Weather experts expressed cautious optimism today that an unexpected shift in a giant offshore high-pressure system over the Pacific Ocean last weekend may bring an end to the West Coast's lingering drought and relief for the chilled and snowbound Northeast.

The high-pressure ridge, which had been sitting about 450 miles off the Pacific Coast from southern Alaska to central California, began breaking up Saturday after causing most of this winter's unseasonable weather across the nation.

"We just don't know why these things happen," said Paul Ellis, chief weather forecaster for the National Weather Service's Seattle station. Ellis said that the disintegration of the ridge is a hopeful sign: "If it holds, it looks like we will go back to what could be considered normal winter weather for the rest of the country."

Rain began falling Sunday over the drought-stricken Pacific Northwest, where low water levels have caused hydroelectric power cutbacks and job layoffs. A storm that blew in off the Pacific on Monday dumped 1 1/2 inches of rain on central California. State officials have predicted a $3 billion crop loss because of the drought.

"We're watching what is happening very closely," said Robin Reynolds, a spokesman for the California Department of Water Resources. Reynolds said federal weather forecasters and his department's meteorologist said today that normal Pacific weather patterns should be in effect for at least a week. "After that," he said, "we're all sitting here with our fingers crossed."

Reynolds said, however, that it would "take 250 per cent of the normal rainfall" before winter's end to "get us out of the hole."

The giant high-pressure ridge has acted as a buffer, holding up the wet, stormy weather that usually afflicts the Northwest each winter and driving the storms northward into Canada. From there they have rolled down on the U.S. Midwest and Northeast together with large polar air masses similarly detoured by the high pressure area.

As the high-pressure ridge has disintegrated, weather experts said the normal west-to-east storm track has areasserted itself, at least for the present, Philip Swain, the weather service official in charge of the regional office at San Francisco airport, said there have lesser disintegrations of the ridge on several occasions this year.

"Each time," he said, "it has returned and built up even stronger. The encouraging thing about this time is that it doesn't seem to be building up into an impenetrable mass the way it did before."

In addition to the wet weather that has moved in on the West Coast, Swain said there are other signs that the nation's weather pattern appears to be shifting back to normal. A large storm moving from the Rocky Mountains east onto the Great Plains is pushing almost spring-like warm weather, Swain said. "Without a doubt, that storm is a reaction to what has happened off the Pacific Coast," he said.

A key sign that the high-pressure ridge has broken down and normal weather is resuming will come this weekend, forecaster here said. A new storm is expected to hit California then and, if it arrives on schedule, it should mean that the high-pressure ridge has dissipated, experts said.

Despite the optimistic signs, weather service officials were holding off today on definitive predictions. We'll try to put the pieces together by the end of the week," said Robert Dickson, deputy chief of the agency's long-range prediction group.

At that time, said Dickson, his department makes its March forecast. "If the weather holds the way it's going, that would be a good sign," he though, before we make any decisions on whether normal weather is here to stay."