More extreme weather on tap for California as series of atmospheric river events continues



CNN

California has been battered by heavy snow, damaging winds and flooding this week – and now another round of storms is set to hit the West Coast this weekend.

“Unending parade of cyclones from the Pacific Ocean will bring more torrential rain and mountain snow to the West Coast with the main focus over northern California,” the Weather Prediction Center said Saturday.

More storms will reach the West Coast over the next few days. The concern isn’t just the rain, snow and wind, but there won’t be much of a break between events for the water to recede or cleanup to complete.

“We expect an even stronger storm to affect the state Sunday night into Tuesday than the one we’ll see early this weekend,” said Matt Solum, a meteorologist at the National Weather Service’s Western Region headquarters. “We encourage everyone to take time over the weekend to make necessary preparations for the next storm to come.”

The next storms come on the heels of a powerful cyclone that flooded roads, toppled trees and knocked out power to most of California. Earlier, a New Year’s weekend storm system also produced flooding.

This weekend, the main concerns for coastal communities will be widespread flooding, gusty winds and dangerous beach and sea conditions. In the higher areas, there will be heavy snow and strong winds, leading to almost whiteout conditions for everyone traveling on the roads.

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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 brush off.

“While these winds will not be on the magnitude of the previous/stronger system, it really won’t take much to bring trees down given the saturated conditions and weakened trees from the previous event,” the San Francisco weather service wrote Friday.

Even a 40 mph wind can do damage when the ground is so saturated from record rainfall earlier this week and the cumulative effect of the new rainfall expected this weekend.

“Implications for infrastructure include but are not limited to; river floods, mudslides, power cuts and snow loads”, was the prediction centre said in a tweet.

Earlier this week, San Francisco experienced its wettest 10-day period registered for downtown since 1871. So far, they’ve had more than a foot of rain just since December 1st, and the forecast calls for another 4-6 inches of rain over the next five days.

Sacramento is also expected to see significant rainfall amounts of 4-7 inches in the valleys and 6-12 inches in the foothills.

“Further rain on already saturated ground will contribute to further flooding problems across much of the state,” Solum told CNN. “There will continue to be an increased risk of rockslides and mudslides across much of the state as well.”

More than 15 million people are under flood watches across the state of California this weekend. There is also a slight to moderate risk of heavy rainfall across much of northern and central California on Saturday and Sunday. It increases to a more widespread moderate risk by Monday.

The rainfall this weekend will bring renewed concern for local creeks, streams and rivers. Colgan Creek, Berryessa Creek, Mark West Creek, Green Valley Creek and the Cosumnes River all have gauges either currently above flood stage or expected to be in the next few days.

“Tuesday is probably the day you’ll probably need to keep a very close eye on the weather as the potential for widespread flooding of rivers, creeks, streams and roads and urban flooding will be at its highest over the next week as all the runoff and heavy rainfall comes together resulting in a mess, the weather service office in Sacramento said.

In addition to heavy rain, significant amounts of snow will fall over the higher elevations.

“The snow looks to be 1-2 feet with some of the higher elevations seeing 3 feet or more leading to significant travel impacts,” the weather service office in Sacramento said.

We are currently under a La Niña advisory for the winter months before returning to a more neutral pattern for spring.

El Niño and La Niña forecast patterns posted by the Climate Prediction Center provide guidelines for what the general forecast may be during a seasonal time 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 fellow at Colorado State University. – This is because the jet stream is pushed further north and has a wave pattern. ”

The problem is that Mother Nature hasn’t exactly followed the expected norms for a La Niña winter so far this year.

“However, over the last three months, Oregon has been a little drier than normal and California has been a little wetter than normal (the opposite of what’s expected),” Arcodia told CNN. While El Niño and La Niña patterns typically have a large influence on seasonal conditions on the West Coast, “there are always multiple factors at play,” she added.

One such factor has been several atmospheric river events that have hit California with intense amounts of moisture.

“Atmospheric rivers typically form in the winter months and can occur during El Niños or La Niñas,” Arcodia said, noting that their strength, frequency and landfall location can be affected by the larger patterns of the Pacific Ocean.

Michael Tippett, professor of physics and mathematics at Columbia University, points out that the forecast patterns are not meant to be used on a day-to-day forecasting scale, but rather the entire season as a whole. This is why it is so important to examine the patterns.

“There is an element of randomness that is not explained by the patterns,” Tippett told CNN. “This can help us understand why one year is different from another.”

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