Mark Losleben - CU INSTAAR Research Staff
The following snowpack conditions on Niwot Ridge have been reported by Mark Losleben for June 2005. Select here for more information about these snowpack reports
Greetings! As the flowers bloom and winter memories rapidly fade, this is the "melt out", and final Niwot Ridge (C1) snow pack season report.
Early snow pack melt out is of concern for summer water supply, and forest fire danger on the short term, and water supply and ecosystem effects on longer time scales. The trend of the past several years of early snow pack melt out was promising to be broken this year. Niwot managed to pull it off, but just barely. On May 22, the snow pack was 102% of average, and cool, wet weather systems were appearing regularly, lending promise to an extended snow pack presence. That changed, and on May 24 the snow pack dropped to 61% (a drop of 41% in two days!), and never slowed down. Niwot melt out occurred on May 30, 2005, just besting the average melt out date of May 29th by one day.
Overall though, there does seem to be a recent trend of earlier melt outs, at Niwot, the South Platte basin, Colorado, and the western US, even if snowpacks are heavier than average. For example, Niwot snow pack peaked this year on May 4th. The average peak date is April 19th, which could be construed as giving us a nice two week cushion towards enjoying a late melt out, and thus longer snow pack season. As shown above, this cushion rapidly evaporated. It is worthy to note, however, that statistically, there are no significant long term trends at Niwot in changes for date of peak, amount of peak snow pack SWE (snow water equivalent), melt out date, number of days from peak to melt out, or in the rate of melt out (inches of SWE per day melting). With a few more years of early melt, the trend in number of days from peak to melt out will be significant, soon followed by the melt out date.
The South Platte basin has not melted out yet, but the pattern is similar to Niwots. The average peak date is April 23rd, and it peaked in early May, although at only about 85% of peak SWE. It then began melting faster than average, and is now appearing to melt out about one and a half weeks early. The good news is that at this time last year the snow pack had just melted out.
Statewide, the longest lasting snow packs are in the southwest, plus the Gunnison, reflecting the highest snow packs throughout the winter (as a percent of average).
In the western US, the Pacific Northwest states did not receive any last minute salvation from their intense lack of snow, and the southern states, including Utah, Nevada, and the Great Basin area of California finished with well above average SWE amounts.
The cumulative winter precipitation is much closer to average than the snow pack in all these areas. Unfortunately, this is not nearly as important to water storage, stream flow, fire danger, or recreation compared to snow pack SWE amounts.
To conclude, heavy snow packs blessed the southern half of the western US, an area suffering from drought and low reservoirs. This should help their recovery, and several more similar years may end their drought. The Pacific Northwest, particularly Washington and Idaho, are in the opposite position; reservoirs at normal capacity now, but with little snow pack runoff to replenish them. Additionally, a wetter than normal summer may be needed to avoid a higher than normal fire season there. Then, ironically, the southwest may experience a higher than average fire season next year due to the good snow pack this year, a result of increased fire fuels growth this summer.
So, weather and water balance remain an interesting game, and continue to provide virtually endless variations for us to hone predictive skills, and test our knowledge of their drivers.
Until next winter, cheers!