Thunderstorms produced two weak tornadoes and hail in Clay County in northwest Iowa during the afternoon of April 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 FSD wrote it up.
Thunderstorms produced two weak tornadoes and hail in Clay County in northwest Iowa during the afternoon of April 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 Sioux Falls, SD wrote its last area forecast discussion before the first event at Apr 21, 1:51 PM CST, 1 hour 36 minutes earlier.
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA NATIONAL WEATHER SERVICE SIOUX FALLS SD 251 PM CDT SAT APR 21 2012 .DISCUSSION... ISOLATED SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE OVER SOUTHWEST MINNESOTA AND NORTHWEST IOWA THROUGH ABOUT 500 PM CDT THIS AFTERNOON...WITH JUST A SMALL CHANCE FOR SHOWERS AFTER THIS THROUGH ABOUT 1000 PM CDT THIS EVENING IN THE SAME AREA. SOME WEAK STORM RELATIVE HELICITY...MARGINAL CAPE VALUES AND RELATIVELY LOW LCL HEIGHTS WILL ALLOW FOR THE CHANCE FOR A COUPLE OF FUNNELS. OTHERWISE...MAINLY A THREAT FOR HAIL TO ABOUT THE SIZE OF DIMES. NORTHWEST WINDS WILL BE ON THE DECREASE AROUND SUNSET...BUT REMAIN AT ABOUT 10 TO 15 MPH THROUGH THE NIGHT. THIS SHOULD KEEP TEMPERATURES RELATIVELY MILD...ALTHOUGH SOME COLD AIR ADVECTION WILL BE DRAGGING DOWN SOME COOLER TEMPERATURES. EXPECTED LOWS TO RANGE FROM THE MID 30S IN CENTRAL SD TO THE LOWER 40S IN PARTS OF SOUTHWEST MINNESOTA AND NORTHWEST IOWA WHERE CLOUDS MAY HANG A LITTLE LONGER AND AND WINDS MAY STAY UP ALL NIGHT. SUNDAY SHOULD PROVE TO BE A DECENT BUT CHILLY DAY AS WINDS DECREASE THROUGH THE DAY...STARTING OUT ABOUT 10 TO 20 MPH AND DECREASING TO AROUND 10 MPH BY LATE AFTERNOON. WITH A COOLER LOW LEVEL AIR MASS HIGHS WILL TOP OUT FROM THE MID 50S IN THE EAST TO THE LOWER 60S IN CENTRAL SD. /08 RELATIVELY QUIET WEATHER IS EXPECTED FOR THE FIRST HALF OF THE WEEK AS A LARGE UPPER LEVEL RIDGE BUILDS INTO THE NORTHERN PLAINS THROUGH TUESDAY NIGHT. THIS WILL RESULT IN A FAIRLY SUBSTANTIAL WARMING TREND...ESPECIALLY ON TUESDAY AS 850 HPA TEMPS WARM TO NEAR 20 C. WITH A WEST TO NORTHWEST UNIDIECTIONAL WIND AND 12Z MODELS TRENDING UPWARDS SLIGHTLY WITH TEMPERATURES ALOFT ON TUESDAY...HAVE RAISED FORECAST HIGHS. GOING FORECAST STILL MAY BE ON THE CONSERVATIVE SIDE OF REALITY THOUGH DEPENDING ON INCREASING CIRRUS SHIELD FILTERING FROM WEST TO EAST THROUGHOUT THE DAY. MODEST LOW LEVEL COLD AIR ADVECTION SETS UP TUESDAY NIGHT INTO WEDNESDAY AS LOW LEVEL FLOW TAKES ON A NORTH TO NORTHEASTERLY DIRECTION. UPPER LEVEL PATTERN FLATTENS OUT MUCH MORE AND MODELS HINT AT DIRTY FLOW WITH EMBEDDED SHORT WAVES IN THE FLOW. AS SUCH...LEFT A MENTION OF SHOWERS/ISOLATED T IN THE FORECAST FOR TUESDAY NIGHT INTO WEDNESDAY. THEREAFTER...ANOTHER FAIRLY SUBSTANTIAL RIDGE BUILDS INTO THE AREA LATE IN THE WEEK AHEAD OF A LONGITUDINAL TROUGH THAT MOVES INTO THE WEST COAST ON THURSDAY. THE TROUGH IS COMPOSED OF PHASED WAVES WHICH ARE EXPECTED TO MOVE EAST ON FRIDAY BEFORE IMPACTING THE PLAINS NEXT WEEKEND. RIGHT NOW...MODELS ARE SUGGESTING THE SOUTHERN WAVE WOULD MOVE NORTHEAST ACROSS THE PLAINS ON SATURDAY...POTENTIALLY IGNITING CONVECTION ACROSS THE AREA. GIVEN UNCERTAINTY ON TIMING...BACKED LIKELY POPS INTO THE CHANCE CATEGORY FOR NEXT SATURDAY...BUT WILL HAVE TO KEEP AN EYE ON THIS SYSTEM FOR SEVERE POTENTIAL. && .AVIATION.../FOR THE 18Z TAF ISSUANCE/ MAINLY VFR THROUGH THE PERIOD. THE MAIN CONCERNS WILL BE SOME THREAT FOR ISOLATED THUNDERSTORMS OVER MAINLY SOUTHWEST MINNESOTA FROM ABOUT 19Z THROUGH 23Z. ALSO SOME ISOLATED AREAS OF HIGHER END MVFR CEILINGS DURING THAT TIME AS WELL FROM NEAR HON TO FSD. NORTHWEST WINDS OF 20 TO 35 MPH WILL BE LIKELY ALL AFTERNOON BEFORE DROPPING OFF TO 10 TO 15 MPH AROUND SUNSET. /08 && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. &&
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE SIOUX FALLS SD 143 PM CDT SAT APR 21 2012 SDZ038>040-050-052>071-MNZ071-072-080-081-089-090-097-098- IAZ001>003-012>014-020>022-031-032-NEZ013-014-221200- AURORA-BEADLE-BON HOMME-BROOKINGS-BRULE-BUENA VISTA IA- CHARLES MIX-CHEROKEE IA-CLAY-CLAY IA-COTTONWOOD MN-DAKOTA NE- DAVISON-DICKINSON IA-DIXON NE-DOUGLAS-GREGORY-HANSON-HUTCHINSON- IDA IA-JACKSON MN-JERAULD-KINGSBURY-LAKE-LINCOLN-LINCOLN MN- LYON IA-LYON MN-MCCOOK-MINER-MINNEHAHA-MOODY-MURRAY MN-NOBLES MN- OBRIEN IA-OSCEOLA IA-PIPESTONE MN-PLYMOUTH IA-ROCK MN-SANBORN- SIOUX IA-TURNER-UNION-WOODBURY IA-YANKTON- 143 PM CDT SAT APR 21 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST SOUTH DAKOTA... SOUTHWEST MINNESOTA...NORTHWEST IOWA...AND NORTHEAST NEBRASKA. .DAY ONE...TODAY AND TONIGHT THUNDERSTORMS... SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL BE POSSIBLE OVER MAINLY SOUTHWEST MINNESOTA THROUGH 400 PM CDT THIS AFTERNOON. WHILE THE STORMS ARE NOT EXPECTED TO BECOME SEVERE A FEW COULD PRODUCE BRIEF FUNNEL CLOUDS THAT ARE NOT EXPECTED TO REACH THE GROUND. WIND AND FOG... WIND GUSTS OF 35 TO 40 MPH WILL BE POSSIBLE WEST OF INTERSTATE 29 THIS AFTERNOON. THE WINDS WILL DIMINISH AROUND SUNSET. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT. && FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT WWW.WEATHER.GOV/SIOUXFALLS. THIS INCLUDES THE GRAPHICAL HAZARDOUS WEATHER OUTLOOK.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
243 PM CDT SAT APR 21 2012
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0240 PM HAIL 4 NE MARSHALL 44.49N 95.73W
04/21/2012 M0.75 INCH LYON MN TRAINED SPOTTER
&&
KWEISSERPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
420 PM CDT SAT APR 21 2012
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0405 PM FUNNEL CLOUD 7 WSW LAKEFIELD 43.65N 95.30W
04/21/2012 JACKSON MN PUBLIC
DID NOT SEE IT TOUCH DOWN
&&
LAFLINThe Sioux Falls radar (KFSD), 141 km away, was scanning. The volume nearest the first event began at 21:29 UTC.
2 tornado, 1 hail. Local standard time, as filed.
A weak rope tornado caused no reported damage.
Hail partially covered the ground.
A weak tornado caused no reported damage.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2012Every state in 2012This day in weather historyThe tornado archive for Iowa, 2012Warnings in Iowa, April 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: 374957, 374958, 374959.