Not really. I mean, it depends on how deep and big this hemisphere is. I've been able to sorta mold and form pleather, with mixed results. I used a hair drying on low setting (to not melt it but soften it as much as possible), then sorta pounded it around a shape, but the fabric backing of pleather really doesn't hold much shape and makes it hard for the rubber/vinyl pleather front to keep a form.
In general, it hasn't worked too well, but I was able to get some decent shapes. One suggestion would be to make a positive mold of the hemisphere, let's say a small metal bowl for argument sake, heat up a small sheet of pleather and then aggressively stretch it around the bowl and wait for it to cool, then trim the excess.
Any reason you can't use real leather? That you can form easy and looks better. Unless the job really would benefit from pleather (like sewing in an insert or something where leather would be difficult to use) I never use the stuff and just go with the real thing.