This is what to expect as atmospheric river moves through Sierra, Sacramento
Three weeks ago, California was staring at a disastrously dry winter that had conjured up fears of another drought. Now, with yet another major round of rain and snow starting Tuesday, the state's rain gauges are starting to look a bit closer to normal.
"We are definitely getting a pretty wet month," said Michelle Mead, warning coordination meteorologist at the National Weather Service in Sacramento.
The National Weather Service said the latest storm, which began with light rain Tuesday morning in the Sacramento area and Sierra Nevada, is expected to turn into an "atmospheric river" that will bring 2 inches of rain to the Sacramento area and up to 4 feet of snow in the mountains by the time it tapers off Saturday. An atmospheric river is a stream of moisture blown horizontally by strong winds.
It's the third in a series of storms this month that has helped the state at least partially recover from five mostly dry months that had Californians worrying about another drought. It's unclear whether the state is getting a "March miracle," but this month's weather represents a significant upgrade from what had gone previously.
"In the spectrum of March miracles, it might end up being on the lightweight side" but is still making a dent in California's rain shortfall, said Marty Ralph of the Center for Western Weather & Water Extremes at UC San Diego. He said this week's storm is expected to be exceptionally strong in Southern California, where mandatory evacuations were ordered Tuesday in areas around Santa Barbara susceptible to mudslides.
The Department of Water Resources' Michael Anderson, the state's climatologist, said March is turning wet enough that it could completely offset months of dry weather.
"In the end, we'll probably end up at or a little below average for the water year," Anderson said.
As it is, much of the Sacramento Valley has already received more rain this month than it normally gets in all of March. The city of Sacramento has received 3.72 inches; a normal March means 3.02 inches for the entire month.
On the other hand, the weather service said it thinks this week's storm will be the last major storm of the season, and the accumulated water deficit at the end of February might be too great to overcome.
Rainfall in Sacramento heading into Tuesday's storm was 70 percent of average, and the situation is worse in the Bay Area, most coastal cities and vast stretches of Southern California. The Sierra snowpack has more than doubled in size since March 1 but was still just 48 percent of average before the latest storm began.
A healthy snowpack is considered crucial because it can store as much as 30 percent of the state's water supply; melting snow replenishes the reservoirs and helps the state get through the dry summer and fall.
The latest storm is expected to start out considerably warmer than last week's, bringing rain instead of snow to most of the Sierra through Wednesday. By Thursday, however, temperatures will drop and snow will fall at elevations as low as 3,000 feet.
The National Weather Service said rain is expected to fall steadily but not heavily in the valley. Traveling in the mountains could be difficult, however. Forecasters said Thursday should be the roughest day; a winter storm watch will be in effect from 5 p.m. Wednesday to 5 a.m. Friday, with as much as 18 inches of snow expected west of Highway 89 and wind gusts approaching 45 mph. Total snowfall in the mountain peak areas should reach 4 feet.