The thru hiker message boards are gonna erupt soon with frantic posts about how nobody will make it through the Sierra this year on the PCT.
It happens every year. Snow reports come out and people panic.
It's funny cause for a hiker leaving the Mexican Border in Late april they can expect to reach Kennedy Meadows (South) some 700 PCT trail miles later in early June.
What happens then is they wait for the "magic day" when it is suddenly declared safe to enter the Sierra. It used to be called "Ray Day" after the thru hiking guru Ray Jardine. June 15th was "Ray Day".
Now there is a calculation made based on the depth of snow on the Big Horn Plateu to achieve "Kennedy Meadows Day" The reality is hikers stack up at the kennedy meadows store for a few days, eating Ben and Jerry's Icecream and cleaning out the little store's supply of Beer before hauling off into the Sierra anyways regardless of snow.
Anyhow here is a sample of the "kennedy Meadows Day" table. It is basically a recommendation that thru hikers use although some take it very serious. The issue we have is we need to cross the Sierra early enough in the season to leave time to finish up the PCT in Canada before winter closes in up there.
The theory is to predict the earliest optimum day to enter the Sierra northbound and encounter the least amount of resistance from snow.
I left the formula out so you math buffs could have a puzzle as to how they come up with the day.
Year-----Big Horn Plateau snow depth inches(April)--------Calculated day to leave Kennedy Meadows
2000--------------56-------------June 17
2001--------------37------------ June 12
2002--------------65-------------June 20
2003--------------49-------------June 15
2004------------- 41-------------June 13
2005-------------90.1-----------June 27
2006--------------53----------- June 17
2007--------------20------------June 7
2008--------------65------------June 20
2009--------------59.3---------June 18
So.. whats the formula?
I entered June 3rd in 2009 and there was plenty of snow. Forrester Pass, Mt Whitney, Kearsarge, Glenn, Pinchot, Muir, Mather, Selden and Silver were all snow covered for a few miles before on their south facing slopes to several miles after on the north sides. Finally when I reached Donahue pass the snow was merely rotted and spotty. I turned out to be easier for me to just climb the passes in the morning when the snow was crusted and descend the north slopes before afternoon postholing began. It worked until Donahue.
Anyhow I saw this record snowfall post and thought about "Kennedy Meadows Day" and my thru hiker brothers and sisters sitting on the front porch of KM eating icecream and trying to figure out the proper way to hold their shiny new iceaxes while watching someone try and stuff a bearvault 500 into a UL pack while waiting for the snow to melt.
Answer below vvv
Kennedy Meadows Day= June 1 + April snow depth (in.) at Bighorn Plateau divided by 3.5