Albino black widow?
I have heard about these female black widow look-alikes, but this is the first time I have seen one. Your spider is actually known as the female brown widow, Latrodectus geometricus. It is common to California and the Southernmost US States.
According to BugGuide, "The brown widow is highly variable in color. It may be almost white to almost black." The darker the spider's color, the more difficult it is to distinguish this spider from the black widow. The banded legs is another feature that helps us distinguish between the brown and the closely related black widow female spider. Incidentally, the egg masses are also typical of the spiders in this Latrodectus genus.
"Be very careful when working around areas where widow spiders may be established. Take proper precautions-wear gloves and pay attention to where you are working. The reaction to a widow bite can be painful, and the victim should go to the doctor immediately for treatment." -BugGuide
Hope this helps.