A slow moving thunderstorm brought heavy rain to the Four Mile Canyon burn area northwest of Boulder. The heavy rain triggered rock and mudslides along Fourmile Canyon Drive near Logan Mill, Nancy Mine and Gold Run Roads.
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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 BOU wrote it up.
A slow moving thunderstorm brought heavy rain to the Four Mile Canyon burn area northwest of Boulder. The heavy rain triggered rock and mudslides along Fourmile Canyon Drive near Logan Mill, Nancy Mine and Gold Run Roads. In addition, Crisman Road and Wall Street were also closed until the debris could be removed. Nearly an inch of rainfall, 0.90 inches, fell in a 30 minute period.
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 5, 2:10 PM MST, 1 hour 30 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DENVER CO 310 PM MDT THU JUL 5 2012 .SHORT TERM...CONVECTION CONTINUES TO FIRE IN THE HIGH COUNTRY WITH STORMS PRODUCING LOCALLY HEAVY RAINFALL. MEANWHILE...THE PLAINS HAVE REMAINED CAPPED UNDER THE UPPER LEVEL DRYING AND SUBSIDENCE SEEN IN THE WATER VAPOR LOOP. HOWEVER...WE WERE APPROACHING CONVECTIVE TEMPERATURE ON THE PLAINS PER THE LATEST ACARS SOUNDINGS AND DEWPOINTS WERE ONLY DROPPING INTO THE MID/UPPER 40S. AS A RESULT...WE COULD STILL SEE A FEW STORMS DEVELOP ON THE PLAINS ALTHOUGH LOW LEVEL CONVERGENCE IS RATHER WEAK WITH MAINLY SOUTH/SOUTHEASTERLY FLOW. CONVECTION IS EXPECTED TO DECREASE LATER THIS EVENING WITH LITTLE SUPPORT FOR STORMS AFTER MIDNIGHT. ON FRIDAY...A COLD FRONT PUSHES ACROSS THE PLAINS IN THE MORNING WITH GRADUAL MOISTENING AND DESTABILIZATION OF THE AIRMASS. PRECIPITABLE WATER VALUES ARE ADVERTISED TO INCREASE TO 1.1 TO 1.2 INCHES ALONG THE FRONT RANGE AND A DEEPER THETA-E RIDGE IS ALSO EXPECTED TO DEVELOP. AT THIS TIME WE DONT SEE MUCH OF A CAP TO PREVENT CONVECTION EITHER. AS A RESULT...THE HIGHER POPS AND BETTER CHANCE OF STORMS PRODUCING HEAVY RAINFALL LOOKS GOOD. SEE HYDRO SECTION BELOW FOR MORE DETAILS. .LONG TERM...MODELS HAVE THE UPPER HIGH CENTERED WELL EAST OF COLORADO FRIDAY NIGHT INTO SATURDAY NIGHT. BY SUNDAY...CONTINUING SUNDAY NIGHT...THE CENTER IS PROGGED TO SHIFT WESTWARD INTO WESTERN AND NORTHWESTERN UTAH. THE FLOW ALOFT WILL MAINLY BE WESTERLY THROUGH THOSE PERIODS...AND VERY WEAK. THE QG VERTICAL VELOCITY FIELDS SHOW WEAK UPWARD VERTICAL VELOCITY FOR ALL FIVE PERIODS ...FRIDAY NIGHT THROUGH SUNDAY NIGHT. A COLD FRONT IS PROGGED TO MOVE INTO THE CWA FRIDAY AFTERNOON. THE BOUNDARY LAYER FLOW PROGGS SHOW UPSLOPE FLOW...NORTHEASTERLIES TO EAST-SOUTHEASTERLIES FROM FRIDAY NIGHT THROUGH SUNDAY NIGHT. MODELS SHOW MOISTURE TO BE QUITE UBIQUITOUS FRIDAY NIGHT ONWARD...ESPECIALLY COMPARED TO THE PATTERN WE HAVE SEEN FOR THE PAST SEVERAL WEEKS. PRECIPITABLE WATER VALUE PROGGS ARE IN THE 1.10 TO 1.50 INCH RANGE FRIDAY NIGHT THROUGH SUNDAY NIGHT. PROGGED DEW POINT VALUES ARE MAINLY IN THE 40S OVER THE MOUNTAINS...THE 50S F IN THE FOOTHILLS...AND MID 50S TO LOWER 60S F OVER THE PLAINS FOR ALL FIVE PERIODS. THERE ARE BETTER CAPE NUMBERS ON THE NAM COMPARED TO THE GFS FROM FRIDAY NIGHT THROUGH SATURDAY NIGHT. BOTH MODELS SHOW SIMILAR AMOUNTS BY SUNDAY. CAPE VALUES ARE MAINLY IN THE 400-1400 J/KG RANGE THROUGH THE PERIODS. LAPSE RATES ARE NOT VERY STEEP THROUGH THE PERIODS...ESPECIALLY ON SATURDAY IN THE LOWER LEVELS WITH THE NEW COOLER AIRMASS IN PLACE. CONVECTION COULD GET GOING ABOVE THIS LEVEL HOWEVER. THE QPF FIELDS SHOW SIGNIFICANT AMOUNTS OF MEASURABLE RAINFALL THROUGH MOST OF THE PERIODS. EVEN THE ECMWF...NORMALLY DRIER...HAS QUITE A BIT PROGGED. WILL STAY THE COURSE AND KEEP 30-50%S GOING FOR ALL AREAS FRIDAY NIGHT INTO SUNDAY NIGHT. FOR TEMPERATURES...SATURDAY'S HIGHS ARE 4-8 C COOLER THAN FRIDAY'S. SUNDAY HIGH'S A TAD WARMER THAN SATURDAY'S. SATURDAY'S MOS GUIDANCE HIGHS ARE IN THE 70S FROM BOTH THE NAM AND GFS. FOR THE LATER DAYS...MONDAY THROUGH THURSDAY ...MODELS HAVE THE UPPER RIDGE CENTERED TO OUR WEST. THE FLOW ALOFT IS WEAK WEST-NORTHWESTERLY. MOISTURE DECREASES QUITE A BIT THROUGH THE PERIOD...COMPARED TO THIS COMING WEEKEND'S MOISTURE. TEMPERATURES GET TO OR ARE JUST A TAD ABOVE SEASONAL NORMALS FROM TUESDAY ONWARD. && .AVIATION...STORM THREAT THIS EVENING IS SOMEWHAT ON THE LOW SIDE BUT WE ARE JUST REACHING CONVECTIVE TEMPS. WILL CONTINUE TO MONITOR STORM THREAT BUT BEST CHANCE WOULD BE BETWEEN 23Z AND 03Z. FRONTAL PASSAGE EXPECTED AROUND 14Z-16Z FRIDAY WITH NORTHEASTERLY WINDS AROUND 15 KTS THROUGH THE DAY. STORM CHANCES WILL INCREASE AFTER 20Z FRIDAY WITH POSSIBLE VISIBILITY RESTRICTIONS WITH STRONGER STORMS PRODUCING HEAVIER RAINFALL. && .HYDROLOGY...HEAVY RAIN THREAT THIS EVENING SHOULD BE MAINLY CONFINED TO THE MOUNTAINS AND FOOTHILLS WITH 1 INCH AMOUNTS IN 30 MINUTES POSSIBLE FROM THE STRONGER STORMS. THIS COULD CREATE LOCAL FLOODING ISSUES IF THESE MOVE OVER THE BURN SCARS. ON FRIDAY...STORMS WILL LIKELY BE MORE NUMEROUS AND STRONGER WITH HIGHER PRECIPITABLE WATER VALUES. RAINFALL RATES FROM THE STRONGER STORMS FRIDAY AFTERNOON AND EVENING COULD REACH 2 INCHES IN AN HOUR AS FAVORABLE LOW LEVEL INFLOW AND SLOW NORTHERLY STORM MOTION OF 5-15 MPH EXPECTED. THE LOW LEVEL INFLOW WOULD ALSO HELP STORMS REGENERATE IN ROUGHLY THE SAME LOCATIONS ALONG STORM OUTFLOWS. A FLASH FLOOD WATCH MAY BE ISSUED FOR FRIDAY AFTERNOON AND EVENING IF LATEST DATA CONTINUES TO SUPPORT THE HIGHER PRECIPITABLE WATER. MOST LIKELY LOCATION OF A WATCH WOULD BE IN THE FOOTHILLS MAINLY FOR THE BURN SCARS. && .BOU WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...BARJENBRUCH LONG TERM....RJK AVIATION...BARJENBRUCH
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DENVER CO 1113 AM MDT THU JUL 05 2012 COZ030>051-061200- 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- 1113 AM MDT THU JUL 05 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHEAST AND NORTH CENTRAL COLORADO. .DAY ONE...TODAY AND TONIGHT MOISTURE LEVELS HAVE INCREASED ACROSS THE ENTIRE AREA SINCE YESTERDAY. THIS SHOULD RESULT IN A BETTER CHANCE OF SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND EVENING...WITH THE HIGHEST COVERAGE EXPECTED IN THE MOUNTAINS AND FOOTHILLS AS WELL AS NEAR THE WYOMING BORDER. EXPECT HEAVY RAIN...SMALL HAIL...FREQUENT LIGHTNING...AND GUSTY WINDS WITH THE STORMS. RAINFALL RATES MAY APPROACH AN INCH IN 30 MINUTES WITH THE STRONGER STORMS WHICH COULD CREATE SOME FLOODING ISSUES IF ONE OF THESE MOVES OVER A BURN SCAR. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY THERE WILL BE A CHANCE OF AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS FROM FRIDAY THROUGH NEXT WEDNESDAY FOR ALL THE FORECAST AREA. WITH HOW DRY IT HAS BEEN FOR THE LAST SEVERAL WEEKS...ANY FLOODING ISSUES WILL INITIALLY BE MINIMAL...WITH THE EXCEPTION OF THE PREVIOUS BURNED AREAS IN THE MOUNTAINS AND FOOTHILLS. IF THIS EXPECTED PERIOD OF INCREASED MOISTURE AVAILABILITY DOES IN FACT COME TO FRUITION...REPEATED EXCESSIVE RAINFALL EVENTS WILL OBVIOUSLY INCREASE THE THREAT OF FLASH FLOODING. TEMPERATURES SHOULD BE MORE NEAR SEASONAL NORMALS THROUGH THE PERIOD AS WELL. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY OR TONIGHT. DBB/RJK
The Denver radar (KFTG), 80 km away, was scanning. The volume nearest the first event began at 22:39 UTC.
1 flash flood. Local standard time, as filed.
Flash flooding occurred in the Four Mile Canyon 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: 397931.