“This is a tremendous winter storm for us,” said Mark Deutschendorf, a meteorologist with the National Weather Service in Reno, Nevada. “Traveling is not recommended Tuesday night through Friday through the Sierra and Lake Tahoe, including western Nevada. If you do go outside, be prepared to spend longer in your car.”
A dramatic shift in the landscape will occur as winter picks up a gear.
The foothills could see 6 inches to 12 inches of snow, while the mountains could see 1 to 1 meter long. In some areas, up to 7 feet is forecast over the Sierra Nevada’s favored terrain through Friday.
Ridgetops in the Sierra could see gusts of wind in excess of 200 mph.
Atmospheric rivers are long, narrow areas of the atmosphere – like rivers in the air – that carry water vapor, according to the National Oceanic and Atmospheric Administration.
“The Owens Valley (Great Basin Desert) could receive nearly record amounts of snow over a two-day period. Their previous record of 48 hours of snowfall was 23 inches back in 1969,” NWS Meteorologist Jenn Varian told CNN.
Atmospheric river creates potential for flash flooding
As the atmospheric river directs its fire hose along the central coast, excessive rainfall of 10 to 20 cm threatens flash flooding in the region.
San Francisco has an average of 4.19 inches of rain in January. Suppose the atmospheric river concentrates the heaviest rainfall in the Bay Area: in that case, the city could get a month’s worth of rainfall in a few days.
Depending on the precise placement of the atmospheric river, coastal locations south of San Francisco to Santa Barbara can receive between 5 and 10 inches of rain with higher amounts locally. Smaller but still significant 1 to 2 inch rain totals are likely from Los Angeles to San Diego.
Evacuations in progress as the risk of debris flows increases
Intense forest fires can affect soil structure, making sloping terrain more vulnerable to debris and mudslides during heavy downpours.
If enough rain falls on a recent burn scar, a torrent of mud, rocks and debris can spill downhill and endanger communities. Properties directly affected by recent fires or located directly downstream from combustion areas are most at risk.
The storms could ease the current drought
While atmospheric rivers can be dangerous, residents rely on them to bring favorable rainfall to the region.
California’s wintry snowpack, fed in part by atmospheric rivers, is critical to the state’s water supply. Warmer spring temperatures melt the snow and fill the reservoirs, so fresh water is available during the drier summer months.
This AR event can be considered a much needed relief as the current statewide snowpack is only 40% of the average to date.
This storm, along with an active weather pattern forecast in early February, will help ease droughts in California and the Great Basin.
Nearly 80% of California is in severe drought.
However, like anything in moderation, it is possible to have too much of a good thing.
This ‘weather whiplash’ will occur more often
Drastic swings from extremely wet to extremely dry and vice versa will be nearly twice as likely, once every 25 years on average, by 2100.