I would like to add a comment to the thorough response above. Most of us who read "The Story of an Hour" believe, on the basis of the story's narrative, that Mrs. Mallard's marriage is particularly unsuccessful and, in a sense, that is correct. After all, Louise Mallard, in commenting on her love of Brently Mallard, notes that "and yet she had loved him--sometimes," not exactly a glowing recommendation for marital bliss. And earlier, Mrs. Mallard imagines how she would react when she sees her husband in his casket--"she knew that she would weep again when she saw the kind, tender hands folded in death," implying that Brently Mallard was a kind, gentle, and loving husband. These two scenes seem to create some uncertainty about Mrs. Mallard's real problem with marriage--until we get to the explanation.
A few lines later we discover that Mrs. Mallard does not differentiate between her marriage, which might be characterized as a loving one, and the institution of marriage, in which there are literally no good marriages:
There would be no powerful will bending hers in that blind persistence with which men and women believe they have a right to impose a private will upon a fellow-creature.
To Mrs. Mallard, then, even though she might be married to a good and loving husband, the pair are yoked in an institution, marriage, that requires them to impose their "private will" on one another, and that imposition creates the lack of freedom that has recently become so appealing to Mrs. Mallard when she realizes she has been freed of the marriage bonds by the accident of her husband's death.
In sum, then, the story is not about a single unsuccessful marriage; rather, Chopin makes a much broader comment about how marriage restricts freedom, and it doesn't matter whether the marriage is "good" because, in the end, marriage creates bonds that are more like shackles than anything else.
Let's begin by defining the terms symbol and foreshadowing. A symbol is something that stands for something else. Foreshadowing is a moment in a story that can show you, the reader, that something will happen later. Let's discuss the two important literary elements in turn.
First, one must consider the name "Mallard" as a symbol. A mallard duck can freely migrate. Loise Mallard, above all, values freedom as exemplified and symbolized in nature. Even the "open square" of sky she can see from her window and other birds "twittering" can be seen as symbols of freedom that she longs for.
Second, nature is a more general symbol. Look at Chopin's description when Louise first hears about her husband's death:
When the storm of grief had spent itself she went away to her room alone.
It is no mistake that a storm is used here to represent her avid grief. However, as Louise contemplates "her grief" more and more, you can hear the call of freedom in nature.
Trees that were all aquiver with the new spring life. The delicious breath of rain was in the air ... and countless sparrows were twittering in the eaves. ... There were patches of blue sky showing here and there through the clouds.
Here, nature symbolizes new life and a new beginning. It is a new beginning only possible because of the death of her husband. Later, nature (this time in regards to the seasons) is again used to symbolize her coming freedom: "Spring days, and summer days, and all sorts of days that would be her own."
Third, we have to speak about the stairs. Where nature represents new life, the stairs symbolize Louise's transformation TO new life. As she goes up the stairs, it is to isolate herself in grief. As she goes down the stairs, it is to descend as a free woman:
There was a feverish triumph in her eyes, and she carried herself unwittingly like a goddess of Victory. She clasped her sister's waist, and together they descended the stairs.
The only issue is that, "Richard stood waiting for them at the bottom."
Now, we need to talk a bit about foreshadowing. In my opinion, the biggest piece of foreshadowing that Louise will die from "the joy that kills" is that from the beginning of the story we are told that Louise has "heart trouble." This may seem insignificant, but it is precisely the thing that causes her death.
There is quite a bit of foreshadowing also about Mrs. Mallard being not so happy in her marriage and that she just might be happy that her husband has passed away. For example, Chopin talks about her pretty face "whose lines bespoke repression."
Suddenly the weather that is a symbol from above can also foreshadow her new elation at her freedom. (See the large block quote above.) She has not formally stated her freedom at this point, but the nature screams her elation.
Thus, both symbol and foreshadowing can be found in Chopin's work of literature.