Our guide, Rajendra, began to furrow his brow for the first time as we finally arrived at our destination. He expressed worry that the Thorong La Pass could be cut off if the thunderstorms we'd been pushing through turned into snow. We had planned to cross it on the ninth day of our Annapurna trek in Nepal. If the rain did in fact turn to snow, there would be no alternative but to turn around and go back the way we came.