Slow moving thunderstorms across extreme northern Converse County produced rainfall estimates of one to three inches in a two-hour period. This heavy rainfall resulted in flash flooding.
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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 CYS wrote it up.
Slow moving thunderstorms across extreme northern Converse County produced rainfall estimates of one to three inches in a two-hour period. This heavy rainfall resulted in flash flooding.
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 Aug 9, 5:41 PM MST, 3 hours 14 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHEYENNE WY 641 PM MDT FRI AUG 9 2013 .SHORT TERM...(THIS EVENING THROUGH SUNDAY) ISSUED AT 150 PM MDT FRI AUG 9 2013 SHOWERS AND THUNDERSTORMS HAVE BEEN DEVELOPING MAINLY OVER THE WEST AND NORTH PARTS OF THE CWA SINCE THE LATE MORNING. THE ACTIVITY SHOULD CONTINUE TO INCREASE IN COVERAGE AND INTENSITY THROUGH THE EARLY EVENING WITH A SOUTHEAST MOVEMENT. A WEAK MID LEVEL CIRCULATION OVER NORTHEAST WYOMING WILL MOVE SLOWLY EAST TONIGHT. A SHORTWAVE TROUGH WAS ALSO LIFTING NORTHEAST INTO THE NORTH PART OF THE CWA AT THAT TIME. PRECIPITABLE WATER VALUES WERE ALSO STILL NEAR AN INCH OVER THE NORTH PART OF THE CWA. SURFACE BOUNDARIES EXIST ALONG THE CONTINENTAL DIVIDE AND THE FAR NORTH PART OF THE CWA. STRONGER STORMS WERE CURRENTLY FORMING ALONG THE BOUNDARY NEAR THE PINE RIDGE. A PERIOD OF HEAVY RAIN... SMALL HAIL AND BRIEF WIND GUSTS TO 50 MPH WILL BE POSSIBLE WITH THE STORMS THROUGH THE EVENING. SOME SHOWERS AND STORMS WILL LINGER FOR MUCH OF TONIGHT OVER THE NORTH PART OF THE CWA. THE ATMOSPHERE CONTINUE TO SLOWLY DRY ON SATURDAY AS HEIGHTS RISE OVER THE CWA AND THE PRECIPITABLE WATER VALUES LOWER A BIT. THE MAIN SURFACE BOUNDARY WILL BE OVER THE NORTHERN PANHANDLE ON SATURDAY...WITH A SOUTH OR SOUTHWEST SURFACE GRADIENT OVER THE REST OF THE CWA. STILL ENOUGH MOISTURE AND INSTABILITY PRESENT SATURDAY AFTERNOON AND EVENING FOR AT LEAST ISOLATED SHOWERS AND STORMS. THE STORMS WILL BE MOST WIDESPREAD NEAR AND NORTH OF THE SURFACE BOUNDARY WITH SOME STRONG STORMS POSSIBLE. A SIMILAR SITUATION WILL EXIST FOR SUNDAY WITH THE FOCUS OF THE STORMS BEING MAINLY OVER THE NORTHEAST PART OF THE CWA. TEMPERATURES WILL WARM SOME OVER THE WEEKEND AS HEIGHTS ALOFT RISE AND 700 MB TEMPERATURES INCREASE SLIGHTLY. .LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY) ISSUED AT 150 PM MDT FRI AUG 9 2013 SUNDAY NIGHT...ISOLATED EVENING THUNDERSTORMS ON TAP ALONG AND EAST OF THE LARAMIE RANGE IN UPSLOPE REGIME WITH A PASSING SHORTWAVE IN NORTHWEST FLOW ALOFT. MONDAY...MONSOONAL MOISTURE IN PLACE ALONG WITH MOIST UPSLOPE LOW LEVEL WIND REGIME WILL AID IN PRODUCTION OF ISOLATED TO SCATTERED THUNDERSTORMS...MOST NUMEROUS EAST OF THE LARAMIE RANGE AND INTERSTATE 25. TUESDAY...MONSOONAL MOISTURE FEED STRETCHES FROM SOUTHEAST WYOMING THROUGH EASTERN COLORADO TO WESTERN KANSAS. EXPECTING SCATTERED THUNDERSTORMS TO ERUPT...FOCUSED ALONG AND NORTH OF AN INVERTED SURFACE TROUGH AXIS FROM DENVER TO NORTH PLATTE...WITH SCATTERED THUNDERSTORMS OVER OUR EASTERN PLAINS AND OVER THE MOUNTAINS. WEDNESDAY...THOUGH LOW LEVEL UPSLOPE REGIME CONTINUES...MONSOONAL MOISTURE FEED NUDGED SOUTH OF OUR COUNTIES...THUS ONLY ISOLATED LATE DAY THUNDERSTORMS EXPECTED...MOST NUMEROUS EAST OF THE MOUNTAINS. THURSDAY...LESS MOISTURE FUEL FOR THUNDERSTORMS IN THE LOW AND MID LEVELS...THUS ONLY ISOLATED THUNDERSTORMS ON PAR EAST OF THE LARAMIE RANGE. FRIDAY...DRY DAY AS MINIMAL LOW AND MID LEVEL MOISTURE PREVAILS WITH INCREASING TEMPERATURES ALOFT DUE TO HEIGHT RISES...PROVIDING INCREASING CONVECTIVE INHIBITION...CIN...TO LIMIT OR SUPPRESS CONVECTIVE INITIATION AND SUSTENANCE. && .AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY AFTERNOON) ISSUED AT 634 PM MDT FRI AUG 9 2013 MAIN CONCERN ONCE AGAIN WILL BE ISOLATED -SHRA/-TSRA THROUGH AROUND 04Z. RADAR RETURNS SHOW DECENT LINE OF SHOWERS AND THUNDERSTORMS EXTENDING ACROSS EAST CENTRAL WYOMING INTO THE NORTHERN NEBRASKA PANHANDLE. SEE THE LOWEST THREAT AT KLAR AND KCYS SO HAVE EXCLUDED THESE FROM ANY VCTS MENTION. OTHERWISE...MAY SEE MVFR CIGS/VSBYS WITH ANY OF THIS ACTIVITY THIS EVENING. ANOTHER ROUND OF AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE AGAIN AFTER 18Z SATURDAY. && .FIRE WEATHER... ISSUED AT 150 PM MDT FRI AUG 9 2013 FIRE WEATHER CONCERNS WILL BE MINIMAL THROUGH THE MID PART OF NEXT WEEK. HIGH PRESSURE IN THE UPPER ATMOSPHERE WILL REMAIN OVER THE ROCKIES DURING THAT TIME AND WILL HELP PRODUCE TEMPERATURES AT OR JUST ABOVE NORMAL. THE ATMOSPHERE WILL SLOWLY DRY THROUGH SUNDAY OVER MUCH OF THE CWA...WITH A STATIONARY FROM ACROSS THE NORTHEAST PART OF THE CWA. THE UPPER LEVEL FLOW WILL ALLOW THE MID AND UPPER LEVEL MOISTURE TO ROTATE OVER THE REGION AT TIMES. THAT WILL HELP TO PRODUCE ISOLATED TO SCATTERED LATE DAY SHOWERS AND THUNDERSTORMS EACH DAY. MINIMUM RELATIVE HUMIDITY VALUES WILL BE AS LOW AS 12 TO 18 PERCENT OVER THE LOWER ELEVATIONS OF CARBON AND ALBANY COUNTIES THROUGH THE MID PART OF NEXT WEEK. WIND GUSTS WILL REMAIN BELOW 20 TO 25 MPH OVER THE CWA DURING THE DAYTIME HOURS. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...NONE. NE...NONE. && SHORT TERM...WEILAND LONG TERM...RUBIN AVIATION...HAHN FIRE WEATHER...WEILAND
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE CHEYENNE WY 743 PM MDT FRI AUG 9 2013 NEZ002-003-095-096-WYZ101>103-106>108-110145- DAWES-BOX BUTTE-NORTH SIOUX-SOUTH SIOUX- CONVERSE COUNTY LOWER ELEVATIONS-NIOBRARA COUNTY- NORTH LARAMIE RANGE- CENTRAL LARAMIE RANGE AND SOUTHWEST PLATTE COUNTY- EAST PLATTE COUNTY-GOSHEN COUNTY- 743 PM MDT FRI AUG 9 2013 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE WESTERN NEBRASKA PANHANDLE AND EAST CENTRAL WYOMING. .DAY ONE...TONIGHT NUMEROUS SHOWERS AND SCATTERED THUNDERSTORMS WILL CONTINUE THIS EVENING...THEN DECREASE IN COVERAGE LATE TONIGHT. THE STRONGER STORMS WILL BE CAPABLE OF PRODUCING SMALL HAIL... GUSTY WINDS TO 40 MPH...AND HEAVY RAIN. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY ISOLATED TO SCATTERED AFTERNOON AND EVENING THUNDERSTORMS WILL BE POSSIBLE THROUGH WEDNESDAY. SEVERE THUNDERSTORMS ARE NOT EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE REQUIRED TONIGHT. && THIS PRODUCT...ALONG WITH OTHER WEATHER...HYDROLOGIC...AND CLIMATE INFORMATION IS AVAILABLE ON THE WEB AT... HTTP://WEATHER.GOV/CHEYENNE NEZ019>021-054-055-WYZ104-105-109>119-110145- SCOTTS BLUFF-BANNER-MORRILL-KIMBALL-CHEYENNE- FERRIS/SEMINOE/SHIRLEY MOUNTAINS-SHIRLEY BASIN- 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- CENTRAL LARAMIE COUNTY-EAST LARAMIE COUNTY- 743 PM MDT FRI AUG 9 2013 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE WESTERN NEBRASKA PANHANDLE...SOUTH CENTRAL WYOMING AND SOUTHEAST WYOMING. .DAY ONE...TONIGHT SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL CONTINUE THIS EVENING...THEN DECREASE IN COVERAGE LATE TONIGHT. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY ISOLATED TO SCATTERED AFTERNOON AND EVENING THUNDERSTORMS WILL BE POSSIBLE THROUGH WEDNESDAY. SEVERE THUNDERSTORMS ARE NOT EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE REQUIRED TONIGHT. && THIS PRODUCT...ALONG WITH OTHER WEATHER...HYDROLOGIC...AND CLIMATE INFORMATION IS AVAILABLE ON THE WEB AT... HTTP://WEATHER.GOV/CHEYENNE JAMSKI
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE CHEYENNE WY
625 PM MDT FRI AUG 9 2013
WYZ101-103-100130-
CONVERSE COUNTY LOWER ELEVATIONS WY-NORTH LARAMIE RANGE WY-
625 PM MDT FRI AUG 9 2013
...SIGNIFICANT WEATHER ADVISORY FOR WESTERN CONVERSE COUNTY UNTIL 730
PM MDT...
AT 623 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM 12 MILES NORTHEAST OF EVANSVILLE...MOVING
SOUTHEAST AT 20 MPH.
HAIL UP TO ONE-HALF INCH IN DIAMETER AND WIND GUSTS UP TO 50 MPH ARE
EXPECTED WITH THIS STORM...ALONG WITH HEAVY RAIN.
LOCATIONS NEAR THE PATH OF THIS STORM INCLUDE...
ROLLING HILLS ESTATES...
GLENROCK...
DEER CREEK...
THIS INCLUDES INTERSTATE 25 IN WYOMING BETWEEN MILE MARKERS 151 AND
175.
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.
&&
LAT...LON 4305 10549 4262 10569 4284 10609 4310 10609
4311 10608
TIME...MOT...LOC 0025Z 296DEG 19KT 4300 10608
HAHNSPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE CHEYENNE WY
652 PM MDT FRI AUG 9 2013
WYZ101-100145-
CONVERSE COUNTY LOWER ELEVATIONS WY-
652 PM MDT FRI AUG 9 2013
...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL CONVERSE COUNTY UNTIL 745
PM MDT...
AT 647 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM 13 MILES NORTHWEST OF ROLLING HILLS ESTATES...OR
19 MILES NORTHEAST OF EVANSVILLE...MOVING EAST AT 15 MPH.
HAIL UP TO THE SIZE OF NICKELS AND WIND GUSTS UP TO 50 MPH ARE
EXPECTED WITH THIS STORM...ALONG WITH HEAVY RAIN.
THIS THUNDERSTORM HAS A HISTORY OF PRODUCING SIGNIFICANT RAINFALL
AND LOCALIZED FLOODING WHEN IT CROSSED INTERSTATE 25 NORTH OF
CASPER.
LOCATIONS NEAR THE PATH OF THIS STORM INCLUDE...
MAINLY RURAL AREAS OF WESTERN CONVERSE 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.
&&
LAT...LON 4287 10540 4296 10608 4310 10609 4315 10609
4328 10540
TIME...MOT...LOC 0051Z 261DEG 17KT 4307 10596
HAHNPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHEYENNE WY
859 PM MDT FRI AUG 09 2013
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0854 PM FLASH FLOOD 21 NNW BILL 43.49N 105.42W
08/09/2013 CONVERSE WY LAW ENFORCEMENT
WATER AND DEBRIS FLOWING OVER HIGHWAY 59 NEAR CAMPBELL
COUNTY LINE. ONE LANE TRAFFIC.
&&
HAHNThe Rapid City radar (KUDX), 219 km away, was scanning. The volume nearest the first event began at 03:53 UTC.
1 flash flood. Local standard time, as filed.
Water and debris were flowing across Highway 59 north of Bill.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2013Every state in 2013This day in weather historyWarnings in Wyoming, August 2013
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: 466641.