Heavy Snow Could Benefit Drought Areas of the West

HEAVY SNOW COULD BENEFIT DROUGHT AREAS OF THE WEST

Despite the adverse impacts of recent winter storms that have battered the western states, these storm clouds may have a silver lining. Since October significant snowpack has been piling up from the Sierras to the southern and central Rockies. Despite little improvement in large reservoir storage levels in the West so far this season, the unusually heavy snowfall could set the stage for some drought relief when the snow melts this spring. This is significant because the spring snowpack supplies are around three-fourths of the ultimate water supply for the West. Today’s announcement is based on the National Oceanic and Atmospheric Administration’s assessment of the drought situation in the United States. NOAA is an agency of the U.S. Department of Commerce.

NOAA cautions the public of the need for a conservative approach when it comes to forecasting drought relief. “At the beginning of March last year, much of the West had experienced the build up of an ample snowpack. Then a drastic and largely unexpected circulation pattern developed, and changed the picture entirely. Record warm, dry weather during the last three weeks of March 2004 quickly reduced mountain snow supplies,” said Douglas LeComte, drought specialist at NOAA’s Climate Prediction Center. “There is really no way to know if something like that will happen again this year, this far ahead of time. Also, we have seen near-record low snowpack in parts of the Pacific Northwest and northern Rockies this season, so this remains a region of concern.”

The latest U.S. Drought Monitor combines the efforts of the National Oceanic and Atmospheric Administration, U.S. Department of Agriculture and the National Drought Mitigation Center. It continues to show drought eroding in some of the West. “The winter snowstorms during late December and early January have improved conditions over the Southwest, while there has been less improvement over northern portions of the West,” said LeComte. He added, “even the Pacific Northwest and northern Rockies have benefited from the most recent storm, though less than regions farther south.”

Record storms in October dumped up to 80 inches of snow in the mountains of California and Utah. Since December 27, storms have added to the snowpacks. Up to eight feet of snow fell on the ski areas of Lake Tahoe, Calif., in a seven-day period ending January 2, with the bulk of the snow falling from December 28 to 31. National Weather Service spotters reported 48 inches of snow in just 36 hours near Donner Pass, Calif., on December 30-31, and 60 inches in the two-day period at 6,700 feet near Truckee, Calif. Several Lake Tahoe ski areas reported near 100 inches for the week ending on January 3, with 12 to 14 feet snowdepth. Elsewhere, accumulations of 16 to 30-inches were common on the mountains of Nevada, Utah, and Arizona, with generally one foot or less in western Colorado.

A new round of storms that began on January 7 further added to the rain and snow totals this season, including abundant mountain snows eastward to the Upper Colorado Basin, which has seen fewer impacts this cold season than areas further to the west.

“Another piece of good news is that the snowpack water content is over 150 percent of normal across much of the Southwest from southern and central California into Nevada, Utah, and western Arizona as the New Year begins,” said LeComte. “If the rest of the snow season continues like this, the spring-snowmelt season could bring significant streamflows to these sections of the West” he added.

Other portions of the West have not fared so well. Below-average snowpack across the Northwest and northern Rockies could increase the odds for below-average spring streamflows in drought-affected areas of Wyoming, Montana, Idaho, and Oregon.

Larger reservoirs comprising the Colorado River Basin remain mired near their lowest levels in more than two decades, meaning that it may well take several good winters to bring all the water supplies up to normal levels. Nevertheless, the wet autumn resulted in Lake Powell recording above-average inflow during November for the first time since September 1999, around the time the Colorado River Basin drought began. As of January 6, before the most recent storm hit, snowpack had risen to 117 percent of average above Powell in the Upper Colorado Basin, the key region that includes western Colorado, eastern Utah, and parts of Wyoming and New Mexico.

NOAA’s Climate Prediction Center and its partners update the U.S. Drought Monitor weekly and its U.S. Drought Outlook monthly. Both drought products are published via the Internet.

NOAA’s Climate Prediction Center, an arm of the National Weather Service, serves the public by assessing and forecasting the impacts of short-term climate variability, emphasizing enhanced risks of weather-related extreme events, for use in mitigating losses and maximizing economic gains.

NOAA is dedicated to enhancing economic security and national safety through the prediction and research of weather and climate-related events and providing environmental stewardship of the nation’s coastal and marine resources.

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