I wonder which ways the prevailing winds blow? (Do they follow the jetstream?) Salt Lake City, Denver, and Los Angeles all suffer significant air pollution from

I wonder which ways the prevailing winds blow? (Do they follow the jetstream?) Salt Lake City, Denver, and Los Angeles all suffer significant air pollution from neighboring states and cities- air pollution is a regional, not local, problem. In other words- they ship the cars off, but the pollution could blow right back to them!