(CN) — Drivers passing through Donner Summit along Interstate 80 in the high Sierra, over 7,000 feet above sea level, didn’t expect significant snow.
People thought Wednesday would bring rain with only a light amount of snow. That changed around 2 p.m., according to Officer Carlos Perez with the California Highway Patrol.
“We were prepared, but a lot of people were not prepared,” the Truckee-based officer said. “It was definitely winter-driving conditions.”
Wednesday marked th first time this season that authorities implemented chain control over the summit on I-80, starting at 2:15 p.m. and lasting until 6:10 p.m. Vehicles needed four-wheel drive or chains to pass through.
The UC Berkeley Central Sierra Snow Lab, at 6,800 feet in Soda Springs, recorded 3.9 inches of snow over the 24-hour period ending at 8 a.m. Thursday. Only 1 to 3 inches was expected.
Chain controls, and sometimes full road closures, are the norm in the Sierra Nevada during this season. And, if weather predictions prove true, this upcoming winter could bring more chain controls to the upper elevations.
The National Oceanic and Atmospheric Administration this month predicted wetter than usual conditions from December through February for parts of the West, northern Alaska, the southern Plains, Southeast, Gulf Coast and lower mid-Atlantic.
Scott Rowe, a meteorologist with the National Weather Service, said that means Central California has about a 40% to 50% chance of having above-normal precipitation, and a 30% chance of near-normal precipitation. The remaining percentage is for below-normal chances.
“It’s good guidance, but that’s always to be taken with a grain of salt,” said Andrew Schwartz, lead scientist and manager at the Central Sierra Snow Laboratory. “But it’s the best that we have.”
Last winter’s rains helped fill the state’s reservoirs, with Lake Oroville in Butte County seeing the largest jump. As of late Wednesday, that reservoir sat at 69% of its total capacity and 134% of its historical average — the latter a 64% climb from a year ago.
Since Dec. 1, 2022, 3.5 million acre-feet of water has been caught in state reservoirs.
The state had been suffering from a three-year drought leading up to Christmas 2022.
“After Christmas, things changed dramatically,” said Michael Anderson, state climatologist with the Department of Water Resources. “We head into the new year, from a statewide perspective, we’re above average.”
El Niño conditions are now in effect, Anderson said. Those conditions mean higher temperatures from the equator to the pole, which in turn means a greater chance of storms reaching Southern California.
El Niño years can be wetter than other years, though by itself it’s not the best indicator. According to Anderson, California has seen seven El Niño events this century. Of those, two trended wet, two dry and the remaining three had average rainfall.
Anderson is interested in the timing, pace and scale of storms. The jet stream’s location can help with that. It’s currently farther north, though it will move south as winter approaches. December through February are California’s biggest months for rainfall.
However, despite factors like El Niño and the jet stream, nothing about the weather is certain.
“We can do a pretty good job for a week or 10 days,” Anderson said about forecasting.
The coming days may show how fickle nature can be.
After a heavier-than-expected snowfall, the next week is forecast to be dry and breezy, with the strongest winds over the weekend, Rowe said.
Jeremy Linder, public information officer with Caltrans District 3, said Wednesday’s snow is a good reminder for people.
“The big one for us is always pack chains,” he said.
Perez added that people going over the pass also should have a full tank of gas, food and blankets.
Some drivers try to avoid chain controls by using alternate routes, Linder said. That potentially puts them in a dangerous situation, forcing authorities to stretch resources.
For now, Interstate traffic has returned to normal.
“It was very serene,” Schwartz said. “It’s always nice to have the first snowfall of the year. Fingers crossed that we get another good winter.”
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