Atmospheric River Brings Record Rain, Flooding, and Heavy Snowfall to Northern California

Atmospheric River Brings Record Rain, Flooding, and Heavy Snowfall to Northern California

 In Event News

A powerful storm swept through Northern California on Thursday, delivering heavy snowfall and record-breaking rainfall that caused flooding in several areas. The Weather Prediction Center has issued a rare Level 4 of 4 high-risk warning for flooding rainfall, in effect through Friday morning. This warning comes as an atmospheric river, fueled by remnants of a bomb cyclone and continues to direct a concentrated stream of moisture toward the region.

Forecasters predict an additional 5 to 7 inches of rain across Northern California over the next 48 hours, with some localized areas potentially receiving more than 10 inches. By Thursday night, parts of Northern California had already recorded 11 to 17 inches of rain. In Sonoma County’s Santa Rosa, a city north of San Francisco with a population of approximately 170,000, over 10 inches of rain fell within 48 hours. Landslides and rockslides have forced the closure of highways in Humboldt and Lake counties, according to the National Weather Service office in Eureka, California.

Snowfall has also blanketed portions of the Northern California and Oregon Cascades. More than a foot of snow had accumulated in the Cascade Mountains and parts of California by Thursday morning. Forecasters anticipate an additional 1 to 4 feet of snow in Northern California through the weekend and into Tuesday. Wind gusts in mountain regions could exceed 75 mph (121 kph).

While the bomb cyclone responsible for fueling the atmospheric river begins to move away from the coast, the National Weather Service is monitoring a second storm expected to approach the Northwest coast on Friday. Although the likelihood of this storm intensifying into another bomb cyclone is decreasing, it is still expected to bring gusty winds, rain, and snow to the region.

Atmospheric River Brings Record Rain, Flooding, and Heavy Snowfall to Northern California: Actionable Analytics on EigenPrism

Post-Event

All EigenPrism® users can assess the post-event impact of the snow accumulation and wind using the following report template:

California Atmospheric River 2024 Post-Event Report Template

The report template auto-updates with the latest available forecasts, which include:

  • 72-hr Observed Snow Accumulation by NOHRSC
  • Daily Peak Wind Gusts Across North America by Adiabat

 

Canopy Weather

Subscribers of Canopy Weather can assess the impact of Winds from Nov 21, 2024 using this footprint within EigenPrism®:

Daily CONUS Peak Wind Gusts- Prelim 3 as of Nov 21, 2024

 

Forecast

All EigenPrism® users can assess the forecast of this multi-peril event using the following report template:

California Atmospheric River 2024 Forecast Report Template

The report template auto-updates with the latest available forecasts, which include:

  • 72-hr Forecast Snow Accumulation by NWS
  • 72-hr Forecast Freezing Rain Accumulation by NWS
  • Potential Winter Storm Overall Impact by NWS
  • WPC 3-Day Excessive Rainfall Outlook from NWS
  • North America Flood Potential from Adiabat
  • Landslide Potential from NASA

 

Winter Severity Component Report Template

This report template consists of the summary level (Potential Overall Winter Storm Impact) and all six component WSSI datasets from NWS:

  • Potential Snow Amount Impact
  • Potential Snow Load Impact
  • Potential Ground Blizzard Impact
  • Potential Ice Accumulation Impact
  • Potential Blowing Snow Impact
  • Potential Winter Storm Flash Freeze Impact

The report template auto-updates with the latest available datasets.

 

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