LOS ANGELES -- More rain has fallen in Los Angeles over the last three months --15.68 inches -- than normally falls in an entire year, making this the wettest start to a rainy season since 1966.

Now, forecasters expect that a storm that has come from the north and which has been drawing moisture from warmer southern waters will dump as much as 15 inches of rain in the mountains and up to 5 inches in Los Angeles through the weekend.

The storms point to a larger weather phenomenon across the West, with Southwestern regions such as California, Arizona, New Mexico and southern Nevada receiving more rain than normal while Washington, Oregon, Idaho, Montana and Wyoming are receiving less.

Forecasters admit that they are puzzled by exactly what is causing the abnormally heavy rains in the Southwest.

The rain has eased southern California's drought conditions, although many major reservoirs and lakes such as Lake Mead remain at below-normal levels, and it would take several years of above-normal rain to end the West's six-year drought.

It has also created brisk business for auto-repair shops fixing fender-benders and roofers responding to leaky and collapsed roofs.

Officials are most concerned about possible damage along parts of the San Bernardino Mountains, where the warm storm system could melt snow, increasing the threat of flash floods and mudslides in areas burned in 2003's wildfires.

One thing the sustained rain would likely do is significantly lessen the danger of wildfires that have plagued California and other Western states during the drought years.