Updated

For farmers and ranchers caught in the grip of the long and ruinous drought across the West, the heavy snow falling in the Sierra Nevada (search) and other parts of the region is nothing short of white gold.

"The roads are a little icy, so you have to drive a little slower, but being farmers, we welcome all this moisture," Sue Frey of Fallon said from her family's third-generation Rambling River Ranch in Nevada.

The Sierra Nevada has gotten more than 12 feet of snow over the past two weeks — the most in nearly a century — and Southern California and the Southwest have been drenched with some of the heaviest rains on record.

The snow and the torrential rain have not broken the drought yet. It could take years of such weather to do that. But it's a start, and it has raised people's spirits, especially in Nevada, Arizona, New Mexico and Utah.

"We've kicked over that first domino and are chipping away at long-term drought," said Mark Svoboda, a climatologist for the National Drought Mitigation Center (search) at the University of Nebraska at Lincoln.

Drought has gripped the Western United States for five to seven years in most places, and up to a decade in some spots. Scientists at the U.S. Geological Survey say it could be the worst drought in 500 years. Reservoirs have drained, rivers have dropped, and the mountain snowpack — the source of three-fourths of the West's water — has been meager.

The dry weather has taken its toll in the form of water shortages, catastrophic wildfires and crop failures that have put farmers out of business and sent small farm towns into a slow, sad decline.

Against that background, the deluge is bringing smiles, but the joy is tempered. Climatologists warn the record rain and snow have missed the Northwest, and the gains could be erased by another hot, dry spring.

Moreover, a deluge of rain — downtown Los Angeles had its wettest 15 consecutive days on record, with 17 inches falling in the period ending Monday — is not the best for drought-busting.

Heavy rain quickly saturates the topsoil. Then the rest runs off rather than soaking into the ground. Gradual rain over long periods, or slowly melting snow, allows water to seep down, doing a far better job of replenishing groundwater.

Most of the Western United States remains in some sort of drought, from Canada to Mexico, from the Sierra Nevada range to east of the Rocky Mountains. The most severe conditions are in Montana, Idaho and Wyoming.

"No optimism here yet," said Ted Day, a water engineer for the U.S. Bureau of Reclamation's Pacific Northwest Region in Boise, Idaho. "What is going on down there in California and Nevada is just missing us."

Runoff from the storms is expected to raise the level of Lake Mead, the main source of water for Las Vegas, by 2 feet. However, over the years the reservoir has fallen 90 feet below full. Boat ramps and marinas were designed for a lake at least 49 feet higher than the current level.

In Arizona, the entire eastern half of which is in a severe drought, the heavy rains have some rivers running for the first time in seven years.

"It makes us feel pleasantly optimistic, but we have a long way to go," said Herb Guenther, director of the Arizona Department of Water Resources.

"We are in year seven of drought here. We have been behind the normal curve by anywhere from 20 percent to 70 percent," he said. "So if you are down 20 percent in year one, you need 120 percent in year two. If you're down 30 percent again, you need 150 percent the next year."

He added: "We are several hundred percent behind so it is going to take us a while to catch up. If we got it all in one year, we would meet down in the Gulf of Mexico somewhere."