by Brandon Mercer

NORTH BAY (KPIX) — The massive storm bearing down on the Bay Area will dump up to 10 inches of rain on the highest local mountains, triggering a rise in the Russian River of a whopping 20 feet, 6 inches by 3 p.m. Saturday, according to National Weather Service river forecasts.

TRACK THE RUSSIAN RIVER: Real-Time River Monitoring And Forecasts

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Russian River Rise Projected As Of 2-4-2015

Russian River Rise Projected As Of 2-4-2015

The storm is nowhere near as strong as the December deluge that led to one of the wettest Decembers on record, but it will be significant, and dangerous in places. Three counties are already under a Flash Flood Watch: Marin, Napa, and Sonoma.

Wednesday, workers were working ahead of the system to clear storm drains and fallen limbs around the trails on Mount Tamalpais as six inches of rain is expected there by Monday.

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“We’re aiming to accommodate a 100-year event, or hydrological event, in terms of runoff,” Marin water district’s Carl Sanders told KPIX 5’s Mike Sugerman.

“I don’t think we’ll see that this weekend with the atmospheric river, but it could be close, [and it] could fill this culvert almost fill to the brim if the forecast is correct,” he added.

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The Conservation Corps is working on 100 miles of unpaved roads and hundreds more miles of trails that get damaged in the winter storms, requiring constant maintenance.