Winter is typically the wettest time of year in the San Francisco Bay area, and the region will get its share the next couple of days. Unfortunately, it could do more harm than good.
An atmospheric river of moisture off the Pacific, nicknamed “The Pineapple Express” because of its origins near Hawaii, will take aim at the San Francisco Bay area and California’s Central Coast from tonight (Tuesday) through part of Valentine’s Day. Rainfall rates of at least one-half inch per hour are possible during the heaviest showers, with more intense rates in the higher terrain. Several inches could end up in area rain gauges.
San Francisco International Airport (ICAO code: SFO) has already recorded 7.30 inches of rain this year, 1.5 inches above normal. The coming rain will help the region, which is still suffering from abnormally dry conditions, according to the U.S. Drought Monitor, but possibly at a cost. Recent rainfall has saturated soils across the area, and the additional downpours will create the potential for widespread shallow landslides and rockslides, as well as debris flows from nearby areas impacted by wildfires that burned last summer and fall. Also, periods of heavy rainfall will likely inundate storm drains with rapid rises of small creeks and streams. Other waterways like the Big Sur, Carmel and Pajaro rivers could see big rises.
A Flash Flood Watch has been posted by the National Weather Service (NWS) for the entire San Francisco Bay area and Central Coast, except for the hills of San Benito County (just south of San Jose) and the East Bay Valley (towns of Antioch, Concord, Dublin, Livermore, Pittsburg and Walnut Creek). For now the Watch lasts until 10:00 a.m. Pacific Standard Time on Thursday, February 14, and flooding could lead to closures on sections of I-5 and I-80, in addition to US-101 and CA-1 (Pacific Coast Highway).
Rain won’t be the only problem, however, as powerful winds are expected to accompany the storm. Sustained winds from the south across the San Francisco Bay area up to Santa Rosa will reach 25 to 35 mph, with gusts up to 60 mph. There’s a potential for downed trees and power lines blocking some roads, and scattered power outages are possible. Winds will also be fierce in portions of northern California, from Fort Bragg and Eureka to the Oregon border. Deadheading will be risky on east-west routes, and even hauling full loads could be difficult. Carriers may want to wait to send drivers through these areas or find other routes, if possible.
Gale Watches and Small Craft Advisories have also been posted as strong winds will create high surf and choppy water.