[Snowpack] in the Arkansas and Rio Grande basins [was] near normal this year. That snow was not enough to relieve the on-going drought. Runoff in both basins is expected to be well below normal and looks to be coming early. Warm temperatures and lack of precipitation in April have accelerated the snowmelt. Models indicate the runoff may peak about 2-3 weeks ahead of an average year; the Rio Grande slightly earlier than the Arkansas. Runoff in the Arkansas and Rio Grande basins will be well-below average.
Drought conditions began to develop in the early fall of 2019. Below average rainfall during the summer and into the fall depleted soil moisture and groundwater going into the winter. Those dry soils and groundwater reservoirs are currently absorbing snow melt that would run off in a wetter year.
Forecasts from both the NRCS and the NWS reflected these dry soils and ground water deficits earlier this winter. Water users in the Arkansas River basin are fortunate to have a number of dams available within the system. Snowpack and runoff in 2018-2019 were abundant and some of it remains available in storage.
According to the United States Department of Agriculture, Colorado’s current snowpack is at just 43 percent of where the snowpack was this time last year and 64 percent of the average for this date, despite reaching a peak snowpack at 103 percent of the norm this season. This low snowpack is due to warm temperatures and a dry spring, which has resulted in a faster melt and less snow…
One spot that’s particularly dry is the Upper Rio Grande Basin, which is at 25 percent of the median snow water equivalent as of May 13. This includes spots like Medano Pass, Wolf Creek Summit, and Hayden Pass. The Arkansas River Basin is also lacking quite a bit of snow – currently at 59 percent of the median snow water equivalent on May 13. The Arkansas River Basin includes areas like Saint Elmo, Glen Cove, and Fremont Pass…
While things do seem quite dry right now around the state, the 2018 snowpack was worse, as seen by the yellow line in the graph below.
Colorado Statewide Times Series Snowpack Summary May 15, 2020 via the NRCS.
There was a notably wide gap in snowfall totals from the west side of Denver to the east side this winter, with the east side of the city seeing only about half of the snowfall that the west side received. Consider, for example, Wheat Ridge’s approximately 100 inches of snowfall this winter compared to the 48 inches of snow that Brighton received.
To be clear, most winters feature some sort of noticeable gradient between all sides of the Denver metro area. But as evidenced in part by Boulder’s record-breaking snowfall season, this winter favored the east-facing foothills west of Denver in a perhaps slightly unusual way.
For example: Denver generally saw a slightly above average season’s worth of snowfall (57.6 inches at Denver International Airport, and about 71 inches at the Stapleton Airport weather observation site). This was a generally decent-sized winter (30-year average Denver snowfall: about 50 inches) for the immediate Denver area, but it wasn’t off-the-charts for local standards.
But if you push ever-so-slightly west into the west side of Denver and into the first suburbs on the other side of the city line, like Lakewood and Wheat Ridge, and those seasonal snow totals jumped dramatically. Wheat Ridge saw over 100 inches this winter, while Lakewood saw almost 90 inches of seasonal snowfall.
While there’s typically a gap between the east and west sides of Denver, the fact that the west side of the metro area almost doubled the east side’s snowfall is a bit of a wider spread than usual.
“There weren’t a lot of big synoptic storms that were widespread (in producing more evenly-distributed snowfall),” said Scott Entrekin, a meteorologist at the National Weather Service office in Boulder. “Most of the folks on the plains only had 20 to 30 inches of snow, which is a bit below normal out there. We did have some upslope-heavy storms.”
If you stretch out the geography a bit, the gap gets even wider: Colorado’s Eastern Plains saw only about 20 to 30 inches of snow this winter, below average in most cases. Meanwhile, the foothills west of Denver saw as much as 200 inches worth of snowfall, well above the climatological average there.
This was likely due to a high number of snowstorms that primarily pushed in easterly winds, or ones that strongly favor the foothills and the west side of the Denver area. Because elevation begins its sharp climb just west of Denver, easterly winds are forced to climb with the terrain as well. When air rises, it condenses into moisture…
Traditionally, the wider snowfall gap comes between the south side of the metro area and the rest of the city. The Palmer Divide, the mountainous area between Denver and Colorado Springs that rises up to 7,000 feet in elevation, is typically one of the more significant areas of snowfall across the metro area. The Palmer Divide’s elevation difference and geography is why places like Castle Rock (83.5 inches of snow this winter) and Sedalia (about 80 inches) often wind up with some of the higher seasonal totals over the course of a full winter.
The divide, however, usually relies on a bit more of a northerly component to the winds to bring in both colder and more upslope-dominant winds that’ll rise more efficiently against the east-west orientated range.
But this winter, those Palmer Divide areas actually saw slightly less snowfall than places like Wheat Ridge and Lakewood, and Castle Rock barely half of Boulder’s 152 inches of seasonal snowfall. That’s far from unheard of, but it certainly is a bit unusual, and yet another indicator of the huge snow season that the foothills specifically had.
That led to a big difference in snowfall totals over just a few miles across the Denver area this winter, including slightly below average seasonal amounts for areas just north of the city.
