Answer: correct but not a simple sentence
The result: “the snow is falling heavily this morning but won't last long” is correct but still not a simple sentence. A simple sentence would be "The snow falling heavily this morning won't last long" (without is).
I belive the correct answer is: A narrative describes events in sequence.
It is Hasty generalization. Hope this helps and I'm not too late!
A poet can use imagery to help establish the setting of the poem and in some cases the mood.
I.e. If you were in a dark mansion the mood would be more melancholy.