Let me correct myself. Looking at the UL book for USE-2 (TYLZ) I see that USE and USE-2 are suitable for use where exposed to sun. But they are also NOT suitabe for use above ground, or in the premises, except to terminate at the service equipment or metering equipment. Default temerature rating is 75 degrees.
USE is designed to be used underground, but is allowed to be terminated aboveground at the service. I would venture to say it should NOT be used as a service riser.