A fast-moving band of thunderstorms, known as a squall line, was expected to sweep across the Bay Area between 1 and 4 a.m., bringing a brief but intense burst of heavy rain and wind gusts over 50 mph in some spots. The strongest winds and any potential for water spouts were forecast to be focused closer to the Central Coast and Monterey Bay, where atmospheric instability is greatest.
With freezing air just a few thousand feet above the surface, the atmosphere will be unstable enough to support strong storm cells. These storms could produce brief downpours and small hail. Snow will fall along the higher hills of the Bay Area, with a few inches likely in the Diablo range in Santa Clara County.
Northwest winds will pick up as the squall line approaches, with sustained winds of 20 to 30 mph and gusts up to 45 mph in San Francisco, along the Peninsula and across coastal parts of the East Bay. Even stronger winds will develop across higher elevations. Some 50+ mph gusts are likely as the squall line moves through, especially along the immediate coast and through the typically windy gaps…