What current flows southward along the west coast of the United States and causes extensive fog in that area?

The California Current is a cold oceanic current that flows southward along the west coast of the United States. This current originates in the North Pacific Ocean and is characterized by its cooler temperatures compared to the surrounding water. The interaction between the cold current and the warmer air above it is a significant factor contributing to the formation of extensive fog in coastal areas, particularly in California.

As the cold water of the California Current comes into contact with warmer air from the land and the ocean, the moisture in the air cools down and condenses into fog. This phenomenon is especially prevalent in the summer months when warm air masses dominate the region. The result is thick marine fog that can reduce visibility and impact navigation.

In contrast, other currents mentioned, such as the Gulf Stream, primarily transport warm water and are located on the east coast of the United States. The Alaska Current is more associated with the northern regions and also does not contribute to the foggy conditions experienced along the California coastline. The North Pacific Current flows westward and does not have the same direct influence on coastal fog along the west coast. Thus, the California Current is the key current that influences fog formation in that region.