UPDATE, Nov. 19, 12 p.m.: PG&E said Tuesday afternoon it had sent 24-hour shut-off notices to 171,581 customers in the North Bay, North Valley and Sierra foothills. Meteorologists are still monitoring wind forecasts for the other Bay Area counties to determine if preventative blackouts would be necessary there. The list of cities and counties affected has also been updated. Read the full original story below.

Pacific Gas and Electric announced it would shut off power for the fourth time in two months to a wide swath of Northern California in another attempt to prevent wildfires from igniting.