SAN FRANCISCO >> Forecasters say a storm stretching from California to Montana could as drop as much as 6 feet of snow on high elevations of the Sierra Nevada, a prediction that’s down from an original forecast of 8 feet.

Winds gusting in excess of 100 mph over ridgetops are likely to create whiteout conditions today.

Nearly 2 feet of snow fell at several Lake Tahoe area ski resorts Monday night and early this morning and a winter storm warning was in effect for the Tahoe area through Thursday morning.

Lake Tahoe officials urged residents to clear roofs of snow and ice after falling ice ruptured a natural gas line and injured a child. Officials say the child was treated last weekend at a hospital for a leg injury after a 150-pound icicle nearly crushed him.

The National Weather Service says travel could be very difficult to impossible tonight and Wednesday morning with snowfall rates of up to 3 inches per hour.

The storm is drenching an already soaked Northern California, where authorities are advising residents that several rivers and creeks could overflow.

North of San Francisco, Sonoma County officials activated an emergency center because of threats of flash floods and mudslides.

Sonoma County Board of Supervisors chairman David Rabbit says in a statement it is “time to locate emergency kits.”

The National Weather Service says some rivers and streams could hit flood stage by late today. It issued several flood watches for Sonoma, Napa and Marin counties.

Sonoma County officials issued a flood warning, saying the Russian River near the community of Guerneville is expected to hit flood stage early Wednesday.

In neighboring Napa County, the Napa River in San Helena could also overflow.