6 inches was observed from southeast Denver and Aurora, and extended south southwest to Castle Pines, west of Castle Rock and into Roxborough State Park. Most of the rainfall fell in less than 45 minutes.
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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.
Torrential rainfall, up to 2.6 inches was observed from southeast Denver and Aurora, and extended south southwest to Castle Pines, west of Castle Rock and into Roxborough State Park. Most of the rainfall fell in less than 45 minutes. A storm drain at Quincy and Parker was clogged up by rocks that got pulled out from near the sidewalk by running water. Several cars were towed out of the flooded area. Minor flooding was reported on the Dry Creek exit of I-25 with standing water on Iliff Ave. near Buckley Rd. Parker and Quincy Roads and Dartmouth and Chambers Roads also were impassable. Multiple accidents occurred due to the rain and flooding. A few severe storms brought large hail up to quarter size, and strong winds from 60 to 65 mph in Arapahoe, Douglas and Elbert counties.
In Larimer County, flash flooding was reported In the Cameron Peak burn area along Streamside Drive. Dangerous flooding is occurring in the area of Glen Haven, including County Road 43 to Drake. Highway 34 was closed from County Road 29 due to rockslides east of Drake.
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 Aug 15, 10:09 AM MST, 2 hours 51 minutes earlier.
Area Forecast Discussion National Weather Service Denver/Boulder CO 1109 AM MDT Mon Aug 15 2022 .UPDATE... Issued at 1109 AM MDT Mon Aug 15 2022 The convective cloudiness has just begun to developing in the last 45 minutes. Some of the CWA has heated up a bit more than expected this morning with less cloudiness earlier. Surface dew points are in the 60s F for the plains and foothills right now with even some mid and upper 60s over the northeast corner. There is significant moisture in place. For the grids and forecast adjustments will up temperatures a tad. Also started the pops over the CWA an hour or two later based on current reality. The flood watch still looks on track, and in fact, with a tad more heating expected the heavy rains in some places are a good bet. && .SHORT TERM...(Today and tonight) Issued at 433 AM MDT Mon Aug 15 2022 ...FLASH FLOOD THREAT TODAY... Ingredients will be in place today for thunderstorms with locally heavy rain and flash flooding, it's just the details that still make this a tricky forecast. In favor for heavy rain, we'll have the following: 1) Precipitable water values about 170% of normal, or about 1.25" for the I-25 Corridor. 2) Warm cloud depth around 5,000 feet. 3) Relatively slow storm motions of 15-20 mph. 4) Upslope component into the foothills. 5) Weak shortwave (upper speed max) riding across the top of the ridge. The combination of these factors suggests storm capable of producing very heavy rain, with efficient rain processes. Given the above, would expect the strongest storms to produce up to 2" of rain in just 30-45 minutes. Factors against heavy rain would be: 1) Cloud cover. Locations that see more persistent clouds this morning could essentially remain too stable. Most likely that favors the northern half of our forecast area. 2) Instability. With a weak surge today and deeper north/northeast flow, the best instability is expected to orient itself from the southern Front Range Foothills and Palmer Divide area southward. 3) Outflow being strong enough to overcome any upslope, effectively pushing stronger convection/development farther to the south and east. Thus, we still expect the highest risk of flash flooding to occur over the foothills and Palmer Divide this afternoon and evening. However, the Denver metro area is certainly not in the clear - if we see some sunshine and sufficient destabilization then the flash flood potential and Flood Watch could still be expanded to include the metro area. The incoming shifts will have to watch satellite trends and monitor this expansion potential. For later this evening, we expect more widespread showers and embedded storms to continue. This would be the result of relatively deep upslope flow (past 700 mb), near neutral lapse rates and moist adiabatic/skinny CAPE profiles, and continued lift under the right entrance region of the upper jet - although latest model trends are a bit further north with this feature overnight. That upslope could focus more rain in/near the foothills and Palmer Divide, even past midnight. We do think there will be a decrease in intensity, although the skinny CAPE profiles and relatively high warm cloud depth could still result in locally heavy rainfall and efficient rainfall processes. .LONG TERM...(Tuesday through Sunday) Issued at 457 AM MDT Mon Aug 15 2022 Tuesday, temperatures will remain cool under persistent pressure heights over Colorado. Ridging upstream over Pacific Northwest and Great Basin will begin to stream in dry air aloft from the north. There should still be well above normal precipitable water across the high country through the afternoon; expect scattered to widespread storms through the evening, heavily favoring the southern Front Range, South Park and Palmer Divide. Storm intensity should be pretty well limited by a general lack of instability and shear, and forecast soundings are showing mid level stability. Moderate precipitation and gusts. Much drier air across the lower elevations will keep coverage generally more isolated and precipitation light. Wednesday, pressure heights should continue to rise over the Pacific Northwest and Great Basin, and now Colorado as well. Drier air aloft will also promote partly cloudy to mostly clear skies through the day. High temperatures will probably be back up to near normal: mid 80s across the plains, 70s and 80s in the foothills and mountain valleys, and 60s and 70s in the mountains. Afternoon and evening precipitation will be similar to Tuesday but with slightly lesser coverage and intensity, especially across the plains. Thursday, could be a bit warmer yet but this depends on the timing and strength of a cool front associated with a shortwave passing to our northeast. If the front is early and strong enough it could keep temperatures near normal another day, otherwise expect a few degrees warming. That wave might also bring some mid level forcing over our northeast corner in the afternoon and evening, but there is not much else to work with and therefore probably little impact. Friday through the weekend, there is much less certainty in forecast details due to a somewhat disorganized synoptic system. Generally, it looks like falling heights - possibly including a weak cutoff low over the Great Basin - and weak flow aloft, with gradually increasing moisture over the high country again as another plume of moisture works in from the west. This all should lead to cool temperatures across the area, and gradually increasing precipitation across the mountains. Models have it quite dry across the lower elevations for a while longer. && .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) Issued at 1105 AM MDT Mon Aug 15 2022 Models continue to show the upslope winds at DIA. Will keep a northeasterly and/or easterly component to the winds into the early/mid evening hours, before drainage wind patterns kick in around 06Z. Will leave the TEMPO group in for thunderstorms, and the heavy rains are possible. Ceilings could be BKN030-045 from 22Z-05Z with the precipitation. && .HYDROLOGY... Issued at 457 AM MDT Mon Aug 15 2022 The threat of flash flooding will be higher today, given the following favorable ingredients: Precipitable water around 170% of normal, warm cloud depth near 5,000 feet, relatively slow storm motions of 15-20 mph, and upslope component which could slow eastward progression a bit. Thus, a Flood Watch remains in effect for the Front Range Mountains and Foothills (burn areas included) and the Palmer Divide area. Stronger storms would be capable of producing up to 2 inches of rain in 30-45 minutes, as long as enough instability can be generated in the presence of mid level clouds and a cooler north/northeast surge. Because of the instability factor, the Denver metro area has a lower threat, but it is certainly not in the clear given the above mentioned parameters and potential for enough heating/destabilization. The next shifts will continue to monitor the cloud cover, mesoscale details, and flash flood that threat closely. Storms with locally heavy rain should continue through much of the evening, with a lower threat overnight as we gradually transition into more stratiform rainfall. Finally, we did move up the start time of the current Watch to 1 pm as storms should be firing in the higher terrain by then. Drier conditions will mean a lower threat of flooding for Tuesday through the end of the week. There may still be a low threat over the burn areas at times. Some increase in moisture is possible by next weekend. && .BOU WATCHES/WARNINGS/ADVISORIES... Flood Watch through this evening for COZ033>037-041. && UPDATE.......RJK SHORT TERM...Barjenbruch LONG TERM....EJD AVIATION.....RJK HYDROLOGY....Barjenbruch/EJD
Hazardous Weather Outlook National Weather Service Denver/Boulder CO 1121 AM MDT Mon Aug 15 2022 COZ030>051-161730- 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- 1121 AM MDT Mon Aug 15 2022 ...FLASH FLOODING POSSIBLE THROUGH THIS EVENING IN THE FRONT RANGE MOUNTAINS AND FOOTHILLS, SOUTH PARK, AND PALMER DIVIDE... This hazardous weather outlook is for northeast and north central Colorado. .DAY ONE...This Afternoon and Tonight Widespread showers and thunderstorms are expected over much of the forecast area this afternoon and evening. Heavy rainfall causing flash flooding will be the main threat with the storms. While burn areas would be most at risk, the threat of flash flooding also exists outside of the burn areas across the foothills and Palmer Divide area. Heavier rain and urbanized flooding will also be possible in portions of the Denver metro area and adjacent plains. The stronger storms could produce 2 inches of rain in 45 minutes. Be weather aware this afternoon and evening, and do not drive on flooded roads. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday A few showers and thunderstorms may linger mainly over the mountains Tuesday, but the threat of burn area flooding will be low. Drier weather is expected through the middle of the week, though there will still be some afternoon storms over the mountains with a low threat of burn area flooding. Some increase in thunderstorm activity is expected for the weekend. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed today or tonight. However, any reports of heavy rainfall or flooding would be appreciated. RJK/Gimmestad
The Cheyenne radar (KCYS), 94 km away, was scanning. The volume nearest the first event began at 19:57 UTC.
2 flash flood, 2 thunderstorm wind, 1 hail. Local standard time, as filed.
Roads closures around The Retreat due to flooding, with rockslides east of Drake.
Heavy rain produced flash flooding. Several intersections were flooded covered in 6 to 12 inches of water, and resulted in several road closures.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2022Every state in 2022This day in weather historyWarnings in Colorado, August 2022
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: 1052511, 1055491, 1052503, 1055492, 1055493.