Last month was the snowiest May in Aspen in two decades, with 20 more inches added to the already substantial snowpack, reports the Aspen Daily News. Total snowfall for May was 400% average and follows the second snowiest March EVER recorded and makes up for only 6 inches falling in April.
Winter and spring storms were fueled by weak El Niño conditions that shifted atmospheric rivers laden with moisture farther south than in an average year. (El Niño occurs when, among other conditions, sea-surface temperatures are warmer than average.)
Storm systems that usually blanket the Northwest, Alaska, and Canada instead pounded California’s Sierra Nevada mountain range. The Sierra Nevada snowpack was 162 percent of average, more than triple what the number was at the same time last year, and Colorado got the storms’ leftovers.
- Related: Huge Snowpack Leads to Concern About Flooding in Colorado’s High Country | 1093% Normal in San Juans
While the wet, cool spring has meant little snowmelt and allowed for many resorts to stay open well into June, the Colorado Water Conservation Board and local emergency managers are keeping a close watch on river levels. The state board on May 30 said nearly every river basin in Colorado is over 350 percent of average, and that only 35 percent of the measured snowpack in the Colorado River basin had melted by the end of May.
“Widespread, regional snowmelt flooding is not common for Colorado,” the board’s May executive summary says. “However, isolated flooding and extended periods of high water are likely to occur this season. It is also important to note that Colorado’s worst flood events have historically occurred from general spring rainfall and summer thunderstorms, which are completely unrelated to snowmelt flooding resulting from mountain snowpack,” the summary adds.
Floods directly related to the melting snowpack are possible but unlikely, and for boaters, an extended season of high water is a near certainty this year, the board reported.