Why we’ve been seeing unusually foggy mornings in SoCal

People have been waking up to dense fog from the coastal areas all the way inland, and this weather is expected to stick around until early next week.

We’re used to seeing these conditions for “May Gray” and “June Gloom,” but it is unusual for this time of year.

Rose Schoenfeld, a National Weather Service meteorologist, told LAist we’ve been dealing with a long period of high pressure above us, which starts to compress the marine layer and bring that down to the surface — hence the fog.

“We haven’t really had, at the same time, Santa Ana winds or offshore winds,” she said. “And that’ll really clear that marine layer influence away, if we have winds blowing from inland out towards the ocean.”

So if it seems a bit strange for October, that’s because it is, despite it fitting in well with the spooky season.

What you need to know about the forecast

A dense fog advisory was issued for much of the Southern California coastal waters earlier this week, but it could pop up again Thursday for Los Angeles County beaches, the Malibu coast, and Ventura County beaches.

The chance of fog will generally go where the marine layer clouds are able to reach overnight, Schoenfeld said.

Exactly how extensive it is in the inland areas can be affected by what direction and flow the air at the surface is moving. It’s also affected by the upper level pressure, which again we’ve been seeing for quite some time.

Once the sun starts shining down throughout the day, it’ll generally start to thin out the fog. But once evening rolls in, the marine layer will start to move inland again.

So don’t be surprised if the conditions return later Wednesday.

What’s next

This period of high pressure is expected to stick around, likely through the weekend into early Monday.

Which means we could see more of this dense fog through as late as Tuesday morning.

“It is a little fall-like, which is often unusual because this is the season where we’ll generally have more clear and Santa Ana type conditions,” Schoenfeld said.

Safety tips to keep in mind

Schoenfeld added dense fog can be “pretty hazardous” for drivers and boaters.

Your visibility can change quite quickly, especially if the fog is patchy. So generally speaking, keep the speed down and use your fog lights if possible.

“Just be aware that it's much more hazardous when that visibility is really low,” she said.