Red Flag Warning issued across Bay Area for critical fire weather conditions

Critical fire weather conditions were building across the Bay Area, prompting a Red Flag Warning for the region beginning Tuesday.

The National Weather Service said the warning was in effect for all interior Bay Area zones, the city of San Francisco, the Peninsula Coast, the Bay Shoreline, and higher terrains of the Central Coast from 11 a.m. Tuesday through 7 a.m. Thursday.   

Strong winds from a high-pressure system in the Pacific Northwest are combining with low humidity to create the conditions triggering the warning. Monday morning, strong winds in the 20-30 mph range were already being felt along with gusts up to 50 mph in the higher elevations, the Weather Service said.

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By Tuesday, daytime relative humidity was expected to drop as low as 15%, and the Weather Service said although recent rainfall will help alleviate fire weather concerns in the short term, the dry winds will help cure the fuels in advance of a second offshore wind event beginning Tuesday evening. 

The worsen fire weather conditions also prompted Pacific Gas and Electric to warn some 15,000 customers in Northern California their power could be shut off for public safety beginning on Tuesday evening.