The problem has been that US Immigration has refused to let the student travel out without a return ticket within 90 days, if the student had not presented a visa when travelling out. Consequently, we advise US students to arrange the visa issues prior to their arrival. This implies that the application to UiS must be sent within 1. March / 1. Sept.
Exchange students on a bilateral agreement between UiS and a institution of higher education in USA are exempt from the requirement that the permit must be granted before entry into Norway. Please refer to the following information: http://www.udi.no/templates/Tema.aspx?id=7417#How (your situation is covered in section "How do I apply?", last bullet point.). Hence, from the Norwegian Immigration Authorities point of view this procedure is approved.
If you are able to arrange a ticked with an open return, we can not see that the airport officers can deny you to travel out. In any case it might be useful to check in advance if they are up to date on the visa regulations.
