPER MICHIGAN. .DAY ONE...TONIGHT NUMEROUS THUNDERSTORMS WILL CONTINUE INTO THIS EVENING...ESPECIALLY OVER THE SOUTH HALF OF UPPER MICHIGAN. SOME OF THESE THUNDERSTORMS COULD BECOME SEVERE AND CAUSE DAMAGING WINDS AND LARGE HAIL. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY THUNDERSTORMS ARE POSSIBLE SATURDAY AFTERNOON OVER THE WEST HALF OF UPPER MICHIGAN AND FOR ALL OF WESTERN AND CENTRAL UPPER MICHIGAN SATURDAY NIGHT THROUGH TUESDAY. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO SUBMIT REPORTS TO THE NATIONAL WEATHER SERVICE IN MARQUETTE. THE PUBLIC MAY ALSO SUBMIT REPORTS AT OUR WEBPAGE...FACEBOOK PAGE...OR ON TWITTER. LSZ162-240>251-263>267-221200- 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- 314 PM EDT WED AUG 21 2013 /214 PM CDT WED AUG 21 2013/ THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EASTERN LAKE SUPERIOR...CENTRAL LAKE SUPERIOR AND WESTERN LAKE SUPERIOR. .DAY ONE...TONIGHT EXPECT SCATTERED THUNDERSTORMS THROUGH THIS EVENING. SOME OF THE THUNDERSTORMS MAY BE STRONG AND CAUSE GUSTY WINDS OVER EASTERN LAKE SUPERIOR THIS EVENING. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY THUNDERSTORMS ARE POSSIBLE ON SATURDAY OVER THE WEST HALF OF LAKE SUPERIOR AND FOR ALL OF LAKE SUPERIOR SATURDAY NIGHT THROUGH TUESDAY. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO SUBMIT REPORTS TO THE NATIONAL WEATHER SERVICE IN MARQUETTE. THE PUBLIC MAY ALSO SUBMIT REPORTS AT OUR WEBPAGE...FACEBOOK PAGE...OR ON TWITTER. LMZ221-248-250-221200- 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- 314 PM EDT WED AUG 21 2013 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHERN LAKE MICHIGAN. .DAY ONE...TONIGHT NUMEROUS THUNDERSTORMS WILL OCCUR THIS EVENING. SOME OF THESE STORMS MAY BE SEVERE AND CAUSE DAMAGING WINDS AND LARGE HAIL. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY THUNDERSTORMS ARE POSSIBLE SATURDAY NIGHT THROUGH TUESDAY. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO SUBMIT REPORTS TO THE NATIONAL WEATHER SERVICE IN MARQUETTE. THE PUBLIC MAY ALSO SUBMIT REPORTS AT OUR WEBPAGE...FACEBOOK PAGE...OR ON TWITTER. 07
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE MARQUETTE MI 302 PM EDT WED AUG 21 2013 MIZ002-009-212000- GOGEBIC-ONTONAGON- 202 PM CDT WED AUG 21 2013 ...SIGNIFICANT WEATHER ALERT FOR GOGEBIC AND ONTONAGON COUNTIES UNTIL 300 PM CDT/400 PM EDT/... AT 258 PM EDT...DOPPLER RADAR INDICATED THAT THUNDERSTORMS WERE DEVELOPING ALONG A LINE EXTENDING FROM 23 MILES WEST OF SILVER CITY TO 22 MILES WEST OF UPSON WISCONSIN. THESE STORMS WERE MOVING EAST AT 40 MPH. DIME SIZE HAIL AND WINDS UP TO 50 MPH ARE EXPECTED WITH THESE STORMS. PEOPLE IN GOGEBIC AND WESTERN ONTONAGON COUNTIES...INCLUDING THE CITIES OF SILVER CITY...IRONWOOD...BESSEMER...WAKEFIELD AND BERGLAND...SHOULD MONITOR THE WEATHER SITUATION CLOSELY. LISTEN FOR POSSIBLE WARNINGS AND BE PREPARED TO TAKE APPROPRIATE ACTION SHOULD SEVERE WEATHER THREATEN. REMEMBER...IF YOU CAN HEAR THUNDER...YOU ARE CLOSE ENOUGH TO THE STORM TO BE STRUCK BY LIGHTNING. SEEK SAFE SHELTER IMMEDIATELY. STAY TUNED TO NOAA WEATHER RADIO...COMMERCIAL RADIO...OR YOUR LOCAL TELEVISION STATIONS FOR LATER STATEMENTS AND POSSIBLE WARNINGS CONCERNING THIS WEATHER SITUATION. JLA
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE MARQUETTE MI 332 PM EDT WED AUG 21 2013 MIZ004-005-010-212015- BARAGA-IRON-MARQUETTE- 332 PM EDT WED AUG 21 2013 ...SIGNIFICANT WEATHER ALERT FOR BARAGA...IRON AND MARQUETTE COUNTIES UNTIL 415 PM EDT/315 PM CDT/... AT 324 PM EDT/224 PM CDT/...DOPPLER RADAR INDICATED THAT THUNDERSTORMS WERE RAPIDLY DEVELOPING ALONG A LINE EXTENDING FROM 20 MILES NORTHEAST OF MARQUETTE TO MARQUETTE...NEGAUNEE...AND ISHPEMING AND TO 15 MILES NORTH OF IRON RIVER. THESE STORMS WERE MOVING EAST AT 25 MPH. PEA SIZE HAIL AND WINDS UP TO 50 MPH ARE EXPECTED WITH THESE STORMS. ADDITIONAL STORMS ARE ALSO EXPECTED INTO EARLY THIS EVENING. PEOPLE IN MARQUETTE...IRON AND BARAGA COUNTIES...INCLUDING THE CITIES OF NEGAUNEE...ISHPEMING...MARQUETTE...HARVEY...WITCH LAKE AND K I SAWYER...SHOULD MONITOR THE WEATHER SITUATION CLOSELY. LISTEN FOR POSSIBLE WARNINGS AND BE PREPARED TO TAKE APPROPRIATE ACTION SHOULD SEVERE WEATHER THREATEN. REMEMBER...IF YOU CAN HEAR THUNDER...YOU ARE CLOSE ENOUGH TO THE STORM TO BE STRUCK BY LIGHTNING. SEEK SAFE SHELTER IMMEDIATELY. STAY TUNED TO NOAA WEATHER RADIO...COMMERCIAL RADIO...OR YOUR LOCAL TELEVISION STATIONS FOR LATER STATEMENTS AND POSSIBLE WARNINGS CONCERNING THIS WEATHER SITUATION. JLA
The Marquette radar (KMQT), 7 km away, was scanning. The volume nearest the first event began at 19:52 UTC.
14 hail, 1 thunderstorm wind. Local standard time, as filed.
Dime-sized hail with a few up to penny-sized hailstones reported near Wright Street and Highway US-41.
Quarter to dime-sized hail fell for about five to ten minutes.
Several trees were downed, and one of the trees was estimated to have a 12-15 inch diameter. Time of the event was estimated from radar.
Gusty winds were also observed which knocked down some small limbs.
Penny-sized hail was observed near Au Train.
Mostly quarter-sized hail was observed in Grand Marais. There were a few flat stones approaching the diameter of a golf ball.
Penny-sized hail was observed near Skandia.
Some quarter-sized hail was reported with a lot of pea to dime-sized hail.
Quarter-sized hail was reported at Eben Junction.
Hail report near Chatham was received via WLUC-TV Facebook page. Time of report was estimated from radar.
Penny-sized hail was reported near Chatham.
Penny-sized hail was reported northeast of Iron River.
There were several reports of dime to quarter-sized hail in Trenary.
Spotter near Round Lake reported that two different storms dropped quarter-sized hail. The first storm passed through around 17:05 EST and the second went through around 17:23 EST.
Penny-sized hail was reported near Iron Mountain.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Michigan in 2013Every state in 2013This day in weather historyWarnings in Michigan, August 2013
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: 466391, 466398, 466412, 466416, 466417, 466418, 466422, 466433, 466437, 466438, 466443, 466446, 466447, 466449, 466450.