On April 1 this year, a snow survey in California’s Sierra Nevadas near Echo Peak had to be conducted on bare grass – an unprecedented April Fool’s joke from Mother Nature.
Fast forward to December, and the same area has had modest improvement – now 53 percent of normal – but go just south near Sequoia National Park, and snow survey sites are buried, reporting nearly 200 percent snowpack for early winter. Farther south still, the change is dramatic; sites in the Central Valley that would typically be measuring a few centimeters by now, haven’t seen any snow.
That pattern is holding up across the West.
Taken as a whole, Western snowpack measurements in early December paint a widely varied picture – some places are far above historic normals, while others are still far below. For watersheds, that means things are looking better than they have been, but we’re not out of the woods yet.
According to the Natural Resources Conservation Service’s SNOTEL sites, which measure snow depth at thousands of stations nationwide, only two Western states – Nevada and Idaho – are above the historic benchmark for “normal” at this time of year.
That means the other Western states are adding to their water deficit, especially in places that have experienced multi-year drought, such as California.
“There’s a tremendous deficit that’s built up,” says Alan Haynes, a hydrologist for the California Nevada River Forecast Center. “It would take three times the normal precipitation in just one year to recover the shortage of water.”
But, if early winter weather patterns are any indication, precipitation is falling at fortuitous locations. While the Central Valley is still mostly dry, many survey sites in the Sierra Nevada Mountains and Tahoe Basin are at or above normal for this time of year. That’s good news for the state’s water supply and reservoirs, which will swell when snowpack melts in the spring.
Still, hydrologists say it’s too early to tell if this winter will ultimately fall above or below the average snowpack levels and make up for the shortfalls.
In California, the snow-water equivalent, or the depth of water in the snowpack if melted entirely, currently measures about 90 percent of historic readings. Compared with the past four years, that’s a significant improvement.
Haynes says a few more winter storms in the Sierra, where more than half of the state’s agriculture and urban water users get their supply, could put the state above normal.
Nevada, Idaho, Alaska and Colorado have had nearly normal to above-normal snowpack readings so far, according to state data compiled by SNOTEL.
The states’ overall averages, however, can be misleading, Haynes says. It’s important to look at where the snow is falling in the states. As long as precipitation is falling within important watersheds for municipal water supply, areas that have been dry will still benefit from more fortunate areas.
In Colorado, the Rocky Mountains, which provide water for the bulk of the state’s urban population, have had above normal early season snowpack readings, but a cluster of low readings near the Gunnison National Forest on the Western slope have brought the state’s average just slightly below normal.
So far, Montana is lagging for early season snowpack in the West. The state has the lowest reading in the region – only 73 percent of the historic average. In Nevada, much of the state is experiencing the opposite. The state’s average snowpack readings are 117 percent of normal, and much of the early winter precipitation has fallen in the western edge of the state near Truckee and Tahoe, which bodes well for reservoirs in neighboring California.
Other parts of the region are beginning to see problems from too much early season snow. Snowpack readings in the Pacific Northwest are above normal and at lower elevations above-normal rainfall is predicted. NOAA is telling residents to prepare for flooding through the Bellingham, Seattle, Olympia and Yakima areas for the remainder of December.
Already, numerous highways have been closed from landslides and floods in Washington, and a woman in Oregon drowned after her vehicle was submerged in a flood about 60 miles northwest of Portland.
And of course, the question remains: When will El Niño show up? The weather anomaly, as High Country News reported recently, is set to impact most heavily parts of Southern California and the Pacific Northwest, with higher precipitation and warmer temperatures. Since the first week of November, the Sierras have been in a cycle of storms that have brought snow each week.
“It’s impossible to tie one storm – or even a series of storms – to El Niño. It’s too bold to say these storms are a symptom of that phenomenon,” says Randall Osterhuber, a research at the UC Berkeley Central Sierra Snow Lab.
But overall, NOAA long-range forecasts call for above-average snowfall for Southern California, Haynes says.
In Colorado, Nevada, Idaho and Washington, the bulk of winter precipitation is expected in January through March. Osterhuber says late season flurries that maintain snowpack through the spring months are crucial across the region. “When snowpacks don’t even make it to mid-March, that’s a huge problem,” he says.
“California has tremendous demands on its water resources, and we rely on the Sierras. After four years of minuscule snowpack, we need this.”
