So I have to talk to Alvor in Riverwood to continue the quest "Before the storm"...

The quest points me towards him, and he just sits there in his house. I've talked to him several times and clicked on all the conversation topics, but the quest wont progress further than that.

Can anyone help?

Based on what others who have encountered similar bugs wrote, if you wait him out, he'll eventually leave the house.

Alternatively, if you wait a while and find the right time of day he might activate. Apparently some of these NPCs only care about the fate of all humankind based on a day planner schedule.

Hilarious commentary, and true.

Argh, this is frustrating. Just waiting, sleeping and waiting for the npc's to move. But they all just stay at the same place in the house no matter what time of day it is

EDIT: Okay, I got the quest working, I just asked Alvor "Do you have any supplies I could take?", which I had already done, but now I just left it there, and then he suddenly started talking about the next step and I got the quest.