It's really easy....skip the Sierra and come back in September. The Sierra is beautiful in the September. There are hardly any mosquitoes; there are less people; and there is no snow. An additional bonus is there are an abundance of red currants to eat along the trail.
NOBO or SOBO is going to have a very rough time this year with snow without taking a break and/or skipping ahead. Snow is dangerous, especially in Northern Cascades where avalanches and landslides are very common.