The night of the attack on Myth Drannor a snow storm raged through the area, leaving behind a two feet thick layer of snow on the ground in the lowlands. This was still there in the morning after the attack on Myth Drannor and would have lasted long into the day, becoming more and more slushy due to the heavy rains and eventually disappearing. But the Krag took a much heavier snowfall, leaving behind eight feet of snow that would disrupt the Zhents patrols and supply lines. Due to the cold weather up at the Krag the snow would linger for far longer time than in the lowlands and the Zhents would have to clear the roads for their supplies to be able to get through.
((Event was run by DM_Muse))