I wouldn't mix the two. Without more about the given context, I understand that searching a knowledge base would be more of a secondary option, so why put it in primary focus? I would advise against using two input fields close to each other. If it's a weather app, focus on weather searches by location, if you need a knowledge base section, I would include it as a secondary search feature or I would have terms have a ? icon that points you to each term's definition, where you could also search the knowledge base.

I wouldn't mix the two. Without more about the given context, I understand that searching a knowledge base would be more of a secondary option, so why put it in primary focus? I would advise against using two input fields close to each other. If it's a weather app, focus on weather searches by location, if you need a knowledge base section, I would include it as a secondary search feature or I would have an ? icon next to specific words(terminology), something that points you to each term's definition, where you could also search the knowledge base.