The 2013 Colorado floods were a series of natural disasters occurring in the U.S. state of Colorado. Starting on September 11, 2013, a slow-moving cold front stalled over Colorado, clashing with warm humid monsoonal air from the south.[1] This resulted in heavy rain and catastrophic flooding along Colorado's Front Range from Colorado Springs north to Fort Collins. The situation intensified on September 11 and 12. Boulder County was worst hit, with 9.08 inches (231 mm) recorded September 12 and up to 18 inches (460 mm) of rain recorded by September 15,[2][3][4] which is comparable to Boulder County's average annual precipitation (20.7 inches, 525 mm).[5] This event has also been referred to as the 2013 Colorado Front Range Flood,[6][7][8] reflecting a more precise geographic extent in and along the Colorado Front Range mountains.
The National Weather Service's Hydrometeorological Design Studies Center stated in a document that the annual exceedance probability (AEP) for the entire rainfall event was as low as 1/1000 (0.1%) in places.[9]
^Yochum, Steven E.; Moore, Daniel S. (2013). "Colorado Front Range Flood of 2013: Peak Flow Estimates at Selected Mountain Stream Locations". doi:10.13140/2.1.2593.0242. {{cite journal}}: Cite journal requires |journal= (help)
^Yochum, Steven E. (2015). "Colorado Front Range Flood of 2013: Peak Flows and Flood Frequencies". doi:10.13140/rg.2.1.3439.1520. {{cite journal}}: Cite journal requires |journal= (help)
^Gochis, David; Schumacher, Russ; Friedrich, Katja; Doesken, Nolan; Kelsch, Matt; Sun, Juanzhen; Ikeda, Kyoko; Lindsey, Daniel; Wood, Andy (December 11, 2014). "The Great Colorado Flood of September 2013". Bulletin of the American Meteorological Society. 96 (9): 1461–1487. Bibcode:2015BAMS...96.1461G. doi:10.1175/BAMS-D-13-00241.1. hdl:2117/78527. ISSN0003-0007. S2CID46600790.