The author uses vivd language to describe the setting and the emotions the characters are feeling.
By describing the posture, the fact that they're squinting their eyes, and the grip of "Andre's" hands shows that the character is tense, or nervous. They're feeling this way because of the setting.
The setting is described as a road with lots of snow (or an onslaught of snow), which makes it hard to see. Andre probably is concerned about crashing the car due to the low visability.
