A northwest flow over the Ozarks and cold front interacted with a very unstable airmass. Strong to severe storms occurred across the Ozarks with isolated large hail and wind damage reported.
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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 SGF wrote it up.
A northwest flow over the Ozarks and cold front interacted with a very unstable airmass. Strong to severe storms occurred across the Ozarks with isolated large hail and wind damage reported.
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 Springfield, MO wrote its last area forecast discussion before the first event at Aug 12, 1:50 PM CST, 1 hour 55 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SPRINGFIELD MO 250 PM CDT FRI AUG 12 2011 .DISCUSSION... PRIOR TO STORMS MOVING INTO THE REGION EARLY THIS AFTERNOON...FANTASTIC CONDITIONS WERE OBSERVED OVER EXTREME SOUTHEAST KANSAS AND THE MISSOURI OZARKS THROUGH MOST OF THE DAY. THESE STORMS WILL CONTINUE TO IMPACT THE AREA THROUGH THE REST OF THE AFTERNOON AND EVENING. A SPECIAL UPPER AIR OBSERVATION WAS PERFORMED AT 18Z TODAY TO ASSESS THE POTENTIAL FOR STRONG TO SEVERE STORMS. THIS SOUNDING REVEALED THAT THE INSTABILITY - SHEAR COMBINATION IS NOT LIKELY SUFFICIENT FOR A HIGH FREQUENCY OF SEVERE WEATHER. AS A MATTER OF FACT...MOST THUNDERSTORMS THROUGH TONIGHT SHOULD REMAIN BELOW SEVERE LIMITS...AS MIXED LAYER CAPE VALUES ONLY MEASURED 576 J/KG. DESPITE DEEP LAYER SHEAR BEING DECENT FOR THE TIME OF YEAR (30 TO 35 KNOTS)...LOW LEVEL SHEAR WAS RATHER WEAK...WHICH WOULD TEND TO MITIGATE THE RISK FOR TORNADOES AND DAMAGING WIND GUSTS. MEANWHILE THE LACK OF CAPE WOULD MITIGATE THE STRENGTH OF UPDRAFTS...ULTIMATELY LOWERING THE RISK FOR LARGE HAIL. IT'S NOT OUT OF THE REALM OF POSSIBILITY THAT AN ISOLATED SEVERE STORM WILL DEVELOP LATE THIS AFTERNOON AND THIS EVENING...BUT AGAIN...A HIGH FREQUENCY OF SEVERE STORMS IS NOT LIKELY. WITH THE SYNOPTIC FRONT STILL POSITIONED ACROSS THE KANSAS AND NEBRASKA BORDER...ADDITIONAL STORMS WILL BE POSSIBLE LATER TONIGHT. WITH THE CONTINUED LACK OF INSTABILITY...THE RISK FOR ORGANIZED SEVERE STORMS SEEMS MINIMAL AT THIS TIME. STORMS SHOULD EXIT THE REGION EARLY SATURDAY MORNING...SETTING THE STAGE FOR DRY WEATHER. THIS DRY WEATHER WILL PERSIST FROM SATURDAY AFTERNOON THROUGH AT LEAST TUESDAY IN RESPONSE TO A DRY / STABLE AIRMASS THAT WILL SPREAD ACROSS SOUTHERN MISSOURI. THE SUMMERTIME RIDGE OF HIGH PRESSURE WILL REMAIN SUPPRESSED ACROSS NEW MEXICO THROUGH THIS TIME PERIOD...HELPING TO KEEP AFTERNOON TEMPERATURES IN THE 80S ON A DAILY BASIS THROUGH TUESDAY. BY WEDNESDAY AND BEYOND...MODELS SUGGEST THAT THE SUMMERTIME RIDGE WILL BEGIN TO BUILD BACK OVER NORTHERN TEXAS. THIS SLIGHT PATTERN SHIFT WOULD BRING WARMER TEMPERATURES BACK INTO THE OZARKS...MOST LIKELY 90 DEGREE TEMPERATURES. HOWEVER...RAIN CHANCES CAN NOT NECESSARILY BE RULED OUT EITHER...SINCE WE'LL BE POSITIONED UNDERNEATH THE NORTHEAST PERIPHERY OF THE SUMMERTIME HIGH CENTER. CRAMER && .AVIATION... FOR THE 1800Z TAFS: EXPECT VFR CONDITIONS TO PREVAIL OVER SOUTHWESTERN MISSOURI AIRFIELDS THOUGH THE FORECAST PERIOD WITH THE EXCEPTION OF PERIODS OF MVFR DUE TO CEILINGS AND VISIBILITY DURING HEAVIER PRECIPITATION TONIGHT AND CEILINGS DURING POST FRONTAL CLOUDINESS EARLY TOMORROW. WITH A WARM...HUMID AND INCREASINGLY UNSTABLE AIR MASS IN PLACE EARLY THIS AFTERNOON...DECIDED TO BRING THE RISK OF SHOWERS AND THUNDERSTORMS INTO THE AREA EARLY IN THE TAF FORECAST PERIOD. GIVEN THAT THE MORE DYNAMIC UPPER LEVEL SUPPORT WILL APPROACH THE AREA CLOSER TO OR JUST AFTER MIDNIGHT TONIGHT...INCLUDED THE HEAVIEST AND MOST CONCENTRATED THUNDERSTORM ACTIVITY AROUND THAT TIME. AT LEAST SOME SHOWER ACTIVITY MAY LINGER INTO TOMORROW MORNING AS A SECOND UPPER LEVEL SHORTWAVE APPROACHES THE AREA. LOOKS LIKE CLEARING WILL TAKE PLACE SLOWLY FROM MID MORNING ON TOMORROW AS AN UPPER LEVEL TROF AXIS MOVES EAST OF THE AREA AND SURFACE HIGH PRESSURE BUILDS IN BEHIND IT. COLUCCI && .SGF WATCHES/WARNINGS/ADVISORIES... MO...NONE. KS...NONE. &&
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE SPRINGFIELD MO 355 PM CDT FRI AUG 12 2011 KSZ073-097-101-MOZ055>058-066>071-077>083-088>098-101>106-132100- BOURBON-CRAWFORD-CHEROKEE-BENTON-MORGAN-MILLER-MARIES-VERNON- ST. CLAIR-HICKORY-CAMDEN-PULASKI-PHELPS-BARTON-CEDAR-POLK-DALLAS- LACLEDE-TEXAS-DENT-JASPER-DADE-GREENE-WEBSTER-WRIGHT-NEWTON- LAWRENCE-CHRISTIAN-DOUGLAS-HOWELL-SHANNON-MCDONALD-BARRY-STONE- TANEY-OZARK-OREGON- 355 PM CDT FRI AUG 12 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF THE MISSOURI OZARKS AND EXTREME SOUTHEAST KANSAS. .DAY ONE...THIS AFTERNOON AND TONIGHT. THE HAZARDOUS WEATHER RISK LEVEL IS...SIGNIFICANT. WEATHER HAZARDS EXPECTED... LIMITED HAIL RISK. LIMITED THUNDERSTORM WIND DAMAGE RISK. LIMITED FLOODING RISK. SIGNIFICANT LIGHTNING RISK. DISCUSSION... SCATTERED THUNDERSTORMS WILL CONTINUE TO IMPACT EXTREME SOUTHEAST KANSAS AND THE MISSOURI OZARKS THIS AFTERNOON AND TONIGHT. MOST OF THESE STORMS WILL REMAIN BELOW SEVERE INTENSITY. HOWEVER...THERE REMAINS A CHANCE THAT AN ISOLATED SEVERE STORM OR TWO COULD DEVELOP...PRODUCING WIND GUSTS TO 60 MPH AND HAIL UP TO THE SIZE OF QUARTERS. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY. STORMS MAY LINGER INTO SATURDAY MORNING ACROSS PORTIONS OF SOUTH CENTRAL MISSOURI. A FEW STRONG STORMS CANNOT BE RULED OUT. AN UPPER LEVEL RIDGE WILL BUILD BACK OVER THE REGION THROUGH MUCH OF NEXT WEEKEND. HEAT INDEX VALUES WARMING INTO THE MIDDLE TO UPPER 90S IS EXPECTED ON A DAILY BASIS FROM TUESDAY THROUGH THURSDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED THROUGH TONIGHT. && THIS PRODUCT IS NOW AVAILABLE IN GRAPHICAL FORMAT...ALONG WITH OTHER WEATHER...HYDROLOGICAL AND CLIMATE INFORMATION...AT HTTP://WWW.CRH.NOAA.GOV/SGF(ALL LOWERCASE) CRAMER
The St Louis radar (KLSX), 139 km away, was scanning. The volume nearest the first event began at 21:45 UTC.
2 thunderstorm wind, 1 hail. Local standard time, as filed.
Emergency manager estimated wind gusts up to 60 mph. Several trees and power lines were blown down in the city of Salem. A tree fell on a house.
Several trees were blown down. There was minor roof damage to an outbuilding.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Missouri in 2011Every state in 2011This day in weather historyWarnings in Missouri, August 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: 321913, 321914, 321912.