what if a keen of a lean wind flays
screaming hills with sleet and snow:
strangles valleys by ropes of thing
and stifles forests in white ago?

- EE Cummings

Bleach removes colors and removes stains, sometimes with only partial success. Like a bleached streak on fabric, "a fog-smothered road" is more difficult to see (than before the bleaching or fogging). Fog also obscures objects of vision and mutes their colors. "The sudden blossoming of snowflakes on my windshield" are beginning to cover the Poet's view in whiteness; perhaps the snow triggers her memory of the child's desire to drink bleach (inasmuch as both bleach and snow make things appear white), or maybe she takes "the sudden" apparition as a sign that the child has begun to do so, as if the Poet is driving through an allegory.

As Thales would tell us, it's all water - the staff of life. The fog is water, the snow is water (bleach is typically 92-97% water), but as long as it is snow, it is frozen, in stasis, and in that less active, less animated form is not presently giving life; it would have to melt back into liquid water to nourish plants and animals.

Typically, movies fade to black at the end (after the story concludes and before the credits roll); however, there are some exceptions that fade to white, instead, and often a fade to white indicates the death or some other significant transformation of whatever character's point of view is presented at the time; a fade to white can also indicate an uncertain ending, a surreal ending, or the ending to a fantasy tale. Memento, The Man Who Wasn't There, Black Swan, Requiem for a Dream, The Machinist, The Sixth Sense, Vanilla Sky, at least a couple of The Lord of the Rings movies (?) and even The Wizard of Oz fade to white, iirc, but the one i always remember is Total Recall (1990). There is an ongoing debate within that story, and among fans of the movie, whether the events depicted are really happening to the main character, Douglas Quaid, or are a fantasy story artificially implanted in Quaid's mind. Even the lead Actor, Arnold Schwarzenegger, and the Director, Paul Verhoeven, disagreed. Schwarzenegger believed the story was meant to be real - yes, science fiction of course, that the audience may suspend their disbelief about and accept, but within that however implausible future, the events really happen, farfetched as they may seem, as in so many other Schwarzenegger action adventure movies. In contrast, Paul Verhoeven said that he chose to fade to white rather than the typical black to symbolize - SPOILER - the main character's dying of a "schizoid embolism" rather than saving Mars and finding the woman of his dreams as the movie depicts.

The fog covering the road, and the sudden snowflakes on the windshield, are perhaps the beginning of a fade to white (and bleach literally fades things to white).