SANTA ROSA (CBS SF) — A storm front filled with cold unstable air rolled into the San Francisco Bay Area Christmas morning, bringing with it lightning, thunder and hail to neighborhoods in Santa Rosa and another drenching to hills already saturated by the December storms.

The brunt of the storm front was expected to roll through the San Francisco Bay Area early Christmas afternoon, but waves of intense downpours began much earlier.

Lightning, thunder and hail was reported in the Santa Rosa area while an intense downpour drenched Alameda around 8:30 a.m.

There were confirmed reports of heavy rain mixing with hail in Marin County.

The National Weather Service Bay Area office was also reporting gusty winds, particularly at higher elevations in the East and North Bay. Weather officials warned that the combination of wind and saturated soil could bring some trees down.

Problems already were developing during the morning hours.

San Mateo officials reported that trees down on the roadway was blocking Crystal Springs Rd between Donner Ave. and Cunningham Way.

The California Highway Patrol reported flooding on San Clemente Dr. in Corte Madera, Highway 80 near Red Top Rd. in Solano County and on the Bodega Highway in Sonoma County.

The weather service issued a flood advisory for Alameda, Contra Costa, San Mateo and Santa Clara counties at least until 10:45 a.m.

“Doppler radar indicated heavy rain moving across the East Bay with additional rain showers likely to impact the region,” the weather service said. “This will cause urban and small stream flooding.”

Meanwhile, A winter storm warning stretching all the way to Tuesday has been issued by the National Weather Service for the Lake Tahoe area.

“Additional snow accumulations of 1 to 3 feet, except 3 to 5 feet above 7,000 feet,” the weather service in Reno warned. “Wind gusts 30 to 40 mph. Sierra ridges may see gusts in excess of 100 mph.”

Another dose of blinding snow storms and high winds were creating a scenario ripe for avalanches.

“High avalanche danger is expected through Monday morning in the mountains,” NWS forecasters said. “Heavy snowfall and extremely strong winds have created unstable avalanche conditions in the mountains. Large natural avalanches and human-triggered avalanches are expected.”

This is a developing story. Details will be added as information becomes available.