Quick Take:
Moving south over the Bay Area, rain should pick up later in the afternoon Christmas Day and persist early into Saturday. Then another, smaller system will move through.
Christmas is ushering in a wet weekend, though likely not the kind of downpour dreaded in the fire-scorched Santa Cruz Mountains.
Rainfall is expected to begin in earnest Friday afternoon. Moving south over the Bay Area, rain should pick up later in the afternoon Christmas Day and persist early into Saturday, according to the National Weather Service. A second round of showers is forecast Sunday afternoon into Monday.
Most of Santa Cruz County can expect .25-.50 inches of rain from the Christmas Day downpour, while areas of the North Bay are set for a more substantial drenching — up to 1.5 inches.
Pockets of the Santa Cruz Mountains may see up to inch of rain — enough to prompt some concern about debris flow in the vast burn scar left by the CZU Lightning Complex fire.
Officials are closely monitoring the threat. But the risk this weekend appears low.
“We don’t at this time plan to issue any warnings or evacuations,” said Jason Hoppin, Santa Cruz County’s spokesperson, after meeting with a group of officials Thursday morning to assess the risk. “Right now it looks OK, and that’s both for Christmas Day and Sunday.”
The expected level of rain does carry “some potential” for debris flow in burned areas, according to National Weather Service geologist Gerry Diaz. “But really, overall, because we’re not expecting those heavy rains to last over a long period of time, they’re not substantial concerns.”
Often called mudslides, debris flows are an especially deadly kind of landslide most commonly caused by heavy rain after a wildfire.
Wildfires leave terrain stripped of plant cover coated in a blanket of scorched soil and ash that repels water. In 2018, debris flows killed 23 people and leveled hundreds of homes in Montecito in the wake of the Thomas Fire
The deadly slides can be triggered by even a short burst of intense rain falling at a rate of about 1/2 inch per hour. According to Hoppin, current forecasts suggest rainfall in the Santa Cruz Mountains won’t exceed 4/10 inch over a six hour period this weekend.
Still, he urged residents in at-risk areas to stay vigilant, monitor news and social media, and sign up for emergency alerts through the CodeRED notification system.