PROJECT ALERT NOTICE (CA) continued high flows and flooding in California

Date: Sun, 01 Jan 2023 14:27:38 EST

Summary: Strong tropical storm causes flooding in California

A strong tropical system continued to produce moderate to heavy precipitation and strong winds in northern California throughout yesterday, wrapping up multiple days of rainfall throughout the area. Heavy rainfall caused localized and stream flooding throughout most of the San Francisco Bay and Sacramento metro areas, and heavy snow fell in the Sierras. Many roadways, including a few major highways, were closed due to flooding, mudslides, and rockslides, or due to snow in the Sierras. In some flooded areas, officials ordered residents to evacuate from their homes, but some orders quickly changed to shelter in place as rapidly rising floodwaters made exit roadways unsafe. There were reports of many rescues. Over 200,000 homes and businesses were reported to have lost power yesterday, primarily due to high winds.

Yesterday, CA WSC field crews made 28 measurements at 23 USGS streamgages, with several measurements at the highest recorded for the respective gages. One gage was damaged and is still offline.

Overnight, the system moved to southern California. Although southern California is not expecting high amounts of rain and flooding, many streams are already at high flows due to multiple days of near continuous rainfall.

Today, four CA WSC field offices sent 9 crews of 17 people to measure additional streamgages still at higher flows in coastal basins and at Cache Creek.

Mid-week, another strong tropical system is predicted to affect northern California.