The West Coast has been riding an exceptional winter with record snowfall. So much snow, in fact, that Yosemite Park has closed, places like Tahoe have gotten as much as eight feet in a single week, and even Southern California has enjoyed (or not enjoyed) an unusually cold winter. An atmospheric river like the one that brought all the recent snow in late February and early March is reportedly going to bring a whole new type of alert to parts of the Golden State: flood watch.
The National Weather Service is now reporting that a new storm is headed through the Pacific and should come to California by late Thursday. But while the last few weeks have seen storms with lower temperatures, bringing snow to lower elevations while blanketing the Sierras with fresh powder, this new one is expected to come with heavy rainfall and a mild airmass that may cause rapid snowmelt in places. Experts believe this won’t cause issues with the deepest snowpack up high, which should absorb any rain. But lower elevations below about 5,500 will be on flood watch, according to the NWS, where the unusual snowpack is obviously much shallower.
“If you live in a flood-prone area or near rivers and streams, now would be a good time to prepare and have an evacuation plan in place in the event high water becomes a threat to your safety,” the National Weather Service announced for San Joaquin Valley.
With this warm, wet storm bringing alerts for new risks in parts of California, climate scientist Daniel Swain says we shouldn’t necessarily worry about “extreme” or “catastrophic” flooding. Instead, Swain says he is more concerned about additional warm atmospheric rivers coming in mid March. “If we get successive warm atmospheric rivers, that’s when big problems would begin,” he said, and tweeted that this mid-week break from storms would be a good window for people to prepare for structural impacts from snow and subsequent flooding in California.