In a high snow year, the biggest schedule danger for many NOBO thru-hikers is waiting for the snow in the Sierras to melt. As of May 16, 2019 the "Sierra Entry Indicator" suggests June 15th as the first safe entry day for the Sierras. This timing will just barely work for hikers that were comfortable banging out 22.5 miles on an average day by the time they reached KM. For slower hikers, June 15th is already too late. See this post for more details: When you should leave Kennedy Meadows
One option is to go into the Sierras early enough to get through before the melt takes hold. This is tough for all but the more aggressive hikers, so if you hiked 18 to 22 miles on a typical day as you finished up the desert section, making it through the Sierras starting on May 20th or so is a risky plan. You have a high likelihood of getting into conditions that you aren't comfortable with, especially high stream crossings.
Another good option for hikers that feel comfortable doing 18 to 22 miles a day is to flip up to Dunsmuir around mile 1500 and start hiking south. This looked doable starting around May 20th and will be easier as the weather warms and snow melts off. June 1st would be a very reasonable start for this section, much earlier than going up into the Sierras. The 300 miles from Dunsmuir to Sierra City include some short snowy sections, but these are relatively easy to traverse -- more like Mt. Baden Powell than like Fuller Ridge. You will still want your microspikes, but won't use them often. Once you reach Sierra City, you will already be well into June and the Sierras will start to look friendlier. Most of the really tough stream crossings are south of Sonora Pass, which is around mile 1000, so you will be hitting them later still. If you want to see the snow conditions as of right now, please take a look at this page: Postholer.Com PCT Snow Conditions Page
If you do this flip, you have to travel from Kennedy Meadows to Dunsmuir twice. First, get a ride out of Kennedy Meadows and hitch or get a bus to Mojave or Bakersfield. From there you can use Greyhound and Amtrak to get up to Dunsmuir. For each trip, there is a total elapsed time of about 2 days, and cost about $100, although it can be done in just over a day if you get a perfect hitch out of KM.
I did this exact flip in 2018, and did a skip from Kennedy Meadows to Quincy and then hiked north in 2017 due to the snow conditions. While not everyone likes the idea of a flip, if you aren't pounding out 25 mile days routinely, this is a good way to "bank" miles during late May and early June that you will need to complete the trail in 2019.
