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<br />Table 8,
<br />Greatest two-day precipitation totals measured at the Fort Collins weathar station on the
<br />campus of Colorado State University for the period January 1,1889 - December 31,1997.
<br /><AU totals are for the 48-h0ur peIlod ending at 1900 MST on the last dale indioated.)
<br />Precipilalion
<br />TolaI mches
<br />6.22
<br />
<br />6.17
<br />
<br />Ie
<br />
<br />Rank
<br />1
<br />2
<br />
<br />Dale of Observation
<br />bar 20-21, 1902
<br />
<br />July 28-29, 1997
<br />
<br />3 6,07 A usl3-4, 1951
<br />4 4.76 24-25, 1977
<br />5 4.68 bar 2-3, 1938
<br />6 3.99 Ma 12-13, 1982
<br />7 3.83 March 6-7, 1990
<br />8 3.80 May 2-3, 1904
<br />9 3.73 June 3-4,1949
<br />10 3.70 May21-22, 1901
<br />11 3.68 12-13,1961
<br />12 3.32 ~16-17,1942
<br />13 3Z1 28-29, 1975
<br />14 3.09 . 28-29, 1900
<br />t5 3,04 June 15-16, 1983
<br />16 3.03 June 24-25, 1992
<br />17 2.99 Ju 9-10,1918
<br />18 2.96 Junell-12,l970
<br />19 2,89 June 6-9, 1974
<br />20 2.86 June 16-17, 1965
<br />. Expanded description of each event is given in Appendix C.
<br />
<br />Remarks .
<br />Rain intense at first, then gentle
<br />Flash flood, 5 killed, most fell in less than 5 hIS on
<br />evening of 28th
<br />V intense rain, fell less than 4 hours
<br />Rain, in 15 hours
<br />Intense rain and flood'
<br />and rain
<br />Alia.-, andwel
<br />L and rain
<br />rain but not too intense
<br />Rain and hail, 2 successlve heavy rain events. 3.24
<br />inches in 4 hrs late on 20th and 2.36 inches in 4
<br />hIS late on 21 st.
<br />rain cha . to a.-
<br />a ' intense then long and st
<br />and rain
<br />Mixed rain and a.-, and
<br />Widespread steedy rain
<br />H lh<r1der and hail, fell less than 1.5 houlS
<br />P intense rain
<br />and rain
<br />Rain, but. intense
<br />Brief but intense rain.
<br />
<br />Figures 15 and 16 show the maximum one-day and two-day rainfall totals for each year since
<br />1889. Based on these data, the July 1997 stonn ranks as the greatest one-day rainfa1I (4.63
<br />inches for the official climatological day) and the second greatest two-day total in recorded
<br />history (6.17"). The totals, however, are not greatly different than two other storms. For
<br />one-day totals, July 25, 1977 and September 21, 1902 were only slightly less. For two-day
<br />totals, the July 1997 stonn ranks 2nd behind the 1902 event with August 2-3, 1951 (also a
<br />significant flood episode in Fort Collins) a close third.
<br />
<br />In recent decades, the use of recording rain gauges has made it possible to determine hourly
<br />rainfall totals as well as daily or other intervals. This provides infonnation on rainfall intensity
<br />which, of course, is a crucial factor in determining flash flood potential. The maximum rainfa1I
<br />for each year beginning in 1940 for periods of one, three and six hours are shown in Figure
<br />17. The maximum one hour rainfall on the CSU campus for the July 1997 stonn was 2.31
<br />inches (keep in mind that the campus weather station was not at the center of the stonn). This
<br />is very heavy rain, but not unprecedented. Comparable rainfall rates at the campus weather
<br />station were observed for a one hour time period August 18, 1961 (2.33 inches) and on June
<br />17, 1965 (2.31 inches). The greatest one hour rainfall total measured at the campus weather
<br />station was 2.40 inches on June 24, 1992. The June 1992 storm was very intense,
<br />accompanied by hail and strong winds. Areas one to three miles northwest of the main
<br />campus received even heavier rains from that stonn with maximum hourly totals close to 3.50
<br />inches. Some flooding resulted.
<br />
<br />36
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