For almost a week the Cut-Off Low you see in the imagery below has been spinning west to the Oregon/Washington border. This low has gridlocked the normal East to West movement of weather over west coast. But for the Bay Area is is perfectly located. The low itself is send SW flow aloft and marine layer clouds into the Bay Area. While its position is stopping the North Pacific High from its normal drifting about so the Bay Area has seen NW wind for days and days.