Wednesday Wonders: Rainbow in the Western Sky

In Vermont the only rainbows we have ever seen are always in the east. Even here in Oregon all the rainbows we have seen have been in the east.  Until Monday morning!  On this day, we were pulling into the parking lot at the office, and there in front of us was a lovely wide short rainbow, though very pale.

Here it is:

What do you suppose a western-sky rainbow means?