Each year, Pacific Crest Trail thru-hikers encounter the question of whether the snow pack in the Sierra Nevada will permit easy passage or be a long, drawn-out slog. In 2011, hikers experienced one of the highest snow packs on record. Many found the Sierra extremely difficult to travel through and opted to skip ahead north of the range and come back after reaching Canada. Some simply chose to bypass the Sierra altogether. In contrast, 2007, the year I thru-hiked, was one of the lowest snow packs on record and I remember making my usual 25 miles per day without much trouble. I never had to once use any equipment like crampons or an ice axe.
So if you’re planning a thru-hike this year, what’s the best way to tell if you’re going to encounter heavy snow? I recommend looking at the average snow depth in the Sierra Nevada on April 1st. Why April 1st? Although spring snowstorms can happen, by April 1st there isn’t usually a lot more snow to come in the High Sierra and it’s also prime planning time for thru-hikers.
Snow depth information can be found online for free. The National Weather Service maintains snow analysis data at the National Operational Hydrologic Remote Sensing Center and they have a dedicated region for the Sierra Nevada.
A handy way for hikers to interpret the Sierra Nevada snow pack data is to split it up into heavy, medium, and low snow years. A heavy snow year can be considered a year where the average snow depth on April 1st exceeds 40 inches. In this scenario, thru-hikers should plan to come to the High Sierra well-equipped to handle deep snow, dangerous stream fords, and possibly consider flip-flopping (skipping ahead to less snowy areas and returning later in the year when snow has melted.) Progress through the High Sierra will be quite slow and thru-hikers can expect to take 5-10 miles off their usual daily mileage.
An average snow depth between 20in and 40in can be considered a medium year. The High Sierra should be passable for most hikers starting in mid-June. Expect to slow down and make around 5 miles less than your accustomed daily mileage. Come prepared with an ice axe for self-arrest and crampons for traction.
An average snow depth below 20in can be considered a low snow year. You can expect to make pretty close to your average daily mileage and can leave the crampons at home. You should still carry an ice axe for self-arrest.