Heavy rain produced flash flooding in and near the Front Range Foothills. In central Larimer County, heavy rain from nearly stationary thunderstorms caused flash flooding in the High Park burn scar.
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 BOU wrote it up.
Heavy rain produced flash flooding in and near the Front Range Foothills. In central Larimer County, heavy rain from nearly stationary thunderstorms caused flash flooding in the High Park burn scar. The heavy rain caused debris flows of rock, mud and ash onto the roadway, which forced the closure of State Highway 14, between Stove Praire and Ted's Place. Rist Canyon was also closed briefly near Stove Praire. The mudslides ranged in depth from 1 to 3 feet. The more significant debris was reported on the Hewlett side of High Park. The heavy rain also flooded numerous basements across Larimer County. In a neighborhood west of Horsetooth Reservoir, water created a debris dam in a drainage area, which backed into a nearby garage, basement and crawlspace. In Wellington, some basements were extensively flooded; one was filled with 8 feet of brown, muddy water.
In Boulder County, heavy rainfall caused flooding problems near Jamestown. James Canyon Drive was closed after heavy rain washed out a section of the roadway. Heavy rain washed out a section of Magnolia Road, east-southeast of Nederland. Nearby, a trained spotter 4 miles east-northeast of Nederland, measured 2.20 inches of rainfall. Flash flooding was also reported in the Fourmile burn area along Summerville Road. In Dacono, in southern Weld County, the Colorado Department of Transportation used snowplows to clear standing water, up to 6 inches deep, from a section of Interstate 25. The interstate was closed in both directions for nearly two hours. South of the Denver area, in central Douglas County, flash flooding was reported near Perry Park, where 2.5 inches of rain fell in one hour.
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 Denver/Boulder, CO wrote its last area forecast discussion before the first event at Jul 7, 2:07 PM MST, 1 hour 29 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DENVER CO 307 PM MDT SAT JUL 7 2012 .SHORT TERM...A MOIST AND UNSTABLE AIRMASS WILL REMAIN IN PLACE THROUGH SUNDAY. CLOUD COVER AND A COOLER AIRMASS HAS SLOWED THE DEVELOPMENT OF THUNDERSTORMS ACROSS THE CWFA THIS AFTN...BUT COVERAGE IS INCREASING IN THE MOUNTAINS AND ALONG THE PALMER DIVIDE. THE HRRR...AS WELL AS THE REST OF THE FCST MDLS CONTINUE TO DEVELOP PRECIPITATION ACROSS THE REGION TONIGHT. SURFACE BASED CAPES THIS AFTERNOON IN THE 1000-1500 J/KG RANGE WITH PRECIPITABLE WATER VALUES WELL OVER ONE INCH. IN ADDITION...THE STORM MOTIONS ARE PROGGED TO REMAIN LESS THAN 10 KTS. THE STORMS WILL GENERALLY MOVE IN A NORTH TO NORTHEAST DIRECTION. WILL CONTINUE WITH THE FLASH FLOOD WATCH FOR THE FRONT RANGE FOOTHILLS AS WELL AS PORTIONS OF THE URBAN CORRIDOR AND NORTHEAST PLAINS TONIGHT. RAINFALL RATES OF 1 TO 2 INCHES A GOOD POSSIBILITY WITH WILL PRODUCE FLASH FLOODING IF IT OCCURS OVER ALREADY SATURATED SOILS. A FEW OF THE STORMS OVER THE NORTHEAST PLAINS COULD BECOME SEVERE. WET MICROBURSTS PRODUCING DAMAGING WINDS TO 60 MPH...HAIL TO ONE INCH IN DIAMETER AND HEAVY RAIN UP TO 3 INCHES PER HOUR. SHOWERS AND THUNDERSTORMS WILL DECREASE BUT NOT DIMINISH ALTOGETHER AFTER MIDNIGHT...WITH THE MDLS HINTING AT AREAS OF STRATUS AND POSSIBLE FOG BY SUNDAY MORNING. OVERALL SUNDAY VERY SIMILAR TO TODAY. THE CENTER OF THE UPPER RIDGE WILL SHIFT FM THE CENTRAL PLAINS TO THE DESERT SOUTHWEST. AS A RESULT...THE FLOW ALOFT MAY BE MORE WESTERLY VS SOUTHERLY. THE AMS WILL REMAIN MOIST WITH PW WELL OVER ONE INCH. FLASH FLOODING WILL CONTINUE TO BE AN ISSUE...ESPECIALLY FOR THE FOOTHILL BURN AREAS. .LONG TERM...MODELS HAVE THE UPPER RIDGE CENTERED OVER UTAH SUNDAY NIGHT THROUGH TUESDAY NIGHT. THE FLOW ALOFT IS WESTERLY SUNDAY NIGHT THROUGH MONDAY...THEN IT BECOMES NORTHWESTERLY AS THE UPPER HIGH BUILDS NORTHWARD TO OUR WEST. THE QG VERTICAL VELOCITY FIELDS SHOW BENIGN SYNOPTIC SCALE ENERGY OVER THE CWA ALL FIVE PERIOD. THE BOUNDARY LAYER FLOW LOOKS TO BE EASTERLY SUNDAY NIGHT AND MONDAY ...THEN A RETURN TO NORMAL DIURNAL PATTERNS MONDAY NIGHT THROUGH TUESDAY NIGHT. FOR MOISTURE...THERE IS STILL PLENTY PROGGED OVER THE MOUNTAINS AND PLAINS SUNDAY NIGHT. THERE IS LESS AROUND MONDAY...BUT STILL SOME. TUESDAY DRIES OUT MORE...ESPECIALLY ON THE GFS...BUT THERE STILL IS SOME AROUND. BOUNDARY LAYER DEW POINTS ARE STILL IN THE 40S F WEST TO LOWER 60S F EAST SUNDAY NIGHT. FOR MONDAY AND MONDAY NIGHT...THEY ONLY DECREASE SLIGHTLY ON BOTH THE GFS AND NAM. FOR TUESDAY AND TUESDAY NIGHT...PROGGS KEEP 40S F IN THE MOUNTAINS...WITH 50S F OVER THE PLAINS. THE PRECIPITABLE WATER VALUES DROP THROUGH THE FIVE PERIODS...WITH VALUES OVER AN INCH SUNDAY...DROPPING INTO THE 0.60 TO 0.75 INCH RANGE TUESDAY NIGHT. LAPSE RATES ARE NOT VERY STEP THROUGH THE PERIODS...WITH IN FACT A WEAK MID LEVEL CAP AROUND MUCH OF THE TIME. THE NAM KEEPS SOME CAPE OVER THE CWA SUNDAY NIGHT...THE GFS DOES NOT. FOR LATE DAY MONDAY ...CAPE VALUES ARE UNDER 800 J/KG OVER ALL THE CWA ON BOTH MODELS. THEY COME UP A BIT FOR LATE DAY TUESDAY. QPF FIELDS HAVE AMPLE AMOUNTS OF MEASURABLE RAINFALL SUNDAY NIGHT...LESS ON MONDAY...THEN SIGNIFICANTLY LESS FOR LATE DAY TUESDAY. FOR POPS...WILL GO WITH 30%S WEST TO 60%S FOR MOST AREAS SUNDAY EVENING...THEN DECREASE THEM OVERNIGHT AND MONDAY MORNING. WILL GO WITH 20-30%S FOR LATE DAY MONDAY...AND 0-30%S FOR LATE DAY TUESDAY. FOR TEMPERATURES... MONDAY'S HIGHS STAY ABOUT THE SAME AS SUNDAY'S. TUESDAY'S HIGHS WARM-UP SOME 2 TO 4 C OVER MONDAY'S. FOR THE LATER DAYS...WEDNESDAY THROUGH SATURDAY...THE CENTER OF THE UPPER RIDGE/HIGH STAYS OVER UTAH WEDNESDAY THROUGH THURSDAY NIGHT. BY FRIDAY IT MOVES EASTWARD SOMEWHAT AND IS CENTERED AROUND THE WESTERN COLORADO BORDER INTO EARLY SATURDAY. IT IS RIGHT OVER COLORADO THE REST OF SATURDAY. THE FLOW ALOFT FOR THE CWA IS WEAK NORTHWESTERLY WEDNESDAY THROUGH FRIDAY...THEN MORE WESTERLY ON SATURDAY. THE MOISTURE WILL DEFINITELY DECREASE FROM THE CURRENT SITUATION...BUT THERE WILL BE SOME AROUND WEDNESDAY THROUGH SATURDAY. THE 850-500 MB LAYER RELATIVE HUMIDITY FIELDS DO KEEP A WEAKER VERSION OF A SUB-TROPICAL MOISTURE PLUME AROUND IN SPITE OF THE UPPER HIGH BEING TO OUR WEST. && .AVIATION...CIGS WILL REMAIN AOB 5K FT AGL OVER THE NEXT 12-18 HOURS. MOIST LOW LEVEL MOISTURE WILL CONTINUE TO ADVECT INTO THE DENVER AREA FROM THE EAST. COULD SEE SOME PATCHY FOG DEVELOP AFTER 12Z OR IT MAY JUST BE A SOLID DECK OF STRATUS. WL LET THE SWING SHIFT ASSESS THE INCLUSION OF FOG IN THE UPCOMING TAFS. IF THE TSTM WITH HEAVY RAIN MOVES INTO THE AIRPORTS...THEN IFR CONDITIONS POSSIBLE WITH CIGS LESS THAN 1K FT AND VSBYS LESS THAN ONE MILE. SHOWERS MAY LINGER AFTER 12Z SUNDAY...WITH A GOOD POTENTIAL FOR TSTMS AGAIN SUNDAY AFTN. && .HYDROLOGY...A FLASH FLOOD WATCH WILL REMAIN IN EFFECT FOR THE FRONT RANGE FOOTHILLS THROUGH TONIGHT. RAINFALL RATES GENERALLY 0.5 TO 1 INCH PER HOUR WITH THE STRONGER STORMS...WITH A SLIGHT CHC OF HIGHER RAINFALL RATES OF 1-2 INCHES PER HOUR. SOILS IN THE HIGH PARK AND 4-MILE BURN AREA STILL MOIST OF RAINFALL YESTERDAY SO THE SITUATION WILL NEED TO BE MONITORED CLOSELY. SIMILAR CONDITIONS ANTICIPATED FOR SUNDAY AFTERNOON. && .BOU WATCHES/WARNINGS/ADVISORIES... FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR COZ035-036-038-039- 041-044-048-049. && SHORT TERM...COOP LONG TERM....KOOP AVIATION...COOP
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DENVER CO 1033 AM MDT SAT JUL 07 2012 COZ030>051-081200- JACKSON COUNTY BELOW 9000 FEET-WEST JACKSON AND WEST GRAND COUNTIES ABOVE 9000 FEET-GRAND AND SUMMIT COUNTIES BELOW 9000 FEET-SOUTH AND EAST JACKSON/LARIMER/NORTH AND NORTHEAST GRAND/ NORTHWEST BOULDER COUNTIES ABOVE 9000 FEET-SOUTH AND SOUTHEAST GRAND/WEST CENTRAL AND SOUTHWEST BOULDER/GILPIN/CLEAR CREEK/ SUMMIT/NORTH AND WEST PARK COUNTIES ABOVE 9000 FEET-LARIMER AND BOULDER COUNTIES BETWEEN 6000 AND 9000 FEET-JEFFERSON AND WEST DOUGLAS COUNTIES ABOVE 6000 FEET/GILPIN/CLEAR CREEK/NORTHEAST PARK COUNTIES BELOW 9000 FEET-CENTRAL AND SOUTHEAST PARK COUNTY-LARIMER COUNTY BELOW 6000 FEET/NORTHWEST WELD COUNTY-BOULDER AND JEFFERSON COUNTIES BELOW 6000 FEET/WEST BROOMFIELD COUNTY-NORTH DOUGLAS COUNTY BELOW 6000 FEET/DENVER/WEST ADAMS AND ARAPAHOE COUNTIES/ EAST BROOMFIELD COUNTY-ELBERT/CENTRAL AND EAST DOUGLAS COUNTIES ABOVE 6000 FEET-NORTHEAST WELD COUNTY-CENTRAL AND SOUTH WELD COUNTY-MORGAN COUNTY-CENTRAL AND EAST ADAMS AND ARAPAHOE COUNTIES- NORTH AND NORTHEAST ELBERT COUNTY BELOW 6000 FEET/NORTH LINCOLN COUNTY-SOUTHEAST ELBERT COUNTY BELOW 6000 FEET/SOUTH LINCOLN COUNTY-LOGAN COUNTY-WASHINGTON COUNTY-SEDGWICK COUNTY-PHILLIPS COUNTY- 1033 AM MDT SAT JUL 07 2012 ...FLASH FLOOD WATCH IN EFFECT THROUGH TONIGHT FOR THE FRONT RANGE FOOTHILLS AS WELL AS PORTIONS OF URBAN CORRIDOR AND NORTHEAST PLAINS... THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHEAST AND NORTH CENTRAL COLORADO. .DAY ONE...TODAY AND TONIGHT STORMS WILL BECOME MORE NUMEROUS AND INTENSIFY THIS AFTERNOON OVER THE MOUNTAINS AND NORTHEAST PLAINS BEFORE DIMINISHING LATER TONIGHT. THE MAIN IMPACT WITH STORMS WILL BE VERY HEAVY RAIN AND THE POTENTIAL FOR FLASH FLOODING. RAINFALL RATES WILL APPROACH 2 INCHES IN AN HOUR OR LESS WITH THE STRONGER STORMS. THE THREAT OF FLASH FLOODING WILL BE GREATEST IN THE BURN AREAS...AND IN AREAS ALREADY SATURATED FROM HEAVY RAINFALL YESTERDAY. THERE IS A SLIGHT CHANCE FOR SEVERE STORMS OVER THE NORTHEAST PLAINS LATE THIS AFTERNOON AND TONIGHT DUE TO STRONGER INSTABILITY. WET MICROBURSTS MAY PRODUCE DAMAGING WINDS TO 60 MPH...HAIL UP TO ONE INCH IN DIAMETER ALONG AND VERY HEAVY RAINFALL...UP TO 3 INCHES PER HOUR. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS WILL CONTINUE ON SUNDAY AND SUNDAY NIGHT FOR ALL THE FORECAST AREA. FLASH FLOODING IS AGAIN POSSIBLE ESPECIALLY OVER THE BURNED AREAS AND PREVIOUSLY RAIN SOAKED AREAS. THERE WILL BE A CHANCE OF LATE DAY SHOWERS AND THUNDERSTORMS ON MONDAY. FROM TUESDAY ONWARD...THERE WILL BE A SLIGHT CHANCE OF LATE DAY SHOWERS AND THUNDERSTORMS...ESPECIALLY OVER THE HIGH COUNTRY. TEMPERATURES WILL REMAIN BELOW SEASONAL NORMALS SUNDAY AND MONDAY...THEN WARM UP THROUGH NEXT WEEK. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY OR TONIGHT. HOWEVER HEAVY RAINFALL AND FLOODING REPORTS WILL BE GREATLY APPRECIATED. COOPER/KOOPMEINERS
The Cheyenne radar (KCYS), 93 km away, was scanning. The volume nearest the first event began at 22:34 UTC.
3 flash flood, 1 heavy rain. Local standard time, as filed.
Heavy rain caused flash flooding and mudslides in parts of the central Larimer County, including the High Park burn scar.
Heavy rain caused rock and mudslides in central Boulder County.
Heavy rain produced flash flooding in the Fourmile burn area.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2012Every state in 2012This day in weather historyWarnings in Colorado, July 2012
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: 397614, 397621, 402461, 397622.