A severe weather outbreak unfolded during the late afternoon and evening of the 15th as thunderstorms developed and intensified along several boundaries over southwest and south central North Dakota. Supercell storms formed initially over the west central and southwest, then formed into an organized bowing segment as the storms progressed eastward into the south central.
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 BIS wrote it up.
A severe weather outbreak unfolded during the late afternoon and evening of the 15th as thunderstorms developed and intensified along several boundaries over southwest and south central North Dakota. Supercell storms formed initially over the west central and southwest, then formed into an organized bowing segment as the storms progressed eastward into the south central. Severe Thunderstorm Watch number 782 was in effect for this event. Numerous warnings were issued.
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 Bismarck, ND wrote its last area forecast discussion before the first event at Aug 15, 1:48 PM MST, 1 hour 17 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BISMARCK ND 348 PM CDT MON AUG 15 2011 .SHORT TERM...TONIGHT THROUGH TUESDAY NIGHT... THE MAIN FORECAST CONCERN WILL BE THE SEVERE POTENTIAL ACROSS NORTH DAKOTA TONIGHT. ONGOING ELEVATED CONVECTION OVER EASTERN MONTANA WILL SLOWLY SPREAD INTO WESTERN NORTH DAKOTA THIS AFTERNOON. AN OUTFLOW BOUNDARY FROM THE ONGOING CONVECTION IS NOTED ON VISIBLE SATELLITE IMAGERY MOVING INTO NORTH CENTRAL NORTH DAKOTA. THIS MAY SERVE AS A FOCUS FOR THUNDERSTORM DEVELOPMENT LATER THIS AFTERNOON. WILL CONTINUE TO MONITOR AS TIME PROGRESSES. THE MAIN EVENT IS STILL EXPECTED TO OCCUR TONIGHT. THE MEDIUM RANGE MODELS ARE NOW IN BETTER AGREEMENT WITH RESPECT TO THE PLACEMENT AND TIMING OF POTENTIALLY SEVERE WEATHER. THE LARGE SCALE UPPER LEVEL TROUGH IS PROGGED TO ENTER CENTRAL MONTANA BY 06Z TUESDAY. MODELS ARE PAINTING THE HIGHEST QPF ACROSS NORTHWESTERN NORTH DAKOTA IN THE LFQ OF AN UPPER LEVEL JET STREAK ALONG AN APPROACHING COLD FRONT FROM 00-06Z TUESDAY. THIS ACTIVITY IS THEN EXPECTED TO PUSH INTO THE CENTRAL AND EASTERN PORTIONS OF THE CWA AFTER MIDNIGHT. THE GREATEST POTENTIAL FOR SEVERE WEATHER WILL BE ACROSS THE NORTHERN CWA PROXIMATE TO THE STRONGEST UPPER LEVEL FORCING. FURTHERMORE...PERIODS OF HEAVY RAINFALL ARE ALSO EXPECTED. SINCE STORM MOTIONS SHOULD BE RELATIVELY FAST (RANGE BETWEEN 30-35 KNOTS USING THE 850MB-300MB MEAN WIND AS A PROXY)...DO NOT THINK A FLASH FLOOD WATCH IS WARRANTED AT THIS TIME. THE THUNDERSTORM ACTIVITY IS THEN EXPECTED TO END FROM WEST TO EAST TUESDAY. STRONG GRADIENT FLOW IN THE WAKE OF THE FRONT COMBINED WITH UNSTABLE LOW-LEVEL LAPSE RATES WILL ALLOW FOR WINDY/GUSTY CONDITIONS TO DEVELOP AREAWIDE BY TUESDAY AFTERNOON. IN ADDITION...MUCH DRIER AIR FILTERING INTO THE REGION SHOULD ALLOW FOR DEWPOINTS TO MIX OUT TO UPPER 30S WEST. HOWEVER...STRONG CAA SHOULD KEEP TEMPERATURES WELL BELOW NORMAL ALLOWING FOR RH VALUES TO REMAIN NEAR TO SLIGHTLY BELOW NORMAL TUESDAY AFTERNOON. SURFACE HIGH PRESSURE WILL THEN SLIDE ACROSS SOUTHWESTERN NORTH DAKOTA TUESDAY NIGHT AND BECOME CENTERED OVER SOUTH DAKOTA WEDNESDAY MORNING. THE LIGHT WINDS COMBINED WITH CLEAR SKIES SHOULD ALLOW OVERNIGHT LOWS TO RADIATE TO THE MID/UPPER 40S. A LITTLE HIGHER WINDS NORTH SHOULD KEEP LOWS IN THE LOW/MID 50S NORTH OF I-94. && .LONG TERM...WEDNESDAY THROUGH MONDAY... THE START OF THE LONG TERM PERIOD WILL BEGIN WITH NORTHWEST FLOW ALOFT WEDNESDAY...TRANSITIONING TO ZONAL WEST-TO-EAST FLOW ON THURSDAY. DRY SURFACE HIGH PRESSURE INFLUENCES THE STATE WEDNESDAY...SLIDING SOUTHEAST OF THE STATE WEDNESDAY NIGHT...WITH RETURN SOUTHERLY FLOW WEDNESDAY NIGHT AS LOW PRESSURE DEVELOPS IN THE LEE OF THE ROCKIES. A WEAK LOW PRESSURE TROUGH IS FORECAST TO MOVE EASTWARD ACROSS THE STATE THURSDAY...BUT WITHOUT MUCH FORCING FROM ALOFT...THUS DID NOT INTRODUCE CHANCES OF SHOWERS OR THUNDERSTORMS THURSDAY. MODEL SOLUTIONS DIVERGE FROM THURSDAY AND BEYOND...AND USED THE MORE CONSISTENT EUROPEAN MODEL. ON FRIDAY A LARGE UPPER LEVEL LOW PRESSURE SYSTEM POSITIONED OVER MUCH OF NORTHERN CANADA SWINGS A SHORTWAVE ACROSS SOUTH CENTRAL CANADA AND NORTHERN NORTH DAKOTA FRIDAY. KEPT SLIGHT CHANCE OF THUNDERSTORM MENTION AS PER PREVIOUS FORECAST PACKAGE. THE WEEKEND AND INTO MONDAY KEPT DRY...AS EUROPEAN MODEL INDICATES ZONAL FLOW ALOFT SATURDAY...THEN A BUILDING RIDGE OVER THE WESTERN US/ROCKIES WITH A DRY NORTHWESTERLY FLOW SUNDAY AND MONDAY. TEMPERATURES DURING THE EXTENDED PERIOD ARE FORECAST TO REMAIN NEAR OF SLIGHTLY BELOW AVERAGE FOR MID AUGUST. && .AVIATION...A LOW PRESSURE TROUGH EXTENDED FROM A LOW IN NORTHERN SASKATCHEWAN TO ANOTHER LOW OVER THE BLACK HILLS AREA TO EASTERN COLORADO. A MID-LEVEL CAP WAS KEEPING CONVECTION FROM OCCURRING. EXPECT THAT AS THE TROUGH MOVES EASTWARD INTO WESTERN NORTH DAKOTA LATER THIS AFTERNOON/EVENING...AND AS THE MID-LEVEL CAP WEAKENS TOWARDS SUNSET OR AROUND 00Z-03Z...WILL SEE SCATTERED THUNDERSTORMS OVER KISN/KDIK AND BECOME MORE NUMEROUS AFTER 03Z. THIS ACTIVITY TO SPREAD EAST ACROSS THE STATE TONIGHT TO KMOT/KBIS AROUND 06Z AND TO KJMS AROUND 09-12Z. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && TM...SHORT TERM JV...LONG TERM/AVIATION
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE BISMARCK ND 1014 AM CDT MON AUG 15 2011 NDZ001>005-009>013-017>023-025-031>037-040>048-050-051-161515- DIVIDE-BURKE-RENVILLE-BOTTINEAU-ROLETTE-WILLIAMS-MOUNTRAIL-WARD- MCHENRY-PIERCE-MCKENZIE-DUNN-MERCER-OLIVER-MCLEAN-SHERIDAN-WELLS- FOSTER-GOLDEN VALLEY-BILLINGS-STARK-MORTON-BURLEIGH-KIDDER- STUTSMAN-SLOPE-HETTINGER-GRANT-BOWMAN-ADAMS-SIOUX-EMMONS-LOGAN- LA MOURE-MCINTOSH-DICKEY- 1014 AM CDT MON AUG 15 2011 /914 AM MDT MON AUG 15 2011/ THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL NORTH DAKOTA...NORTHWEST NORTH DAKOTA...SOUTH CENTRAL NORTH DAKOTA...SOUTHEAST NORTH DAKOTA AND SOUTHWEST NORTH DAKOTA. .DAY ONE...TODAY AND TONIGHT CHANCES FOR SEVERE THUNDERSTORMS WILL DEVELOP THIS AFTERNOON...MAINLY OVER WESTERN PORTIONS OF THE STATE. CHANCES FOR THUNDERSTORMS WILL INCREASE TONIGHT OVER ALL OF WEST AND CENTRAL NORTH DAKOTA. STRONG TO SEVERE STORMS ARE LIKELY OVER SOME AREAS. THE MAIN SEVERE WEATHER THREATS WILL BE LARGE HAIL AND STRONG WINDS. ISOLATED TORNADOES WILL BE POSSIBLE AS WELL. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY CHANCES FOR THUNDERSTORMS WILL CONTINUE OVER NORTHWEST AND CENTRAL NORTH DAKOTA TUESDAY MORNING...THEN MAINLY OVER EASTERN NORTH DAKOTA TUESDAY AFTERNOON. A FEW STORMS MAY BE SEVERE. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL LIKELY OCCUR THIS AFTERNOON THROUGH TUESDAY MORNING. TM
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BISMARCK ND
1111 AM CDT MON AUG 15 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0500 AM HAIL 2 NW BEULAH 47.28N 101.81W
08/15/2011 M1.00 INCH MERCER ND CO-OP OBSERVER
SLIGHTLY LARGER THAN QUARTER SIZED HAIL. ESTIMATED WIND
SPEEDS OF 75-80 MPH.
&&
TMPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BISMARCK ND
319 PM CDT MON AUG 15 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1015 PM HEAVY RAIN 13 W HAZELTON 46.48N 100.55W
08/14/2011 M1.90 INCH EMMONS ND MESONET
ALSO PENNY SIZED HAIL
&&
JVININGPRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE BISMARCK ND
455 PM CDT MON AUG 15 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0202 AM HAIL 11 W KEENE 47.94N 103.17W
08/15/2011 M0.88 INCH MCKENZIE ND CO-OP OBSERVER
ARB OBSERVER REPORTED PENNY TO NICKEL SIZE HAIL.
0420 AM HAIL HALLIDAY 47.35N 102.34W
08/15/2011 M0.88 INCH DUNN ND CO-OP OBSERVER
0426 AM HAIL 4 WSW DAKOTA WATERS REC 47.47N 101.87W
08/15/2011 M0.88 INCH MERCER ND COCORAHS
COCORAHS OBSERVER REPORTED DIME TO NICKEL SIZE HAIL.
0456 AM TSTM WND GST 2 ESE HAZEN 47.28N 101.58W
08/15/2011 M64.00 MPH MERCER ND AWOS
MEASURED WIND GUST AT THE HAZEN AIRPORT.
0456 AM TSTM WND GST 3 E HAZEN 47.29N 101.56W
08/15/2011 E60.00 MPH MERCER ND TRAINED SPOTTER
60 MPH GUST WITH PEA SIZED HAIL OBSERVED...
0500 AM HAIL 2 NW BEULAH 47.28N 101.81W
08/15/2011 M1.00 INCH MERCER ND CO-OP OBSERVER
SLIGHTLY LARGER THAN QUARTER SIZED HAIL. ESTIMATED WIND
SPEEDS OF 75-80 MPH.
&&
JTAEGERSPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE BISMARCK ND 455 PM CDT MON AUG 15 2011 NDZ018-019-152300- DUNN-MERCER- 355 PM MDT MON AUG 15 2011 ...SPECIAL WEATHER STATEMENT... AT 352 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A STRONG THUNDERSTORM OVER WEST CENTRAL DUNN COUNTY...MOVING EAST AT 25 MPH. PENNY SIZE HAIL...WINDS GREATER THAN 40 MPH...OCCASIONAL CLOUD TO GROUND LIGHTNING...ARE POSSIBLE WITH THIS STORM. LOCATIONS IMPACTED INCLUDE... MANNING... HIRSCHVILLE... MARSHALL... GUSTY WINDS MAY CAUSE SMALL OBJECTS SUCH AS TRASH BINS TO BLOW AROUND. STAY AWAY FROM HIGH OBJECTS OUTDOORS SUCH AS TREES. SEEK SHELTER IN A STURDY STRUCTURE UNTIL THIS STORM HAS PASSED. TM
The Bismarck radar (KBIS), 154 km away, was scanning. The volume nearest the first event began at 22:06 UTC.
12 hail, 8 thunderstorm wind, 1 heavy rain, 1 flash flood. Local standard time, as filed.
The large hail resulted in broken windows and damage to a vehicle.
Strong winds were reported.
Strong winds were reported.
Pea size hail accompanied the strong winds.
Heavy rain measuring 2.9 inches fell in one hour.
Flooded roads were reported throughout Bismarck with water as much as two feet deep on streets. Water was running over curbs and through yards. Ditches in rural north Bismarck were full to overflowing and threatening homes. Two to three inches of rain fell on Bismarck. Rain at the airport measured 2.48 inches.
Heavy rain accompanied the strong winds.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in North Dakota in 2011Every state in 2011This day in weather historyWarnings in North Dakota, 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: 332596, 332597, 332599, 332600, 332601, 332605, 332602, 332603, 332604, 332608, 332611, 332615, 332591, 332617, 332613, 332620, 332621, 332622, 332594, 332623, 332624, 332626.