San Francisco Bay stunned under a blanket of fog on Friday

The sky over much of the San Francisco Bay Area was crystal clear on Friday morning, but low-lying fog blanketed the bay as if a baker had spread whipped cream across the expanse of water. The sight was stunning for anyone who saw it.

The National Weather Service said conditions were just right this morning for the fog to unroll across the bay and not spread into land areas. 

A light onshore breeze blowing across the Pacific Ocean gently nudged the fog through the Golden Gate, and the clouds spread over the cool waters, explained weather service meteorologist Alexis Clouser. A light offshore wind was also blowing from inland valleys toward the ocean, which prevented the fog from pushing inland and held the clouds over the bay. 

What's more, Clouser explained, "Those temperatures over the bay are cooler than the temperatures over land, so they can sustain that fog."

By late morning, the fog was disappearing. "As the sun rises, things warm up, and the fog starts to burn off," Clouser said. 

While most of the land flanking the San Francisco Bay was fog-free on Friday morning, the North Bay did see what's known as radiation fog. "This occurs with still winds, and the air temperatures cool down to the dew point, and the air becomes saturated and forms clouds," she said.

There's a slight chance that a similar fog setup could occur again early on Saturday, before burning off throughout the morning, Clouser told SFGATE on the phone.