A short story is confined to one mood, to which everything in the story pertains. Characters, setting, time, events, are all subject to the mood. And you can try more ephemeral, more fleeting things in a story - you can work more by suggestion - than in a novel. Less is resolved, more is suggested, perhaps.
Eudora WeltyMaking reality real is art's responsibility. It is a practical assignment, then, a self-assignment: to achieve, by a cultivated sensitivity for observing life, a capacity for receiving impressions, a lonely, unremitting, unaided, unaidable vision, and transferring this vision without distortion to it onto the pages of a novel, where, if the reader is so persuaded, it will turn into the reader's illusion.
Eudora Welty