The pothole is on the Cummings Skyway on-ramp to eastbound Interstate Highway 80, CHP Officer Tom Maguire said.
Caltrans spokesman Allyn Amsk said the hole is 4 to 5 feet wide, about 10 feet long and about 6 inches deep.
Amsk said crews will complete repairs today but that the ramp will remain closed for 24 hours so that it can be monitored during the storm that will hit the Bay Area Tuesday night.
It is scheduled to reopen at 3:30 p.m. on Wednesday.
Amsk said he has not received any reports of accidents or property damage caused by the pothole.
Maguire said motorists are being directed on a short detour while the ramp is closed.
KGO contributed to this report