A deluge of heavy rain occurred in and around Nederland when the storm dumped nearly 2 inches of rain in 30 minutes. The heavy rainfall washed out hillsides and dirt 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 deluge of heavy rain occurred in and around Nederland when the storm dumped nearly 2 inches of rain in 30 minutes. The heavy rainfall washed out hillsides and dirt roads. In Nederland, a culvert became blocked with debris and forced the water to spread into a nearby bookstore. The rainfall also damaged several residential roads in the Sunnyside Subdivision and Navajo Road became impassable. Several homes suffered flood damage as the runoff from a nearby Beaver Creek jumped its banks and flooded garages, living rooms and bedrooms of nearby houses.
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 17, 2:31 PM MST, 1 hour 29 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DENVER CO 331 PM MDT SUN JUL 17 2011 .SHORT TERM...SCATTERED CONVECTION CURRENTLY MOVING NORTHWARD ACROSS MOUNTAINS WITH LESS COVERAGE ALONG FOOTHILLS. SO FAR...NO CELLS OVER URBAN CORRIDOR. RADAR SHOWED ONE POTENTIALLY SEVERE CELL OVER GILPIN COUNTY AROUND 225 PM MDT. ACROSS PLAINS...AIRMASS STILL CAPPED AS NOTED BY ACARS SOUNDINGS WITH GUSTY SOUTHERLY WINDS PREVAILING. MODELS SHOW PRECIP CHANCES CONTINUING ACROSS MOUNTAINS AND FOOTHILLS THIS EVENING AND WILL KEEP THE CHANCE POPS THERE. PRECIPITABLE WATER VALUES STILL HOVERING AROUND 1.10 INCHES MOST LOCALS...AS SHOWN BY CURRENT IPW VALUES. HEAVY RAIN A GOOD POSSIBILITY ALONG WITH SOME LOCALIZED FLOODING. POTENTIAL FOR SOME CELL TRAINING AS WELL...BASED ON CURRENT MOVEMENT...WHICH WILL ALSO BE A CONCERN. ACROSS PLAINS... CHANCES FOR STORMS MUCH LOWER GIVEN SOUTHERLY MOVEMENT OF THE STORMS AND THE CAPPED AIRMASS. WILL KEEP A SLIGHT CHANCE FOR THE URBAN CORRIDOR AND ADJACENT PLAINS IN CASE THERE ARE SOME OUTFLOW BOUNDARIES HELPING TO GENERATE STORMS. CAN'T FIND MUCH IN THE WAY OF ANY UPPER DYNAMICS TO KEEP CONVECTION GOING PAST MIDNIGHT SO WILL DROP THE SLIGHT CHANCE OF STORMS OVERNIGHT AND INTO THE EARLY MORNING HOURS. TEMPERATURES OVERNIGHT TO BE ON THE WARM SIDE AS THERE COULD BE ENOUGH CLOUD COVER AROUND TO MODERATE TEMPS. ON MONDAY...LITTLE CHANGE IN THE OVERALL PATTERN WITH THE UPPER HIGH ACROSS THE CENTRAL PLAINS. SHOULD SEE CONVECTION AGAIN DEVELOPING OVER THE MOUNTAINS AND FOOTHILLS. FORECAST SOUNDINGS INDICATE AIRMASS WILL BE CAPPED FOR MOST OF THE DAY...AND CELL MOVEMENT PROGGED TO BE NORTHERLY. THIS SHOULD KEEP THE BEST CONVECTION CHANCES OVER THE HIGH COUNTRY. THIS ALREADY INDICATED IN THE GRIDS. POPS TO BE LOWER ALONG URBAN CORRIDOR AND ADJACENT PLAINS. AIRMASS TOO STABLE FURTHER EAST SO DROPPED POPS THERE. AS FOR TEMPERATURES GUIDANCE AGAIN LOOKS A BIT WARM...SO WILL KEEP WHAT IS SHOWN FOR THE CURRENT TEMPERATURE GRIDS. .LONG TERM...MODELS CONTINUE TO PUT THE UPPER RIDGE CENTER OVER EASTERN KANSAS/WESTERN MISSOURI MONDAY EVENING THROUGH TUESDAY NIGHT. BY WEDNESDAY AND WEDNESDAY NIGHT...THE UPPER RIDGE ELONGATES SIGNIFICANTLY FROM ARIZONA INTO THE MID MISSISSIPPI VALLEY. THE FLOW ALOFT IS MAINLY DUE SOUTHERLY MONDAY NIGHT INTO EARLY WEDNESDAY...THEN IT BECOMES SOUTHWESTERLY INTO THURSDAY MORNING. THERE IS NO SYNOPTIC SCALE ENERGY INDICATED FOR THE CWA MONDAY NIGHT THROUGH WEDNESDAY NIGHT. THE BOUNDARY LAYER FLOW LOOKS PRETTY WEAK THROUGH THE PERIODS...AND THERE IS A WEAK LOW LEVEL TROUGH OVER THE PLAINS ON WEDNESDAY. FOR MOISTURE...MODELS KEEP THE MID AND UPPER LEVEL MOISTURE PLUME COMING UP FROM MEXICO THROUGH THE PERIODS. IT IS NOT QUITE AS STRONG AS IT WAS LAST WEEK. THE LOW LEVEL DEW POINT PROGGS MAINLY KEEP MID 40S TO UPPER 50S OVER ALL THE CWA THROUGH THE PERIODS. THE PRECIPITABLE WATER VALUES...ARE IN THE 0.75 TO 1.20 INCH RANGE THROUGH THE PERIODS...THE DRIEST PERIOD BEING MONDAY NIGHT. THERE IS PRETTY DECENT CAPE OVER THE MOUNTAINS AND FOOTHILLS MONDAY EVENING. THERE IS LESS OVER THE HIGH COUNTRY LATE DAY TUESDAY...AS WELL AS SOME OVER THE PALMER RIDGE. THERE IS LIMITED CAPE OVER THE WESTERN MOUNTAINS...AND THE PLAINS LATE DAY WEDNESDAY. THE QPF FIELDS SHOW SOME MEASURABLE RAINFALL OVER THE MOUNTAINS AND FOOTHILLS ONLY MONDAY EVENING AND AGAIN LATE DAY TUESDAY. MORE IS INDICATED ON TUESDAY. FOR LATE DAY WEDNESDAY... THERE IS MEASURABLE RAINFALL OVER THE HIGH COUNTRY AS WELL AS WESTERN PLAINS AND PALMER RIDGE. THE GFS HAS A CONVECTIVE BULLS-EYE OVER THE PALMER RIDGE WEDNESDAY EVENING. FOR POPS...WILL GO WITH 30-40%S IN THE MOUNTAINS...AND 10-20%S OVER THE PLAINS. THE TEMPERATURES...TUESDAY'S HIGHS LOOK SIMILAR TO MONDAY'S. WEDNESDAY'S HIGHS ARE 0-1.5 C LOWER THAN TUESDAY'S. FOR THE LATER DAYS...THURSDAY THROUGH SUNDAY...MODELS STILL KEEP THE MAIN CENTER OF THE UPPER RIDGE WELL EAST-SOUTHEAST OF COLORADO THROUGH THE PERIODS...HOWEVER THE UPPER HIGH IS VERY ELONGATED ACROSS THE ENTIRE SOUTHERN UNITED STATES. THE FLOW ALOFT STAYS SOUTHWESTERLY INTO NEXT WEEKEND...BUT BECOMES DUE WESTERLY SATURDAY AFTERNOON THROUGH SUNDAY. THE MOISTURE FETCH FROM THE MEXICAN HIGHLANDS IS PROGGED TO CONTINUE THROUGH ALL FOUR DAYS. WILL GO WITH PERSISTENCE CONCERNING BOTH POPS AND TEMPERATURES. && .AVIATION...STILL A SLIGHT CHANCE OF STORMS THIS EVENING...WITH THE BEST CHANCE AT KBJC. THE MAIN THREAT WILL BE BRIEF HEAVY RAIN AND ERRATIC WIND GUSTS TO 40KT WITH THE STRONGER STORMS. VFR CONDITIONS TO PREVAIL...WITH A SLIGHT CHANCE OF MVFR IF STORMS AFFECT AREA AIRPORTS. DRAINAGE FLOW TO DEVELOP AFTER 04Z. ON MONDAY...STORMS TO AGAIN DEVELOP ACROSS MOUNTAINS AND FOOTHILLS...WITH ONLY A SLIGHT CHANCE AT THE AREA AIRPORTS. WILL HOLD OFF ON VCTS AT THIS POINT. VFR CONDITIONS TO PERSIST. && .HYDROLOGY...SCATTERED THUNDERSTORMS WILL CONTINUE ACROSS THE MOUTNAINS AND FOOTHILLS THIS EVENING. WITH SOUTHERLY STORM MOTION...THE POTENTIAL EXISTS FOR ECHO TRAINING. STORMS WILL BE CAPABLE OF PRODUCING AN INCH IN ABOUT 30 MINUTES...SO THERE WILL BE FLOODING CONCERNS...ESPECIALLY OVER THE BURN AREAS OF BOULDER AND LARIMER COUNTIES. SOUTH PLATTE RIVER CONTINUES TO RISE THROUGH WELD AND MORGAN COUNTIES WITH FLOOD ADVISORIES CONTINUING FROM KERSEY TO BALZAC. && .BOU WATCHES/WARNINGS/ADVISORIES...NONE && D-L/RJK
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DENVER CO 1049 AM MDT SUN JUL 17 2011 COZ030>051-181200- 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- 1049 AM MDT SUN JUL 17 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHEAST AND NORTH CENTRAL COLORADO. .DAY ONE...TODAY AND TONIGHT SCATTERED THUNDERSTORMS WILL DEVELOP ACROSS THE MOUNTAINS... FOOTHILLS AND THE URBAN CORRIDOR THIS AFTERNOON...POSSIBLY SPREADING OVER THE PLAINS BY LATE AFTERNOON. THE STORMS WILL PRODUCE LIGHTNING AND BRIEF HEAVY RAIN WITH RAINFALL RATES UP TO AN INCH PER HOUR POSSIBLE. GUSTY SOUTHERLY WINDS OF 15 TO 25 MPH WILL OCCUR ACROSS THE EASTERN PLAINS LATE THIS AFTERNOON AND EVENING. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY LITTLE CHANGE IN THE WEATHER PATTERN IS EXPECTED. THE BEST CHANCE OF THUNDERSTORMS WILL BE OVER THE MOUNTAINS EACH DAY...WITH A SLIGHT CHANCE OF THUNDERSTORMS OVER THE NORTHEAST PLAINS OF COLORADO. TEMPERATURES WILL BE ABOVE SEASONAL NORMALS IN MOST AREAS... ESPECIALLY OUT OF THE PLAINS. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY OR TONIGHT. D_L/RJK
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE DENVER CO 220 PM MDT SUN JUL 17 2011 COZ034-036-172045- SOUTH AND SOUTHEAST GRAND/WEST CENTRAL AND SOUTHWEST BOULDER/GILPIN/CLEAR CREEK/SUMMIT/NORTH AND WEST PARK COUNTIES ABOVE 9000 FEET CO- JEFFERSON AND WEST DOUGLAS COUNTIES ABOVE 6000 FEET/GILPIN/CLEAR CREEK/NORTHEAST PARK COUNTIES BELOW 9000 FEET CO- 220 PM MDT SUN JUL 17 2011 THE NATIONAL WEATHER SERVICE IN DENVER HAS ISSUED A SIGNIFICANT WEATHER ADVISORY FOR CENTRAL GILPIN COUNTY AT 220 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A THUNDERSTORM CAPABLE OF PRODUCING NICKEL SIZE HAIL...AND WIND GUSTS TO AROUND 40 MPH. THIS STORM WAS LOCATED 3 MILES NORTHWEST OF CENTRAL CITY...OR 32 MILES WEST OF DENVER...MOVING NORTH AT 10 MPH. LOCATIONS IN THE ADVISORY INCLUDE BUT ARE NOT LIMITED TO TOLLAND... CENTRAL CITY...BLACK HAWK AND ASPEN SPRINGS. PRECAUTIONARY/PREPAREDNESS ACTIONS... HEAVY RAINS MAY ALSO OCCUR WITH THIS STORM...WHICH MAY FLOOD LOW-LYING AREAS SUCH AS DITCHES AND UNDERPASSES. DO NOT DRIVE YOUR VEHICLE ON A FLOODED ROADWAY. && LAT...LON 3991 10562 3992 10545 3978 10549 3985 10562 TIME...MOT...LOC 2020Z 175DEG 10KT 3985 10555
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE DENVER CO 333 PM MDT SUN JUL 17 2011 COZ034-035-172200- SOUTH AND SOUTHEAST GRAND/WEST CENTRAL AND SOUTHWEST BOULDER/GILPIN/CLEAR CREEK/SUMMIT/NORTH AND WEST PARK COUNTIES ABOVE 9000 FEET CO- LARIMER AND BOULDER COUNTIES BETWEEN 6000 AND 9000 FEET CO- 333 PM MDT SUN JUL 17 2011 THE NATIONAL WEATHER SERVICE IN DENVER HAS ISSUED A SIGNIFICANT WEATHER ADVISORY FOR CENTRAL BOULDER COUNTY AT 333 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A THUNDERSTORM CAPABLE OF PRODUCING PENNY SIZE HAIL. THIS STORM WAS LOCATED NEAR NEDERLAND...OR 32 MILES NORTHWEST OF DENVER...MOVING NORTH AT 10 MPH. LOCATIONS IN THE ADVISORY INCLUDE BUT ARE NOT LIMITED TO WARD AND NEDERLAND. PRECAUTIONARY/PREPAREDNESS ACTIONS... HEAVY RAINS MAY ALSO OCCUR WITH THIS STORM...WHICH MAY FLOOD LOW-LYING AREAS SUCH AS DITCHES AND UNDERPASSES. DO NOT DRIVE YOUR VEHICLE ON A FLOODED ROADWAY. && LAT...LON 4012 10556 4010 10543 3994 10544 3994 10557 TIME...MOT...LOC 2133Z 164DEG 9KT 3995 10550
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE DENVER CO 359 PM MDT SUN JUL 17 2011 COZ033>035-172230- SOUTH AND EAST JACKSON/LARIMER/NORTH AND NORTHEAST GRAND/NORTHWEST BOULDER COUNTIES ABOVE 9000 FEET CO- SOUTH AND SOUTHEAST GRAND/WEST CENTRAL AND SOUTHWEST BOULDER/GILPIN/CLEAR CREEK/SUMMIT/NORTH AND WEST PARK COUNTIES ABOVE 9000 FEET CO- LARIMER AND BOULDER COUNTIES BETWEEN 6000 AND 9000 FEET CO- 359 PM MDT SUN JUL 17 2011 THE NATIONAL WEATHER SERVICE IN DENVER HAS ISSUED A SIGNIFICANT WEATHER ADVISORY FOR WESTERN BOULDER COUNTY AT 359 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A THUNDERSTORM CAPABLE OF PRODUCING PENNY SIZE HAIL...AND WIND GUSTS TO AROUND 50 MPH. THIS STORM WAS LOCATED 3 MILES SOUTH OF WARD...OR 35 MILES NORTHWEST OF DENVER...MOVING NORTH AT 15 MPH. LOCATIONS IN THE ADVISORY INCLUDE BUT ARE NOT LIMITED TO WARD...RAYMOND...PEACEFUL VALLEY...MEEKER PARK AND ALLENSPARK. PRECAUTIONARY/PREPAREDNESS ACTIONS... HEAVY RAINS MAY ALSO OCCUR WITH THIS STORM...WHICH MAY FLOOD LOW-LYING AREAS SUCH AS DITCHES AND UNDERPASSES. DO NOT DRIVE YOUR VEHICLE ON A FLOODED ROADWAY. && LAT...LON 4023 10557 4024 10539 4000 10540 3999 10556 TIME...MOT...LOC 2159Z 181DEG 14KT 4006 10550
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE DENVER CO 431 PM MDT SUN JUL 17 2011 COZ033>035-172300- SOUTH AND EAST JACKSON/LARIMER/NORTH AND NORTHEAST GRAND/NORTHWEST BOULDER COUNTIES ABOVE 9000 FEET CO- SOUTH AND SOUTHEAST GRAND/WEST CENTRAL AND SOUTHWEST BOULDER/GILPIN/CLEAR CREEK/SUMMIT/NORTH AND WEST PARK COUNTIES ABOVE 9000 FEET CO- LARIMER AND BOULDER COUNTIES BETWEEN 6000 AND 9000 FEET CO- 431 PM MDT SUN JUL 17 2011 THE NATIONAL WEATHER SERVICE IN DENVER HAS ISSUED A SIGNIFICANT WEATHER ADVISORY FOR NORTH CENTRAL BOULDER COUNTY AT 431 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A THUNDERSTORM CAPABLE OF PRODUCING NICKEL SIZE HAIL...AND WIND GUSTS TO AROUND 50 MPH. THIS STORM WAS LOCATED 2 MILES SOUTH OF RAYMOND... OR 36 MILES SOUTHWEST OF FORT COLLINS...MOVING NORTH AT 15 MPH. LOCATIONS IN THE ADVISORY INCLUDE BUT ARE NOT LIMITED TO RAYMOND... PEACEFUL VALLEY AND JAMESTOWN. PRECAUTIONARY/PREPAREDNESS ACTIONS... HEAVY RAINS MAY ALSO OCCUR WITH THIS STORM...WHICH MAY FLOOD LOW-LYING AREAS SUCH AS DITCHES AND UNDERPASSES. DO NOT DRIVE YOUR VEHICLE ON A FLOODED ROADWAY. && LAT...LON 4026 10551 4026 10535 4010 10536 4010 10552 TIME...MOT...LOC 2231Z 182DEG 16KT 4015 10544
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE DENVER CO
457 PM MDT SUN JUL 17 2011
COZ033>035-172330-
SOUTH AND EAST JACKSON/LARIMER/NORTH AND NORTHEAST GRAND/NORTHWEST
BOULDER COUNTIES ABOVE 9000 FEET CO-
SOUTH AND SOUTHEAST GRAND/WEST CENTRAL AND SOUTHWEST
BOULDER/GILPIN/CLEAR CREEK/SUMMIT/NORTH AND WEST PARK COUNTIES ABOVE
9000 FEET CO-
LARIMER AND BOULDER COUNTIES BETWEEN 6000 AND 9000 FEET CO-
457 PM MDT SUN JUL 17 2011
THE NATIONAL WEATHER SERVICE IN DENVER HAS ISSUED A SIGNIFICANT
WEATHER ADVISORY FOR
SOUTHWESTERN BOULDER COUNTY
AT 457 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
THUNDERSTORM CAPABLE OF PRODUCING NICKEL SIZE HAIL...AND WIND GUSTS
TO AROUND 50 MPH. THIS STORM WAS LOCATED NEAR ELDORA...OR 37 MILES
NORTHWEST OF DENVER...MOVING NORTH AT 15 MPH.
LOCATIONS IN THE ADVISORY INCLUDE BUT ARE NOT LIMITED TO WARD...
PEACEFUL VALLEY...ELDORA AND BRAINARD LAKE.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
HEAVY RAINS MAY ALSO OCCUR WITH THIS STORM...WHICH MAY FLOOD
LOW-LYING AREAS SUCH AS DITCHES AND UNDERPASSES. DO NOT DRIVE YOUR
VEHICLE ON A FLOODED ROADWAY.
&&
LAT...LON 4004 10564 4017 10559 4014 10549 3994 10552
3994 10568
TIME...MOT...LOC 2257Z 181DEG 17KT 3999 10559The Denver radar (KFTG), 88 km away, was scanning. The volume nearest the first event began at 23:02 UTC.
1 flash flood. Local standard time, as filed.
Heavy rain produced extensive flash flooding.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2011Every state in 2011This day in weather historyWarnings in Colorado, 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: 338836.