The Pineapple Express storm bearing down on Southern California could bring heavy rain and strong winds throughout Christmas week, potentially triggering mudslides, downing trees and flooding not only freeways but also homes and businesses.
If the forecasts are right, this could be one of the stormiest Christmases in recent memory for Southern California. There’s an 80% chance downtown Los Angeles will get 2 or more inches of rain from Tuesday through Christmas Day. The last time downtown got 2 or more inches of rain over Christmas Eve and Christmas Day was in 1971.
Here’s what you need to know.
Timing
The peak of the system is expected Tuesday through Thursday, according to the National Weather Service.
There’s an 80% to 100% chance of rain in Los Angeles, Ventura, Santa Barbara and San Luis Obispo counties starting Tuesday night and lasting into Wednesday and Thursday.
In Orange County, the Inland Empire and San Diego County, light showers are possible Tuesday, but the heaviest rainfall is expected Wednesday, with officials warning of heavy rainfall, increased flooding risks and possible mudslides. Flood and mudslide risks will continue Thursday.
Worst-case scenario
Forecasters are warning that there’s a 40% chance of “very high” amounts of rain for Los Angeles, Ventura and southern Santa Barbara counties, and a 30% chance of the same for northern Santa Barbara County and San Luis Obispo County.
That scenario would see 4 or more inches of rain fall on the coast and in the valleys, with 8 or more inches in the mountains and foothills, Tuesday through Thursday. Peak rainfall rates would be half an inch to 1 inch per hour.
According to the National Weather Service, that could cause:
• Significant mudslides • Flooded freeways • Streams and rivers flooding over their banks • Localized flooding that could rise above curbs and into homes and businesses • Moderate coastal flooding in south-facing areas • Downed trees and power lines • Dangerous sea conditions • Swiftwater rescues
Between Tuesday and Thursday, numerous areas have a high chance of seeing 3 or more inches of rain. There’s a 77% chance of that occurring in Anaheim and Yorba Linda, a 74% chance in Santa Ana, a 73% chance in Ontario, a 71% chance in Mission Viejo, a 69% chance in Irvine, a 68% chance in Chino, a 65% chance in Laguna Niguel and a 60% chance in San Clemente.
‘High amounts’ of rain scenario
There’s also a 40% chance of “high amounts” of rain in L.A., Ventura and southern Santa Barbara counties, and a 50% chance of the same in northern Santa Barbara and San Luis Obispo counties. That scenario would entail 2 to 4 inches of rain falling along the coast and in the valleys, with 4 to 8 inches in the mountains and foothills.
Rain to that extent would risk flooding freeway lanes; causing minor coastal flooding, mudslides and debris flows; and potentially force swiftwater rescues in fast-moving rivers and streams.
Wind
There’s a potential for gusty winds from the south, said Robbie Munroe, meteorologist with the National Weather Service’s Oxnard office, which issues forecasts for L.A., Ventura, Santa Barbara and San Luis Obispo counties.
That risks toppling trees and power lines. On Tuesday night, Los Angeles could see peak gusts of 31 mph; Woodland Hills, 38 mph; Paso Robles, 52 mph; and San Luis Obispo, 53 mph.
“Avoid parking under trees,” the weather service said. “Secure loose outdoor objects.”
There’s a 65% chance of gusts exceeding 35 mph in Huntington Beach, a 60% chance in San Diego, a 45% chance in Big Bear Lake and Ramona, a 40% chance in Escondido and a 35% chance in Riverside, according to the weather service office in San Diego.
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