California’s Huge Storm Could Cause Disastrous Melting in the Mountains
Then comes a wet warm stream from out by Hawaii. Water vapor becomes cubic miles of falling water. Maybe that’s this weekend. But this storm is counfounding the models, forecasts keep shifting. Californians, brace for the worst and yet well, maybe this is just a drill.
California is having a notably wet winter. Since October, a succession of weather systems has greened the Golden State’s valleys, whitened its mountains, and washed its rivers and reservoirs in rippling blue-green.
The state is currently between storms. The one that just ended was cold. It dropped snow as low as 2,500 feet in California’s highlands. The successor storm, expected to hit on Saturday, will be warmer—forecasters are calling for snow levels to rise up to 9,000 feet. The temperature difference means some of the snow dropped by the former will get melted by rain from the latter. Short term, it could also be a disaster. Flooding could kill people, destroy homes, wreck roads. Longer term, the succession of storms might be a drought-buster. Or it could be the opposite, with rain melting the precious mountain snow that California relies on to survive its hot, dry summers.
These storms are a type of weather system called atmospheric rivers, narrow bands of high altitude, highly-concentrated water vapor. “They start in the tropics, and get carried to the midlatitudes by the front end of storm systems,” says Mike Anderson, state climatologist with California’s Department of Water Resources. The storms are important contributors to California’s annual water budget. They can also beget major disasters. In 1997, an atmospheric river caused over a billion dollars worth of flooding across the state. NOAA is predicting that some rivers and streams—like the Merced River running through the Yosemite Valley—will reach similarly epic levels this weekend.