CNN
—
California has been battered by heavy snowfall, damaging winds and flooding this week – and now another round of storms are expected to hit the West Coast this weekend.
“The relentless parade of Pacific cyclones will bring more torrential rains and mountain snowfalls to the West Coast, with particular emphasis on Northern California,” the Weather Prediction Center said Saturday.
Several storms will reach the west coast over the next few days. The worry isn’t just rain, snow and wind, but there won’t be much of a break between events for the water to recede or the cleanup to be completed.
“We expect an even stronger storm to affect the state Sunday evening through Tuesday than what we will see early this weekend,” said Matt Solum, meteorologist at the National’s West Region headquarters. Weather Service. “We encourage everyone to take time over the weekend to make the necessary preparations for the next storm to come.”
The following storms come on the heels of a powerful cyclone that flooded roads, toppled trees and knocked out power to most parts of California. Earlier, a New Year’s weekend storm system also caused flooding.
The main concerns for coastal communities this weekend will be widespread flooding, gusty winds and dangerous beach and sea conditions. At higher elevations there will be heavy snow and strong winds driving on near-whiteout terms for anyone traveling on the roads.
FOLLOW THE STORMS HERE >>>>
Winds are forecast to be around 40-50 mph in the valleys and up to 70 mph in the mountains, which is lower than the storm earlier this week, but still nothing to sweep through.
“While these winds are not in the range of the previous/stronger system, it really won’t take much to knock down the trees given the saturated conditions and weakened trees since the last event,” the San Francisco Weather Service.
Even a 40 mph wind can do damage when the ground is so saturated from the record rainfall earlier in the week and the cumulative effect of further rainfall expected this weekend.
“Impacts on infrastructure include, but are not limited to; river floods, mudslides, power outages and snow load”, the prediction center said in a tweet.
Surely the most widespread concern over the next week will be flooding thanks to several atmospheric river events. Atmospheric rivers are a narrow band of moisture concentrated in the atmosphere.
The Center for Western Weather and Water Extremes, which monitors atmospheric river events, now predicts a Level 5 atmospheric river event – the highest possible level – in the coming days. While the focal point of this event will be near Monterey and Big Sur, California, intense humidity will also spread to surrounding areas of San Francisco and San Jose where a level 4 atmospheric riverine event is predicted.
Earlier this week, San Francisco experienced its wettest 10 day period on file for downtown since 1871. So far they’ve had over a foot of rain just since Dec. 1, and forecasts call for another 4-6 inches of rain over the next five days.
Sacramento is also expected to experience significant rainfall of 4 to 7 inches in the valleys and 6 to 12 inches in the foothills.
“Additional rains on already saturated ground will contribute to additional flooding issues across much of the state,” Solum told CNN. “There will continue to be an increased risk of landslides and mudslides across much of the state as well.”
More than 15 million people are under flood watch across the state of California this weekend. There is also a light to moderate risk of excessive precipitation across much of northern and central California on Saturday and Sunday. It increases to more widespread moderate risk by Monday.
The weekend rainfall will bring new concerns for local creeks, streams and rivers. Colgan Creek, Berryessa Creek, Mark West Creek, Green Valley Creek, and the Cosumnes River all have gauges currently above flood stage or expected to be in the next few days.
“Tuesday is probably the day you will probably have to watch the weather very closely as the potential for widespread flooding of rivers, creeks, creeks and roads and urban flooding will be at its highest over the next week, as all the runoff and heavy rainfall combine, resulting in a mess,” the Sacramento Weather Service office said.
In addition to heavy rain, there will be significant amounts of snow at the higher elevations.
“Snow totals are expected to be 1 to 2 feet, with some of the higher elevations reaching 3 feet or more, resulting in significant travel impacts,” the Sacramento Weather Services office said.
We are currently under a La Niña advisory for the winter months before returning to a more neutral pattern in the spring.
The El Niño and La Niña forecast patterns published by the Climate Prediction Center give indications of what the overall forecast may be over a seasonal period.
“During a La Niña, typically the Pacific Northwest sees wetter than normal conditions and Southern California sees drier than normal conditions,” said Marybeth Arcodia, a postdoctoral researcher at Colorado State University. “This is because the jet stream is pushed further north and has a more wavy pattern.”
The problem is that Mother Nature hasn’t exactly followed the predicted standards for a La Niña winter so far this year.
“However, over the past three months, Oregon has been slightly drier than normal and California has been slightly wetter than normal (the opposite of what is expected),” Arcodia told CNN. Although El Niño and La Niña patterns generally have a big influence on seasonal conditions on the West Coast, “there are always additional factors at play,” she added.
One of those factors was multiple atmospheric river events that hit California with intense amounts of humidity.
“Atmospheric rivers typically form during the winter months and can occur during El Niños or La Niñas,” Arcodia said, noting that their strength, frequency and location can be influenced by broader Pacific patterns.
Michael Tippett, professor of physics and mathematics at Columbia University, points out that forecasting models are not intended to be used on a day-to-day forecasting scale, but rather over the entire season as a whole. This is why looking for patterns is so important.
“There’s an element of chance that isn’t explained by the models,” Tippett told CNN. “It might help us understand why one year is different from another.”
