Lakewood- A return to wet weather during April allowed Colorado′s snowpack to briefly increase to above average accumulations. Based on data collected at remote automated sites, called SNOTEL (SNOwpack TELemetry), snowpack accumulations reached their maximum seasonal totals during April and exceeded the average seasonal maximum in all of the state′s major river basins with only one exception. That exception was the combined San Juan, Animas, Dolores, and San Miguel in southwestern Colorado which didn′t benefit significantly from the early April storms. Warmer and drier weather during late April caused the snowpack percentages to decrease quickly to slightly below average by May 1, according to the USDA-Natural Resources Conservation Service (NRCS).
Maximum snowpack totals were reached on April 19th across most of the state, which is about a week later than the long-term average date of peak accumulation. "Those wet storms really improved our water supplies, especially along the Front Range", said Allen Green, State Conservationist with the NRCS. Snowpack totals in the South Platte basin increased from 93 percent of average to 112 percent of average during a single storm in mid-April. Since that storm, snowpack readings have been tracking at a higher level than at any time during the entire winter in the South Platte basin.
By May 1, when about 100 additional manual snow surveys were conducted across the state, snowpack percentages had decreased in all basins and were below average in all basins except the South Platte.
The statewide snowpack on May 1 had decreased to 90 percent of average after reaching a high of 109 percent of average on April 19th. Although temperatures have not been notably warmer than average during late April, there has been speculation that this year′s snow cover, which has been coated with numerous dust storms, will melt quicker than usual as solar radiation is absorbed into the snowpack rather than reflected back into the atmosphere.
With the additional snowfall in April the water supply outlook has improved in most of the state′s major river basins this month. Near average to slightly above average runoff is now forecast across Colorado with the exception of those basins across the southwestern portion of the state where runoff is expected to be below average. While just a month ago, the expected runoff from snowmelt was consistently below average along the Front Range, conditions have improved to much closer to average as of May 1. In many basins across the remainder of the state, this years runoff volumes will be near average but significantly less than last year′s runoff.
Reservoir storage continues to track at near average levels across much of the state on May 1. Storage volumes are significantly below average only in the Rio Grande basin this year. Elsewhere, the additional storage can help to extend water supplies further into the summer season. This year′s May 1 reservoir storage remains at 112 percent of last year′s storage levels.