Are you going to miss me when I leave for college next week?

[tulipflower]

I don't know why 'be going to' has been used in the following sentences? Does it show prediction?

1) Dad. Are you going to miss me when I leave for college next week?

Source: https://www.esl-lab.com/difficult/university-degrees/

2) She's going to turn 17 in two months.

 

[5jj]

Does it show prediction?

No. BE going to usually suggests that there is some form of present evidence for the future situation.

 

[jutfrank]

1) I say yes, it clearly is about prediction.
2) Here I'd say no, as it's really a statement of fact.

BE going to usually suggests that there is some form of present evidence for the future situation.

Right, but this works very well for predictions. Predictions can certainly be made on present evidence, and often are.