JMT S->N Start Date/Snowpack??

It's still to early to predict. The winter of 1990-91 was way worse than this one. Mammoth Mountain had only received 4' of total snow before March. (This year they've seen 10' total). Then March Madness happened with 15' of snow, plus some in April and May.

If early June is your only option then I suggest going N-S instead. You won't have trouble with a walk-in permit. If the Spring snowfall picks up you might need to make some route changes, but it would still be an awesome trip.

There have been several recent threads on this subject.

I was in the Sierra a week ago. Having been in the Sierra (mainly summer, but some winter) for over 50 years; following Sierra snow reports; reading Sierra long-range weather forecasts; etc., it appears this will be a low snowfall year, but "low" is a relative term.

2012 is a La Nina year, but 2011 was also a La Nina year. Last winter, Arctic Oscillation, predicted two weeks out, prevailed and resulted in very heavy snowfall. There is still time for a "Pineapple Express" condition to set up and dump significant snow.

March, April and May (yes – May) often are significant Sierra snow months. Total snow is part of the summer "hike ability" equation – the other part is snowmelt: when melting starts, snowmelt rate, etc. Snowmelt also determines mosquito hatch.

Last year, snowmelt started late April/May and then snowstorms with cold weather would arrive and stop the melting process. Last summer, high passes were snowbound well into July. I went over Forester Pass mid September last summer and hiked through snowfields.

Consider starting at Yosemite and going over high passes later in your hike; more time for snow, if any, to melt. There are many threads on this subject: day hike from TM to Happy Isles, etc.

Late June is better than early June.

Do not bring crampons and ice axe. By early/mid June, PCT through hikers will have cut defined paths through snowfields, if any. In the unlikely event snowfields are frozen, just wait until sun softens the snow.

I would do the trip as late in June as possible. There is no reason to push it earlier unless you like snow and high stream crossing or you have no other choice. Can you do it earlier, sure, PCT hikers do it every year in early June. But they have also had 700 miles to toughen up and generally a more flexible schedule than the typical JMT hiker.

Big system coming in this week. Could be like last March, wet.