Atmospheric River to Lash Bay Area With ‘Significant’ Rainfall

A flood watch for the North Bay and Santa Cruz Mountains will take effect late Thursday and last through Saturday morning, according to weather officials

UPDATE: Yosemite Valley is closing Friday afternoon due to potential flooding from the incoming storm. All other areas of the park will remain open conditions permitting, officials say.

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Don't put away those umbrellas and rain boots just yet.

An incoming atmospheric river packing moisture from Hawaii is expected to douse the Bay Area with "significant" rainfall beginning Thursday and continuing into the weekend, according to the National Weather Service.

A flood watch for the North Bay and Santa Cruz Mountains will take effect late Thursday and last through Saturday morning, according to the NWS.

From Thursday through Saturday, anywhere from three to six inches of rainfall could fall across the region's coastal mountains, according to the NWS. Most other locations across the Bay Area could receive anywhere from 1.25 to 3 inches. 

Specifically, locations in Half Moon Bay could rack up 4 to 6 inches of rain, according to the NWS. Areas in and around Santa Rosa, Napa, San Rafael and Santa Cruz could pick up anywhere from 3 to 4 inches. San Francisco and Concord could accumulate 2 to 3 inches. Livermore could receive 1.5 to 2 inches. San Jose is expected to collect 1 to 1.5 inches.

An atmospheric river (AR) is a flowing column of water vapor in the atmosphere which can produce "significant levels of rain and snow, especially in the Western United States," according to the NWS.

The moderate to heavy rain could lead to localized flooding, roadway ponding and potential mudslides, especially in the North Bay wildfire burn areas, according to the NWS. Gusty winds ranging from 25 mph to 40 mph could also trigger power outages.

The warm system is expected to melt a small percentage of the Sierra Nevada snowpack, according to the NWS.

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