A considerable amount of snow had accumulated during the previous winter across northern Iowa and southern Minnesota. As the snow melted, river levels rose across northern Iowa with numerous sites reaching minor to moderate flood levels.
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 considerable amount of snow had accumulated during the previous winter across northern Iowa and southern Minnesota. As the snow melted, river levels rose across northern Iowa with numerous sites reaching minor to moderate flood levels. A couple of the sites, most notably Estherville and Cedar Falls, briefly reached low end major levels. It was fortunate that the snow melted relatively slowly and also the fact that no significant rainfall occurred during the melt. Rainfall that occurred later in the month was held in check by sub-freezing temperatures. The fact that reduced the flooding was a cold spell that moved into the state after the 22nd. Temperatures were highly variable during the month as is typical for this time of year as the weather transitions from winter to spring. A very mild period prevailed from the 14th through the 22nd but was followed by nine consecutive colder than normal days to finish out the month. Sibley recorded the March’s lowest temperature with a low of -5 on the 2nd while Shenandoah and Sidney tied for the highest temperatures with 81 readings on the 22nd. Temperatures for the month as a whole averaged slightly below normal over the northwest and a little above normal over the southeast. Precipitation was fairly evenly distributed throughout the month and was generally greater than normal over the northeast one-third of Iowa and well below normal over the western third of the state. About half of the month’s precipitation came in two storms. The first storm, on the 8th-9th, started with rain statewide but transitioned to snow over the northwestern two-thirds of Iowa. Greatest snow amounts of three to five inches fell over north central and northeast Iowa while rain totals locally exceeded an inch over the southeast. The second event on the 22nd-23rd brought thunderstorms and rainfall statewide with rain amounts up to two inches over parts of north central Iowa. Damage from the river flooding was limited to agricultural areas for the most part. Considerable advance preparation in more flood prone areas also helped to reduce losses.
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 Mar 21, 2:30 PM CST, 1 hour 15 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DES MOINES IA 330 PM CDT MON MAR 21 2011 .SHORT TERM /TONIGHT/... THETA-E ADVECTION WILL CONTINUE TO LIFT NORTH THROUGH IOWA OVERNIGHT AND EXPECT A FEW SHOWERS AND THUNDERSTORMS TO SPROUT FROM CENTRAL TO NORTHERN IOWA THE REMAINDER OF THE AFTERNOON AND INTO EARLY THIS EVENING. THE LOW LEVEL JET INCREASES SIGNIFICANTLY OVER BETWEEN 03Z AND 09Z ACROSS ERN KANSAS AND NEBRASKA AND WILL APPROACH 60-65KTS LATE TONIGHT. THIS WILL FOCUS STRONG MOISTURE TRANSPORT ESPECIALLY OVER WRN IA AND EXPECT A CLUSTER OF STORMS TO DEVELOP OVER WRN AND CNTRL IA. MUCAPES IN EXCESS OF 1000 J/KG AND MID LEVEL LAPSE RATES GREATER THAN 8 C/KM SHOULD PROMOTE A FEW STRONG TO SEVERE HAILERS. IN THE LOW LEVELS...MOISTURE SHOULD BECOME TRAPPED UNDER INCREASING INVERSION WITH ANOTHER STRATUS DECK DEVELOPING. BREEZY SOUTHEAST WINDS SHOULD PREVENT WIDESPREAD DENSE FOG STILL VSBYS LIKELY WILL DECREASE...ESPECIALLY ACROSS THE NORTH. SFC WARM FRONT SHOULD REACH THE FAR SOUTH BY 12Z. .LONG TERM /TUESDAY THROUGH SUNDAY/... VERY LITTLE HAS CHANGED IN OVERALL FORECAST THINKING OF THE EVOLUTION OF THE SYSTEM THAT WILL AFFECT CENTRAL IOWA THROUGH WEDNESDAY. LIKEWISE...THERE IS STILL SOME UNCERTAINTY REGARDING TIMING OF THE FRONT LIFTING ACROSS THE CWA AND THE LOCATION OF THE SURFACE LOW. THE NAM BEING THE OUTLIER HERE KEEPING THE SURFACE LOW TO THE SOUTH AND MOVING IT ACROSS SOUTHERN IOWA DURING THE DAY TOMORROW. HOWEVER THE NAM HANDLED YESTERDAYS/ CONVECTION WELL AND THE 06Z RUN ALSO PAINTED SOME LIGHT POPS ALONG I-80 TODAY WHERE WE HAD SOME CELLS POP. ALL OTHER MODELS LIFT THE LOW NORTHEAST PLACING THE SURFACE LOW IN CENTRAL/NORTH CENTRAL IOWA. THE DIFFERENCE HERE BEING A WARM FRONT THAT IS STRETCHED ACROSS I-80 DURING PEAK HEATING OR ONE THAT IS CONSIDERABLY FURTHER TO THE NORTH. ALOFT THE UPPER WAVE LIFTS ACROSS WESTERN IOWA THROUGH 03Z WEDNESDAY BEFORE A CLOSED LOW EVOLVES OVER THE NORTHERN PLAINS THIS WILL THEN PUSH SLOWLY EAST THROUGH WEDNESDAY NIGHT. IN ADDITION TO THE FORCING AND SHEAR WITH THIS SYSTEM...WAVES OF THETA-E ADVECTION MOVE ACROSS THE CWA THROUGH TUESDAY NIGHT. COLDER AIR WILL MOVE INTO THE CWA WEDNESDAY/WEDNESDAY NIGHT AND LINGERING PRECIP AS A LOBE OF THE LOW MOVES BACK ACROSS NORTHERN IOWA WILL BE A MIX AND POSSIBLY CHANGE OVER TO SNOW OVER NIGHT UP NORTH. AS FOR SEVERE POTENTIAL TUESDAY/TUESDAY NIGHT...INGREDIENTS THERE FOR A SEVERE EVENT. JUST WISH THERE WAS BETTER CONSENSUS ON LOCATION. POSITION OF THE FRONTAL BOUNDARY AND SURFACE LOW MAKE IT DIFFICULT TO ASCERTAIN THE BEST LOCATION BUT THERE IS A NARROW BAND OF CAPE PUSHING INTO SOUTHERN IOWA LATE IN THE DAY AND SOUNDING SUGGEST THE POTENTIAL TO GO SURFACE BASED ALONG/NEAR THE DRY LINE AND TRIPLE POINT...WHEREVER THAT MAY END UP. SEVERE POTENTIAL FOR LARGE HAIL AND DAMAGING WINDS WITH AT LEAST ISOLATED TORNADOES FROM 21Z THROUGH MID EVENING. UPPER LEVEL WINDS ARE 50+KTS SO STORMS WILL BE MOVING VERY FAST. BEYOND MID WEEK...AGAIN LITTLE CHANGE TO CURRENT THINKING. RIDGING BUILDS INTO THE AREA THURSDAY BUT SEVERAL WEAK SHORT WAVES WILL FLATTEN THE RIDGE AND BRING CHANCES FOR PRECIP. COLD TEMPS WILL MEAN A MIX IS LIKELY WITH RAIN AND SNOW DURING THE DAY AND SNOW NORTH AT NIGHT. && .AVIATION...21/18Z STRATUS IS EXPECTED TO DIMINISH OVER THE NORTH THIS AFTERNOON. CIGS ARE EXPECTED TO REDEVELOP AND LOWER AGAIN OVERNIGHT ALONG WITH INCREASING THUNDERSTORM CHANCES. THE STORMS ARE MOSTLY LIKELY THIS EVENING THOUGH 09Z. LIFR TO IFR CIGS AND SOME FOG IS LIKELY OVER THE NORTH LATE TONIGHT THROUGH TUESDAY MORNING WITH VFR RETURNING TO THE FAR SOUTH LATE IN THE PERIOD. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && SHORT TERM...DONAVON LONG TERM...FAB AVIATION...DONAVON
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DES MOINES IA 402 PM CDT MON MAR 21 2011 IAZ033>037-044>050-057>062-070>075-081>086-092>097-222115- SAC-CALHOUN-WEBSTER-HAMILTON-HARDIN-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- 402 PM CDT MON MAR 21 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA. .DAY ONE...THIS AFTERNOON AND TONIGHT THUNDERSTORMS ARE EXPECTED TO DEVELOP MAINLY THIS EVENING THOUGH A FEW STORMS ARE POSSIBLE LATE THIS AFTERNOON. A FEW STORMS COULD BE SEVERE FROM LATE AFTERNOON INTO EARLY TONIGHT...WITH LARGE HAIL THE PRIMARY THREAT. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY PERIODS OF THUNDERSTORMS ARE EXPECTED ON TUESDAY AND TUESDAY EVENING. SOME STORMS COULD BE SEVERE ESPECIALLY DURING THE AFTERNOON AND EVENING HOURS...WITH ALL MODES OF SEVERE WEATHER POSSIBLE. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS POSSIBLE LATE IN THE DAY ON TUESDAY. IAZ004>007-015>017-023>028-038-039-222115- EMMET-KOSSUTH-WINNEBAGO-WORTH-PALO ALTO-HANCOCK-CERRO GORDO- POCAHONTAS-HUMBOLDT-WRIGHT-FRANKLIN-BUTLER-BREMER-GRUNDY-BLACK HAWK- 402 PM CDT MON MAR 21 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA. .DAY ONE...THIS AFTERNOON AND TONIGHT THUNDERSTORMS ARE EXPECTED TO DEVELOP LATE THIS EVENING AND CONTINUE TO MOVE ACROSS THE AREA AT INTERVALS. A FEW STORMS COULD BE SEVERE MAINLY OVERNIGHT...WITH LARGE HAIL THE PRIMARY THREAT. MINOR TO POSSIBLY MODERATE FLOODING IS OCCURRING OR EXPECTED ALONG STREAMS AND RIVERS IN NORTHERN IOWA. RIVER FLOOD WARNINGS ARE ALREADY IN EFFECT IN SOME AREAS. PLEASE REFER TO THE NATIONAL WEATHER SERVICE WEBSITE AT WEATHER.GOV/DESMOINES FOR FURTHER DETAILS. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY PERIODS OF THUNDERSTORMS ARE EXPECTED ON TUESDAY AND TUESDAY EVENING. SOME STORMS COULD BE SEVERE ESPECIALLY DURING THE AFTERNOON AND EVENING HOURS...WITH ALL MODES OF SEVERE WEATHER POSSIBLE. MINOR TO POSSIBLY MODERATE FLOODING IS OCCURRING OR EXPECTED ALONG STREAMS AND RIVERS IN NORTHERN IOWA. RIVER FLOOD WARNINGS ARE ALREADY IN EFFECT IN SOME AREAS. PLEASE REFER TO THE NATIONAL WEATHER SERVICE WEBSITE AT WEATHER.GOV/DESMOINES FOR FURTHER DETAILS. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS POSSIBLE LATE IN THE DAY ON TUESDAY. FAB
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
1156 AM CDT MON MAR 21 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1150 AM HAIL 1 NNW DES MOINES 41.59N 93.62W
03/21/2011 E0.88 INCH POLK IA TRAINED SPOTTER
INTERSECTION OF I35 AND GRAND AVENUE
&&
DEROYPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
1249 PM CDT MON MAR 21 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1216 PM HAIL 1 S RUNNELLS 41.50N 93.36W
03/21/2011 E1.00 INCH POLK IA BROADCAST MEDIA
REPORTED .98 INCH DIAMETER HAIL JUST SOUTH OF RUNNELS
&&
DONAVONThe national radar mosaic for the moment the first event began.
7 flood. Local standard time, as filed.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2011Every state in 2011This day in weather historyWarnings in Iowa, March 2011
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: 283421, 283420, 283417, 283418, 283415, 283416, 283419.