|500 millibar map for 6:00 a.m. MDT September 12|
Rocky Mountains, producing a conveyor belt of thunderstorms that have dropped up to a foot of rain on some locations in the past few days . The most recent event is the widespread and destructive flash flooding that occurred in the foothills from Boulder to Fort Collins, CO Wednesday night and Thursday. 24-hour rainfall amounts in Boulder County this morning exceeded eight inches, with a relatively narrow band of 7.00 to more than 8.00 inches of rain through the city of Boulder.
|24 hour rainfall ending at 0700 MDT September 12|
|The rain gauge at Centennial Middle School in Boulder, CO (CO-BO-337) this morning with 8.43 inches of rain.|
The radar-estimated precipitation map for the period from September 9 through 10:00 a.m. MDT September 12 (just a little less than three days) shows the two bands of heavy rainfall, one northwest of Denver and the other just east.
|Radar estimated precipitation from the Denver NWS radar|
The flooding the last two days is much like the heavy rainfall event that is behind the formation of the CoCoRaHS program. on July 28, 1997 a major flash flood hit Fort Collins causing devastation in excess of $140 million and five fatalities.
It was the attempt to document and explain this event that is behind the origins of CoCoRaHS. Rainfall data was available from only a few "official' rain gauges. In this situation rainfall varied from 2 inches to more than ten inches over a distance of about three miles, and none of the official gauges captured the rainfall maximum. You can read more about the rainfall for this event at this link: An Analysis of Rainfall for the July 28, 1997 Flood in FortCollins, Colorado.
An excellent source of information on rainfall-induced floods that have caused damage in the Front Rain since 1953, including the 1997 Fort Collins flood, can be found on the Colorado Front Range Historical Flood Summaries web site provided by the National Center for Atmospheric Research. There is little doubt that this week's flooding will make its way on to the list.