A weak boundary was in place across southern Iowa during the morning of the 1st. The airmass was quite unstable with dewpoint temperatures in the mid 70s.
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 DMX wrote it up.
A weak boundary was in place across southern Iowa during the morning of the 1st. The airmass was quite unstable with dewpoint temperatures in the mid 70s. An area of thunderstorms formed initially over northern Missouri. A band of thunderstorms formed northwest out of the main complex. One storm became severe in Mahaska County and produced high winds and dime size hail. The wind blew down power lines and an elevated fuel tank on a farm north of Oskaloosa. A barn door was also blown about 20 feet.
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 Des Moines, IA wrote its last area forecast discussion before the first event at Jul 1, 5:46 AM CST, 4 hours 21 minutes earlier.
AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE DES MOINES IA 646 AM CDT SUN JUL 1 2012 ...UPDATED AVIATION DISCUSSION... .SHORT TERM /TODAY/... THINGS APPEAR A BIT QUIETER THIS MORNING THAN THE PREVIOUS SEVERAL DAYS...BUT WE ARE LIKELY IN FOR MORE STORMS LATER TODAY. CURRENTLY SURFACE FEATURES ARE SIMILAR TO LAST NIGHT...WITH HIGH PRESSURE OFF TO OUR NORTHEAST RESULTING IN COOL TEMPS AND AREAS OF LIGHT FOG ACROSS OUR NORTHEASTERN TWO THIRDS OR SO...AND OUR OLD FRIEND THE DECAYED FRONTAL BOUNDARY LOITERING IN OUR FAR SOUTHERN COUNTIES. RADAR DEPICTS A FEW STORMS OVER FAR SOUTHWESTERN IA AND NORTHERN MO NEAR THE FRONTAL ZONE. MEANWHILE A 500 MB SHORTWAVE IS KICKING OFF SOME SPRINKLES AND VIRGA ACROSS SOUTHERN MN THAT WILL LIKELY CREEP INTO OUR FAR NORTH BUT HAVE A HARD TIME PRODUCING MEASURABLE RAINFALL. IN WAKE OF THE 500 MB SHORTWAVE A DEEP LAYER RIDGE TO OUR WEST WILL ATTEMPT TO BUILD EASTWARD TOWARD OUR AREA TODAY...BRINGING SOUTH SOUTHWESTERLY STEERING FLOW THAT SHOULD PUSH THE OLD FRONTAL BOUNDARY NORTHWARD INTO CENTRAL IOWA BY THIS AFTERNOON. THIS WILL RESULT IN SIGNIFICANT DESTABILIZATION AND CONVECTION SHOULD INITIATE NEAR THE FRONTAL ZONE THIS AFTERNOON. THIS WILL MAKE THE LOCATION OF THE BOUNDARY CRITICAL AND THERE IS SOME UNCERTAINTY THERE SO HAVE KEPT POPS SOMEWHAT BROADBRUSHED...BUT BELIEVE THE MOST LIKELY AREA FOR STORMS WILL BE BETWEEN ABOUT THE HIGHWAY 30 AND 20 CORRIDORS AND HAVE GONE 40-50 POP IN THAT AREA. DRIED OUT THIS MORNING QUITE A BIT...EXCEPT ACROSS OUR SOUTH NEAR THE LIFTING BOUNDARY...AS IT APPEARS WE WILL HAVE TO WAIT FOR DIURNAL MAX FOR ANY ORGANIZED STORM DEVELOPMENT. THERE IS SOME SEVERE WEATHER POTENTIAL THIS AFTERNOON GIVEN THE DEGREE OF INSTABILITY IN PLACE DESPITE MODEST SHEAR FIELDS...AND DAMAGING WINDS AND LARGE HAIL SHOULD BE THE PRIMARY THREATS. THE SPC OUTLOOK HANDLES THIS...AS WELL AS THE UNCERTAINTIES IN TIMING/LOCATION...QUITE WELL. .LONG TERM.../TONIGHT SATURDAY/ AFTER TONIGHT...THE FRONTAL BOUNDARY WILL LIFT NORTH OF THE STATE AS HEIGHTS BUILD ACROSS THE CENTRAL U.S. CONSISTENCY IN MODELS AND ALSO RUN TO RUN CONTINUITY IS GOOD AND SEE NO REASON TO MAKE MANY CHANGES. RING OF FIRE WILL LIKELY REMAIN NORTH OF IOWA THROUGH THE WORK WEEK AND GRADUALLY PUSH SOUTH AGAIN TOWARD THE WEEKEND. DELAYED THE ONSET OF CONVECTION UNTIL ABOUT SUNDAY. GFS IS A LITTLE FASTER THAN THE ECMWF AND SINCE THE GFS IS TYPICALLY TOO FAST IN BREAKING DOWN THE UPPER RIDGES WILL LEAN TOWARD THE EC SOLUTION. MAIN WEATHER PROBLEM FOR THE WEEK WILL BE WITH THE HEAT INDICES. NIGHTTIME CRITERIA BEGINS TO BE MET BY MONDAY NIGHT AND WILL CONTINUE THROUGH THE WEEK. WITH DEW POINTS EXPECTED TO BE IN THE 60S INSTEAD OF THE 70S...AFTERNOON HI'S ARE LIKELY TO BE CLOSE TO 105 EACH AFTERNOON FROM TUE ON. OVERNIGHT HI'S ARE EXPECTED TO BE 75 OR HIGHER FROM MON NIGHT ON. HEADLINES WILL BE LIKELY BY LATER IN THE WEEK. INITIALLY AN ADVISORY SITUATION...BUT PERSISTENCE OF THE THE HEAT COULD WELL LEAD TO A WARNING SITUATION BASED ON DURATION OF 4+ DAYS. ONE THING WORTH POINTING OUT AND ONE THAT NEEDS TO BE MONITORED IS THE ECMWF CONSISTENCY OF FORECASTING 3 TO 5 DAYS OF CONSECUTIVE HIGHS OF 100+ AND MINS IN THE 80S. ECMWF IS TYPICALLY TOO WARM AND HAVE REMAINED BELOW THAT BY SEVERAL DEGREES...BUT SOMETHING TO KEEP IN MIND. IF THERE IS ONE POSITIVE IN THE FORECAST...ALBEIT PAST DAY 7...IT IS THAT THE LONGER TERM FORECASTS OF TROUGHING IN THE EAST AND THE UPPER HIGH RETROGRADING...AND HENCE COOLER WEATHER FOR IA...IS SUPPORTED FOR NEXT WEEK IN THE CHANGES TAKING PLACE WITH THE MJO PATTERN. && .AVIATION...01/12Z SCT TSRA ARE SLIDING ACROSS KOTM ATTM...BUT BELIEVE THEY WILL MISS KOTM OR THAT ANY EFFECTS WILL BE BRIEF SO HAVE NOT INCLUDED IN THE 12Z TAF. AS THE WEAK FRONT RESPONSIBLE FOR THESE STORMS MOVES NORTHWARD TODAY IT SHOULD ACTIVATE IN THE LATE AFTN OR EVE...RESULTING IN MORE WIDESPREAD TSRA FOR SEVERAL HOURS. WHILE THIS APPEARS MORE LIKELY UP TOWARD KMCW/KALO...THERE IS SO MUCH UNCERTAINTY REGARDING CONVECTIVE INITIATION AND TIMING THAT I DO NOT HAVE THE CONFIDENCE TO INCLUDE VCTS IN THE TAFS ATTM WITHOUT MAKING IT OVER PROHIBITIVELY LONG DURATION. BEST GUESS IS THAT TSRA MAY AFFECT THOSE TERMINALS BTWN ABT 21Z AND 02Z...BUT WILL LEAVE IT FOR THE 18Z TAF ISSUANCE TO REFINE BASED ON ADDITIONAL DATA. OTHER THAN THESE POTENTIAL SHRA/TSRA EFFECTS VFR CONDITIONS ARE ANTICIPATED. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && SHORT TERM...LEE LONG TERM...MS JUL 12 AVIATION...LEE
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DES MOINES IA 542 AM CDT SUN JUL 1 2012 IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086- 092>097-021100- EMMET-KOSSUTH-WINNEBAGO-WORTH-PALO ALTO-HANCOCK-CERRO GORDO- POCAHONTAS-HUMBOLDT-WRIGHT-FRANKLIN-BUTLER-BREMER-SAC-CALHOUN- WEBSTER-HAMILTON-HARDIN-GRUNDY-BLACK HAWK-CRAWFORD-CARROLL-GREENE- BOONE-STORY-MARSHALL-TAMA-AUDUBON-GUTHRIE-DALLAS-POLK-JASPER- POWESHIEK-CASS-ADAIR-MADISON-WARREN-MARION-MAHASKA-ADAMS-UNION- CLARKE-LUCAS-MONROE-WAPELLO-TAYLOR-RINGGOLD-DECATUR-WAYNE-APPANOOSE- DAVIS- 542 AM CDT SUN JUL 1 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA. .DAY ONE...TODAY AND TONIGHT SCATTERED THUNDERSTORMS ARE EXPECTED TODAY INTO TONIGHT. SOME STORMS MAY BECOME SEVERE WITH HIGH WIND THE PRIMARY THREAT. LARGE HAIL WILL BE A SECONDARY THREAT. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY AN EXTENDED PERIOD OF HOT AND HUMID WEATHER IS EXPECTED THROUGH THE PERIOD. OVERNIGHT LOWS WILL BE IN THE LOW TO MID 70S MONDAY AND TUESDAY...AND MID TO UPPER 70S BEGINNING WEDNESDAY. HIGHS WILL BE IN THE MID TO UPPER 90S THROUGH THE WEEK. HEAT INDICES WILL BE AROUND 100 TUESDAY AND AROUND 105 WEDNESDAY THROUGH AT LEAST FRIDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND EVENING.
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE DES MOINES IA
759 AM CDT SUN JUL 1 2012
IAZ086-011330-
WAPELLO-
759 AM CDT SUN JUL 1 2012
...STRONG SLOW MOVING THUNDERSTORMS OVER WAPELLO COUNTY...
AT 752 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
STRONG THUNDERSTORMS ALONG A LINE EXTENDING FROM NORTH CENTRAL
WAPELLO COUNTY TO EXTREME SOUTH CENTRAL JEFFERSON COUNTY...MOVING
EAST AT 15 MPH.
PENNY SIZE HAIL AND FREQUENT DOWNPOURS WITH TORRENTIAL RAINS ARE
POSSIBLE WITH THESE STORMS. PONDING WATER ON ROADS MAY OCCUR WITH
RAINFALL UP TO AN INCH PER HOUR.
LOCATIONS IMPACTED INCLUDE...
RURAL WAPELLO COUNTY NORTH AND EAST OF OTTUMWA
SEEK SHELTER IN A STURDY STRUCTURE UNTIL THESE STORMS HAVE PASSED.
SMALLSPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE DES MOINES IA 957 AM CDT SUN JUL 1 2012 IAZ075-011545- MAHASKA- 957 AM CDT SUN JUL 1 2012 ...LINE OF STRONG THUNDERSTORMS TRACKING ACROSS NORTHERN MAHASKA COUNTY... AT 948 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A LINE OF THUNDERSTORMS TRACKING ACROSS NORTHERN MAHASKA COUNTY. THIS LINE WAS MOVING TO THE EAST AT 15 MPH. SEVERAL ROUNDS OF THUNDERSTORMS WITH HEAVY RAIN HAVE TRACKED ACROSS THE AREA AND SATURATED THE GROUND. THESE ADDITIONAL THUNDERSTORMS WILL BRING HEAVY DOWNPOURS THAT MAY LEAD TO PONDING OF WATER IN LOW LYING AREAS. IN ADDITION...PENNY SIZE HAIL AND FREQUENT CLOUD TO GROUND LIGHTNING ARE POSSIBLE WITH THE STRONGER STORMS. LOCATIONS IMPACTED INCLUDE... NEW SHARON... ROSE HILL... STAY AWAY FROM HIGH OBJECTS OUTDOORS SUCH AS TREES. SEEK SHELTER IN A STURDY STRUCTURE UNTIL THIS STORM HAS PASSED. SKOW
The Des Moines radar (KDMX), 100 km away, was scanning. The volume nearest the first event began at 16:06 UTC.
1 thunderstorm wind. Local standard time, as filed.
Power lines were downed by high winds. An elevated fuel tank was blown over and a barn door blown 20 feet. Dime size hail also fell.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2012Every state in 2012This day in weather historyWarnings in Iowa, July 2012
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: 380519.