A very warm and moist pacific storm system allowed for a deep east to southeasterly upslope flow to develop along portions of the Front Range Foothills. Heavy snow occurred in the foothills above 7000 feet with a steady period of moderate rainfall below this elevation.
Every event with a place to put it; 2 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS BOU wrote it up.
A very warm and moist pacific storm system allowed for a deep east to southeasterly upslope flow to develop along portions of the Front Range Foothills. Heavy snow occurred in the foothills above 7000 feet with a steady period of moderate rainfall below this elevation. As a result, the normal runoff was accelerated, causing the Cache La Poudre, the Big Thompson and the South Platte Rivers to jump their banks. Several rural roads were either closed due the floodwaters or washed out completely. Damage to roads in Larimer County alone were estimated to be $200,000. Substantial lowland and agricultural flooding was also reported. In Rist Canyon, near Fort Collins, a trained spotters recorded between 10 to 12 inches of rainfall through the course of the event, about a week's time. In Laporte, water ran through several subdivisions forcing residents to use sump pumps all night. Sewers backed up and damaged a number of basements. In Windsor, the Cache La Poudre flooded the basements of several homes along the river.
The national radar mosaic for the moment the first event began.
2 flood. Local standard time, as filed.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 1999Every state in 1999This day in weather historyWarnings in Colorado, May 1999
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 5699836, 5699837.