Foreshadowing is used early in the story to give us clues that the man's chances of survival are against him. He's a newcomer to the Klondike wilderness which means he's never been through the harsh winters. He isn't using a sled, traveling by foot. He's taking very little with him -- a bacon sandwich, tobacco, matches, kindling -- that will help him to survive in the wilderness. He's been warned never to travel in temperatures of fifty degrees below zero, and he ignores that warning. An old man also advises him against traveling by himself, a warning that is repeated frequently throughout the story. This gives us a sense of what's going to happen to him. The man also ignores the warning of the old man. All of these clues (foreshadowing) let us know right away the man won't survive.
The man's dog is one of the early foreshadows of the trouble that is to come. It is far too cold even for this breed used to the cold. It makes the dog depressed, as "(i)ts instict told it a truer tale than was told to the man by the man's judgment."
Another example is when the man takes off his glove and is "astonished at the swift numbness that smote them" (his fingers). The gravity of his situation is beginning to sink in.
One of the most telling foreshadows is the revealtion by the "old-timer" about when it was unsafe to travel:
"The old-timer had been very serious in laying down the law that no man must travel alone in the Klondike after fifty below." Even though the advice is sound and from experience, the man is smug and prideful, thinking he has outwitted nature and experience for a short time.
When he burns up all his matches at once, it is another foreshadow of his impending death. Rashness cannot win out over reason in the end.