Final answer:
Fog formation along the west coast of the U.S. is caused by cold ocean currents, the rain shadow effect of mountain ranges such as the Cascades and Sierra Nevada, and ocean upwelling.
Step-by-step explanation:
The conditions along the west coast of the U.S. that contribute to fog formation include the presence of cold ocean currents that help to cool the air above them, leading to condensation and fog creation. Another contributing factor is the coastal topography, particularly the mountain ranges such as the Cascades and the Sierra Nevada. These ranges play a role in the rain shadow effect, where moist ocean air rises and precipitates on the windward side of the mountains, leaving drier air on the leeward side, which contributes to fog formation when it comes into contact with the cool, moist marine layer. The process of ocean upwelling also contributes to fog when deeper, cooler waters rise to the surface, cooling the air above it to the dew point, leading to condensation and fog.