‘Drastic change’ in Bay Area weather could hamper Fleet Week air shows

The Bay Area is in for a weather whiplash as triple-digit temperatures are expected to plummet after a multi-day heat wave in October, leading to possible impacts that could hamper viewing conditions at this weekend’s Fleet Week air shows.

“A sea change is coming,” Dylan Flynn, a meteorologist with the National Weather Service Bay Area office, told SFGATE Wednesday afternoon.

As towns like Livermore have reached a high of 100 degrees every day since last Saturday and other inland parts of the region have seen widespread temperatures in the 90s, Flynn said a “sharp chill” is expected to arrive by the weekend. This coming Saturday, temperatures will likely stay closer to the 70s, or in the upper 50s and low 60s along the coastline.

Three distinct disturbances are merging to contribute to the colder weather: The jet stream, or a narrow, fast-moving band of strong wind in the upper atmosphere, is plunging toward Northern California. A weak depression is also expected to arrive from the west by Thursday. And from the south, the remnants of Hurricane Rachel are also expected to head towards California.

“Together they will bring us a high-amplitude trough of low pressure that will completely flip the script,” Flynn said.

High winds are forecast as early as Friday afternoon, which could impact this afternoon’s air show, including the highly anticipated return of the Blue Angels following last year’s government shutdown. Winds up to 30 mph are expected to blow from the northwest, peaking Saturday and decreasing Sunday. Flynn said no advisories are in effect at this time — criteria generally includes wind speeds of at least 39 mph — but forecasters continue to monitor the situation.

The good news is that while some fog has remained confined along the coastline during the warmer days this week, winds could push it back into the night Thursday. “If there are clouds, they should move pretty quickly,” Flynn said. With that in mind, he encouraged people heading to the air show to bundle up and expect cool conditions.

“I am not an expert, but there could be disruptions in the programming,” he stressed. “We’re looking at strong offshore winds and southerly swells with waves 10 to 12 feet high, which is quite violent. This could be an issue that could impact flying conditions.”

Weather services are in close contact with the U.S. Coast Guard to ensure the show continues safely.

The Bay Area is also set to enter a coastal flood advisory at 9 a.m. Friday that will remain in effect until 3 p.m. Tuesday, as just over a foot of water is expected in low-lying areas along the coastline. The new moon exerts the influence of the tides, which Flynn described as a normal phenomenon that occurs twice a month. But with El Niño and warming waters, “the tides are a foot higher than they should be,” he said.

“So when you add an extra foot of water to a normal spring tide, we’re talking about king tide territory,” he said.

Normally, forecasters see main tide levels with a strong storm surge. “But what’s unusual and what I’ve never seen is we have a foot of storm surge on a warm, sunny day before the storm hits,” Flynn continued. “Everything that’s built on this foundation means it’s going to be a very impactful year from a coastal flooding perspective. We’re very likely going to break records in November.”

The Fleet Week air shows begin with opening ceremonies on Friday at 12:15 p.m. and the Blue Angels flight at 3 p.m. The program runs until Sunday afternoon.

Check with the weather service for the latest forecast updates.