Atmospheric River: Hurricane Hunters Fly Into Storm; Residents Flee Homes In Santa Cruz Mountains

SANTA CRUZ (CBS SF) -- Hundreds of residents packed up their treasured belongings early Tuesday, preparing to evacuate homes in the burn zone of last fall's devastating Santa Cruz Mountains wildfire, as a powerful Pacific storm edged ever closer with as much as a foot of rain and the threat of deadly mudslides.

Hurricane Hunters from the famed 53rd Weather Reconnaissance Squadron, more commonly deployed to the Gulf Coast, have begun daily flights into the storm, measuring its potency and accessing the dangers it might present.

The National Weather Service, meanwhile, has issued several warnings for the region including a flash flood watch for the San Francisco Bay Area, an avalanche watch for the Sierra were as much as seven feet or more of new snow could fall in the highest elevations and a high wind warning for "locally up to 70 mph in southwest facing slopes and coastal areas" in the San Francisco region.

"This atmospheric river is still on track to be hazardous to a large portion of NorCal with heavy rains, gusty winds, and a Sierra snow dump," the National Weather Service said.

Forecasters were predicting 2-3 inches of rain in San Francisco and the Central Bay Area with as much as 10-12 inches of rain in the Santa Cruz Mountains and along the Big Sur coast.

Officials in Sonoma County posted Tuesday afternoon that the National Weather Service had issued a flash flood watch that was expected to be upgraded to a Flash Flood Warning in the evening. Officials noted that there was no immediate evacuation order.

While the threat of mudslides captures the headlines, experts say it the debris flows -- torrents carrying massive boulders, soil, trees and other objects — that can be more deadly. The Jan. 9, 2018, debris flow that blasted the Santa Barbara County community of Montecito killed 23 people.

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For residents still weary from last summer's fires, the threat of heavy winter rains and potential mudslides have been weighing on their minds.

Adam Legros is evacuating his home on Hwy. 236, and heading over the hill to be closer to his workplace. Last week's windstorm knocked down trees and heavy branches, and triggered a small mudslide behind his home.

"We just went through this with the fires and everything, so we're kind of used to it at this point we knew it was coming up so. Staying is not worth the risk," said Legros.

Susan Strouse had just returned from a long evacuation from the CZU, and must now evacuate again, heading to her son's house in San Jose.

"But we're glad to be leaving, because this storm is gonna be bad. It's kinda dangerous up here, it's good to get out," said Strouse.

The CZU Lightning Complex fire scorched 86,509 acres, leaving behind scorched "hydrophobic" soil that does not readily absorb water, according to Dr. Laura Sullivan-Green, department chair of Civil and Environmental Engineering at San Jose State University.

"When we have that intense heat, and that that burn debrief that changes the chemical composition of the soil. So instead of soil absorbing water like it normally would. It absorbs very little, if any, and then most of that water just runs off and it takes anything that's loose on on the top of the ground with it," said Sullivan-Green. "And these flows tend to be quick, so there's no outrunning them."

Battalion Chief Nate Armstrong said for those in the evacuation zones, it's critical to leave when asked to do so.

"By the time the rain starts falling, at that intensity, it's already too late if you aren't already gone," he said. "If you hear a debris flow coming, it's already too late."

The threat of landslides wasn't limited to the Santa Cruz Mountains. Residents in Wine Country and the North Bay were also on alert where the LNU Complex and the Glass fires burned more than 400,000 acres last fall. The flash flood warning has also been issued for the region.

It is a real concern, Sonoma Valley Fire Battalion Chief Spencer Andreis told KPIX 5.

"This is all different areas in the county that are impacted with the fires," said Andreis. "So we're going to be maintaining a heightened awareness and closely monitor the situation."

Along St. Helena Road, there is still heavy fire damage visible. Many homes were lost, but one house survived. Owners Jim and Betty Doerksen are worried about the coming storm.

"From the top of that mountain over there, it's all burned, right? And that's my neighbor's property. There was already erosion over there, lots of erosion," said Jim Doerksen. "Now with all those tree gone, the canopy gone, I can see a small catastrophe."