Another wet season helped improve California’s snow drought, but other parts of the western United States have not been so fortunate.
By Natalie Hanson, Courthouse News Service
Another winter without enough snow and rain has left much of the western United States parched for water, according to scientists monitoring a snow drought.
Thanks to below-normal precipitation during the water season, snow drought conditions persist across most of the West, according to a June 12 report from scientists at the National Oceanic and Atmospheric Administration.
While some regions such as the Sierra Nevada range, improved over the winter, scientists say many places will see further drought development or intensification this summer.
The greater Western US continues to struggle
Many locations in Washington and the northern Rocky Mountains received less than 15% of the average rainfall, with eight weather stations in Montana and two in Washington reporting record low rainfall values.
In Idaho, Montana and Washington, snow drought developed early in the season and persisted, bringing snow water equivalent — the water contained in a mountain’s snowpack — to 55 to 75% of the normal amount.
Throughout the region, temperatures were often above what’s typical, and led to early snow melts at 77% of all Montana snow stations.
Those warm temperatures hurt the gains made early in the season during a series of extreme storms in the Cascade Range. Snow drought conditions in Washington state, which developed during the winter, have only intensified as precipitation deficits continue.
As of June, measurements of snow water equivalent were below 40 to 60% of normal across most of Washington, and 85% of all stations reported snow melting several weeks earlier than normal. The Climate Prediction Center’s Seasonal Drought Outlook predicts drought is likely to develop across most of the state by the end of the summer.
Oregon had a better outcome from late 2023 through the spring, with a statewide snow water equivalent between 80 and 120% of normal. Several atmospheric river events helped Oregon’s mountains maintain an average snowpack, although some locations near Mount Hood measured below average due to previous droughts.
Most of the West faces ongoing problems with abysmal water supply. The Missouri Headwaters, upper Missouri and Marias basins are among the lowest at 69%, 65% and 55% of normal, respectively. The Spokane Basin, including parts of eastern Washington, will likely receive about 63% of the normal snowpack runoff and drought conditions are likely to worsen over the summer.
The central and southern Rocky Mountains fared much better for snow during the winter’s El Niño conditions. The snow water equivalent in southern Wyoming and Colorado measures between 85 and 110% of normal, and up to 130% of normal in northern Utah. However, southwest Wyoming, southwest Colorado and southeast Utah fared poorly, and likely will experience drought conditions during the summer, scientists say.
Better news in the Southwest
By contrast, California, Arizona and New Mexico saw an above-average snow season. It was a welcome improvement to water supplies, which are still recovering from historic droughts.
Many locations in Arizona and New Mexico had above-normal snow water equivalent measurements, particularly after snow melted much later than normal in central and southeast Arizona.
Reservoirs in the Upper Colorado River Basin are still recovering. Blue Mesa is 63% full and Navajo is 72% full, according to the U.S. Bureau of Reclamation. However, the lower Colorado River’s supply remains extremely low, with Lake Powell and Lake Mead at 38% and 34% capacity, respectively.
Meanwhile, much of New Mexico is in moderate or severe drought, and southern New Mexico faces extreme and exceptional drought conditions.
The good news, scientists said, really came to California’s Sierra Nevada range. While the region began the year in a snow drought, storms from January through March helped drive a big increase in snowpack. A March blizzard in particular brought snow water equivalent to 90 to 110% of normal. California is now largely free of drought except for areas along the Oregon border and the state’s southeast corner bordering Arizona, according to U.S. Drought Monitor totals.
That good fortune also kept the Great Basin — including northern Nevada, southeast Oregon and southern Idaho — out of snow drought with a snow water equivalent up to 150% of normal, thanks to storms in December. Water supply concerns improved across the basin, and in northeast Nevada scientists expect seasonal runoff volumes to reach 120% to 150% of normal.
Much will depend on how summer conditions across the West turn out, the scientists noted.
Since the start of June, two heat waves already have affected parts of the Pacific coast. Regions of Northern California suffering from triple-digit temperatures and low humidity, combined with gusty winds, are under excessive heat warnings and critical fire risk, according to the National Weather Service’s Sacramento station.
