The series of storms that have brought a deluge of precipitation to the state have pushed California’s snowpack to levels that are significantly above seasonal averages, with some parts of the state seeing more than double these amounts.
But experts are concerned that this snow, particularly at low elevations, is vulnerable to melt with future storms, exacerbating issues like flooding and mudslides that have devastated parts of the state in recent weeks.
With the normal wet season nearing its end at the beginning of April, the state appears to be on track to have one of the best snowfalls in recent history.
“We’re in third place, after a couple weeks of very heavy snowfall,” said Andrew Schwartz, lead scientist with the UC Berkeley Central Sierra Snow Laboratory which monitors the snowpack in the state’s largest mountains. “We are only three inches away from beating the winter of 1983 to be the second snowiest winter on record at the snow lab.”
As of March 16, the laboratory has recorded nearly 670 inches of snow in the central Sierra Nevada snowpack, translating to about 68.3 inches in snow water equivalent in the section of the mountain range at high elevations.
The reporting stations across the Sierra Nevada are showing similarly high numbers, with an average of 55.8 inches in snow water equivalent for all stations in the state accounting for about 215% of normal April 1 numbers.
Lower elevations have also seen snowfall amounts that exceed normal numbers.
Lake Arrowhead, which sits at an elevation of about 5,175 feet in the San Bernardino Mountains has snow berms towering as high as 10 feet. Meanwhile, Crestline, another community at a lower elevation in the San Bernardino Mountains, has piles of snow close to 12 feet tall.
Relatively warmer precipitation, however, poses a risk to this historic amount of snow, as rain can cause snow to melt prematurely.
The last few atmospheric rivers that have rolled into the region have trended warmer than previous downpours, worrying experts about these storms’ ability to melt vulnerable, low elevation snow – potentially contributing to unprecedented damages in parts of the state.
“For the lower elevations in Southern California, it’s a concern and it’s occurring right now, with rain on snow,” Alexander Tardy, warning coordination meteorologist with the National Weather Service San Diego.
The greatest concern for flooding with the recent – and future – storms stems from the ground’s inability to absorb the additional rain, as the consecutive weather events have prevented the soil from drying out and resetting.
More precipitation coming next week with another atmospheric river could prompt premature melt of this snow, thus adding to the amount of water flowing with nowhere to go given these already over saturated grounds.
“At lower elevations where snowpack hasn’t disappeared… it could be concerning if we do get substantial amounts of rain on top of a snowpack that’s primed to melt, simply because we could see further flooding,” Schwartz said.
Higher elevations are unlikely to see any significant melt with next week’s atmospheric river, or any other warmer storms that might be on the horizon, because of the snowpack’s current density and still colder-than-normal temperatures.
“We’ve got so much snow up here at higher elevations that if it does rain or if we experience a little bit of melt, chances are the rest of the snowpack will store that water instead of running off,” Schwartz said.
But that could change if temperatures begin to rise at a rapid pace or even warmer subtropical storms roll in.
“The big snowpack above 7,000 feet is still in good shape,” Tardy said. “Now if we get a big heat wave this spring, or if we get another one of these warm atmospheric rivers… it’s going to aggravate the snowpack and cause it to melt a little faster than we want to see.”
Meteorologists say that the state could see drier conditions moving into April, although additional rain is likely to happen after next week’s atmospheric river.
Experts say it’ll be difficult to predict warming trends moving into April.