Prolific Pacific storms set to punch California with blockbuster rain, snow
A series of powerful storms are dumping potentially damaging amounts of rain and snow in California. By tapping into subtropical moisture like a needle tapping into a vein, the storm systems are transporting huge amounts of water vapor, which is being converted to low elevation downpours and mountain snow.
While forecast uncertainties remain, it's possible that some areas will receive up to a foot or more of rain before the skies clear early next week. In addition, the higher peaks of the Cascades and Sierra Nevada Mountains stand to get blitzed with up to 10 feet of snow.
The storms, one of which is currently hitting the state, leading to flash flood warnings and several feet of mountain snow, have the potential to cause widespread flooding the likes of which California has not seen since 1997.
Based on computer model projections, the San Francisco Bay area may see 7-day precipitation totals reach 5 to 7 inches or more, while parts of the Sierra Nevada Mountains may receive upwards of 20 inches of rain.
Already, 56 inches of snow have fallen in parts of the Sierra Nevada Mountains, with 53 inches of skiers gold at Squaw/Alpine in California. And this is just from the ongoing storm, with much more precipitation yet to come.
One of the biggest concerns with the second storm that will hit California beginning on Saturday and lasting at least through Monday concerns the mild air it may push into the state. If snow levels rise significantly and remain high for a long duration, it would cause melting of the recent snow cover that fell between about 2,500 feet and 8,000 feet, causing problems with freshwater runoff.
It's too early to say precisely how high snow levels will go with the next storm, but some projections show any mountains below about 9,000 feet seeing rain for at least part of the second storm. Still, several feet of snow are likely in the Sierra Nevada Mountains, according to the Weather Prediction Center, part of the National Oceanic and Atmospheric Administration (NOAA).
The bottom line is that a high-impact weather event is underway in California, and it's the opposite of what the state has been dealing with for the past 6-plus years. According to NOAA, flooding, mudslides, debris flows and other water-related hazards could come into play. The NOAA has also issued avalanche watches for some mountains, due to heavy snowfall and fluctuating temperatures.
Drought context
This is the winter weather that Californians have been hoping for during the past six years, as the state has been mired in an epic drought -- the worst in recorded history.
However, atmospheric river events such as these can deliver too much rain and snow, too quickly.
Atmospheric rivers can be understood as the veins in the atmosphere's circulatory system, channeling high amounts of water vapor from the tropics to the midlatitudes.
According to the National Oceanic and Atmospheric Administration (NOAA), a strong atmospheric river can transport "an amount of water vapor roughly equivalent to 7.5–15 times the average flow of liquid water at the mouth of the Mississippi River."
Compared to other states, California is unusually dependent on atmospheric river events for its annual precipitation. The lack of such events during the winter rainy season in the past several years has been a factor in the drought.
Even if these blockbuster atmospheric river storms do live up to their full potential, the drought won't actually be over for California. Like a college student racking up student loan debt, California is deep in a precipitation hole, with a lot more rainfall needed to make up for losses in groundwater and reservoirs.
In fact, if the second storm melts much of the snow currently sitting below 8,000 feet, that would reduce the runoff that would occur in the spring, when reservoirs get recharged. This could make the storm somewhat counterproductive, or at least not as beneficial as it could otherwise be, from a water resources perspective.
Andrew Freedman is Mashable's Senior Editor for Science and Special Projects. Prior to working at Mashable, Freedman was a Senior Science writer for Climate Central. He has also worked as a reporter for Congressional Quarterly and Greenwire/E&E Daily. His writing has also appeared in the Washington Post, online at The Weather Channel, and washingtonpost.com, where he wrote a weekly climate science column for the "Capital Weather Gang" blog. He has provided commentary on climate science and policy for Sky News, CBC Radio, NPR, Al Jazeera, Sirius XM Radio, PBS NewsHour, and other national and international outlets. He holds a Masters in Climate and Society from Columbia University, and a Masters in Law and Diplomacy from The Fletcher School at Tufts University.
