A storm will douse San Francisco this week as tens of thousands of visitors arrive for the Asia-Pacific Economic Cooperation summit—the city’s largest international gathering since world leaders founded the United Nations in Civic Center in 1945.
National Weather Service meteorologist Matt Mehle said residents and visitors can expect periods of rain to wax and wane through Friday, with first drops due to fall late Monday before a brief break Tuesday afternoon and evening. Rain should return in earnest Wednesday through Friday, with rainfall totals for the week reaching 1 to 1.5 inches.
"We're not fully into our wettest period," Mehle said.
Drying conditions won't return until midday Saturday, with clear skies set to return Sunday.
Mehle said forecasting this week's weather had challenges, due to the positioning of a developing low-pressure system off the coast.
"Where that low [pressure] actually develops can have a big impact on how much rain and the timing of said rain," Mehle said. "Last week, we sent out a message to our partners saying, 'Hey, we're watching a system about 10 days out.' Since then, we've been fine-tuning those amounts of rainfall, all based on the position of where that low is forecasted."
That difficulty has taken on more importance with the expected arrival of top government officials and key foreign dignitaries for the Asia-Pacific Economic Cooperation forum, Mehle acknowledged.
President Joe Biden, Chinese President Xi Jinping, Canadian Prime Minister Justin Trudeau and others are among the dignitaries expected in town this week, along with scores of CEOs of global companies including Microsoft, Google and Citi. Overall, APEC events are expected to bring tens of thousands of people into San Francisco.
"I mean, we do all the aviation forecasting in the Bay Area. As you can imagine, there's going to be increased air traffic," he said. "So we're definitely paying attention to how this weather will impact our partners in the airports in the Bay Area as well."
Mehle also said a potential for thunderstorms could lead the weather service to issue localized alerts as necessary, but said he didn't anticipate any flooding or winter-style alerts for high elevations, thanks in part to the low-pressure system's warmer temperature profile, which will keep temperatures fairly even with a maximum in the low to mid-60s.
At San Francisco International Airport, spokesman Doug Yakel said the Federal Aviation Administration would use weather conditions to adjust operations as needed.
"On fair weather days, when aircraft can operate side-by-side, SFO can accommodate approximately 60 arrivals per hour," Yakel said. "During periods of reduced visibility, the FAA may no longer permit side-by-side arrivals and may reduce the rate of arrivals to increase aircraft separation to account for the reduced visibility."
Yakel added that ground delay programs that could meter flights, delaying arrival times, would be reflected on the FAA's website.
Airspace restrictions will also be imposed in the Bay Area due to security concerns, the U.S. Secret Service has said, further complicating the situation.
APEC was formed in 1989 to promote trade policy free of tariffs, subsidies or sanctions throughout the Asia-Pacific region. To that end, it hosts multiple meetings each year in a given host nation.
In 2023, the United States is the host, and San Francisco is the stage for APEC’s annual culmination, known as Economic Leaders’ Week, through Friday.
The climactic week of the conference will bring together heads of state and economic and trade ministers from the 21 APEC member economies, as well as hundreds of corporate executives and other high-ranking business leaders for the forum’s CEO Summit from Tuesday through Thursday.
Besides Biden and Xi Jinping, dignitaries coming for the conference include Australian Prime Minister Anthony Albanese, Japanese Prime Minister Fumio Kishida and Peruvian President Dina Boluarte. U.S. Vice President Kamala Harris is this year's chair.
Moscone Center, the main site of the conference, will be cordoned off by a security perimeter, with transit lines rerouted and some streets closed.
As in years past, wherever APEC is held, activists plan to flock to those security lines to promote their causes at a widely watched forum that draws media attention from around the globe.
George Kelly can be reached at email@example.com