SAN FRANCISCO – A “brutal” storm system building over the Pacific Ocean is poised to slam across Northern California on Wednesday, battering a region already struggling from a weekend of record rains and flooding.
The storm could drop as much as 8 inches of rain in some areas, falling on already overflowing rivers and saturated ground, according to the National Weather Service in San Francisco.
“The impacts will include widespread flooding, roads washing out, hillside collapsing, trees down (potentially full groves), widespread power outages, immediate disruption to commerce, and the worst of all, likely loss of human life,” the weather service warned in a statement. “This is truly a brutal system that we are looking at and needs to be taken seriously.”
A weather phenomenon known as an “atmospheric river” that swept across much of the state over the weekend dumped more than 5 inches of rain on San Francisco and nearly 10 inches elsewhere in the state.
On Wednesday the state will face another atmospheric river – or, the term more common years ago, a Pineapple Express. These are storms with heavy rainfall that occur when a line of warm, moist air flows from near the Hawaiian Islands across the Pacific Ocean to the West Coast.
When it reaches the cooler air over the western landmass, the water vapor falls as heavy rain. Atmospheric rivers are long, flowing regions of the atmosphere that carry water vapor across a swath of sky 250 to 375 miles wide. They can be more than 1,000 miles long – and can carry more water than the Mississippi River.
WHAT IS AN ‘ATMOSPHERIC RIVER’? These rivers of water vapor can extend thousands of miles
►Heavy snow was forecast to return to the Sierra Nevada on Wednesday.
►Winter Storm Warnings and Winter Weather Advisories were in effect for much of Wyoming, Colorado, South Dakota, Nebraska, Iowa, Minnesota, and Wisconsin, and for portions of northern Michigan and the higher elevations of Arizona and New Mexico.
►Ice Storm Warnings were in effect for portions of central and eastern Nebraska through northwestern Iowa and southern Minnesota.
►High Wind Warnings were in effect for portions of southeastern New Mexico and west Texas.
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The storm could impact a broad swath of coastal California, reaching as far south as Los Angeles and well past San Francisco to the north, Daniel Swain, a University of California, Los Angeles climate scientist said in a news conference Tuesday.
The worst will be felt in the northern part of the state. Because the ground is already saturated due to the New Year’s Eve storm, Wednesday’s tempest could result in localized mudslides from Monterey Bay up the coast, he said. There’s a high risk of flash floods, urban flooding, shallow landslides and mudslides, he said, though major river flooding is unlikely.
“The big wildcard is what happens next week,” Swain said, warning that one and possibly two more atmospheric river events target the coast. “Then all bets are off and the potential for much more significant flooding could very realistically emerge.”
San Francisco has distributed more than 8,000 sandbags since Saturday – and was running out. “Please save sandbags for people who need them,” San Francisco Public Works tweeted. “Those whose properties are prone to flooding.”
In San Mateo County, authorities said they were replenishing depleted sandbag supplies and provided updated lists of locations where they could be acquired.
Sen. Dianne Feinstein urged residents to monitor updates on the storm and follow the directives of local officials.
“Dangerous weather including strong rain, snow and wind is expected to hit California this week,” she tweeted. “It’s imperative that everyone is ready.”
In California’s Sacramento County, crews rushed to repair a 200-foot section of a levee system along the Cosumnes River that protects more than 53 square miles of vineyards and cattle ranches. Flooding caused by rainfall and the swelling Mokelumne and Cosumnes rivers may rapidly inundate some areas, the National Weather Service warned.
Saturday’s storm prompted county officials to order the evacuation of the Point Pleasant Community – including 1,075 inmates and staff at the Rio Cosumnes Correctional Center. Inmates were taken to nearby jails with no timetable for their return, according to County Sheriff’s Department spokesperson Amar Gandhi.
The wave of storms comes months after the release of a study warning that a “megafloods” crisis could be looming for California. The state faces an increasing risk of floods that could submerge cities and displace millions of people across the state, according to a study released in August. Swain, the UCLA climate scientist, was a co-author of the study. It warned that a monthlong storm could bring feet of rain to hundreds of miles of California.
Similarly, unrelenting storms have happened in the past before the region became home to tens of millions of people. Now, each degree of global warming dramatically increases the odds and size of the next megaflood, the study said.
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At least three tornadoes were reported Monday in the South-Central U.S. The National Weather Service said it had reports of a damaging twister in Montrose, Arkansas, that trapped people in their homes. Another near Jessieville, Arkansas, damaged at least 14 homes and multiple commercial and government buildings including a local high school, AccuWeather reported.
The storm with little warning, Jessieville School District Superintendent Melissa Speers told the Northwest Arkansas Democrat Gazette. It was the first day of school after the holiday break.
“Out of the blue, high winds, awnings began to blow away, the flagpole blows over,” she said. “Students and staff began moving to the safe room. We didn’t have any prior warning.”
Flash flooding was prompting water rescues and school closures in parts of Kentucky, and severe thunderstorm warnings were posted for much of the state. In Muhlenberg County, near the Tennessee border, the Greenville Fire Department said it had responded to numerous stranded motorists and provided water rescues from residences. Numerous roadways were flooded, and first responders and road crews were blocking flooded roadways. The school district was one of several across Kentucky that canceled classes.
Forecasters issued severe thunderstorm warnings across much of Mississippi. In Alabama, forecasters warned of severe storms and possible tornadoes Tuesday and Wednesday. The weather service said moisture from the Western Gulf of Mexico surging northward over the Lower Mississippi Valley and much of the Southeast was fueling the foul weather.
Across much of the Midwest, heavy snow, significant freezing rain, and some sleet were expected Tuesday and Wednesday. Intense snow rates of 1-3 inches per hour, in some instances accompanied by thunder, were forecast for parts of Nebraska, South Dakota and Minnesota.
Gusty, 30 mph winds will produce areas of blowing and drifting snow throughout the day Tuesday. The precipitation will result in snow-covered roads, reduced visibility, and “difficult-to-impossible travel,” the National Weather Service warned.
The young season’s snowfall totals are already well above average across much of the nation’s Plains and Upper Midwest. Minneapolis has received 32.6 inches of snow since Nov. 1, compared to the average of 18 inches, AccuWeather reports. Rapid City and Sioux Falls, South Dakota, and Fargo, North Dakota, have also seen snow amounts 150%-160% of normal since Nov. 1.
Contributing: Doyle Rice, USA TODAY; The Associated Press