Anybody know what this movie is?

I can't look it up on IMDb because I have no idea who's in it. I just know that it came out in the early (?) `80's and it was on HBO. I'm pretty sure it takes place around Christmas time and it's in California in the valley. It's kind of a comedy but not heavily comedic. I've only seen it twice: once in the `80's and again about 20 years ago.
In the movie, some young valley girl (about 15 years old) who is a cute little blonde with curly hair and she's wearing a short scooter skirt is hanging out with friends of her and ends up underground someplace and then a nuclear blast hits very close by and kills just about everyone else except her and someone that was working at a radio station. She goes off to the station to get into touch with this DJ who also doesn't seem to know what happened. They go out looking for other survivors and only find about half a dozen others. From what I recall, the premise of the movie is that she saved the world.

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+1 y
The mystery has been solved!! Thank you all for trying! gamela 1 found it!

https://youtu.be/me4pOQOt20s
Anybody know what this movie is?
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