A warm front was located across far southern Lower Michigan during the afternoon of the 9th. An upper level disturbance moved across the southern part of the state, triggering thunderstorms along the warm front.
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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 DTX wrote it up.
A warm front was located across far southern Lower Michigan during the afternoon of the 9th. An upper level disturbance moved across the southern part of the state, triggering thunderstorms along the warm front. Some of these storms produced damaging winds.
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 Detroit, MI wrote its last area forecast discussion before the first event at May 9, 1:25 PM EST, 3 hours 37 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 225 PM EDT SUN MAY 9 2004 .DISCUSSION... BUSY LATE AFTERNOON/EVENING. SEVERE THUNDERSTORM WATCH HAS BEEN ISSUED FOR ALL OF SOUTHEAST MICHIGAN UNTIL 00Z. VERY UNSTABLE AIRMASS DEVELOPING OVER SOUTHEAST MICHIGAN THIS AFTERNOON...AS A WARM FRONT SLOWLY HEADS NORTHWARD. SURFACE TEMPERATURES HAVE CLIMBED INTO THE 80S OVER THE NORTHERN OHIO VALLEY...ALONG WITH DEW POINTS IN THE MID 60S. THIS HAS/WILL ALLOW CAPES TO CLIMB TO 2000 J/KG OR BETTER. NICE MCV EVIDENT ON SATELLITE IMAGERY APPROACHING SOUTHERN LAKE MICHIGAN. THIS FEATURE WILL BE ENOUGH TO FIRE UP THUNDERSTORMS LATE THIS AFTERNOON/EARLY EVENING AS THERE IS NO CAP PRESENT. A SUPERCELL OR TWO POSSIBLE HERE IN SOUTHEAST MICHIGAN. WITH THE FRONTAL BOUNDARY LINGERING NEAR THE CWA AND THE SURFACE FLOW BACKED FROM THE EAST...THERE IS A CHANCE OF A TORNADO WITH ANY SUPERCELL. WILL ALSO HAVE TO KEEP AN EYE OUT FOR HEAVY RAINFALL...AS AREA RIVERS OVER THE NORTHERN HALF OF THE CWA ARE RUNNING HIGH. WITH PRECIPITABLE WATER VALUES APPROACHING 1.5 INCHES...ANY SLOW MOVING THUNDERSTORM(S) COULD DUMP 1 TO 2 INCHES EASILY. TITTABAWASSEE RIVER AT MIDLAND ALREADY EXPECTED TO CREST NEAR FLOOD STAGE TOMORROW MORNING. HEAVY RAINFALL TONIGHT COULD PUT THEM OVER THE TOP. POTENT NORTHERN STREAM SHORTWAVE/CLOSED LOW WILL CONTINUE TO TRACK EAST THROUGH CENTRAL CANADA TONIGHT. THE BEST DYNAMICS WITH THIS SYSTEM SHOULD STAY NORTH OF SOUTHERN LOWER MICHIGAN. 500 MB HEIGHTS BASICALLY REMAIN THE SAME OVER SOUTHEAST MICHIGAN THROUGH TOMORROW NIGHT...BEFORE RISING ON TUESDAY. HOWEVER...THIS SYSTEM WILL DRIVE AN ACTIVE FRONTAL BOUNDARY SOUTH THROUGH THE LOWER GREAT LAKES TOMORROW/TOMORROW NIGHT. PLENTY OF MOISTURE AND INSTABILITY ALONG AND SOUTH OF THE FRONTAL BOUNDARY SHOULD BE ENOUGH TO FIRE UP STORMS. K INDICES LOOK TO BE IN THE LOW TO MID 30S FOR MUCH OF THE SHORT TERM. ONCE AGAIN...IT DOES LOOK LIKE WE WILL HAVE A SHOT AT SEVERE WEATHER TOMORROW...AS SURFACE BASED LIS EXPECTED TO DROP TO -5 C AND CAPES EXPECTED TO CLIMB OVER 2000 J/KG. THAT IS ASSUMING MAXES CLIMBING INTO THE LOWER 80S WITH SURFACE DEW POINTS IN THE MID 60S. BOTH THOSE PARAMETERS LOOK REASONABLE. LOOKS LIKE NO CAP TO PREVENT STORMS FROM DEVELOPING. THE WIND FIELDS DO NOT LOOK ALL THAT IMPRESSIVE AS THE STRONGER WESTERLIES REMAIN OVER THE NORTHERN GREAT LAKES AND THE WINDS LOOK TO BE UNIDIRECTIONAL. NONE-THE-LESS...THE GOOD INSTABILITY IS ENOUGH TO MENTION THE POSSIBILITY OF SEVERE STORMS. FOR MONDAY NIGHT...UPPER LEVEL CONFLUENT FLOW OVER THE NORTHERN LAKES/SOUTHERN ONTARIO ALLOWS SURFACE HIGH TO BUILD IN. THE QUESTION IS HOW FAR SOUTH WILL THE FRONTAL BOUNDARY SAG BEFORE THE FRONT BECOMES PARALLEL TO FLOW? TOUGH CALL...BUT ALL SHORT TERM MODELS SHOWING THE SURFACE BOUNDARY REACHING OR PUSHING JUST SOUTH OF THE SOUTHERN MICHIGAN BORDER BY 12Z TUESDAY. BEYOND THAT...ETA AND GFS DIVERGE SIGNIFICANTLY...AS GFS CONTINUES TO DRIVE THE FRONT SOUTH...WHILE ETA INDICATES THE FRONT REMAINING NEARLY STATIONARY OR RETURNING NORTHWARD. UKMET SEEMS LIKE A GOOD COMPROMISE AS FRONTAL BOUNDARY EXPECTED TO LINGER ACROSS EXTREME NORTHERN INDIANA/OHIO ON TUESDAY. PLAN ON STICKING CLOSE TO THE CURRENT FORECAST IN THE GRIDS...BUT WILL BUMP POPS UP NEAR THE OHIO BORDER. BANKING ON ACTIVITY TO BECOME CAPPED BY TUESDAY NIGHT...AS HEIGHTS RISE. STILL MAY NEED TO ACCOUNT FOR A CHANCE EARLY DURING THE EARLY EVENING FROM ANY LEFTOVER DAYTIME ACTIVITY. LOW LEVEL JET REALLY GETS GOING OVER THE NORTHERN MISSISSIPPI VALLEY TUESDAY NIGHT. HOPEFULLY WE WILL NOT HAVE TO WORRY ABOUT ANY MCSS ROLLING INTO LOWER MICHIGAN WEDNESDAY MORNING. && .EXTENDED... BIG PATTERN SHIFT AS AMPLIFYING TROUGH DEVELOPS ACROSS THE WESTERN THIRD OF THE CONUS...WITH A CORRESPONDING LARGE UPPER LEVEL RIDGE DEVELOPING OVER THE EAST COAST. IT LOOKS LIKE LOWER MICHIGAN WILL BE UNDERNEATH THE RIDGE AXIS FOR THE FIRST PART OF THE EXTENDED (TUESDAY/WEDNESDAY)...BEFORE THE LONGWAVE TROUGH OVER THE WESTERN CONUS SLOWLY SPREADS TOWARD/INTO THE CENTRAL CONUS. WILL BE CARRYING MUCH ABOVE NORMAL TEMPS (5+ DEGREES) FOR WEDNESDAY/THURSDAY TIMEFRAME. SIGNIFICANT DIFFERENCES BETWEEN THE MEDIUM RANGE MODELS BY DAYS 6 AND 7 ON AMPLITUDE. OPERATIONAL 00Z GFS TENDING FOR THE FLOW TO BECOME MORE ZONAL BY THE WEEKEND. MEANWHILE...EUROPEAN MODEL...REMAINS AMPLIFIED WITH THE ROCKIES LONGWAVE TROUGH RIGHT INTO THE WEEKEND. PER HPC...FAVOR MORE OF A AMPLIFIED PATTERN INTO THE WEEKEND. WILL GENERALLY FOLLOW THE 00Z ETAXX WHICH SEEMS LIKE A GOOD COMPROMISE BETWEEN THE EUROPEAN/CANADIAN AND GFS. AS USUAL FOR DAYS 6 AND 7...CONFIDENCE SOMEWHAT LOW...WILL NOT STRAY TOO FAR FROM NORMAL (HIGHS NEAR/LOWER 70S...LOWS IN UPPER 40S/NEAR 50). && .DTX WATCHES/WARNINGS/ADVISORIES...SEVERE THUNDERSTORM WATCH IN EFFECT FOR ALL OF SOUTHEAST MICHIGAN UNTIL 00Z. && SF EXPERIMENTAL GRAPHICAL FORECASTS ARE AVAILABLE ONLINE AT HTTP://WWW.CRH.NOAA.GOV/DTX (ALL LOWER CASE)
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 951 PM EDT SUN MAY 8 2004 MIZ060>063-068>070-075-076-082-083-101200- GENESEE-LAPEER-LENAWEE-LIVINGSTON-MACOMB-MONROE-OAKLAND-WASHTENAW- WAYNE-SHIAWASSEE-ST. CLAIR- 951 PM EDT SUN MAY 8 2004 THIS HAZARDOUS WEATHER OUTLOOK IS FOR MOST OF SOUTHEAST MICHIGAN. .DAY ONE...TONIGHT NUMEROUS THUNDERSTORMS WILL BECOME SCATTERED OVERNIGHT. HOWEVER...SEVERE THUNDERSTORMS ARE NO LONGER EXPECTED. THE THUNDERSTORMS WILL CONTINUE TO PRODUCE LOCALLY HEAVY RAINFALL... WHICH WILL CAUSE SOME MINOR LOCALIZED FLOODING...MAINLY FOR THE METRO DETROIT REGION AND NEAR THE OHIO BORDER. THE THUNDERSTORMS OVERNIGHT WILL BE CAPABLE OF PRODUCING WIND GUST TO 35 MPH AND PEA SIZE HAIL. THUNDERSTORM MOVEMENT WILL BE EAST AT 30 MPH. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY THUNDERSTORMS WILL BE POSSIBLE MONDAY AFTERNOON INTO MONDAY NIGHT. THERE IS A SLIGHT RISK OF SEVERE WEATHER WITH THIS ACTIVITY...WITH THE MAIN HAZARDS BEING LARGE HAIL AND DAMAGING WINDS. THESE STORMS WILL BE THE RESULT OF A COLD FRONT MOVING INTO THE AREA. A FEW OF THESE THUNDERSTORMS MAY LINGER INTO TUESDAY...SOUTH OF INTERSTATE 69. THUNDERSTORMS WILL AGAIN BE POSSIBLE THURSDAY AND FRIDAY AS ANOTHER COLD FRONT SLOWLY PROGRESSES THROUGH THE GREAT LAKES. .SPOTTER INFORMATION STATEMENT... DISPATCHERS...PLEASE NOTIFY YOUR EMERGENCY MANAGERS IMMEDIATELY. SPOTTER ACTIVATION IS NOT EXPECTED FOR THE REST OF THE NIGHT...BUT MAY BE NEEDED AGAIN ON MONDAY AFTERNOON OR EVENING. MIZ047>049-053>055-101200- BAY-HURON-MIDLAND-SAGINAW-SANILAC-TUSCOLA- 951 PM EDT SUN MAY 8 2004 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE SAGINAW VALLEY AND NORTHERN THUMB. .DAY ONE...TONIGHT NUMEROUS SHOWERS AND A FEW THUNDERSTORMS WILL COME TO AN END OVERNIGHT. SEVERE THUNDERSTORMS ARE NO LONGER EXPECTED. HOWEVER ANY THUNDERSTORM THAT DOES MOVE THROUGH THE AREA...WILL CONTINUE TO PRODUCE LOCALLY HEAVY RAINFALL...WHICH WILL CAUSE SOME MINOR LOCALIZED FLOODING. THUNDERSTORM MOVEMENT WILL BE EAST AT 30 MPH. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY THUNDERSTORMS ARE POSSIBLE MONDAY AND MONDAY EVENING AS A COLD FRONT PUSHES SOUTH THROUGH THE REGION. THERE IS A SLIGHT RISK OF SEVERE WEATHER WITH THIS ACTIVITY DURING THE AFTERNOON AND EARLY EVENING HOURS...WITH THE MAIN HAZARDS BEING LARGE HAIL AND DAMAGING WINDS. THUNDERSTORMS WILL AGAIN BE POSSIBLE THURSDAY AND FRIDAY AS ANOTHER COLD FRONT SLOWLY PROGRESSES THROUGH THE GREAT LAKES. .SPOTTER INFORMATION STATEMENT... DISPATCHERS...PLEASE NOTIFY YOUR EMERGENCY MANAGERS IMMEDIATELY. SPOTTER ACTIVATION IS NOT EXPECTED FOR THE REST OF THE NIGHT...BUT MAY BE NEEDED AGAIN ON MONDAY AFTERNOON OR EVENING. SF/RBP
The Detroit radar (KDTX), 48 km away, was scanning. The volume nearest the first event began at 22:02 UTC.
3 thunderstorm wind, 1 hail. Local standard time, as filed.
A trained weather spotter reported numerous trees blown down.
A trained weather spotter estimated a 60 mph thunderstorm wind gust.
A trained weather spotter reported small trees blown down.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Michigan in 2004Every state in 2004This day in weather historyWarnings in Michigan, May 2004
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: 5399267, 5399334, 5399268, 5399333.