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THE WASATCH FRONT'S CENTURY STORM INTRODUCTION A major fall storm produced phenominal amounts of ra inf all in northern Utah with the heaviest rainfall in the Salt Lake Valley. The rains began Friday evening, September 24, 1982, and continued with only a few hours respite until Tuesday night, September 28, 1982. Severe flooding was experienced along Big/Little Cottonwood Creeks and the Jordan River with damage estimates in excess of 15 million dollars. Miraculously, no fatalities occurred. However, one woman almost drowned when she suffered an epileptic seizure and fell into a pond formed by the flood waters. The rains were attributed to considerable tropical moisture that moved into Utah from dying Hurricane Olivia and the dynamics supplied from a cold front and its associated cold upper level trough. Hurricane Olivia was one of the strongest and most well organized hurricanes in many years with 165 MPH winds. The rains began in extreme northern Utah Friday evening, September 24, when the tropical moisture was enhanced by a very weak cold front moving into Idaho and Montana. Rainfall amounts associated with this feature were light. The main cold front moved southward and collided with the tropical air on Sunday morning, September 26, and produced torrential rains in Davis, Salt Lake, and Utah Counties. Rainfall amounts were generally around 2 to 3 inches in a l2-hour period with some amounts in the southeast portion of Salt Lake Valley, and in the canyons to the east, nearly 3.50 to 4.00 inches. These values exceed the 100 year 24-hour return for this area in the NOAA Atlas 2-Precipitation Frequency Atlas of the Western United States. A Flash Flood Watch was issued at 9:00 A.M. Sunday, September 26 for the majority of northern Utah. As the severity of the storm was sensed, a Flash Flood Warning was issued immediately at 9:30 A.M., September 26 for Bountiful north due to flooding reported in Willard. As the cold front worked slowly southward along the Wasatch Front, it became apparent that it had the potential to stall in the Salt Lake Valley. A warning was then issued at 11:00 A.M. Sunday, September 26 for the counties along the Wasatch Front from Salt Lake County northward from the Point-of-the-Mountain. The record rainfall began in earnest about 10:00 A.M. and lasted until about 11:00 P.M. Sunday evening. For this l2-hour period rainfall values were in the 2 to 3 inch range with some amounts in the Holladay, Sandy, Big and Little Cottonwood areas in the 3.50 to 4.00 range. The Alta Ranger Station recorded about 3.43 inches on Sunday, but received 1.28 inches of rain on Saturday, saturating the soil. The Cottonwood Weir climataological station recorded 4.10 inches from 10:00 A.M. to 11:00 P.M. Sunday, as did several National Weather Service spotters within several miles of this area. This was but a portion of the rains which were still to come.