The odds are rising that California and the West will be struck by a plume of moisture known as an atmospheric river from Jan. 30 to Feb. 3, the US Climate Prediction Center said in a social media post.
The agency said there is 60% to 80% chance of above normal rain and snow along the West Coast and across the Southwest. Atmospheric rivers rise out of the Pacific and can land as much water onshore as flows through the mouth of the Mississippi River. While weaker events are beneficial, more powerful systems are known to cause widespread destruction and even death from flooding and mudslides.
A year ago a series of atmospheric rivers killed at least 22 people across California and caused $4.6 billion in damage and losses, according to the National Centers for Environmental Information.
“Hazardous, onshore high winds are likely to impact the West Coast as well January 30th to February 2nd, particularly the Pacific Northeast southward through much of California, which could lead to coastal erosion from persistently high waves,” the climate center said.
In addition to the heavy rains and snow, temperatures are set to rise across much of the contiguous US, with the highest chance for milder air to center on the upper Midwest and Great Lakes.
The kind of atmospheric flow necessary to drive such an event would mean mild temperatures will prevail across most of the Northern Hemisphere, said David Roth, a senior branch forecaster at the US Weather Prediction Center. Across the eastern US there are already signs winter’s grip is relaxing.
New York’s Central Park will reach a high of 56F (13.3 C) Friday with rain, the National Weather Service said. Washington will hit 65F, Boston 49F and Philadelphia 59F. The combination of mild air and rain will erase any snow left on the ground.