Petaluma and Penngrove are two of the places the National Weather Service says are vulnerable.
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The warning is in effect until 5:15 p.m. Wednesday.
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Sebastopol, Forestville, and Graton are under a Flash Flood Warning until 5:45 p.m., partly because Green Valley Creek is overflowing its banks.
Residents are advised to move to higher ground and avoid walking or driving through flood waters.
RELATED: Storm triggering early problems on North Bay roadways
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