Authors use foreshadowing to create suspense or to convey information that helps readers understand what comes later.
Explanation:
Foreshadowing can make extraordinary, even fanciful events seem more believable; if the text foreshadows something, the reader feels prepared for the events when they happen.
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).
