Hot in the City: Bay Area, Sierra Nevada Brace for Unusual March Heat Wave

Break out fresh sunscreen, wide-brimmed hats and shorts because forecasters expect California to have its first heat wave of the year starting Wednesday, with well-above-normal temperatures through next week. The wave threatens to break some Bay Area cities’ high temperature records and rapidly melt the Sierra Nevada’s snowpack.

National Weather Service meteorologists said Bay Area cities can expect widespread temperatures in the 70s and some in the 80s this week, and even warmer temperatures on Sunday into next week.

Next Tuesday will likely be the hottest day of the heat wave, said meteorologist Brayden Murdock with the weather service’s Bay Area office. He said Oakland and San José are among cities that could surpass monthly high-temperature records, and San Francisco could sizzle into the 80s by Sunday.

“For us to see this heat wave early does make it a little bit more uncommon, and then the magnitude of some of the temperatures we’re going to be seeing makes it pretty rare,” Murdock said.

A ridge of high pressure from the subtropics is building northwards over the Pacific Ocean, which can create extra warm conditions across Northern California. By early next week, the ridge will sit right over Northern California. Murdock describes it as the jet stream forming an upside-down U-shape and trapping heat. Plus, he said, winds don’t usually blow strongly during a bout of high pressure.

“It’s kind of a one-two punch of us just not being able to really dissipate or transport that heat away from us,” Murdock said.

The ridge of high pressure will cause temperatures to “quickly climb to late spring and early summer levels” in the Sierra Nevada, said Chris Johnston, a meteorologist with the weather service’s Reno office. Mountain communities could see highs in the low 70s by Monday.

Johnston said long-range forecasts suggest the ridge will push towards the eastern U.S. during the fourth week of March, which could shift the weather pattern towards cooler conditions. But the Climate Prediction Center’s six-to-10-day and three-month outlooks forecast warmer temperatures and below-average precipitation.

Dakari Anderson, a meteorologist with the weather service’s Sacramento office, said the Sierra Nevada will likely see temperatures 10 to 15 degrees above normal with the warmest temperatures early next week.

For example, in Blue Canyon, off Interstate 80 in Placer County, the normal temperature this time of year is 49 degrees. But Anderson said the service is “forecasting temperatures to be almost 75 degrees, so it’s an even bigger jump for them.”

The warm-up is bad news for the state’s snowpack, sitting at just about 53% of average for this time of year — and melting daily. After an exceptionally warm winter, state officials said the rapidly melting snowpack is complicating efforts to preserve the state’s water supply, and climate experts claim the loss of snow early could increase wildfire risk in the northern part of the state.

Daniel Swain, a climate scientist with UC Agriculture and Natural Resources, said it’s clear from the warm forecast that “there will be no Miracle March,” or when a dry winter turns into a snowy one with late-season cold storms.

“We’re going to get to April 1, and we’re going to have some scary snowpack numbers, essentially everywhere,” Swain said in his latest YouTube office hours.

Swain said the above-average heat is “not going to be a short-duration heat wave” and could last two weeks, even though it “won’t be equally hot the whole time everywhere.”

A record warm winter and a record snowless winter are the “single most obvious” signals of the effects of human-caused climate change, he added.

“Winters like this one could very much be the norm in just a couple of decades,” Swain said. “They will, in fact, be close to average on our current trajectory. That is the sobering reality. Today’s extraordinary is tomorrow’s ordinary, and I think we’re already living that.”

Snow levels aren’t ubiquitous across the range, varying from 31% in the northern part of the range, 55% around the center, and 73% of normal for this time of year in the southern part.

Swain said there is concern that the low snowpack in the north state is a “major early forest fire signal,” which could present itself later in the year, “unless something changes dramatically.”

He said for the rest of the Sierra Nevada wildfires could pop up early, “with the relatively poor end of the season in the cards.” But he said they could be “mitigated somewhat by the high soil moisture.”

When it comes to water supply, Karla Nemeth, director of the state’s Department of Water Resources, said in a statement that since mountain snow is melting rapidly and “the potential for new heat records next week,” the state will have to release much of the runoff to make room in reservoirs in case of flood conditions.

“That means we forgo having stored that water for release later in the summer, when rivers and streams run lower and warmer,” Nemeth said.

Ski resorts, like Sierra-at-Tahoe, are encouraging outdoor enthusiasts to visit the Sierra Nevada because spring-like conditions — where it freezes overnight and warms up through the day — make for good skiing.

“It’s firm and fast and smooth in the mornings, and it gets a little softer as the day goes on,” said Jake Stern, content and communications manager with the resort. “The beauty of skiing in California is that it can be 70 degrees and people will be skiing in swimsuits.”

The resort often makes snow when there are no storms in the forecast, but Stern said nighttime lows may not be cold enough to create snow. As of now, Stern said there is no final date for the ski season.

“We’re going to keep our skiing and riding open until the last possible day,” Stern said. “This weekend, we will have easy road conditions, and it’ll be fun, warm and slushy snow conditions.”