Amid the relentless rain brought by an atmospheric river soaking Northern California, a flash flood warning was issued Friday afternoon for San Francisco and parts of San Mateo County where instances of flooding deemed "life-threatening" were occurring.

Officials are warning San Francisco residents of dangerous flooding as a powerful atmospheric river propelled by a churning bomb cyclone moves through the region.

A third day of an atmospheric river storm has inundated Northern California and the Bay Area, prompting warnings and advisories about local flooding.