Higher temperatures may lead many people to rivers or streams near the Sierra Nevada and surrounding foothills for recreation just as cold, fast water is moving toward them.
Those who weren’t a fan of the warmer weather this week might be pleased to hear that Bay Area temperatures are forecast to drop steadily over the weekend.
But if you’re looking for a quicker cooldown, be careful about dipping into rivers near the Sierra Nevada, as rapidly-melting snow might create dangerous swift water.
Dial Hong, a National Weather Service meteorologist, said that temperatures are expected to cool this weekend.
That trend began on Friday afternoon, with coastal regions seeing cooler temperatures than much of the region, reaching as low as the mid-60s while areas like San Jose and the interior East Bay moved toward the high 80s.
Overnight lows were expected to reach the lower 50s near the coast and the mid- to upper 50s inland.
Hong said more clouds were expected to form along the coast this weekend, with temperatures continuing to drop around the Bay. However, inland areas, like South Bay and the interior East Bay were expected to remain warm. High temperatures on Saturday were expected to reach 71 in San Francisco and 78 in Oakland, with temperatures approaching Friday’s highs in San Jose and the interior East Bay.
On Sunday, temperatures are expected to continue to cool by a few degrees almost everywhere, Hong said. Cities along the coast can expect highs in the 60s, with San Jose and the interior East Bay sliding down to more comfortable highs in the mid- to upper 80s.
In the Sierra Nevada, temperatures are ranging from the 70s around 6,000 feet to the mid- to upper-50s at 7,000 feet, which will lead to melting snow, said National Weather Service meteorologist Eric Kurth.
“If it’s warm, we’re going to see melting,” Kurth said.
Kurth said that, because of the higher temperatures, there is a concern that people will head to rivers or streams near the Sierra Nevada and surrounding foothills for recreation, unaware of the risk.
Larry Collins, the deputy chief of special operations for the California Office of Emergency Services said increased snowpack and runoff from the recent storms accelerates the speed and volume of water in streams, rivers and floods. He defined swift water as water moving downhill at a speed of at least 2 to 4 mph in natural waterways to 50 to 65 mph in flood control channels.
Collins said that due to recent swift-water drownings in San Bernardino and Stanislaus counties and the expectation of more swift-water rescue calls this season, authorities were taking more precautions and spending more time educating the public on swift-water risks.
Collins said that rivers and streams around the Sierra Nevada and its watershed might see higher water flows; He added that rivers in Yosemite are also seeing a lot more water flow.
The risk of swift water is higher in areas where whitewater rafting is prevalent, Collins added, mentioning the south, middle and north forks of the American River close to the Sierra Nevada and currents that flow in Folsom and Sacramento Valley.
“Where there’s whitewater rafting going on, you get those conditions,” Collins said.
Collins said that the cold water can shock swimmers, causing them to rapidly lose muscle coordination and risk them getting swept downstream and getting hit or trapped by hazards in the waterway. Hong encouraged people to wear wetsuits or drysuits and always wear a life jacket if they’re doing any water activities near the Sierra Nevada.
Collins advised parents to watch their children when they’re playing in water and make sure they and their children have floaties on when they’re in or around moving water.
Collins also advised people to not try to to go into the water when trying to help someone out of the water. He advised people to call 911 and throw something the drowning person could reach for, like a rope, floatie stick or pole.
“Prevention is the main thing. Make sure you’re aware of the conditions,” Collins said. “And be aware that cold water is going to drop your effectiveness by half if you’re trying to swim or self-rescue or rescue someone else.”
