This morning my heat pump sounded like a lawn mower running. It's coming from the outside and it was loud enough for me to think someone had generator running in my back yard.

There are many possibilities: failing compressor, failing fan motor, ice buildup if you live in an area that gets that.

Can you determine where the noise is coming from?

I'm not sure exactly where the noise is coming from. We did have ice & snow last night. We had not noticed the noise til this morning. If it is due to snow & ice should the noise be gone by this afternoon when it melts?

If it is due to snow & ice should the noise be gone by this afternoon when it melts?

Only the weatherman can tell you that. In the meantime, switch over to EM/Aux heat until you can find the cause. A failing fan motor will cause igloo-ing and damage of your OD coil, and an iced out of balanced fan will damage your motor.