The National Weather Service [NWS] predicts rain all week long in the Bay Area starting around 11 A.M. Tuesday, and with it comes risks of flooding in low-lying areas and possibly even more dangerous conditions like mudslides and debris flow.
According to a hazardous weather warning issued by NWS, the oncoming storm will bring some extra dangers with it:
The following hazards are possible between Tuesday and Thursday:
*Localized urban flooding, mainly in low lying areas or poorly drained areas.
*Small stream flooding, mainly streams that flow out of the Santa Lucia Mountains along the Big Sur Coast.
*Gusty winds may result in power outages due to downed trees and powerlines. Strongest winds are expected Wednesday and Wednesday night.
*Mudslides or debris flows could occur if soils become saturated. This is most likely along the Big Sur Coast.
Although the most significant risks are anticipated in areas outside of San Francisco, the warning nevertheless covers the entire area from the North Bay (“including Point Reyes National Seashore”) down to the Santa Cruz Mountains.
According to flood hazard maps prepared by FEMA in 2015, the areas most likely to suffer flooding in SF are Treasure Island, Hunters Point, Mission Bay, and Mission Creek.
Winds could reach speeds of up to 24 miles per hour in some parts of the Bay Area during the next two to four days. While that’s not enough to warrant a separate wind warning on its own—NWS issues gale warnings when speeds pick up to around 39 miles per hour—it still pays to be cautious, particularly in areas prone to windy conditions even on calm days.
The forecast calls for rain beginning early Tuesday and likely continuing a heavy downpour at least until Wednesday evening, with a chance of rain persisting through Thursday. An additional chance of rain will continue through the weekend, not fully dissipating until Sunday.