[pct-l] 2004 Sierra Snow Information & WAG on when to enter the Sierra

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

I offer, on March 1st every year, a wild assed guess (WAG) of when I would 
plan to enter the Sierra if I were planning a thru-hike of the PCT.  The 
discussion of how I glean this WAG from the California Snow Survey site information 
is repeated below for those who are so analy inclined.  

Here's how the Southern Sierra snow situation looks right now compared to 
similar years in the historical record;  

Overall the southern Sierra basins are running almost right on or a bit above 
an "average" snow year.  The Upper Tyndall Creek snow survey site, at 11,400 
feet elevation and near Forester Pass (your biggest hurdle in the Sierra), is 
currently showing about 18.5 inches of snow depth.  This is low on the 
historical record and would suggest an early meltoff from the average of all of the 
information going back to 1970.  1974, 1975, 1988 and 2003 all had 
approximately the same amount of snow at Upper Tyndall Creek on March 1st.  Of these years 
the latest "zero day" (that is the date at which the sensor first reads zero) 
was June 18th (1974) and the earliest was June 2nd (1988).  Thus a simple 
averaging of the zero days of all four of these years would suggest a good guess 
of the earliest day to leave Kennedy Meadows to be June 10th.  

This is not a scientific or otherwise exact science prediction and should not 
be taken as such (although, invariably a few have gotten mad at me for being 
off a week or so in the past, but they, of course, have expected too much from 
this simple WAG).

The Tahoe area has been dumped on with this last series of storms and is 
running at about 120% of normal.  From a thru-hiker perspective you should worry 
about this but not too much, as, when you enter the Sierra and if this is 
approximately when most of the snow has melted off so that you are not postholing 
for the first 100 miles, it will take you two weeks or more to reach the Tahoe 
area from Kennedy Meadows.   Thus the meltoff zero day for the Southern Sierra 
is much more important to you than the zero day for the Lake Tahoe area.

Late Spring storms sometimes throw the snow situation in the Sierra into a 
heavier situation and thus later entry date.  You have to judge these as you are 
hiking from the border to Kennedy Meadows and adjust your schedule as 
necessary.  Stay flexible.  Stay flexible.  Stay flexible.

Tom Reynolds usually provides an alternative view of this, but has wigged out 
this year and tried to get Monte to take his place in chiding my WAG.  Monte 
knows a lot about the snow situation in the Pacific Northwest and is a dear 
friend of mine, but he don't know s#!t about the Sierra snow. ;-)

Good luck 2004'ers!

Greg "Strider" Hummel



<<<
For those of you planning a 2004 thru-hike and interested in this discussion 
of Sierra snow meltoff predictions and thus, estimating your starting date, 
read on, or, delete if not.

The following is where I collect the information, how I process it and then 
how I use this in order to make a wild assed guess about when the earliest 
date 
will be each year to enter the Sierras.

For a database from which to draw analogs from; I look through the available 
Sierra snow survey sites for ones which are 1) on or near the PCT in the 
Southern Sierra, 2) highest elevation, and 3) have fairly complete records 
going 
back to 1970 or 1972 when they started collecting the data.  The Bighorn 
Plateau 
(BGH) survey site has a complete data set, is on the PCT just south of 
Forester Pass and is at 11,350 feet of elevation, and, the Tyndall Creek 
(UTY) snow 
survey site is a bit higher at 11,400 feet, on the PCT, closer to Forester, 
and also has complete historical info.

I then took the historical information from BGH and UTY and looked for 
patterns late in the Winter, thus March 1, which might give an indication of 
the 
eventual meltoff.  June snow amounts were not always recorded, so May snow 
amounts were chosen as a LATE indicator of meltoff status.  

Thus I compiled an "early" indicator of snow status; March 1st from each 
year, and a "late" indicator of snow status; May 1st from each year.  I 
plotted 
these on a graph by year and looked at how the extremely wet and dry years 
look 
at the March 1st time to see if there was a correlation between the March 1st 
and May 1st amounts.  The weather patterns between these two dates are 
critical ones relative to the overall snowpack volume and meltoff scenario.

First, the dry years;
1971, 1972, 1976, 1977, 1981, 1987 thru 1992 stick out as the lowest (driest 
years) snow amounts by far.  None of these had more than just 36 inches of 
snow depth at March 1st at either BGH or UTY.  Of these dry years, only 3 had 
more snow in May than in March.  One of these 3, in 1976, had only 14 inches 
in 
May versus 13.4 inches in March.   Thus of these 11 dry years, you would have 
a 
82 percent chance (9 out of 11) of being correct in predicting that the 
meltoff would be significantly early (by possibly a month! i.e. May 15th!) by 
simply finding that less than 36 inches of snow was present at BGH on March 
1.    
Just how early could be predicted by looking at the rate, on a daily basis, 
that the snow was melting off at the Tyndall Creek, Bighorn Plateau and other 
Kern River -  Southern Sierra snow survey sites in late April and early May.  
 

OF COURSE, a late Spring snowstorm in May can reverse the meltoff or delay 
it.  This happens about only 20% of the time.  By May 1st most thruhikers are 
already on the trail and tuned into the trail information network.   When a 
late 
Spring storm hits the Southern Sierra, it generally also hits the other 
Southern California mountains and the thru-hikers, therefore, they/you are 
likely 
to be able to guage at that point whether their/your schedule to hit the 
Sierras should be delayed or sped up.  

Now, the wet years;
1978, 1980, 1983, 1993, 1997, 1998 and 2000 all had more than 75 inches on 
March 1st at BGH (note BGH gets more snow on the average than UTY).  Two of 
these, 1978 and 1983, had even more snow in May than in March.  So, in "wet" 
years 
the predictions are not so easy, other than to say that entry dates will 
definately be late and possibly very late.  It is important to point out that 
in 
many of these "wet" Sierra years, the Pacific Northwest is dry, thus a North 
to 
South hike is worth considering in these years.

The rest of the years fall into an "average" category which, on March 1st may 
be;
- on the dry side and melt off early, or
- on the dry side and gets late storm systems that delay the meltoff until 
later, or
- on the wet side and melts off early, or
- on the wet side and gets late storms systems that delay the meltoff until 
later, or
- on an average meltoff schedule and stay that way.

Only 6 of these did the last "average" meltoff, 3 of the 6 in last ten years. 
Thus a June 15th entry date for the Sierras is going to be significantly off 
very often based upon this database.

The UTY database gives daily information going all of the way back to 1970.  
Thus it gives the zero snow depth date (only at that location, not the entire 
Sth Sierras, of course, but can be used loosely as a "near zero snow date" 
for 
the Southern Sierra).  The earliest, in 1976 is May 8th, the latest date is 
July 28th in 1983.  This is a 11 1/2 week spread!  Yep, the average date 
works 
out to June 13th.  In 16 years out of the 33 years in record, you would be 
either more than two weeks early or more than two weeks late entering into 
the 
Sierras on June 13th.  So, Ray Jardine's recommendation that you enter the 
Sierras on or about June 15th is correct in one way of looking at it, 
however, way 
off in reality.

>From all of this on a given year, I find the amount of snow at both UTY and 
BGH on March 1 and compare it to similar years in the historical database, 
consider the El Nino weather effects for that year in order to guage whether 
late 
storm systems are likely or not, and then make a wild assed guess.  I have 
percentages and statistics on my side that make this an educated - wild - 
assed 
-guess, but clearly recognize that I do not have a crystal ball and anything 
can happen between March 1st and the date that the snow mostly melts off.  

The date that I gave this year was June 10th.  Yep, that is very close to the 
average and I made that prediction because the amounts of snow at BGH and UTY 
was in the "average" range and the El Nino effect was not a significant 
player this Spring.  I have heard from several thru-hikers who entered the 
Sierras 
on or about this date and found generally no snow at lower elevations and 
snow 
and ice at the high passes.  Those are the conditions that I caveated my 
prediction with as I believe, IMHO,  that is the best time to enter the 
Sierras. 
>>>