Thunderstorms produced a brief tornado near Doon in Lyon County during the afternoon of June 21st. A few funnel clouds were also observed in the area.
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The episode as NWS FSD wrote it up.
Thunderstorms produced a brief tornado near Doon in Lyon County during the afternoon of June 21st. A few funnel clouds were also observed in the area.
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 Jun 21, 3:45 PM CST, 11 minutes earlier.
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA NATIONAL WEATHER SERVICE SIOUX FALLS SD 445 PM CDT SUN JUN 21 2009 .DISCUSSION... SCATTERED LINE OF SHOWERS/THUNDERSTORMS DEVELOPING ALONG WIND SHIFT FROM SOUTHERLY TO WESTERLY WINDS...AND THIS AREA WILL SWING THROUGH NORTHWEST IOWA THROUGH THE LATE AFTERNOON/EARLY EVENING. TORNADIC THREAT WITH LOW CLOUD BASES SEEMS GREATEST SEVERE WEATHER THREAT THROUGH THE NEXT FEW HOURS...THOUGH VERY WARM TEMPS THROUGH THE CLOUD LAYER LEADING TO HEAVY RAINFALL RATES AND POTENTIAL FOR LOCALIZED URBAN FLOODING. STORMS PARTIALLY HEATING DRIVEN...SO EXPECT THEM TO DECREASE IN INTENSITY/COVERAGE TOWARD SUNSET. SKIES SHOULD BECOME MOSTLY CLEAR BEHIND THE WAVE...AND WITH LIGHT WINDS OVER THE AREA AND ABUNDANT LOW LEVEL MOISTURE PERSISTING OVER THE AREA TONIGHT...WILL LIKELY SEE SOME PATCHY FOG DEVELOP TOWARD DAYBREAK. /JH WL TURN UP THE STEAM HEAT ON MONDAY AS HGHTS BUILD ALFT AND MID LVL TMPS CONTINUE TO WARM. WL NOT TAKE LONG TO BURN OFF THE PATCHY FOG...AND THEN AT LEAST PARTIAL SUNSHINE WL DRIVE TMPS UP QUICK EFFECTIVELY...AND THE PREEXISTING INVERSION ACTING TO POOL ALL THE EVAPORATED MOISTURE. FOR THE MOMENT...TMP/DWPT FORECAST ENDS UP RIGHT UP AGAINST THE CRITERION...WITH 100 TO 105 HEAT INDICES THROUGH THE AFTERNOON FOR THE LOWER MO VLY TOWARD KSLB. WL HAVE TO BE SOMETHING TO WATCH GIVEN THE EXTREME HEAT. VERY WARM TMPS ALFT TO THE SOUTH SHUD KEEP CONVECTION AT BAY...WITH WARM FRONT LIFTING TO CNTRL SD TO NERN NEBRASKA LN BY LATE DAY...AND CDFNT DRIVEN BY FIRST NRN STREAM IMPULSE STARTS TO PUSH INTO WRN CWA BY EVENING. LITTLE BIT OF A TRIPLE PT IN S CNTRL SD...AS AS HEATS OUT...WL WORK ON ERODING WHAT IS OTHERWISE A FAIRLY CAPPED ATM AT 40-90 J/KG WHEN MODIFIED SLIGHTLY FOR EXCESSIVE DWPTS. WRN MO VLY MAY BE A FLASH POINT FOR EVNG CONVECTION...WHICH WL BE CONDITIONALLY A LITTLE RAUCOUS ON BASIS OF DEEP SHEAR AND 1500-2000 J/KG INSTABILITY. FOCUS SHOULD BE ON A COUPLE POTENTIAL AREAS THRU MON EVNG...THE LOWER MO VLY NEAR WMFNT...AND SLIGHTLY ELEVATED FROM S CNTRL AREAS TOWARD THE MID JAMES VALLEY...THEN CONGEALING TO A MORE BROAD THREAT AS LLJ INCREASES. SO MUCH WL END UP DEPENDING ON BOUNDARY LOCATION AND CONVECTIVE ACTION FOR THE TUE/WED PERIOD. EXPECT THAN MON NIGHT CONVECTION AND THE FIRST WAVE WL HELP PUSH THE BNDRY DOWN TOWARD A VERMILLION TO KSPW LINE EARLY IN THE DAY. AGAIN...SHUD BE FAIRLY CAPPED BNDRY WITH WARM MID LVL TMPS AND CONTINUED HIGH HGTS. NEXT WAVE MOVES IN LTR TUE AND TUE NIGHT...INDUCING BDNRY TO WAFFLE NWRD...AND SHOULD INCITE ANOTHER UPRISING IN CONVECTION. LKLY THAT WL HAVE TO OCCUR ALG/NORTH OF THE BNDRY...WITH CHANCES INCREASING THRU THE EVNG. SOME SVR WX AGAIN WITHIN EXPECTATIONS ASSUMING DEVELOPMENT...FOCUSING ON DAMAGING WIND AND LARGE HAIL...AND EARLY EVNG TORNADO THREAT ALG BNDRY. POTENTIAL INSTABILITY WL BE EVEN HIGHER. MOISTURE SUGGESTS CONDITIONAL FLOODING THREAT AS WELL. OTHERWISE...A BIG TEMPERATURE CHALLENGE... AS MAY REMAIN IN THE 80S NORTH OF THE BNDRY...AND COULD GET NEAR 100 ARND THE KSUX/KSLB AREA. UPR FORCING IN ENTRANCE REGION OF JET LINGERS MORE ON WED...SO MAY NOT GET THE QUIET DOWN PERIOD...WHICH WL AFFECT TMPS TO THE NORTH OF THE BNDRY. CONTINUED RISK FOR HEAVY RAINFALL...WHILE DEEP SHEAR REMAINS PRESENT...LOWER SHEAR REMAINS CONCENTRATED ONLY NEAR BNDRY LOCATION THRU EXTREME SERN SD/NW IA. ANOTHER DAY OF STRONG CROSS FRONT THERMAL GRADIENT AS WELL...ENHANCED EVEN MORE BY CONTINUED CLOUDS/PCPN ON COOL SIDE. DURING THE EXTENDED RANGE PERIOD /WED NIGHT THROUGH SUN/ WL CONTINUE TO DEAL WITH CHALLENGE OF THE IMPACT OF CONVECTION AND VARIOUS WAVES ON THE SLOWLY RETROGRADING PLAINS RIDGE. A WHOLE SPECTRUM OF SLNS AGAIN AT HAND...VARYING FROM THE 00Z CANADIAN WHICH RETROGRADES THE CORE OF THE RIDGE BACK TO THE SWRN U.S. TO THE FLATTER 06Z GFS...TO THE AMPLIFIED 00Z ECMWF. VARIOUS GFS RUNS JUST TOO FAST AND TOO AGGRESSIVE WITH TROUGHS MOVING INTO MEAN RIDGE...AND IN THE ENSEMBLE...ACTUALLY ENDS UP ALMOST 180 DEGREES OUT OF PHASE BY NEXT WEEKEND WITH THE MEAN/MAJORITY OF MEMBERS. A SLOWER PROGRESSION TO SYSTEMS THROUGH THE STRENGTHENING PLAINS RIDGE SEEMS TO BE SUPPORTED BY MAJORITY OF SLNS...AND FOLLOW GENERALLY ALONG HPC LARGE SCALE REASONING THRU THE FCST. BNDRY SLOWING UP THRU SERN CWA WED EVENING WL FOCUS THREAT FOR THUNDERSTORMS ONCE AGAIN...BUT AS JET ENTRANCE WORKS EWRD AWAY FROM AREA...SHUD COLLAPSE SEWRD THRU THE NIGHT AND EXIT BY EARLY THU. ANOTHER FAIRLY DECENT RIDGE CRASHING WAVE EXPECTED LATER FRIDAY INTO SAT...AND WL DRIVE ANOTHER CDFNT ACROSS THE REGION. WL SEE FIRST WAA THREAT FOR CONVECTION BUILDING LATER THU NIGHT INTO THE WRN CWA... BUILDING EWRD BEFORE ENHANCED FRI EVNG BY APPROACHING WAVE. INDUCING A STRONGER LLJ FRI EVENING...SCENARIO TO GET MCS DEVELOPMENT THRU NERN CWA ON EDGE OF WARMER MID LVL TMPS AND PROGRESSING ESE OVERNIGHT. FOR THE TIME...KEPT SAT INTO SAT NIGHT DRY AS LOW LVL FLOW TURNS N AND NW FLOW ALFT SHUD BE FREE FROM DISTURBANCES FOR A BRIEF TIME. LOW CHC FOR CONVECTION ON SUNDAY TAKES INTO ACCOUNT A SLOWER APPROACH OF ENERGY ALG SRN STREAM OF WLYS LIFTING OUT OF SWRN U.S. /CHAPMAN && .AVIATION... WDSPRD MVFR-LOCALLY IFR CIGS PERSISTING OVER NORTHEAST PORTIONS OF THE FA LATE THIS AFTERNOON SHOULD IMPROVE THROUGH THE EVENING AS WINDS BECOME MORE SOUTHERLY. ISOLATED MVFR CIGS ASSOCIATED WITH SHRA/TSRA ALSO POSSIBLE OVER NORTHWEST IOWA THROUGH SUNSET. AFTER 02Z-03Z...EXPECT CLEARING SKIES AND LIGHT WINDS...THOUGH WITH HIGH AMOUNTS OF BOUNDARY LAYER MOISTURE...WILL LIKELY SEE MVFR-LOCALLY IFR VSBYS IN BR DEVELOP ACROSS MOST OF THE CWA AFTER 06Z. ANY BR SHOULD LIFT BY 14Z...LEAVING VFR CONDITIONS ACROSS THE AREA THE BALANCE OF THE DAY. /JH && .FSD WATCHES/WARNINGS/ADVISORIES... IA...NONE. MN...NONE. NE...NONE. SD...NONE. &&
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE SIOUX FALLS SD 1157 AM CDT SUN JUN 21 2009 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- 1157 AM CDT SUN JUN 21 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST SOUTH DAKOTA... SOUTHWEST MINNESOTA...NORTHWEST IOWA...AND NORTHEAST NEBRASKA. .DAY ONE...TODAY AND TONIGHT THUNDERSTORMS... THERE IS A CHANCE OF THUNDERSTORMS DEVELOPING FROM NORTHWEST IOWA... INTO THE INTERSTATE 90 CORRIDOR IN SOUTHWEST MINNESOTA THIS AFTERNOON. DAMAGING WIND GUSTS IN EXCESS OF 60 MPH AND ISOLATED TORNADOES ARE THE GREATEST THREAT...WITH THE TORNADO THREAT FOCUSED NEAR A WARM FRONT LIFTING THROUGH THE AREA. RELATIVELY WARM AIR ALOFT WILL LIMIT HAIL SIZE...THOUGH HAIL TO THE SIZE OF QUARTERS WILL BE POSSIBLE FROM THE STRONGEST STORMS. LOCALLY HEAVY RAIN IS ALSO POSSIBLE. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY THERE IS A CHANCE OF THUNDERSTORMS OVER THE AREA LATE MONDAY AFTERNOON AND NIGHT...WITH ANOTHER CHANCE LATE TUESDAY AFTERNOON AND NIGHT. SHOULD STORMS DEVELOP...SOME STORMS COULD BECOME SEVERE...CAPABLE OF PRODUCING LARGE HAIL AND DAMAGING WINDS. CHANCES FOR THUNDERSTORMS WILL CONTINUE ACROSS THE AREA ON WENDESDAY...SOME OF WHICH COULD BECOME SEVERE. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL BE POSSIBLE BETWEEN 3 PM AND 8 PM OVER NORTHWEST IOWA AND INTO THE INTERSTATE 90 CORRIDOR OF SOUTHWEST MINNESOTA. && FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT WWW.WEATHER.GOV/SIOUXFALLS. THIS INCLUDES THE GRAPHICAL HAZARDOUS WEATHER OUTLOOK. JH
The Sioux Falls radar (KFSD), 89 km away, was scanning. The volume nearest the first event began at 21:54 UTC.
2 funnel cloud, 1 tornado. Local standard time, as filed.
A funnel cloud was observed by a trained spotter moving southeast.
A brief funnel cloud was observed by a trained spotter.
A brief tornado caused no reported damage.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2009Every state in 2009This day in weather historyThe tornado archive for Iowa, 2009Warnings in Iowa, June 2009
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: 179015, 179016, 179017.