STP 08-31-2016: Very Heavy Rainfall For Denver Metro, Also Farther East

Issue Date: Wednesday, August 31st, 2016
Issue Time: 9:25AM MDT

Summary

Scattered showers and thunderstorms dotted the landscape across large swaths of northeast Colorado. Activity started early, around noon, along the eastern fringes of the Palmer Ridge as well as farther north. These thunderstorms had narrow updrafts and produced only short-term heavy rainfall to the tune of 0.5 inches in 30 minutes. As the afternoon wore on, the smaller updrafts combined to form more threatening storms over the Northeast Plains. Hourly rainfall rates up to 1.5 inches were observed in mostly rural parts of Weld, Washington, Kit Carson and Cheyenne counties. An areal flood advisory was issued for western parts of Cheyenne County for field and roadway flooding.

Later in the afternoon and into the evening, a secondary surge of activity began around 6PM as a push of very moist air, to the tune of dewpoints near 60F and precipitable water around 1.1 inches, moved westward. Intense thunderstorms formed over the northeast part of the Denver metro area, then sent outflow boundaries southward and westward sparking more activity over the next 3-4 hours. With rainfall falling over the most densely gaged area in the state, some very high rainfall rates were recorded. These include: numerous gages exceeding 0.5 inches in 10 minutes, 1.8 inches in 30 minutes near Cherry Creek Reservoir, and close to 3 inches per hour just west of Boulder. Needless to say, roadway and street flooding was common across the entire metro area. Fortunately, the limited area of the heavy rainfall prevented significant riverine flooding, although some impressive spikes were seen in area stream hydrographs. For example, below is the spike on Clear Creek near the South Platte River confluence: 5 to 1000 c.f.s. in a matter of 30 minutes (provisional data).

clearcreek

For rainfall estimates specific to your area, check out our Storm Total Precipitation map below.

STP_20160831
Storm Total Precip Legend