Maybe.
1.) Workaround will require you temporarily connect to update registration.
2.) Updating your antivirus signatures can be done from here using an internet connected machine (not the offline):
https://www.avast.com/download-update3.) Strongly suggest using this program to protect your offline system as well as online ones:
http://www.mcshield.net/ Designed to protect you from USB malwares. Does not require updating.