California faces severe flood threat from “most potent” in barrage of atmospheric rivers

California Gov. Gavin Newsom is asking President Biden to make an emergency declaration in response to a sequence of lethal storms, because the Nationwide Climate Service warned the “most potent system” would arrive Monday.

The large image: The newest in a barrage of harmful atmospheric rivers that’ve triggered widespread energy outages since late final month started unleashing extra highly effective winds and heavy rains on California Sunday night time — prompting Sacramento County to difficulty evacuation orders for Wilton-area residents, with flooding “imminent.”

State of play: Greater than 424,000 Californians had been with out energy, over 2,900 others had been evacuated from their houses and 12 individuals had been confirmed killed within the storms, mentioned Nancy Ward, director of the governor’s Workplace of Emergency Companies at a briefing Sunday.

• An estimated 99,000-plus prospects had been nonetheless with out energy on Sunday night time, because the Workplace of Emergency Administration issued evacuation warnings for a number of areas in Santa Barbara County “as a result of potential flooding and particles flows.”

Menace degree: The atmospheric river arriving Sunday night time “will trigger important impression to journey” and infrastructure as a result of heavy rain, heavy mountain snow and damaging wind gusts by way of Tuesday,” per the NWS. Street closures, tree harm and river flooding had been anticipated.

• “On this climate sample, extra rain on saturated soils will result in appreciable flood impacts, together with speedy water rises, mudslides and burn scar particles flows,” the NWS mentioned in an replace Sunday night.
• “Widespread mountain snow and excessive winds can even produce points throughout the state,” it mentioned.
• “Heavy rain is anticipated so as to add as much as a number of inches throughout a lot of central California by way of Tuesday. The cumulative impact of successive heavy rainfall occasions will result in extra situations of flooding. This contains speedy water rises, mudslides, and the potential for main river flooding.”

Zoom in: There is a average threat of extreme rainfall in most of central California on Monday, extending southward in direction of the Transverse Ranges of southern California, per the NWS.

• “As moisture continues to sink southward on Monday night time and one other push of rainfall enters on Tuesday, flash flooding is growing probably over the southern California coastal ranges by way of early this week,” the climate service mentioned.
• “Prone terrain and areas close to current burn scars can be most in danger for particles flows and speedy runoff.”

In the meantime, for the upper terrain of the Sierra Nevada, extraordinarily” heavy snow and intense snowfall charges” was anticipated to “make journey very harmful to unimaginable at occasions,” with complete snowfall quantities anticipated higher than 6 ft potential above 7,000 ft, based on the NWS.

• “This quantity of extra accumulating snow on high of an already effectively constructed snowpack is more likely to enhance the specter of avalanches and pressure infrastructure,” the climate service mentioned.
• “The mixture of saturated soil and gusty winds may exacerbate the tree harm risk.”

Flashback: Newsom declared an emergency final week in response to an atmospheric river storm related to a bomb cyclone that introduced heavy rains and hurricane-force winds to California.

Between the strains: Atmospheric rivers are potent however slim currents within the air that may carry huge quantities of water vapor 1000’s of miles from the tropics to mid-and-northern latitudes.

Editor’s observe: This can be a breaking information story. Please verify again for updates.