Isolated severe thunderstorms developed during the afternoon and produced a few reports of wind and hail in Niobrara County.
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 CYS wrote it up.
Isolated severe thunderstorms developed during the afternoon and produced a few reports of wind and hail in Niobrara County.
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 Cheyenne, WY wrote its last area forecast discussion before the first event at Jul 11, 2:03 PM MST, 18 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHEYENNE WY 303 PM MDT MON JUL 11 2011 .SHORT TERM...TONIGHT THROUGH WEDNESDAY TODAY IS SHAPING UP TO BE A VERY ACTIVE DAY ACROSS THE FORECAST AREA. THUNDERSTORMS ARE BECOMING QUITE NUMEROUS WITH THE ENVIRONMENT BECOMING MORE AND MORE FAVORABLE FOR SEVERE THUNDERSTORMS. SFC OBS SHOW A PLUME OF SFC MOISTURE NOSING ITS WAY INTO THE PANHANDLE AND EAST CENTRAL WYOMING. CHADRON DEW POINT OF UPPER 60S PAINTS THE PICTURE OF A VERY JUICY AIRMASS IN THE NORTHERN PANHANDLE REGION. ERRANT CLOUD COVER ACROSS THE AREA IS KEEPING THINGS CAPPED EARLY ON...BUT STORMS ARE FIRING IN SIOUX COUNTY SO CAP LOOKS TO BE WEAKENING. BULK SHEAR INCREASING TO 35 TO 50 KT FROM SOUTH TO NORTH WILL HELP ORGANIZE THESE STORMS WITH SOME BECOMING SUPERCELLULAR. NAM FORECASTED 0 TO 1 KM HELICITY ALONG WITH HODOGRAPHS ACROSS NIOBRARA COUNTY AND INTO THE NORTHERN NEBRASKA PANHANDLE SUPPORT THE IDEA THAT AN ISOLATED TORNADO IS NOT OUT OF THE QUESTION IN THIS AREA AS WELL. MODELS ARE CONSISTENT WITH PRODUCING A LOT OF QPF OUT OF THESE STORMS...SO LOCALIZED FLASH FLOODING MAY BECOME AN ISSUE FOR ANY SLOW MOVING STORMS. BUT IN GENERAL THINK THAT THE THREAT WILL BE MINIMIZED DUE TO FASTER GENERAL STORM MOTIONS TO THE NORTHEAST...IN ADDITION TO FAIRLY DRY ANTECEDENT CONDITIONS. THE FOCUS FOR THE HEAVIEST RAIN WILL BE EAST OF A LINE FROM BILL TO CHEYENNE. WEAK ENERGY ALOFT AND STRONG UPSLOPE FLOW IN THE LOW LEVELS WILL MAINTAIN CHANCES FOR SHOWERS AND ISOLATED THUNDERSTORMS THROUGH THE NIGHT ACROSS THE EASTERN ZONES...AS WELL AS THE HIGH COUNTRY. IN BETWEEN STORMS OUT EAST...VERY MOIST AIRMASS WILL LIKELY ALLOW FOR PATCHY FOG TO DEVELOP ACROSS THE EASTERN ZONES AS WELL. PATTERN REMAINS VERY SIMILAR FOR TUESDAY...EXCEPT THE UPPER JET WILL SHIFT FURTHER NORTH SO WILL LOSE SOME OVERALL SHEAR. A DISTURBANCE ALOFT WILL MOVE ACROSS WYOMING IN THE AFTERNOON...AND WITH CONTINUED MOIST SOUTHEASTERLY FLOW AT THE SFC...DEEP LAYER MOISTURE WILL ADVECT FURTHER WEST TOWARD THE LARAMIE RANGE. THUS WILL SEE A SHIFT OF STORM INITIATION OVER THE LARAMIE RANGE...WITH AGAIN VERY HEAVY RAIN EXPECTED OUT OF THESE THUNDERSTORMS. WILL WAIT UNTIL AFTER TODAY'S EVENT TO DIAGNOSE THE MAIN AREA FOR FLASH FLOOD THREAT AS TOMORROWS HEAVIEST RAINFALL MAY AGAIN FALL OVER FAIRLY UNSATURATED SOILS. AGAIN EXPECT MUCH OF THE ACTIVITY TO PERSIST THROUGH THE NIGHT WITH PATCHY FOG LIKELY IN BETWEEN STORMS. WEDNESDAY LOOKS TO BEGIN A DRYING TREND AS THE UPPER LEVEL RIDGE AMPLIFIES AND SHIFTS THE TRACK OF SHORTWAVES TO THE WEST. THE LEE TROUGH WILL BEGIN TO SHIFT EAST AS WELL...THUS REINTRODUCING DRIER AIR AT THE SURFACE INTO THE PLAINS. TEMPERATURES WILL ALSO BE WARMER ON WEDNESDAY. .LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY THE 12Z NUMERICAL MODEL GUIDANCE OFFERED LITTLE CHANGE FROM THE 00Z AND 06Z RUNS. THEREFORE...WILL NOT MAKE ANY WHOLESALE CHANGES TO THE EXTENDED PERIOD GRIDS. THE MAIN UPPER LEVEL FEATURES DURING THE MEDIUM RANGE WILL BE A RIDGE OVER THE PLAINS AND TROUGHS OVER THE WEST AND NORTHEAST CONUS. THE UPPER RIDGE IS PROGGED TO BUILD NORTHWARD INTO THE CENTRAL PLAINS LATER THIS WEEK INTO THE UPCOMING WEEKEND. 700 MB TEMPERATURES WILL REMAIN ABOVE 12C...WITH THE WARMEST TEMPERATURES (16 TO 18C) FROM FRIDAY THROUGH SUNDAY. EXPECT HIGHS IN THE UPPER 80S TO MIDDLE 90S EAST OF THE LARAMIE RANGE...AND 70S TO MIDDLE 80S TO THE WEST. A SURFACE LOW PRESSURE TROUGH ALONG THE LARAMIE RANGE WILL GRADUALLY DRIFT EAST ACROSS THE EASTERN FORECAST AREA THROUGH THE WEEKEND. AFTER A WET FIRST HALF OF THE WEEK...PRECIPITABLE WATER VALUES WILL LOWER TO BETWEEN ONE HALF INCH AND ONE INCH. THE MID AND UPPER LEVEL MOISTURE PLUME WILL ALSO SHIFT TO THE SOUTHEAST THURSDAY THROUGH MONDAY. THERE REMAIN SUBTLE DIFFERENCES WITH THE POSITION OF THE SUBTROPICAL MOISTURE...WITH THE ECMWF FARTHER WEST THAN THE GFS. BASICALLY TRENDED TOWARD A ECMWF/GFS COMPROMISE WITH WIDELY SCATTERED MAINLY AFTERNOON AND EVENING THUNDERSTORMS OVER SOUTHERN AND EASTERN PORTIONS OF THE CWA EACH DAY. WITH LESS MOISTURE ALOFT TO WORK WITH...LIGHTER RAINFALL AMOUNTS ARE EXPECTED. GUSTY SOUTHWEST WINDS WILL PRIMARILY AFFECT AREAS WEST OF THE LARAMIE RANGE EACH AFTERNOON. && .AVIATION...18Z TAF ISSUANCE SHOWERS AND SCATTERED TSTORMS WILL CONTINUE TO DEVELOP AND MOVE NORTHEAST ACROSS THE AREA THROUGH THIS EVENING. BRIEF PERIODS OF MVFR VISIBILITY IN LOCALLY HEAVY RAIN ALONG WITH VARIABLE WIND GUSTS TO 40 KT ARE EXPECTED WITH THE TSTORMS. OTHERWISE VFR OUTSIDE OF THE CONVECTION WITH PREVAILING SOUTHERLY WINDS AROUND 10 KNOTS. UPSLOPE LOW LEVEL FLOW AND MOISTURE FROM RAINFALL WILL LIKELY LEAD TO MVFR VISIBILITY IN PATCHY FOG AND IFR CEILINGS FOR AREAS EAST OF THE LARAMIE RANGE...ESPECIALLY IN THE NEBRASKA PANHANDLE FROM LATE TONIGHT THROUGH MID MORNING TUESDAY. MVFR CEILINGS WILL LIKELY LINGER THROUGH MIDDAY FOR THE PANHANDLE TERMINALS. && .FIRE WEATHER... MINIMAL FIRE WEATHER CONCERNS ANTICIPATED THROUGH THE EARLY PART OF THIS WEEK. DECENT CHANCES FOR MAINLY AFTERNOON AND NIGHTTIME SHOWERS AND THUNDERSTORMS WILL CONTINUE THROUGH WEDNESDAY AS MONSOONAL MOISTURE CONTINUES TO RIDE OVER THE REGION. A WARMER AND DRIER PATTERN WITH BREEZY SOUTHWEST WINDS WEST OF THE LARAMIE RANGE WILL BEGIN THURSDAY AS THE UPPER LEVEL RIDGE BUILDS ACROSS THE CENTRAL PLAINS. && .HYDROLOGY... CANCELLED THE FLOOD WARNING FOR THE UPPER NORTH PLATTE RIVER NEAR SINCLAIR AS THE RIVER HAS FALLEN JUST BELOW FLOOD STAGE...AND WILL CONTINUE SLOWLY FALLING THIS WEEK. FLOOD WARNINGS REMAIN IN EFFECT FOR THE UPPER NORTH PLATTE AT SARATOGA THROUGH TUESDAY AFTERNOON ...AND LARAMIE RIVER AT LARAMIE THROUGH THIS EVENING. THE GENERAL TREND ON ALL RIVERS AND STREAMS IN THE CWA WILL BE SLOWLY FALLING WATER LEVELS THROUGH THIS WEEKEND. MONSOONAL MOISTURE WILL CONTINUE TO RESULT IN AFTERNOON AND EVENING THUNDERSTORMS THROUGH TUESDAY. THE ACTIVITY WILL BE LESS WIDESPREAD AND PRODUCE LIGHTER RAINFALL AMOUNTS OVER THE SOUTHEAST HALF OF THE CWA WEDNESDAY THROUGH THE WEEKEND. SOME OF THE STORMS WILL PRODUCE HEAVY RAINFALL TODAY AND TUESDAY AND MAY PRODUCE BRIEF RISES IN AREA RIVERS. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...NONE. NE...NONE. && SHORT TERM/FIRE WEATHER...RJM LONG TERM/AVIATION/HYDROLOGY...JAMSKI
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE CHEYENNE WY 1116 AM MDT MON JUL 11 2011 NEZ002-003-019>021-054-055-095-096-WYZ101-102-107-108-118-119- 121715- DAWES-BOX BUTTE-SCOTTS BLUFF-BANNER-MORRILL-KIMBALL-CHEYENNE- NORTH SIOUX-SOUTH SIOUX-CONVERSE COUNTY LOWER ELEVATIONS- NIOBRARA COUNTY-EAST PLATTE COUNTY-GOSHEN COUNTY- CENTRAL LARAMIE COUNTY-EAST LARAMIE COUNTY- 1116 AM MDT MON JUL 11 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE WESTERN NEBRASKA PANHANDLE...SOUTHEAST WYOMING. .DAY ONE...THIS AFTERNOON AND TONIGHT SCATTERED TO NUMEROUS THUNDERSTORMS WILL BE OVER SOUTHEAST WYOMING AND THE WESTERN NEBRASKA PANHANDLE BETWEEN 2 PM AND 8 PM. SOME OF THESE STORMS COULD BECOME SEVERE WITH LARGE HAIL AND DAMAGING WINDS THE MAIN THREAT. AN ISOLATED TORNADO IS POSSIBLE ACROSS PORTIONS OF THE NORTHERN AND EASTERN AREAS...INCLUDING NIOBRARA COUNTY IN WYOMING AND THE NORTHERN HALF OF THE NEBRASKA PANHANDLE. HEAVY RAINFALL UP TO THREE-QUARTERS OF AN INCH ARE POSSIBLE WITH THESE STORMS AS WELL. AREAS OF FOG WILL FORM AFTER MIDNIGHT MAINLY OVER THE PANHANDLE WITH VISIBILITIES REDUCED TO BETWEEN 1 AND 2 MILES .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY AREAS OF FOG WILL PERSIST THROUGH MID MORNING TUESDAY OVER THE PANHANDLE. OTHERWISE...THUNDERSTORMS WILL BE LIKELY TUESDAY AFTERNOON AND EVENING. SOME OF THE STORMS WILL PRODUCE HEAVY RAIN...HAIL AND STRONG WIND GUSTS. .SPOTTER INFORMATION STATEMENT...SPOTTER ACTIVATION WILL LIKELY BE NEEDED THIS AFTERNOON AND EVENING FOR THE AREA. && THIS PRODUCT...ALONG WITH OTHER WEATHER...HYDROLOGIC...AND CLIMATE INFORMATION IS AVAILABLE ON THE WEB AT... HTTP://WEATHER.GOV/CHEYENNE WYZ103>106-109>117-121715- NORTH LARAMIE RANGE-FERRIS/SEMINOE/SHIRLEY MOUNTAINS- SHIRLEY BASIN-CENTRAL LARAMIE RANGE AND SOUTHWEST PLATTE COUNTY- CENTRAL CARBON COUNTY-NORTH SNOWY RANGE FOOTHILLS- SOUTHWEST CARBON COUNTY-SIERRA MADRE RANGE- UPPER NORTH PLATTE RIVER BASIN-SNOWY RANGE-LARAMIE VALLEY- SOUTH LARAMIE RANGE-SOUTH LARAMIE RANGE FOOTHILLS- 1116 AM MDT MON JUL 11 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR EAST CENTRAL WYOMING... SOUTH CENTRAL WYOMING AND SOUTHEAST WYOMING. .DAY ONE...THIS AFTERNOON AND TONIGHT A SCATTERED COVERAGE OF THUNDERSTORMS WILL BE OVER THE HIGH COUNTRY THIS AFTERNOON. THE ACTIVITY WILL MOVE TO THE NORTHEAST THROUGH 8PM. THE STRONGER STORMS WILL PRODUCE SMALL HAIL...WIND GUSTS TO 45 MPH AND A PERIOD OF HEAVY RAINFALL. MANY LOCATIONS WILL RECEIVE BETWEEN ONE TENTH AND ONE THIRD OF AN INCH OF RAINFALL. MINOR FLOODING WILL CONTINUE TODAY AND TONIGHT ON THE UPPER NORTH PLATTE RIVER AT SARATOGA AND THE LARAMIE RIVER AT LARAMIE. THESE LOCATIONS SHOULD FALL BELOW FLOOD STAGE LATE TONIGHT OR TOMORROW. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY THUNDERSTORMS WILL BE LIKELY TUESDAY AFTERNOON AND EVENING. SOME OF THE STORMS WILL PRODUCE HEAVY RAIN...HAIL AND STRONG WIND GUSTS. ISOLATED WEAKER LATE DAY THUNDERSTORMS WILL AFFECT THE REGION WEDNESDAY THROUGH SUNDAY. VERY WARM AND DRY CONDITIONS AND GUSTY DAYTIME SOUTHWEST WINDS WILL HEIGHTEN FIRE WEATHER CONCERNS OVER THE LOWER ELEVATIONS THURSDAY THROUGH SUNDAY. .SPOTTER INFORMATION STATEMENT...SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND EVENING. && THIS PRODUCT...ALONG WITH OTHER WEATHER...HYDROLOGIC...AND CLIMATE INFORMATION IS AVAILABLE ON THE WEB AT... HTTP://WEATHER.GOV/CHEYENNE
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE CHEYENNE WY 131 PM MDT MON JUL 11 2011 WYZ101-102-112030- CONVERSE COUNTY LOWER ELEVATIONS WY-NIOBRARA COUNTY WY- 131 PM MDT MON JUL 11 2011 ...SIGNIFICANT WEATHER ADVISORY FOR EXTREME NORTHEASTERN CONVERSE AND NORTHWESTERN NIOBRARA COUNTIES UNTIL 230 PM MDT... AT 128 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM NEAR DULL RESERVOIR...OR 49 MILES NORTHWEST OF LUSK...MOVING EAST AT 25 MPH. HAIL UP TO THE SIZE OF PENNIES AND WIND GUSTS UP TO 50 MPH ARE EXPECTED WITH THIS STORM...ALONG WITH HEAVY RAIN. LOCATIONS NEAR THE PATH OF THIS STORM INCLUDE... MAINLY RURAL AREAS OF NORTHERN NIOBRARA COUNTY. TORRENTIAL RAIN...WHICH MAY FLOOD LOW LYING AREAS SUCH AS DITCHES AND UNDERPASSES...IS ALSO LIKELY. DO NOT DRIVE YOUR VEHICLE ON A FLOODED ROADWAY. MAZUR
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE CHEYENNE WY 145 PM MDT MON JUL 11 2011 NEZ019-020-WYZ108-112045- BANNER NE-GOSHEN COUNTY WY-SCOTTS BLUFF NE- 145 PM MDT MON JUL 11 2011 ...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN GOSHEN... SOUTHWESTERN SCOTTS BLUFF AND NORTHWESTERN BANNER COUNTIES UNTIL 245 PM MDT... AT 142 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM NEAR HAWK SPRINGS RECREATION AREA...OR 26 MILES SOUTH OF TORRINGTON...MOVING EAST AT 10 MPH. HAIL UP TO THE SIZE OF PENNIES AND WIND GUSTS UP TO 50 MPH ARE EXPECTED WITH THIS STORM...ALONG WITH HEAVY RAIN. LOCATIONS NEAR THE PATH OF THIS STORM INCLUDE... STEGALL... TORRENTIAL RAIN...WHICH MAY FLOOD LOW LYING AREAS SUCH AS DITCHES AND UNDERPASSES...IS ALSO LIKELY. DO NOT DRIVE YOUR VEHICLE ON A FLOODED ROADWAY. MAZUR
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHEYENNE WY
206 PM MDT MON JUL 11 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0204 PM HAIL 8 NNE BURNS 41.30N 104.30W
07/11/2011 E0.25 INCH LARAMIE WY TRAINED SPOTTER
&&
BCHAPMANPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHEYENNE WY
210 PM MDT MON JUL 11 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0208 PM TSTM WND GST 17 S MORRILL 41.72N 103.92W
07/11/2011 E60 MPH SCOTTS BLUFF NE TRAINED SPOTTER
OBSVR STATED 60 PLUS MPH.
&&
BCHAPMANSPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE CHEYENNE WY 231 PM MDT MON JUL 11 2011 WYZ102-112130- NIOBRARA COUNTY WY- 231 PM MDT MON JUL 11 2011 ...SIGNIFICANT WEATHER ADVISORY FOR NORTHERN NIOBRARA COUNTY UNTIL 330 PM MDT... AT 228 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM 11 MILES NORTHEAST OF MIDDLE CREEK RESERVOIR...OR 43 MILES NORTH OF LUSK...MOVING EAST AT 15 MPH. HAIL UP TO THE SIZE OF PENNIES AND WIND GUSTS UP TO 50 MPH ARE EXPECTED WITH THIS STORM...ALONG WITH HEAVY RAIN. LOCATIONS NEAR THE PATH OF THIS STORM INCLUDE... MAINLY RURAL AREAS OF NORTHERN NIOBRARA COUNTY. THIS STORM MAY INTENSIFY...SO BE CERTAIN TO MONITOR LOCAL RADIO AND TV STATIONS...AS WELL AS LOCAL CABLE TV OUTLETS... FOR ADDITIONAL INFORMATION AND POSSIBLE WARNINGS FROM THE NATIONAL WEATHER SERVICE. TORRENTIAL RAIN...WHICH MAY FLOOD LOW LYING AREAS SUCH AS DITCHES AND UNDERPASSES...IS ALSO LIKELY. DO NOT DRIVE YOUR VEHICLE ON A FLOODED ROADWAY. CLAYCOMB
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE CHEYENNE WY 312 PM MDT MON JUL 11 2011 NEZ002-095-112215- DAWES NE-NORTH SIOUX NE- 312 PM MDT MON JUL 11 2011 ...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN SIOUX AND NORTHERN DAWES COUNTIES UNTIL 415 PM MDT... AT 309 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM 9 MILES NORTH OF CRAWFORD...OR 24 MILES WEST OF CHADRON...MOVING NORTHEAST AT 15 MPH. HAIL UP TO ONE-HALF INCH IN DIAMETER AND WIND GUSTS UP TO 50 MPH ARE EXPECTED WITH THIS STORM. LOCATIONS NEAR THE PATH OF THIS STORM INCLUDE... WHITNEY LAKE... CHADRON AIRPORT... WHITNEY... DAUGHERTY
The Rapid City radar (KUDX), 180 km away, was scanning. The volume nearest the first event began at 21:21 UTC.
2 thunderstorm wind, 2 hail. Local standard time, as filed.
Estimated winds of 50 to 60 mph, along with very heavy rain and dime size hail.
Estimated winds of 50 to 60 mph.
Trees were stripped of their bark and leaves within a one-mile swath near the junction of Highways 85 and 270. The ground was covered with hail.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2011Every state in 2011This day in weather historyWarnings in Wyoming, July 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: 312681, 312682, 312683, 312684.