Rain on tap: Why California desperately needs this atmospheric river

Bay Area

SAN FRANCISCO, Calif. (KRON) – Atmospheric river storms are about to soak the Bay Area, and the timing couldn’t be more perfect.

93% of California is in some level of drought, with 87% in extreme drought, according to the U.S. Drought Monitor.

This level of severe dryness hasn’t been seen since 2017.

California also saw a record warm summer this year with below average precipitation, according to a quarterly report by climate experts.

Dryness combined with heat and high winds are the conditions that spark and spread wildfires, but we’re expected to get a series of storms as well as cooler-than-usual temperatures this week.

This new weather pattern was kicked off Sunday night by rain and 4 to 8 inches of snowfall in the Sierra. 

Rain in the Bay continues Tuesday night with showers likely through the day on Wednesday. Showers will then taper off somewhat on Thursday before an increase in rainfall on Friday.

This weekend, we’ll have a few more showers before rainfall really picks up into Sunday, the day that is likely to bring the Bay Area its heaviest rainfall, according to KRON4 meteorologist John Shrable.

Recently burned areas should be on the lookout for this weather event. It’s likely that the entire Bay Area will be under a watch come this weekend, if this all holds, according to KRON4 meteorologist Dave Spahr.

Atmospheric rivers are “relatively long, narrow regions in the atmosphere that transport most of the water vapor outside of the tropics,” according to NWS Bay Area.

About 30-50% of annual precipitation on the West Coast occurs in just a few atmospheric river events and contributes to the water supply… and flooding risk.

NWS is estimating some cities in the Bay Area will get up to 2-3 inches of total rain by the end of the wet week.

Rain has parts of Santa Cruz and Sonoma Counties worried about possible flooding in areas that have been burned by recent wildfires.

Santa Cruz County is watching how the rain could impact CZU burn scars, and the Santa Rosa fire department is following suit monitoring how the rain might affect the Glass Fire burn scars. 

The county and the fire departments are urging people living near these areas to be prepared in the event of flash flooding and mudslides.

Meteorologists predict that Santa Rosa could get between 2-3 total inches of rain and the potential for very bad flooding.

San Rafael could get 1.5-2 inches, and Half Moon Bay and Napa are both predicted to get between 1-1.5 inches of total rain.

In San Francisco, NWS predicts up to one inch of rain by Saturday.

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