[pct-l] snow pack between Tuolumne Meadows and Lake Tahoe

[Bighummel at aol.com (Bighummel@aol.com)]

This is what I have done, i.e., look at the current year March 1st and April 
1st snow pack information for several high elevation survey sites and then 
look for several similar years with close data at those dates and see what the 
variation is on the "zero" day snow.  Then I make a prediction based on 
averages.  I also compare the March 1st data to the May 1st data (for which all years 
have historical information) to look for late Spring snow storms that reverse 
earlier snow pack conditions.  This happens about 20% of the time, 
irrespective of the earlier conditions.   It isn't perfect as the historical information 
for say Upper Tyndall Creek (11,400' and just south of Forester Pass; THE 
critical pass) or Bighorn Plateau (11,350') only goes back to 1970.  34 years of 
data is nothing statisically but it is what we have to go with on these 
critical survey sites.  Looking at this data you can see that in heavy snow years the 
snow sticks around longer into the Spring, duh.  You can see this heavier 
snow pack as early as in the March 1st reports.  Thus you can make a relatively 
fair educational guess on when zero day will be as early as March 1st.  

Now the definition for "passable";  passable to me is patchy snow to 9,000 or 
10,000 feet, full snow but not deeper than a foot or so from 10,000 and up, 
expecting some serious ice on Forrester and perhaps other high passes to the 
north depending on what time of day you hit them.  You will need an ice axe and 
perhaps in-step crampons in order to climb over Forester Pass, as, early in 
the season there is commonly a vertical wall of ice from a few feet to ten or 15 
feet high there.  Leaving when conditions are this way gives you several 
advantages; few people, the Sierra in glorious white capped condition that few 
people ever get to see or experience, no mosquitos (but you will get them further 
north at one place or another), no bears! and the earliest timing to allow 
you to get to Canada before the snow begins to fall up there.  Of course, there 
are disadvantages;  dealing with traveling in and camping in snow and possibly 
very cold weather, possible high water crossings as this is when the runoff 
generally peaks or is still peaking, possibly a semi-technical ice climb to get 
over Forester, few people (the flip side, loneliness).   

Your definition of "passable" depends entirely upon your experience, your 
gear, your willingness or comfortabiltiy in snow, etc.  Use your own judgement in 
this.  

My prediction is for someone who can handle my definition of passable and has 
experience along these lines and is willing to carry the gear to insure 
safety.  If your definition is different, then a later entry date into the Sierra 
will mean a different set of conditions with a different set of pros and cons.

The entire focus of my prediction is to simply put myself into the shoes of 
someone wanting to thru-hike and attempting to pick the earliest start date 
that will get me through the Sierra.  Forester was the scariest thing that I had 
ever seen in May of 1977 (15 foot vertical wall of ice, 300 foot exposure), 
but now I have climbed much more serious things and would be much more 
comfortable and equipped facing the same conditions again.

Tom Reynolds employs a different method using the runoff data.  My 
predictions have won the past three years and the beer tasted pretty good!

Best regards,

Greg Hummel


In a message dated 12/16/2004 7:24:26 PM Pacific Standard Time, 
jeffmoorehead1@cox.net writes:
 Ideally, if you knew the April 1st average snow depth, then you could make a 
much more refined forecast for the zero day. Instead of an estimate using all 
years of highly varying snowfall, choose those years that had identical 
snowpack, and refine the estimates using only those data. You need lots of data for 
this. The web site that dude recommended has data for snow stations that goes 
way back (I was able to query to 1930 for the Cottonwood Pass snow station).