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FCL until approximately 2230 MDT, As the rainfall began to increase after 2000 MDT, sur, face runoff forced the closing of several streets in western FCL and the opening of the FCL Emergency Operations Center ("G" in Fig, 1), Between 2100 and 2200 MDT, the rainfall be- came especially heavy, exceed, ing 4-5 in, per hour in some locations, Previously saturated soil coupled with urban surface runoff turned city streets, canals, and creeks into fast,moving tor, rents of water. Surface water converged on the campus of CSU ("I" in Fig, I) and began to flood streets, and later, build- ings, By 2134 MDT ("J" in Fig, I) homes in southwestern FCL began to flood and a flash flood warning was issued by the NWS at 2140 MDT ("K" in Fig, I), Spring Creek, a small stream that flows east through southern and central FCL (cf. Fig, 3) began to overflow a major city street in southwestern FCL near 2045 MDT ("H" in Fig, 1), and one hour later (2200; "L" in Fig, 1) it was over its banks in western and south,central FCL. In south-central FCL, a 50, acre detention pond located behind a railroad berm briefly contained the combined overflow of Spring Creek and other drainages (cf Weaver et aL 1998), However, be, tween 2230 and 2300 MDT ("M" in Fig, 1) the deten, tion area reached its 4,6 x 105 m' capacity and began to overflow (Weaver et aL 1998), Hydrostatic pressure ruptured a culvert built into the railroad berm, send, ing the previously detained water directly into a mo, bile home park located on the eastern side ofthe berm, In what could only be described as unfortunate tim- ing, a freight train ("M" in Fig, 1) passed over the same area at approximately 2300 MDT and was subse, quently derailed by the flooding. Tragically, five people were killed during this time period, and the mo, bile home park and many businesses were completely destroyed, Preliminary estimates of the peak discharge along Spring Creek on the night of the flood ex, ceeded 6000 cfs in at least two locations, and in many FIG. 3. Isohyctal maps ofrainfalJ for FeL, contoured in inches: (a) 1600 MDT 27 July 1997-1300 MDT 28 Juty 1997; and (h) 1730-2300 MDT 28 July 1997, The tocation of Spring Creek is highlighted by a bold line that extends from western FeL at the marker "Spring Creek" through the "X" in central peL. Locations of the CSU weather station and Christman Field are indicated by "CSU" and "e", respectively. The intersection of Taft Hill and Drake Roads (cf. Fig. 9) is indicated by "TID", and the approximate locations of the ruptured culvert and flooded mobile home park arc indicated by an "X". Figure adapted from Doesken and McKee (1998). locations were nearly twice that of the "500-year flood" discharge, 1 b, Meteorological data On the night of the flood a variety of instrument a- tion and observations provided extensive meteorologi- cal sampling of the FCL storm and the synoptic environment. The observational database and in- strumentation (see Fig, 2 for relative locations) in, cluded two NWS Next Generation Weather Radar (NEXRAD) Doppler radars located in Denver, Colo, rado (KFTG; 100 km southeast of FCL), and Chey- enne, Wyoming (KCYS; 70 km northeast of FCL); the CSU-CHILL dual-polarized S-band radar (40 km east-southeast of FCL); 251 rain gauges operated by citizens and public institutions in the vicinity of FCL; the National Lightning Detection Network (NLDN); surface mesonet stations; and geostationary satellite platforms (e,g" GOES,S, ,9), These observations were combined with ancillary datasets such as wind profiler, sounding, Aircraft Communication Address, ing and Reporting System (ACARS), synoptic obser, vations/analyses, and numerical model output. This extensive dataset provides an opportunity to study the ICity of FCL, Office of Emergency Management [http://www.ci.fort-collins.co.us/C_SAFETY/OEM//index.htm]. Bulletin of the American Meteorological Saciety r 193