Heavy rainfall from thunderstorms caused flash flooding over parts of the southern Laramie Range foothills west of Cheyenne.
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The episode as NWS CYS wrote it up.
Heavy rainfall from thunderstorms caused flash flooding over parts of the southern Laramie Range foothills west of Cheyenne.
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 Sep 13, 6:27 PM MST, 1 hour 3 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHEYENNE WY 727 PM MDT FRI SEP 13 2013 .UPDATE... ISSUED AT 720 PM MDT FRI SEP 13 2013 AREA OBSERVATIONS ACROSS THE SOUTHERN PANHANDLE AND ALONG THE INTERSTATE 80 CORRIDOR TO THE I-80 SUMMIT STILL REPORT AREAS OF FOG REDUCED TO A MILE OR LESS. WENT AHEAD AND ADDED FOG INTO THE FORECAST FOR THIS EVENING. UPDATES HAVE BEEN SENT. DO BELIEVE OUR WINDS HERE AT CHEYENNE WILL SWITCH MORE WESTERLY AFTER MIDNIGHT THAT COULD MITIGATE THE FOG. SO HAVE THE DENSER FOG THIS EVENING WITH THE UPSLOPING SOUTHEASTERLY WINDS. && .SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT) ISSUED AT 245 PM MDT FRI SEP 13 2013 CURRENT KCYS RADAR LOOP AND SATELLITE IMAGERY SHOWS THE UPPER LEVEL SHORTWAVE DISTURBANCE LIFTING NORTH ACROSS SOUTHEAST WYOMING EARLY THIS AFTERNOON. THE BACK EDGE OF THE PRECIPITATION EXTENDING FROM THE NORTHERN LARAMIE RANGE SOUTHEAST TO CHEYENNE MARKS THE APPROXIMATE POSITION OF THE AXIS OF THE SHORTWAVE TROUGH AT 130 LOCAL TIME. THIS WILL CONTINUE LIFTING NORTH AND EAST WITH PARTLY SUNNY SKIES EXPECTED NEAR THE COLORADO BORDER FOR THE MIDDLE OF THE AFTERNOON AS SHOWN BY VISIBLE SATELLITE. THE ONLY MINOR CONCERN THIS AFTERNOON IS SHOWER AND TSTORM DEVELOPMENT DUE TO LLVL INSTABILITY AND AMPLE MOISTURE. BUT WITH MIDLEVEL SUBSIDENCE OVERHEAD AFTER THE SHORTWAVE PUSHES NORTH...DO NOT EXPECT MUCH OF A HEAVY RAIN AND FLOODING THREAT ACROSS SOUTHEAST WYOMING. A WEAK ELONGATED UPPER LEVEL TROUGH WILL ENTER THE CWA ON SATURDAY. THIS FEATURE IS ACTUALLY THE REMNANTS OF THE MAIN UPPER LEVEL LOW OVER THE GREAT BASIN REGION THIS LAST WEEK...WHICH IS RESPONSIBLE FOR THE FLOODING ACROSS THE ROCKYS AND THE SOUTHWEST UNITED STATES. IN ADDITION...A COOL FRONT WILL MOVE ACROSS EASTERN WYOMING AND NEBRASKA SATURDAY AFTERNOON. UPSLOPE FLOW COMBINED WITH THE ADDED INSTABILITY AND MOISTURE WILL RESULT IN ANOTHER ROUND OF SHOWERS AND ISOLATED TSTORMS...BUT THIS TIME THEY WILL NOT BE QUITE AS WIDESPREAD. PW/S WILL BE SLIGHTLY LOWER SATURDAY COMPARED TO THE LAST WEEK...BUT STILL REMAIN ABOVE NORMAL WITH VALUES AROUND 1 TO 1.25 INCHES. SOME OF THE THUNDERSTORMS WILL PRODUCE VERY HEAVY RAIN CAPE BETWEEN 500 TO 1000 J/KG DURING THE AFTERNOON. CAN NOT RULE OUT SOME FLASH FLOODING ASSOCIATED WITH THE THUNDERSTORM ACTIVITY SATURDAY AND SATURDAY NIGHT DUE TO VERY SATURATED GROUND CONDITIONS WITH ANY ADDITIONAL RAINFALL BECOMING MAINLY RUNOFF. THIS FLASH FLOOD THREAT WILL MAINLY BE ALONG AND WEST OF THE LARAMIE RANGE IN THE MOUNTAINS. HIGH TEMPERATURES WILL REBOUND INTO THE 70S TO LOW 80S ACROSS THE HIGH PLAINS...WITH HIGHS AROUND 70 WEST OF THE LARAMIE RANGE. FOR SATURDAY NIGHT AND SUNDAY...MODELS SHOW THE FRONT STALLING ALONG THE ROCKY MOUNTAINS AND INTERACTING WITH THE REMNANT UPPER LEVEL TROUGH MOVING INTO WESTERN WYOMING AND COLORADO. MODELS INDICATE VERY HEAVY RAIN FROM THE SNOWY AND SIERRA MADRE RANGES SOUTHWARD INTO THE FOOT HILLS OF NORTHERN COLORADO...EXACTLY WHERE THEY DO NOT NEED THE ADDITIONAL RAIN. PREVIOUS MODEL RUNS HAVE NOT SHOWN THIS AREA OF PRECIPITATION...SO CONFIDENCE IS LOW AT THIS TIME. WILL MONITOR THE DEVELOPMENT OF THIS IN CASE FLASH FLOODING IS POSSIBLE. OTHERWISE...SUNDAY WILL BE ANOTHER COOL DAY BEHIND THE COOL FRONT WITH TEMPERATURES RETURNING TO THE UPPER 50S TO UPPER 60S. IT WILL BE MORE STABLE ON SUNDAY...SO DO NOT EXPECTED HEAVY RAINFALL. LIGHT RAIN OR DRIZZLE APPEARS LIKELY ALONG AND WEST OF THE LARAMIE RANGE THROUGH SUNDAY AFTERNOON...ENDING SUNDAY EVENING. .LONG TERM...(MONDAY THROUGH FRIDAY) ISSUED AT 245 PM MDT FRI SEP 13 2013 UPPER TROF WILL PASS ACROSS THE CWA MONDAY AND MAY SET OFF A BIT OF CONVECTION NEAR A SFC TROF THAT SHOULD BE JUST EAST OF THE MTNS. THIS TROF WILL THEN MOVE EAST INTO THE PLAINS MONDAY NIGHT LEAVING A DRIER DOWNSLOPE FLOW ACROSS THE CWA. TUESDAY THROUGH FRIDAY LOOKING MAINLY DRY WITH TEMPERATURES RETURNING TO ABOVE SEASONAL AVERAGES. NEXT UPPER SHORTWAVE WILL EJECT OVER THE NORTHERN AND CENTRAL ROCKYS WEDS AND SHOULD PUSH A WEAK PACIFIC FRONT ACROSS THE CWA. THIS WILL RESULT IN SOME MINOR COOLING FOR THURSDAY AND FRIDAY WITH OTHERWISE DRY CONDITIONS. && .AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY AFTERNOON) ISSUED AT 641 PM MDT FRI SEP 13 2013 WIDESPREAD IFR/LIFR CONDITIONS ACROSS SOUTHEAST WYOMING AND SOUTHERN PANHANDLE IN SOUTHEAST UPSLOPING WINDS. LOOKS LIKE WE KEEP THE UPSLOPING WINDS THROUGH THE OVERNIGHT HOURS BEFORE THEY BECOME MORE WESTERLY TOWARDS 12Z. SHOWERS AND THUNDERSTORMS RETURN SATURDAY AFTERNOON AS THE UPPER LEVEL LOW CURRENTLY OVER UTAH BEGINS TO OPEN UP AND TRACK THROUGH THE STATE. && .FIRE WEATHER... ISSUED AT 245 PM MDT FRI SEP 13 2013 NO FIRE WEATHER CONCERNS OVER THE NEXT WEEK WITH WIDESPREAD WETTING RAINS OVER THE LAST 5 DAYS. A DRYING TREND WILL BEGIN THIS WEEKEND AND INTO EARLY NEXT WEEK WITH DAYTIME MINIMUM HUMIDITIES LOWERING BETWEEN 25 TO 40 PERCENT. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...NONE. NE...NONE. && UPDATE...CLAYCOMB SHORT TERM...TJT LONG TERM...RE AVIATION...CLAYCOMB FIRE WEATHER...TJT
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE CHEYENNE WY 711 PM MDT FRI SEP 13 2013 NEZ054-055-WYZ117>119-150115- KIMBALL-CHEYENNE-SOUTH LARAMIE RANGE FOOTHILLS- CENTRAL LARAMIE COUNTY-EAST LARAMIE COUNTY- 711 PM MDT FRI SEP 13 2013 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE WESTERN NEBRASKA PANHANDLE AND SOUTHEAST WYOMING. .DAY ONE...TONIGHT SOUTHEAST UPSLOPING WINDS WILL BRING VERY LOW CLOUDS AND AREAS OF DENSE FOG TO THE INTERSTATE 80 CORRIDOR FROM LODGE POLE NEBRASKA TO THE INTERSTATE 80 SUMMIT BETWEEN CHEYENNE AND LARAMIE. VISIBILITIES COULD BE REDUCED TO LESS THAN A HALF MILE IN FOG AT TIMES THROUGH THE EVENING HOURS. ADDITIONALLY...SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL CONTINUE THIS EVENING OVER THE INTERSTATE 80 SUMMIT AND THEN MOVE NORTHEAST ACROSS LARAMIE COUNTY. VERY HEAVY RAINFALL WITH LOCALIZED FLOODING IS POSSIBLE THROUGH MIDNIGHT TONIGHT. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL BE POSSIBLE THROUGH SUNDAY. SEVERE STORMS ARE NOT EXPECTED...HOWEVER BRIEF MODERATE TO HEAVY RAIN WILL BE POSSIBLE. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE REQUIRED THROUGH TONIGHT. && THIS PRODUCT...ALONG WITH OTHER WEATHER...HYDROLOGIC...AND CLIMATE INFORMATION IS AVAILABLE ON THE WEB AT... HTTP://WEATHER.GOV/CHEYENNE NEZ002-003-019>021-095-096-WYZ101>116-150115- DAWES-BOX BUTTE-SCOTTS BLUFF-BANNER-MORRILL-NORTH SIOUX- SOUTH SIOUX-CONVERSE COUNTY LOWER ELEVATIONS-NIOBRARA COUNTY- NORTH LARAMIE RANGE-FERRIS/SEMINOE/SHIRLEY MOUNTAINS- SHIRLEY BASIN-CENTRAL LARAMIE RANGE AND SOUTHWEST PLATTE COUNTY- EAST PLATTE COUNTY-GOSHEN 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- 711 PM MDT FRI SEP 13 2013 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE WESTERN NEBRASKA PANHANDLE...EAST CENTRAL WYOMING...SOUTH CENTRAL WYOMING AND SOUTHEAST WYOMING. .DAY ONE...TONIGHT NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL BE POSSIBLE THROUGH SUNDAY. SEVERE STORMS ARE NOT EXPECTED...HOWEVER MODERATE TO HEAVY RAIN WILL BE POSSIBLE. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE REQUIRED THROUGH TONIGHT. && THIS PRODUCT...ALONG WITH OTHER WEATHER...HYDROLOGIC...AND CLIMATE INFORMATION IS AVAILABLE ON THE WEB AT... HTTP://WEATHER.GOV/CHEYENNE
The Cheyenne radar (KCYS), 7 km away, was scanning. The volume nearest the first event began at 02:28 UTC.
1 flash flood. Local standard time, as filed.
Two to four inches of rain in a two-hour period caused flash flooding west of Cheyenne and Warren AFB. Roads that were impassable from high water included Roundtop, Otto and Happy Jack. There was considerable ponding of water on Interstate 80 between mile markers 348 and 358.
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, September 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: 469309.