A deep southerly flow over Colorado, ahead of a near stationary low pressure system over the Great Basin, pumped copious amounts of monsoonal moisture into the area. In addition, a weak stationary front stretched along the Front Range Foothills and Palmer Divide.
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.
A deep southerly flow over Colorado, ahead of a near stationary low pressure system over the Great Basin, pumped copious amounts of monsoonal moisture into the area. In addition, a weak stationary front stretched along the Front Range Foothills and Palmer Divide. As a result, a prolonged period of moderate to heavy rain developed across the Front Range Foothills, Palmer Divide, Urban Corridor. By the 14th, storm totals ranged from 6 to 18 inches, highest in the foothills of Boulder County. The headwaters then moved down the South Platte River and caused widespread flooding with record flood stages at several locations as it made its way downstream into Nebraska. Record high flood stages along the South Platte River were recorded at Balzac, Weldona and Julesburg. As a result, widespread flooding occur along the South Platte for several days as the headwaters continued downstream, with much of the damage reported from Fort Morgan and Brush to around Sterling. The floodwaters resulted in widespread evacuations. Numerous water treatment facilities were contaminated and had to be shut down. The headwaters remained at or above flood stage east of Sterling to Julesburg, but the flooding was not as widespread and the damage not as extensive.
Initially, the showers that developed on the afternoon of the 11th were moving fast enough and were small enough to produce generally moderate rainfall amounts. However, rain along the Front Range began to intensify and become more widespread in the evening. A narrow band of very heavy rain began to organize just north of Denver and move westward toward the foothills. By 9 pm mdt on the 11th, heavy rain was becoming more widespread, with rainfall rates near 2 inches per hour in the heaviest showers. From 10 pm mdt to Midnight mdt, very heavy rain locked itself in against the Front Range. Flash flooding became more widespread, with several road closures from northwest Jefferson County northward through Boulder and Larimer Counties. The heaviest rain in the foothills of Boulder, Larimer and northern Jefferson Counties finally began to abate, but widespread flash flooding continued due to the extremely heavy rainfall during the evening and early morning hours of the 12th. Meanwhile, torrential rain redeveloped in southwest Weld, northeast Adams, eastern Denver and northwest Arapahoe Counties in the early morning hours of the 12th; which impacted northeast Denver and Aurora.
Atypical for September in Colorado, 24-hour rainfall totals ending 7 am mdt on September 12th included 6.5 to 8.6 inches in Boulder; with 3 to 6.5 inches across the Larimer and Boulder County foothills, as well an area stretching from northeastern Metro Denver area into southwest Weld County. By 9 am mdt, heavy rain and considerable flash flooding continued through the morning in the Aurora area. Numerous streams remained at or above bankfull levels across Boulder, Larimer, and southwest Weld counties. By the evening of the 12th, flooding continued in many areas and increased in severity. Heavy rain, while not as widespread as the previous day, had a greater impact on stream levels as streams were already elevated and the ground was completely saturated. Two peaks of flows occurred on Boulder Creek near downtown. The peak flow on the evening of September 12th surpassed the 1969 Boulder flood, but initial indications are that it fell short of the 1938 and 1894 floods. Boulder Stream Gauge peak flows occurred near 0100 mdt on the 12th, and 2100 mdt on the 12th. Similar massive stream flows occurred on many other creeks and rivers up and down the Front Range, including: Big Thompson River, Lefthand Creek, Little Thompson, Cache la Poudre, St Vrain Creek, Coal Creek, South Boulder Creek and Sand Creek. Similar massive stream flows occurred on many other creeks and rivers up and down the Front Range, including: Lefthand Creek, Little Thompson, Cache la Poudre, St Vrain Creek, Coal Creek, South Boulder Creek and Sand Creek. The headwaters moved down the South Platte with floodwaters impacted Weld, Morgan, Washington and Logan Counties. Extensive flooding occurred in and around Greeley, Fort Morgan and Sterling. Large sections of the counties' roads and highways were washed away, with property and crops completely inundated.
After little rainfall on Friday, September 13th, the flash flood threat returned for Saturday. This time, storms with heavy rainfall were concentrated in Douglas County, but also extended northeast into the Aurora area once again. Up to 3 inches of rain fell in one hour. Plum Creek and other small creeks and streams flooded, along with significant street flooding. The last day of this prolonged period of very heavy rainfall was on Sunday, September 15th. Another weak front had pushed through the area Saturday night, leaving the atmosphere unseasonably moist and unstable. Heavy rain developed by mid morning and then became more widespread and peaked in intensity by the noon hour. This time, flash flooding was most significant in the northern portions of the Denver metro area from Northglenn to around Broomfield. Rain finally tapered off during the late afternoon and evening.
The devastating flood damage encompassed 4,500 square miles of the Colorado Front Range, left seven dead, forced thousands to evacuate, and destroyed thousands of homes and farms. Record amounts of rainfall generated flash floods that tore up roads and lines of communication, leaving many stranded. Nearly 19,000 homes were damaged, and over 1,500 destroyed. The Colorado Department of Transportation estimated that at least 30 state highway bridges were destroyed and an additional 20 seriously damaged. A preliminary assessment of the state's infrastructure showed damage of $40 million to roads and $112 million to bridges. Repair costs for state and and county roads were likely to run into the hundreds of millions of dollars. Miles of freight and passenger rail lines were washed out or submerged, including a section servicing Amtrak's iconic California Zephyr. The town of Lyons in Boulder County was isolated by the flooding of St. Vrain Creek, and several earth dams along the Front Range burst or were over-topped. Floodwaters also swept through Estes Park, the gateway to Rocky Mountain National Park and a major tourist attraction, and damaged hundreds of buildings and destroyed large sections of the two main roads that led into town; U.S. 34 from Loveland and U.S. 36 from Lyons/Boulder. U.S. 34 suffered the most damage, with 85 percent of its roadway and bridges destroyed. In Weld County, approximately 1,900 gas wells were damaged and had to be closed off as the floodwaters inundated entire communities.
Sewage treatment plants and other utilities were knocked out in a number of towns, and standing water left by floods on prairie farmlands posed the threat of significant damage to crops already planted in the region. Northeast Colorado Health Department has advised with the local CSU Extension office in Logan County regarding local crops and gardens that had been exposed to flood waters. As the flood waters in our area should be considered contaminated, local crops and gardens may not be considered suitable for human consumption or animal feed. In the flooded areas, an estimated 23,000 acres of cropland was impacted and stretched from Boulder to Logan Counties and included: alfalfa, corn, hay, silage and sugar beets. The estimated loss of production ranged from $3.4 million to $5.5 million.
Governor Hickenlooper declared a disaster emergency on September 13th, in 11 counties across northeast Colorado including: Adams, Arapahoe, Broomfield, Boulder, Denver, Jefferson, Larimer, Logan, Morgan, Washington and Weld. By September 15th, federal emergency declarations covered those counties as well as Clear Creek County. Projected losses from the flooding statewide was nearly $3 billion in property damage. Half of the damage estimate was from housing and half from the commercial and government sectors, according to Eqecat, a catastrophe modeling firm; this was the first comprehensive estimate of the disaster's economic toll. The projected losses for residential property alone were about $900 million. Another $1 billion was attributed to commercial and goverment property, including roads and bridges. In addition, more than 11 thousand people were evacuated, reportedly the largest since Hurricane Katrina. President Obama declared a state of emergency for Boulder and Larimer Counties, with an additional 10 counties added September 16th including: Adams, Arapahoe, Broomfield, Clear Creek, Denver, Jefferson, Morgan, Logan, Washington and Weld Counties. The president also declared a major disaster specifically for Boulder County, which provided for federal recovery assistance.
There were six fatalities directly attributed to flash flooding. By county, those fatalities included 4 in Boulder County and 2 in Larimer County. Two 19-yr old teenagers died on the evening of the 11th, after they were swept away by floodwaters after abandoning their vehicle on Lindon Drive in Boulder. In Jamestown, a 72-yr old man was killed when the building he was in collapsed. An 80-yr old Lyons resident was killed in the early morning hours of the 12th, when his truck was swept into the St. Vrain River near his home. On the evening of the 12th, a 79-yr old Larimer County resident was killed when she was swept away while trying to climb to safety from her home in Cedar Point. A 61-yr old Cedar Point resident died when her home was swept down the Big Thompson River by the floodwaters. An indirect fatality occurred on the 16th. An 80-yr old Idaho Springs resident drowned in Clear Creek when the embankment he was standing on collapsed.
Along the South Platte River, the crest of the flood at Kersey was near 18.8 feet on September 14th, which was significantly higher than the record crest of 11.73 feet set on May 8, 1973. On September 15th, the flood crest was near 13.7 feet at Balzac which exceeded the record of 13.3 feet set on June 18, 1965. On September 18th, the flood crest was at Julesburg was 10.6 feet, which broke the previous record of 10.44 feet set on June 20, 1965.
In Boulder, some of the monthly records broken included: one-day all-time record: 9.08 inches which shattered the previous wettest day of 4.8 inches set on July 31, 1919; one-month record of 18.16 inches, which broke the previous all-time monthly record of 9.59 inches set in May of 1995; wettest September on record which broke the previous record of 5.5 inches set in September of 1940; one-year record of 34.15 inches broke the previous wettest year of 29.93 inches set in 1995. In Denver, the total precipitation for the month of September was 5.61 inches, which was 4.65 inches above the normal of 0.96 inches. This is the most precipitation ever recorded in Denver for the month of September.
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 Sep 11, 1:41 PM MST, 4 hours 9 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DENVER/BOULDER CO 241 PM MDT WED SEP 11 2013 .SHORT TERM...TONIGHT AND THURSDAY...LITTLE CHANGE IN THE PATTERN OVER THE NEXT 24 HOURS. UPPER LEVEL LOW CENTERED NEAR LAS VEGAS WILL SLOWLY LIFT NORTH OVER THE NEXT 24 HOURS. A VERY MOIST SOUTH- SOUTHWEST FLOW ALOFT WILL CONTINUE. A SHORT WAVE TROUGH EMBEDDED IN THE FLOW ALOFT IS OVER SOUTH CENTRAL/SOUTHEAST COLORADO. THIS IS BRING RAIN SHOWERS TO EASTERN AND NORTHEAST COLORADO AT THIS TIME. THE WAVE WILL CONTINUE TO MOVE NORTH-NORTHEAST AND PUSH THE WIDESPREAD SHOWERS EAST OF THE AREA. THERE IS SOMEWHAT DRIER AIR BEHIND THE WAVE AND THERE ARE PARTIAL BREAKS IN THE CLOUDS. THESE BREAKS HAVE ALLOWED SOME LOCATIONS CLIMB TO AROUND 70 DEGREES. EXPECT SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS TO REDEVELOP BEHIND THIS WAVE DUE TO SOME INSTABILITY. HEAVY RAIN WILL BE THE BIGGEST CONCERN THE STRONGER SHOWERS AND THUNDERSTORMS. AIRMASS IS VERY MOIST WITH PRECIPITABLE WATER VALUES AROUND 1.25 INCHES AND DEW POINTS IN THE UPPER 50S AND LOWER 60S. WHERE TEMPERATURES CLIMB TO AROUND 70 DEGREES CAPES WILL BE AROUND 700 J/KG. NOT ENOUGH FOR SEVERE WEATHER...BUT PLENTY OF MOISTURE AND INSTABILITY FOR VERY HEAVY RAIN OUT OF THUNDERSTORMS. RAINFALL RATES OUT OF THE THUNDERSTORMS MAY REACH AN INCH IN 20 TO 30 MINUTES. SHOWERS ARE EXPECTED TO DECREASE OVERNIGHT AND THUNDERSTORMS WILL END. THE FORECAST AREA WILL BE BETWEEN WAVES SO ONLY EXPECT SCATTERED TO ISOLATED SHOWERS OVERNIGHT. THE NEXT WAVE WILL ROTATE INTO SOUTHERN COLORADO THURSDAY AFTERNOON. THIS IS EXPECTED TO BRING ANOTHER ROUND OF RAIN SHOWERS AND ISOLATED THUNDERSTORMS. AIRMASS TO REMAIN VERY MOIST...SO HEAVY RAIN WILL AGAIN BE A THREAT. HIGHS WILL BE COOL OVER NORTHEAST COLORADO WITH HIGHS IN THE MID 60S ALONG THE FRONT RANGE TO LOWER 70S OVER THE EASTERN PLAINS. .LONG TERM...THE UPPER LOW WILL REMAIN ANCHORED OVER THE GREAT BASIN THROUGH SATURDAY...THEN SLOWLY EJECT EASTWARD ACROSS THE ROCKIES SUNDAY AND MONDAY. AHEAD OF THIS LOW THE AIRMASS OVER COLORADO WILL CONTINUE TO BE MOIST AND MARGINALLY UNSTABLE WITH OCCASIONAL TROUGHS LIFTING ACROSS THE STATE. FRIDAY LOOKS LIKE ANOTHER DAY WITH A GOOD CHANCE OF AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS...SATURDAY LOOKS A BIT DRYER AND WARMER. ON SUNDAY A COLD FRONT IS EXPECTED TO DROP ACROSS NORTHEAST COLORADO. THIS WILL INCREASE LOW LEVEL UPSLOPE FLOW...DROP TEMPERATURES A FEW DEGREES...AND INCREASE THE CHANCE OF SHOWERS AND THUNDERSTORMS. THE PATTERN WILL CHANGE EARLY NEXT WEEK WITH SOUTHWEST FLOW DEVELOPING OVER COLORADO...AND A LEE SURFACE TROUGH IN EASTERN COLORODO. THIS WILL RESULT IN WARMER TEMPERATURES. THERE MAY BE A FEW THUNDERSTORMS OVER THE MOUNTAINS EARLY NEXT WEEK BUT THE PLAINS SHOULD REMAIN DRY. && .AVIATION...CEILINGS WILL GENERALLY REMAIN BETWEEN 3000 TO 6000 FEET ACROSS THE DENVER AREA FOR THE REST OF THIS AFTERNOON AND EVENING. CEILING MAY OCCASIONALLY BE HIGHER. AT BJC...CEILINGS WILL BE LOWER...AT 1000 TO 3000 FEET DUE TO UPSLOPE WINDS. CEILINGS WILL FALL OVERNIGHT AGAIN TO 500 TO 1500 FEET. THERE IS A GOOD CHANCE AGAIN FOR FOG AND CEILINGS OF 100 TO 500 FEET BETWEEN 10Z AND 15Z. ISOLATED STORMS WILL BE POSSIBLE THROUGH 02Z. BRIEF HEAVY RAIN WILL BE ACCOMPANY THE STRONGER STORMS. LOW CLOUDS AND RAIN SHOWERS WITH A FEW EMBEDDED AFTERNOON STORMS ARE EXPECTED TO PREVAIL ONCE AGAIN THURSDAY. && .HYDROLOGY...RAINFALL OVER THE PAST FEW DAYS HAVE SATURATED SOILS IN SPOTS. A FEW STREAMS ARE RUNNING HIGH BUT NO FLOODING HAS BEEN REPORTED. THE HEAVIER RAIN SHOWERS ARE PRODUCING RAINFALL RATES OF A QUARTER TO A HALF INCH PER HOUR...NOT A BIG CONCERN. HOWEVER THE THUNDERSTORMS THAT FORM COULD PRODUCE RAINFALL RATES OF 1 INCH IN 20 TO 30 MINUTES...WHICH COULD CAUSE LOCALIZED FLOODING ISSUES. RAIN SHOWERS WITH EMBEDDED THUNDERSTORMS WILL CONTINUE THROUGH FRIDAY. IT WILL DRY OUT SOME THIS WEEKEND BUT AFTERNOON AND EVENING THUNDERSTORMS ARE EXPECTED. && .BOU WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...MEIER LONG TERM....RTG AVIATION...MEIER
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DENVER/BOULDER CO 1056 AM MDT WED SEP 11 2013 COZ030>051-121700- 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- 1056 AM MDT WED SEP 11 2013 THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHEAST AND NORTH CENTRAL COLORADO. .DAY ONE...TODAY AND TONIGHT SHOWERS AND A FEW THUNDERSTORMS WILL OCCUR TODAY AND CONTINUE INTO THE EVENING HOURS. RAINFALL AMOUNTS UP TO AN INCH IN TWO TO THREE HOURS MAY OCCUR IN A FEW LOCATIONS WHERE HEAVIER SHOWERS DEVELOP. UNDER THE STRONGER THUNDERSTORMS...UP TO AN INCH OF RAIN WILL BE POSSIBLE IN 20 MINUTES TO THIRTY MINUTES. SCATTERED RAIN SHOWERS WILL LINGER THROUGH THE NIGHT. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY UNSEASONABLY COOL AND MOIST CONDITIONS WILL PERSIST FOR ONE MORE DAY ON THURSDAY WITH SHOWERS AND THUNDERSTORMS ACROSS MOST OF THE OUTLOOK AREA. SOME STORMS DURING THE AFTERNOON AND EVENING HOURS MAY PRODUCE HEAVY RAINFALL AND POSSIBLY SOME SMALL HAIL...POSSIBLY RESULTING IN LOCALIZED FLOODING. THE HIGHER MOUNTAIN PEAKS MAY ALSO SEE SOME LIGHT SNOW. THERE WILL BE A BIT MORE SUNSHINE FRIDAY AND SATURDAY...BUT SCATTERED SHOWERS WILL STILL BE POSSIBLE ESPECIALLY IN THE AFTERNOON AND EVENING. SUNDAY A COOL FRONT PUSHES INTO NORTHEAST COLORADO INCREASING CHANCES FOR PRECIPITATAION ONCE AGAIN. DRYER AND WARMER WEATHER FINALLY ARRIVES IN NORTHEAST COLORADO BY TUESDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY OR TONIGHT.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DENVER CO
536 PM MDT WED SEP 11 2013
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0212 PM HEAVY RAIN GENESEE 39.69N 105.27W
09/11/2013 M4.15 INCH JEFFERSON CO TRAINED SPOTTER
48 HOUR RAINFALL TOTAL
&&
JKPRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE DENVER CO
636 PM MDT WED SEP 11 2013
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0628 PM HEAVY RAIN ERIE 40.03N 105.05W
09/11/2013 M2.50 INCH WELD CO BROADCAST MEDIA
PAST TWO HOURS.
0614 PM HEAVY RAIN LYONS 40.22N 105.27W
09/11/2013 M1.90 INCH BOULDER CO BROADCAST MEDIA
PAST 24 HOURS
0212 PM HEAVY RAIN GENESEE 39.69N 105.27W
09/11/2013 M4.15 INCH JEFFERSON CO TRAINED SPOTTER
48 HOUR RAINFALL TOTAL
&&
JKThe Denver radar (KFTG), 72 km away, was scanning. The volume nearest the first event began at 00:48 UTC.
63 flash flood, 10 flood. Local standard time, as filed.
Running water, up to a depth of 12 inches, and 50 feet wide was running across the intersection of 95th Street and Lookout Road near Niwot. The floodwaters forced the closure of Erie Parkway. Later a 4 to 5 ft wall of water, was reportedly observed running through the area.
Heavy rainfall produced a mudslide at Left Hand and Olde Stage Road. One foot of debris was reported on the roadway near Gregory Canyon.
Flash flooding forced numerous road closures in the city of Boulder including Lookout Road, from 79th to 95th, and South Boulder Road near Cherryvale. In addition, culverts were reportedly overflowing at 51st and Kelso Road. In Erie, Vista Parkway was inundated with 3 ft of standing water.
Flash flooding was observed in the High Park burn area. It forced the closure of CO14, between Rustic and Teds Place. Other road closures included Larimer County Road 70 between County Roads 20 and 21.
Coal Creek went over its banks and washed out portions of CO72 at Twin Spruce. The highway was completely washed out between Plainview and Twin Spruce. Additional washouts occurred on side streets within Coal Creek Canyon. Many residents were ordered to remain in their homes (Shelter In Place) until rescue teams could reach them.
Flash flooding forced the closure of Erie Parkway, between Briggs Street and Weld County Road 7.
In Boulder, Old Tale Road at McSorley was closed due to debris and downed trees. Debris forced the partial closure of 3rd Street and Canyon and the Eastbound lane of Baseline Road near Foothills Parkway. Flooding was also reported at: 9th and Alpine, 9th and Balsam and South Boulder Road at Manhatten Street. Two teenagers in Boulder were killed when they abandoned their vehicle while trying to flee the floodwaters. The two other occupants suffered minor injuries; one escaped the vehicle while the other remained in the car and was later rescued. In the city of Boulder, 61 properties were destroyed.
In the Fourmile burn area, widespread flash flooding and debris flows forced the closure of Fourmile Canyon at Boulder Canyon. Water was also reportedly flowing over Gold Run Road at Ingram Gulch due to a blocked culvert. Major structural damage occurred in Fourmile Canyon and Jamestown, which forced a mandatory evacuation of all residents. A man in Jamestown was killed when the building he was in collapsed. In the Jamestown area, 26 properties were destroyed. Flash flooding was also reported in Lefthand Canyon. In unincorporated Boulder County, a total of 86 properties were destroyed.
Flash flooding and debris was reportedly washed out a sections of CO72 at the base of Coal Creek Canyon. Road closures included: CO72 , from CO93 to Coal Creek Canyon; CO93, between CO72 and CO128; CO72, between CO93 and Indiana St.; U.S. 36, between Wadsworth Blvd and Flatirons; Interstate 70 west, from Floyd Hill to Hidden Valley due to rock slides. Natural Gas Lines in Coal Creek Canyon were also shut off.
In Boulder, many vehicles were abandoned near Lookout Road and Spine due to floodwaters. Significant flooding was reported at the Justice Center; the Juvenile Detention Center had to be evacuated to the second floor. Floodwaters to a depth of 2 feet inundated Hawthorne Street in north Boulder. Moderate flooding was observed along Boulder Creek. Boulder Canyon was closed due to flash flooding. Numerous rock and mudslides made Lefthand Canyon impassable. Major structures were lost in Jamestown. In Lyons, rock and mud slides were also reported and the Waste Water Treatment Plant was breached. An 80-yr old man was killed when his truck was swept into the St. Vrain River. He had returned to his home to look for his wife. His vehicle was found 200 yards from their residence. In town, 82 properties were destroyed. Mandatory evacuations were ordered in Longmont, along the Lefthand and St. Vrain Creeks. In Longmont, 53 properties were destroyed.
Flooding was occurring along Boulder Creek in Boulder where it crested. Flooding also occurred along South Boulder Creek near Eldorado Springs with flooding impacting nearby homes.
Continuous heavy rainfall produced flash flooding along sections of U.S. 34, through Big Thompson Canyon, and U.S. 36, between Estes Park and Lyons. In addition, a small earth dam was reportedly breached at Big Elk Meadows.
Flash flooding continued with several collapsed homes reported near Jamestown. Major flooding continued on the South St. Vrain River in northern Boulder County. Moderate to major flooding was reported in the Fourmile burn area west of Boulder. Moderate flooding was reported along Boulder Creek through the city of Boulder and in Lefthand Canyon.
Continuous heavy rainfall produced flash flooding. Additional road washouts occurred on side streets within Coal Creek Canyon. CO72 was completely washed out between Plainview and Twin Spruce.
Flash flooding forced the closure of CO36, between Wadsworth Blvd and Flatirons.
Heavy rain, ranging from 6 to 18 inches through the storm event, caused widespread flooding along the entire drainage systems of Boulder and St. Vrain Creeks. Three vehicles were partially submerged when floodwaters undercut Dillon Road near CO287, between Lafayette and Broomfield. When the road first collapsed, several people were able to get out of the water quickly, but three were trapped in their vehicles and had to be rescued. The three drivers were taken to local hospitals for treatment. Extensive flooding was reported in Longmont and forced several road closures. Floodwaters tipped over two storage tanks containing sulfuric acid at the Longmont Brewery. Several shelters were set up for evacuees. Numerous bridges, culverts and roads were damaged in eastern Boulder County. The town of Lyons was completely isolated by floodwaters. The wastewater treatment plant was destroyed. There were numerous rock and mud slides in the area. Mandatory evacuations were ordered for the entire town of Lyons. Train tracks were washed out near the intersection of the Diagonal and Jay Road in Boulder. Boulder Canyon was closed from Nederland to Magnolia. South Boulder Road was closed due to flooding between Cherryvale and 55th. About 40 buildings on the University of Boulder campus were damaged and 400 students evacuated.
According to FEMA, 10,588 homes were impacted by flooding. Preliminary damage assessments for Boulder, Lyons, Longmont, Jamestown, Superior and unincorporated Boulder County included: 337 homes destroyed; 428 homes with major damage; 3,426 homes with minor damage; 33 commercial buildings with major damage; 54 commercial buildings with minor damage. The most extensive damage impacted lakes and rivers; in particular, along and near the St. Vrain River corridor.
The breakdown for the damage estimate in Boulder County included: $132 million for the city of Longmont; $91.2 million in damage to government facilities, roads and bridges in unincorporated Boulder County; $49 million for the city of Boulder's infrastructure, parks and open space; $25 million for the county's parks, trails and open spaces.
Heavy rain caused five very small dams in the Big Elk Meadows area to fail. As a result, a family became trapped when a county road was washed out and floodwaters damaged their home. Road closures included: U.S. 34 east/west, between Loveland and Estes Park; CO14 east/west, between Walden and Ted's Place. Larimer County Roads 27E, 25E, 52E and 54E were all closed near La Porte due to flash flooding. Several roads were also washed out southwest of Loveland and north of Fort Collins.
Continuous heavy rainfall produced flash flooding. Numerous road closures were reported including Highway 36 from Estes Park to Lyons.
Continuous heavy rainfall produced flash flooding. Weld County Roads 18 and 20 were flooded. Roadways running parallel to Interstate 25, near County Road 11, were inundated with 6 to 8 inches of water. In Frederick, County Road 18 was washed out at Godding Hollow Pkwy. County Road 7 was washed out between County Road 20.5 and CO119. Welland Loop Dr. was also washed out between Drake St. and W. Conservation Dr.
Flash flooding in Coal Creek Canyon caused a gas line break which impacted 1500 homes. The areal coverage of the flooding increased along Coal Creek.
Continuous heavy rainfall produced flash flooding. Rainfall amounts up to this point ranged from 4 to 7 inches over central Boulder County. People were trapped as several major creeks flooded including: Coal Creek, Left Hand Canyon, Fourmile Creek and St. Vrain Creek. People were reportedly trapped on their roofs.
Continuous heavy rainfall produced flash flooding. The town of Glen Haven, between Estes Park and Drake, was cut off due to water and debris blocking roads in both directions.
Continuous heavy rainfall produced flash flooding. Floodwaters were reportedly breaking through basement windows west of Brighton.
Flash flooding forced the closure of the Boulder-Denver Turnpike, from McCaslin Blvd. to the Boulder city limits. The roadway was inundated by 2 ft of standing water near Superior. Water was reportedly overtopping all the cross bridges along Table Mesa Blvd, from Lehigh to Broadway. Baseline and 76th was flooded and impassable. Flash flooding was observed on Marshall Road, about 4 miles south of Boulder. Another road was washed out at 4th and Hawthorne. In Superior, one property was destroyed.
Continuous heavy rainfall produced flash flooding. Standing water at Tower Road caused delays for travelers going to and from Denver International Airport.
Heavy rain, ranging from 6 to 12 inches through the storm event caused widespread flooding, including the entire drainage systems of the Big Thompson and Cache La Poudre Rivers. Some of the hardest hit communities included: Estes Park, Drake, Glen Haven, High Park burn area and Loveland. Most of the parks, trails and open spaces in Larimer County suffered some degree of damage. Dams in the Big Elk Meadows area failed which drained into the Little Thompson River. Multiple structures were reportedly damaged, with several rescues from the flood and infrastructure damage. Power lines were also downed. Road closure included U.S. 36, from Estes Park to CO66. Mandatory evacuations were ordered for residents along the Big Thompson River on the west side of Loveland. The county experienced issues with water and wastewater plants due to flooding. In Fort Collins, an estimated 20 businesses and 10 homes were damaged by floodwaters.
Preliminary damage estimates included $89 million to roads and bridges throughout the county. In addition, damage to the sewer system in Estes Park could total more than $20 million. At least 1,700 homes were destroyed in Larimer County, and an estimated 16,300 dwellings were damaged throughout the flood zone.
Continuous heavy rainfall produced flash flooding. County officials also issued flash flood emergencies downstream for Fort Lupton, Dacono, Platteville and other farming areas as debris piled up near bridges.
Continuous heavy rainfall produced flash flooding that inundated much of central Larimer County including the towns of Drake, Estes Park and Glen Haven.
Continuous heavy rainfall produced widespread flash flooding in the Lyons, with life threatening conditions.
Heavy rainfall and flash flooding washed out the east bound lane of James Canyon. Overland Road was also washed out, along the west bound lane of the Peak to Peak Highway near Jamestown.
Continuous heavy rainfall produced flash flooding. East Alameda Parkway between South Chambers Road and South Sable Boulevard was completely underwater.
A prolonged period of heavy rain produced widespread flooding.
Heavy rain, ranging from 4 to 10 inches through the entire storm event, caused widespread flooding along the entire drainage system of the South Platte River. Flooding and flash flooding inpacted Riverdale Golf Course and the Regional Park. The gulch that ran through those two areas caused flooding and erosion in several places including the newly created reservoirs between the Regional Park and 120th Avenue.|The Regional Park shop was also flooded as well as the Riverdale Golf Shop. All combined, the county’s estimated damage at the Park alone, not including the golf course, was about $637,000. Parts of Colorado Boulevard between CO7 and 168th Avenue were closed due to significant damage to the road surface and foundation.|Additional damage also occurred at retention ponds, parks and trails. The cost to roads and bridges was approximately $400,000 for repairs. Approximately 755 households were impacted by flooding.
Heavy rain, ranging from 6 to 16 inches through the storm event, caused widespread flooding and included the entire drainage systems of Bear, Coal, Clear, Leyden, Ralston and Van Bibber Creeks. In Arvada, Quaker St. near W. 82nd Ave. was closed due to flooding and infrastructure damage. Evacuations were ordered in the area of 68th Ave. and 82nd Ave., between McIntyre and Alkire Streets. Flooding washed out sections of W. 82nd Ave, east of CO93. Flooding was reported near the intersection of W. 92nd Ave. and Indiana St. A section of South Golden Road was washed out near Lena Gulch. Golden Gate Canyon was closed between CO93 and Robinson Hill. Many other roads in northern Jefferson County were inundated by floodwaters. Evacuations were also orders between Bear Lake Dam and Echo Lake Drive on Upper Bear Creek.
Preliminary damage estimates totaled more than $6 million. The most significant damage to roadways, homes and commercial buildings occurred in Evergreen, Coal Creek Canyon and Golden Gate Canyon. County officials said 14 residences were destroyed and 215 damaged. In addition, 27 commercial properties were damaged. Thirty-five minor structures were destroyed and 57 damaged.
Heavy rain, ranging from 6 to 10 inches through the entire storm event, caused widespread flooding, including the entire drainage system of South Boulder, Big Dry and Walnut Creeks. Due to extensive flooding, the Spruce Meadows section of the Broomfield Trail was closed due to significant collapses of the embankment between the trail and the adjacent irrigation ditch.
Continuous heavy rainfall produced flash flooding.
Continuous heavy rainfall produced flash flooding in and around Estes Park.
As a result of the heavy rain, a retention pond at the Rocky Mountain Arsenal breached. The retention pond was approximately 300 yards wide, and 15 to 20 feet deep.
Continuous moderate to heavy rainfall produced flash flooding.
Heavy rain continued to produce widespread flash flooding. Non-stop rain caused road closures, washouts and damage throughout the High Park burn area.
Heavy rain, ranging from 4 to 10 inches through the entire storm event, caused widespread flooding along entire drainage system of the Cache La Poudre River including Greeley and vicinity. In Evans, thousands of residents were told not to flush their toilets or shower, prompting Greeley-Evans School District 6 to close schools. Similar problems occurred in Lasalle. County commissioners estimated at least $230 million in damages to properties and infrastructure throughout Weld County. County officials estimated more than 7,000 parcels of land were impacted by floodwaters; 2,900 were residential and 2,300 were agricultural. In addition, 355 commercial and 62 industrial properties were damaged. A total of 140 county roads were closed at some point, with 654 lane miles of the county's roadways impacted by the flood. Sixty-four irrigation canals were also damaged. As a precaution, about 1,900 oil and gas wells had to be shut down.
Heavy rain, ranging from 4 to 12 inches through the entire storm event, caused widespread flooding along the entire drainage systems of East Tollgate and Coal Creeks. The areas around Parker Road and Piney Creek were flooded as several holding ponds did overflow their banks. Some of the worst flooded in Centenniel occurred along Arapahoe Road near Cottonwood. According to FEMA, 2,138 households were impacted by flooding.
Road closures included: East Fitzsimons Pkwy. and North Peoria, East 26th Ave and Fulton St., East 17th Ave and Dayton St., East Colfax and Peoria St., East 12th Ave. between Xanthia St. and Xenia St, East 12th Ave. and Yosemite St., East 11th Ave. and Willow St., East 11th Ave. and Xanthia St., East 11th Ave. and Xenia St., Del Mar Pkwy. and North Havana St., East 1st Ave and Moline St., East Alameda Ave. and South Havana St., South Peoria St. just North of East Ford Ave., South bound 225 and East Alameda Ave., East Alameda Ave. and East Alameda Dr., East Florida Ave. and South Galena St.
Heavy rain continued to produce widespread flash flooding. Denver Police evacuated Colfax Avenue to 11th Avenue from Verbena Street to Xanthia Street due to high water in the area.
Heavy rain continued to produce widespread flash flooding. Aurora's Prairie Waters, a water recycling and purification system, was shut down due to flooding. Four of the facility's 17 wells where water is siphoned from the South Platte River in Brighton were flooded. Prairie Waters provides up to 20 percent of the city's water.
Heavy rain upstream, including the headwaters of the Big Thompson River, its tributaries and Rocky Mountain National Park continued.
Heavy rain continued to produce widespread flash flooding over areas already inundated by floodwaters. Road closures included: East Fitzsimons Pkwy. and North Peoria, East 26th Ave and Fulton St., East 17th Ave and Dayton St., East Colfax and Peoria St., East 12th Ave between Xanthia St. and Xenia St., East 12 Ave. and Yosemite St., East 11th Ave. and Willow St., East 11th Ave. and Xanthia St., East 11th Ave. and Xenia St., Del Mar Pkwy. and North Havana St., East 1st Ave. and Moline St., East Alameda Ave. and South Havana St., South Peoria St. just North of East Ford Ave., South Bound 225 and East Alameda Ave., East Alameda Ave. and East Alameda Dr., East Florida Ave. and South Galena St. In Aurora, a mother and her baby had to be rescued when her car stalled in a flooded street.
Heavy rain continued to produce widespread flash flooding. County roads were closed near Livermore with water overtopping sections of the roadway.
Heavy rain continued to produce widespread flash flooding. A 79-yr old Larimer County resident was killed when she was swept away while trying to climb to safety from her home in Cedar Point. In addition, A 61-yr old Cedar Point resident died when her home was swept down the Big Thompson River by the floodwaters.
Heavy rain continued to produce widespread flash flooding along Leyden Creek. The creek remained near bankfull on the 13th.
Heavy rain continued to produce widespread flash flooding in the High Park burn area and surrounding locations.
Heavy rain continued to produce widespread flash flooding. Between 19th and Lombardi, the road was impassable as it was inundated with 15 feet of standing water. Water was reportedly flowing south to north, approximately 40 feet across Arapahoe Road. Lee Hill was impassable as well.
Continuous heavy rainfall produced flash flooding. Commerce City officials ordered about 400 residents to leave a neighborhood near the Rocky Mountain Arsenal National Wildlife Refuge due to the potential that further retention ponds would breach. Extensive flooding was reported in Commerce City with flooded basements, homes and roads under anywhere from 1 to 3 feet of standing water.
Flash flooding continued to worsen Many roads in the county were impassable with flowing and standing water. All major roadways out of Boulder were impacted by floodwaters. During the event, U.S. 36 was closed from McCaslin Blvd. to Flatiron due to major flooding. Boulder Canyon was reported to be completely washed out. Evacuations were ordered for residents at the mouth of Boulder Canyon to Broadway, and Pearl to Marine. In Boulder Canyon, one mudslide was 400 ft. long and 4 ft. deep making the canyon completely impassable. Boulder Creek was reportedly completely out of its banks in most areas and moving extremely fast. Newton Court and an apartment were flooded at 1444 Folsom. Several cars were inundated up to their doors and the first floors of the apartment complex were flooded. The 1700 block of Marshall was closed during the morning due to major flooding. Significant road damage was reported in Boulder Canyon.
Flash flooding washed out large sections of U.S. 34 along the Big Thompson River in Big Thompson Canyon. Numerous roads and streets in and around Loveland were impassable due to the combination of flooding and flash flooding along the Big Thompson River.
In Erie, Kenosha Rd. between 119th and Lombardi was 15 ft. deep and impassable. CO52 was closed east of the county line road, as it was washed out at Weld County Road 10-1/2. Boulder Creek completely flooded the Boulder/Weld County Line and CO52 intersection. The most extensive flooding occurred where Coal Creek and Boulder Creek merged.
Continuous heavy rainfall produced flash flooding.
Continuous moderate to heavy rainfall produced flash flooding. CO72 was closed from CO119 in Gilpin County to CO93 in Jefferson County. US 6 from Golden to the junction of US 6 and CO119 was closed in both directions due dangerous conditions from falling rocks.
Continuous moderate to heavy rainfall produced flash flooding.
Continuous heavy rainfall produced widespread flash flooding.
Continuous heavy rainfall produced widespread flash flooding. The CO36 Turnpike was also submerged by 3 feet of water at Foothills Parkway.
Continuous heavy rainfall produced flash flooding. Evacuations were ordered for the Fairfax Park neighborhood in Commerce City, with numerous road closures throughout the city.
The combination of heavy rain, coupled with extremely saturated ground conditions, produced additional flash flooding.
The combination of heavy rain, coupled with extremely saturated ground conditions, produced additional flash flooding. According to FEMA, 113 households in the county were impacted by flooding.
The combination of heavy rain, coupled with extremely saturated ground conditions, produced additional flash flooding.
The combination of heavy rain, coupled with extremely saturated ground conditions, produced additional flash flooding.
The combination of heavy rain, coupled with extremely saturated ground conditions, produced additional flash flooding.
The combination of heavy rain, coupled with extremely saturated ground conditions, produced additional flash flooding. Several inches of water was reported running through the intersection of Lincoln Ave. and Parker.
The combination of heavy rain, coupled with extremely saturated ground conditions, produced additional flash flooding. Significant flooding was reported at the intersections of Jordan Road and Broncos Parkway, and at Jordon Road and Bluebell. Cars were stalled in several inches of standing water at the intersections of Alameda Ave. and Havana as well as Mississippi Ave. and Kalispell.
The combination of heavy rain, coupled with extremely saturated ground conditions, produced additional flash flooding. A section of 60th Ave. in Commerce City had to be closed where Sand Creek crossed the road.
The combination of heavy rain, coupled with extremely saturated ground conditions, produced additional flash flooding. Numerous cars were stalled in several inches of standing water near Interstate 225 and Iliff Ave. Significant over running of ponds and streams was also observed near Chambers Road and Quincy Ave.
Other road closures included: 26th and Picadilly, a 50-ft stretch East and West Bound had moving water flowing over it; I-225 South Bound Closed at Alameda, I-225 South Bound just north of Mississippi Ave down to 1 1/2 lanes of traffic; Alameda and Sable East Bound; Alameda and Chambers West and North Bound, Florida and Abilene South Bound, Expo and Abilene North and South Bound, Jewell and Abilene North Bound, Potomac and 6th North Bound, Hoffman and Potomac West Bound, 14th and Potomac South Bound, Alameda and Havana, All directions; and the intersection of 6th and Havana.
The combination of heavy rain, coupled with extremely saturated ground conditions, produced additional flash flooding.
The combination of heavy rain, coupled with extremely saturated ground conditions, produced additional flash flooding. Flash flooding forced the closure of Wolfsenburger Road, west of Castle Rock. In addition, Plum Creek was reportedly one foot above bankfull levels at Sedalia.
Flash flooding forced the closure of Wolfsenburger Road, west of Castle Rock. In addition, Cherry Creek near Parker was 1.5 feet above flood stage.
Heavy rain produced extensive field flooding. Floodwaters inundated and washed out sections of several county roads as well.
As the offices recorded each death: direct deaths were caused by the weather itself, indirect ones by something it set in motion.
| Event | Date | Age | Sex | Where | Kind |
|---|---|---|---|---|---|
| Flash Flood, Boulder | 2013-09-11 | 19 | Female | Outside/Open Areas | Direct |
| Flash Flood, Boulder | 2013-09-11 | 19 | Male | Outside/Open Areas | Direct |
| Flash Flood, Boulder | 2013-09-11 | 72 | Male | Permanent Structure | Direct |
| Flash Flood, Boulder | 2013-09-12 | 80 | Male | Vehicle/Towed Trailer | Direct |
| Flash Flood, Larimer | 2013-09-12 | 79 | Female | Permanent Home | Direct |
| Flash Flood, Larimer | 2013-09-12 | 61 | Female | Permanent Home | Direct |
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2013Every state in 2013This day in weather historyWarnings in Colorado, 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: 473881, 473885, 473891, 473897, 481810, 473893, 473899, 473900, 474056, 474661, 477450, 477454, 477456, 474058, 474687, 474041, 477458, 477459, 474057, 477460, 477461, 477431, 481902, 477444, 474668, 477433, 477435, 477441, 476814, 477442, 477742, 474675, 474685, 474688, 477445, 477448, 478402, 477449, 477462, 474674, and more.