There is a high possibility that my return flight will be cancelled due to bad weather, so I want to get home early. Can I change my return date?

We won't be able to handle your flight matter.  It all will be depended on airline company. So, you need to contact your airline for further information.

Normally, airline doesn't make any changes on flights before any confirmation. Also, in the case of flight cancellation or delay, not always have the transfer flight waiting.