Today we have a strong inversion over the marine layer clouds. The inversion is the warm air that is found above and pressing down on the marine layer clouds. If the inversion is weak the marine layer will have a soft billowy top and the surface wind on the bay will not stick to the surface very well so the wind will be gusty.
Today an upper level high pressure is moving in from the east and the descending warm air from this upper high pressure is compacting the marine layer clouds as you can see in this photo sequence from dawn today.
At the surface this upper level high pressure compacting creates locally dense fog especially on the hills.
When we have an inversion and wind you see the famous San Francisco fog fall which look like water falls made of fog. Check out the bottom image from this morning in the East Bay.
Given today’s compact marine layer I expect relatively steady winds today.
There are much more scientific ways of looking at the inversion such as using the 915 Mhz profilers or the San Carlos SODAR unit but their data presentation is not as pretty as actually seeing the marine layer from above at dawn.