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Northern California Residents on High Alert for Atmospheric River, Risk of Flooding and Mudslides

Residents in Northern California are on high alert as another atmospheric river is set to hit the area Thursday night, bringing with it the risk of flooding, mudslides, feet of mountain snow, and very strong wind gusts. The National Weather Service in Sacramento is warning of several inches of rain and higher snow levels, with a 40% probability that small rivers and streams will rise and the possibility of roadway flooding.[0]

Sandbag locations are available in several counties and cities across the state, including San Joaquin, Contra Costa, and Sonoma.[1] The weather service is also warning of potential roof collapses from the mix of heavy snow and rain.[2]

Heavy rainfall coupled with the mild air mass will result in rapid snow melting from 2,000 feet to 5,000 feet and water levels on rivers and streams will rise, leading to a possible flooding threat. AccuWeather Senior Meteorologist Adam Douty said that it is at the intermediate elevations, from 2,000 feet to 5,000 feet, that enough rain will fall to cause some of the existing snowpack to melt and add to the runoff.

The storm is expected to bring rain to some higher elevations that have been socked by frequent rounds of heavy snow this winter.[3] For now, the Southern California heavy rain threat is highest in Santa Barbara County, but at least some locally heavy rain is possible throughout the Southland, with the chance of rain at elevations of at least 9,000 feet in Southern California, including the snow-sieged San Gabriel mountains.[4]

In addition to the risk of flooding, the deep snowpack can absorb some of the rain, but much will eventually melt, further increasing the potential of flooding downstream.[3] Residents should stay weather aware and prepare an evacuation plan if high water becomes a threat to safety.[5]

0. “California braces for flooding, snowmelt from a warm atmospheric river set to slam state” Yahoo Life, 7 Mar. 2023, https://www.yahoo.com/lifestyle/california-braces-flooding-snowmelt-warm-130035426.html

1. “Here’s where you can pick up sandbags in Northern California ahead of this week's atmospheric river storm” KCRA Sacramento, 7 Mar. 2023, https://www.kcra.com/article/northern-california-sandbag-locations-march-2023/43236310

2. “‘Major storm' expected in Reno-Tahoe area later this week” Reno Gazette Journal, 6 Mar. 2023, https://www.rgj.com/story/news/2023/03/06/major-storm-flood-risk-expected-in-reno-tahoe-area-later-this-week/69977424007

3. “California, Buried By Snow, Now Faces A Flood Threat | Weather.com” The Weather Channel, 7 Mar. 2023, https://weather.com/forecast/regional/news/2023-03-07-california-atmospheric-river-flood-threat

4. “New atmospheric river to raise flood risk, drop more mountain snow in California” Yahoo Life, 6 Mar. 2023, https://www.yahoo.com/lifestyle/atmospheric-river-raise-flood-risk-191507926.html

5. “Update: Possible Flooding Later This Week” MyMotherLode.com, 6 Mar. 2023, https://www.mymotherlode.com/news/local/2984411/possible-flooding-later-this-week.html