A "bomb cyclone" will unleash an atmospheric river Saturday night into Sunday across Northern California. 

"By Saturday night, a rapidly intensifying Pacific cyclone directing a powerful atmospheric river squarely at the West Coast delivers a fire hose of rich subtropical moisture into California," the Weather Prediction Center (WPC) said Friday. 

These two simultaneous weather phenomenons will result in the season's first snow event in the Sierras and torrential rains for the coastline and valleys across central and Northern California. 

"You might hear this term referencing the Sunday-Monday storm coming our way. A bomb cyclone is simply a storm that gets very strong very quickly. It drops at least 24 mb (a unit of pressure) in 24 hours. The lower the pressure, the stronger the storm," said Sacramento-based KTXL's Adam Epstein

In Northern California, rainfall estimates through the end of the weekend are around 2-4 inches. In San Francisco, estimates are upwards of 3 inches. 

WPC warns that some areas could receive 8-10 inches.

The rare level 5 atmospheric river event could be enough rain to alleviate drought-stricken areas ravaged by wildfires. 

"An atmospheric river marked as a category 4 or a 5 is capable of producing remarkable rainfall totals over three or more days, likely to exceed 10% to 15% of a typical year's precipitation in some locations," said Marty Ralph, director of the Center for Western Weather and Water Extremes at the University of California San Diego.

In higher elevations, wet snow across the Sierras could amount to 1-3 feet. 

The news gets better for Northern California and the Pacific Northwest as WPC has declared La Niña conditions, which means wetter than average conditions will ease areas plagued by drought. As for Southern and Central California, La Niña means a drier than average winter. 

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