Answer:
Ominous.
Step-by-step explanation:
This passage is clearly making reference to a situation that is ominous, menacing, worrying, threatening, and unhomely because, as the two hikers are left at the bottom of the mountain and as the SUV drives away, they hear the thunder and the clouds rolling in, which, for a hiker, can only mean rough and challenging times out in the dark and the wild.