SAN FRANCISCO -- Nearly a month of rain finally took its toll on Highway 1 at Devil's Slide Sunday afternoon as giant cracks opened up on the roadway forcing its closure.

CHP Sgt. Wayne Ziese said that the California Department of Transportation and CHP closed the road at 6:18 p.m. between Pacifica and Montara.

"There's something there," Ziese said, "but it's hard to tell what yet." Ziese said a sink-hole might be developing under the roadway.

The road has been closed indefinitely, Ziese said.

Meanwhile, a pair of cold fronts, spawned in the turbulent waters of the Gulf of Alaska and fueled by humid air from the Hawaiian Islands, began their onslaught on Northern California Sunday, bringing with them heavy rains to the already saturated Bay Area hillsides.

The National Weather Service said the first of the two fronts rolled into the area with light showers that intensified as the day progressed. In all, NWS forecasters said, the first front could produce rain totals of .5 to 2 inches mainly in the higher terrain of Napa, Sonoma, Santa Cruz and Monterey.

The second -- and more potent -- front was forecasted to crash into the area early Monday and with it heavy rains.

NWS forecaster Brooke Bingaman had little encouragement for residents living in the Bay Area hills where some slides have already taken place.

"All our computer models are showing frontal system after frontal system coming in," she said. "It looks like April is starting off with the same pattern as last month."

In Sausalito, crews continued their efforts to stabilize a slide that has resulted in four buildings being red-tagged by engineers.

Astrid Kay, who lives in one of the red-tagged buildings, was hoping to soon be back home. She said she was on the phone when Thursday's slide took place.

"Rumble, a big rumble down the hill," she said.

Her husband, Stephen Kay, said the couple was living with relatives until they are given the all-clear.

"We stayed at my brother-in-law's house last night and came back this morning trying to figure out what's going on," he said.

Elsewhere, crews were keeping a wary eye on a slide on the hillside bordering Mill Creek Road in Healdsburg. On Friday, a 100-foot wide wall of mud and debris covered the roadway, making it impassable for local residents. Crews have since been able to reopen the road.

Smaller slides have been reported over the last two weeks in the Oakland hills and in a Hercules neighborhood.

The instability has local officials on alert as the latest weather fronts roll in.