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California storms 2017: what you need to know

What does the recent precipitation mean for the drought?

 A resident named Kayte paddles her canoe through floodwaters on January 11, 2017 in Guerneville, California. 
Justin Sullivan/Getty Images

A relentless storm has been pummeling California since last week, with parts of the state receiving over 28 inches of rain and up to 16 feet of snow. While the largest urban areas—Los Angeles and San Francisco—have survived the storm with just a few power outages, flooded areas, and downed trees, other parts of California were not so lucky.

Much of Northern and Central California is flooding and the storm even toppled the landmark “Pioneer Cabin Tree” in Calaveras. In the midst of all the warnings—blizzards, continued flooding, and high winds—still active across the state, we take stock of exactly how much precipitation California has received and what’s to come next. Is the storm over? What did it do to the drought? We answer these questions, and so much more, below.

How much precipitation did California get?

In the past 7 days, San Francisco recorded a moderate amount of rainfall—about 5 inches in total. The Los Angeles International Airport reported less than 2 inches of rain in 7 days, but the rare phenomena was enough to help #LARain trend on Twitter. Those are lower totals than were forecasted for those metro areas, but elsewhere in California the atmospheric river event (not sure what this is? Head over here to find out) lived up to the hype.

In Monterey County, Three Peaks recorded over 28 inches of rain in 7 days and northeast of Bakersfield, the Sequoia National Forest measured over 10 inches.

The snow totals across the state were even more impressive. In the past week Mammoth Mountain has received between 113-200 inches of snow (depending on the elevation). Mammoth now has the most snow in the Unites States with a base depth of between 120 and 230 inches.

To put that in perspective, after the most recent series of storms, some ski resorts in California have already received their seasonal average snow total. Mt. Rose in Lake Tahoe, for example, normally receives about 350 inches of snow each year. This winter Mt. Rose has already measured 374 inches of snow, with at least 120 inches of that falling in the past week.

What were the consequences?

All of that moisture has created some serious problems. According to weather.com, from Sunday morning through Monday morning, there were 105 reports of flooding, flash flooding, or landslides in California. Sonoma County was especially hard hit and many of the vineyards along the Russian River looked more like lakes than vineyards. Over 3,000 Sonoma County residents were asked to evacuate as the river swelled, and along the Cosumnes River, 2,000 residents in the town of Wilton were told to move to higher ground.

Multiple highways were forced to close during the atmospheric river event as travel became treacherous, including when Interstate 80 near Truckee was closed on Sunday night due to a major mudslide.

The rain also forced the California Department of Water Resources on January 9 to open the gates of the Sacramento Weir—the low-lying dam that projects downtown Sacramento from flooding—for the first time in 11 years. Scenes from the Yuba River showed an incredible amount of water flowing under bridges.

At higher elevations, the snow, destabilizing rain, and the high water content of the snowpack have increased avalanche danger. The Sierra Avalanche Center reports that natural and human triggered avalanches are likely. At Alpine Meadows in Lake Tahoe, a triggered avalanche caused a snow wall of 15-20 feet to bury a house (pictured below).

The snow, high winds, road closures, and rain have meant—rather ironically—that ski areas throughout California have had a hard time operating. Many resorts in Tahoe are still closed on Wednesday, and Mammoth is operating with limited lifts.

Yep... nailed! Think the snow wall could have been 15-20 ft tall...

Posted by Siig Steven on Tuesday, January 10, 2017

Is it over?

Not quite. Fortunately, the heaviest rainfall has ended as of mid-day Wednesday, but rain and snow will continue through Thursday. Most of the rivers have crested and are falling, but there is still risk of significant flooding. The National Weather Service in Sacramento reported on Wednesday that flooding would continue as water works its way downstream. Most locations will see receding water levels by the end of the day on Thursday.

Some highways and roads are still affected as well, either thanks to deep snow or continued flooding. Caltrans is hard at work to clear the 150 lane miles of snow on I-80, but the weather—much of Lake Tahoe remains under a blizzard warning through early Thursday morning—is making it difficult.

Snow in Lake Tahoe and Mammoth will continue until Thursday evening with many ski areas forecasted to pick up another 10-20 inches. Across California, the state will start to dry out on Friday. Warming temperatures will occur over the weekend before the next strong storm moves in around Wednesday of next week.

Did it put a dent in the drought?

Overall, the series of storms over the past 10 days have helped California water supplies. According to the California Department of Water Resources, the latest atmospheric river event has pushed Northern California precipitation well above average (look for the dark blue line in the tweet above).

Hydrologist Maury Roos told the Los Angeles Times that 154 of California’s largest reservoirs had filled to about 97 percent of their collective average for the day. A year ago, most were at or below 50 percent. Roos went on to report that the storms dumped a combined 1.3 million acre-feet of water in the reservoirs since January 1. That’s about 350 billion gallons. The state’s second-largest reservoir—Oroville in Butte County—has risen 35 feet since New Year’s Day.

But regional differences mean that parts of Southern California have seen far less moisture. Key reservoirs like Pine Flat, Castalc, Millerton, and McClure are still below historic averages. It’s also still early to know exactly how this past week’s precipitation will fit into the overall winter. Officials likely won’t rescind Governor Jerry Brown’s emergency drought declaration—signed in January 2014—until water resource managers assess the situation in March or April.

While all this water is important to mitigate drought conditions, even more crucial is the snowpack in the Sierra Nevada. Last week, forecasters were worried that the warm temperatures associated with the atmospheric river event could actually decrease California’s snowpack. That’s what happens when warm rain falls onto snow and causes early snow melt. The state needs a healthy snowpack that slowly melts in the spring and summer to refill reservoirs in the dry summer season.

But despite the rain that fell at high elevations, enough snow fell that the snowpack actually increased over the past 7 days. A survey of the Sierra Nevada snowpack on January 3 measured just 53 percent of average, about one-third as much water as the same time last year. Just 8 days later, the statewide snowpack sits at 158 percent of average.

That’s a marked increase in a short period of time. And while raging rivers and quickly rising reservoirs make headlines, a healthy snowpack will do more than anything else to mitigate the long-term affects of California’s drought.

In short: while California’s drought isn’t over, for the first time in 6 years, it’s getting there.