Storms have returned to California, bringing with them much-needed rain and snow after February came up disappointingly dry. But while this influx of moisture is expected to surpass storms earlier this winter, it won’t end the drought and could bring a downside of flooding and mudslides, experts warn.
“We will have to see how it plays out to sort through the details, but it is one of the bigger events of the season,” California state climatologist Michael Anderson said.
With a strong El Niño influencing weather around the world, Californians had hoped for a sopping wet winter that would begin to erase the drought that has become entrenched over the last four years. El Niño tends to push around the jet stream in a way that amps up the normal winter rainy season for the state, particularly in Southern California.
The season hasn’t turned out quite as expected, though: It started out with a spate of storms, but these were mainly focused on Northern California. On the one hand, that helped build up the critical Sierra snowpack to above-normal levels, but it left Southern California high and dry.
Come February, the spigot turned off, and a series of heat waves chipped away at some of the early gains. Sierra snowpack is now only about 80 percent of normal and short-term drought impacts in parts of Southern California have worsened.
Now there’s only a little more than a month left in the winter rainy season and the strength of the El Niño is starting to wane, leaving precious little time to eke out as much moisture as possible.
“Faced with the specter of a weakening El Niño and the end of the wet season, I dare say this looming two-week period of potential rainy/snowy weather is indeed critical,” Eric Luebehusen, a meteorologist with the U.S. Department of Agriculture and one of the authors of the weekly Drought Monitor, said in an email.
Modeled precipitable water anomalies show the flow of an atmospheric river that will bring rain and snow to California this weekend and early next week. Credit: Weatherbell
The pendulum has swung back to wet because of an area of low pressure that has settled over the Pacific Ocean. Over the next week or so, a series of storms is expected to rotate around that low and hit the West Coast. This wet period looks to last longer than those earlier in the season, Anderson said.
For at least the first few storms, the bulk of the wet weather seems to be aimed at Northern California, but there is potential for Southern California to see more rains than it did earlier.
“Hopefully some moisture will get in there,” Michael Musher, a meteorologist with the National Weather Service’s Weather Prediction Center, said.
As the first storm hits, the warm weather that has been in place will mean that snows will at first only fall very high in the mountains. But as the next systems arrive, conditions should cool and allow snow to build up in lower elevations of the Sierra.
“Right now, conditions are quite mild across the West,” Musher said. “So it’s going to take one or two of these systems to knock the snow level down.”
A good foot or two could fall across the range, according to forecasts.
While all of this will help the drought situation, it will take more than one winter to fully wipe it off the map.
“If the current model forecast projections pan out, I would expect to see some improvement,” Luebehusen said. “But, ending the water year with ‘normal’ snow water equivalents and precipitation would not end this drought, by any means.”
The storms over the next week or so, especially those expected to drop heavy rains this weekend, also come with worries for flooding and mudslides if too much water falls too quickly. This is particularly a concern where dry season wildfires have made the land more impermeable.
“It’s a double-edged sword,” Musher said.
For now, the hope is that the rains are enough to get California back on pace, but not so much that they tip in the other direction.