I think it looks like a white-sided gopher snake crossed with a coastal CA mountain kingsnake.
I'm very interested to learn more details about the snake. Is it still alive? If not, is the dead body in a freezer somewhere so a DNA sample can be taken?
I just did a Google search for snake breeders in Patterson, CA and came up with a hit. Someone named CJ is selling his business on a site called OfferUp. I sent him a message. Hopefully he'll reply.
On the OfferUp site I saw a picture of reptile racks and the name of a website: freedombreeder.com
I searched for FreedomBreeder and found a Facebook page showing some awesome ball python morphs. The FB page says Freedom Breeder is located in Turlock, CA, just a few miles from Patterson.
This makes me wonder if someone in Patterson bought a crazy hybrid or morph and it escaped, then appeared in a neighbor's yard.
That dorsal pattern looks L. pyromelana to me. I have heard of albinos and hets that have been bred. It looks like a mutant/mutt to me. It's worth holding on to and finding out. How big is it?
"Never suspect a conspiracy when stupidity is an adequate explanation." B. Franklin
Looks like a "white-sided" bull snake. I don't keep up with all the fancy morphs, so what pastel, faded, hypo, blonde mutant it might be is uncertain to me. A google search turns up many closely matching images. Maybe some breeder dumped what they couldn't sell(???) to spice up the local gene pool.... Or like Jeff mentioned, an escapee. It wouldn't be the first captive snake to escape...
Looks like pituophis based on its head shape and white sided was the morph that came to my mind. Can't comment on whether or not it might be a released pet or a natural aberrant, but the white sided bull snakes look like a pretty good match.
It does resemble some of the white-sided bull snakes. I didn't see the snake so I don't know the size or other details. I assumed the ranch was far from anywhere a snake could escape from but maybe not. I am under the impression that white-sided gopher snakes occur naturally, so maybe it's a white-sided Pacific Gophersnake.
Seems pretty clear to me that the mystery snake is probably just a white-sided Pituophis morph. The question still remains whether or not it's a naturally occurring or captive bred morph.