The region was getting drenched Thursday by an atmospheric river — a column of moisture out of the west that flowed into north coastal San Diego County just after 5 p.m. and was expected to spread

For San Diego County, rainfall is expected to range from 0.75 to 1.25 inch near the coast to 2 to 3 inches in the mountains through Friday.

To prepare for the spate of inclement conditions, the city of San Diego has been monitoring some 46,000 storm drains and will preemptively close flood-prone Mission Valley roads if deemed necessary.