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[pct-l] RE: April 1 Sierra Snow Prediction



As of April 15, the UTY snow pillar showed 40 inches of equilivent snow.
Forget an early melt.
 
Tom

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From: Reynolds, WT 
Sent: Thursday, March 31, 2005 8:42 AM
To: Reynolds, WT; 'Bighummel@aol.com'; 'pct-l@backcountry.net'
Cc: 'skygeorge@earthlink.net'; 'jstewart01@fs.fed.us'
Subject: April 1 Sierra Snow Prediction



To the Class of 2005

 

I know that persevering in the face of extreme difficulty is the key to
being a successful thruhiker. I also know that as the starting date gets
closer perceptual narrowing occurs as you focus on the adventure ahead and
nothing else. The result, by the way, is that one typically makes stupid
decisions on the trail.

 

The western states are in the midst of a six-year drought 1999-2004. In fact
that drought is continuing EXCEPT in Southern California where we have had
the wettest year in history. The situation is clear. The Southern Sierra has
more than 150% of normal snow. Although the April 1 snow measurements have
not been taken yet, an analysis of the Upper Tyndall Creek (UTY) snow
measurement indicates 153.4% of normal.

 

Since 1998 Greg "strider" Hummel and I have been watching.....and
trying....to predict the best date for a thruhiker to leave Kennedy meadows
and start thru the Sierra. Greg and I disagree when that should be by about
two weeks (Greg proposes leaving about 2 weeks earlier than I) based on how
we think the best way to negotiate Sierra: Go early and get a head start and
deal with the snow versus wait, don't deal with the snow; save yourself for
later. What Greg and I DON'T disagree on is our evaluation of the snowpack.

 

Therefore, please either:

1-Carry crampons and learn to use them [An ice axe is a given]

2-Plan on flip flopping, doing some sections from the north to the south
before attacking the Sierra Mountains.

3-Plan on leaving Kennedy Meadows very late and counting on a late start to
the 2005 winter weather in the Pacific Northwest.

 

You may not need to actually do any of the above. However, you should
develop your contingency plan now while you can still concentrate on
something other than one-foot-ahead-of-the-other. 

 

The facts: 

(If you find this complicated now, try it after walking 500 miles!)

 

150% of normal is a big snow year. 1998 was the worst followed by 1997. 1996
and 1995 were more normal years. However 1995 had a late storm so it acted
like a big snow year for thruhiking purposes.

 

For a thruhiker the question becomes: "When is the Sierra passable for a
thruhiker equipped with an ice axe and possessing a modicum of wintereering
skills?" The answer to this question is based on two facts and an
assumption.

1-How much snow accumulation is there?

2-How fast does it melt?

3-What are the correct conditions.

 

We are sure that the April 1 snowpack measurement will show 38-40" on UTY
and 150% of normal. We disagree on the optimum time to enter by about two
weeks. The decision on the optimum time really depends on the thruhikers
experience with snow. Greg goes and plays in the snow. I avoid it. 

 

The question is then the snowmelt. A graph of the UTY snow readings during
the last 10 years indicates that the snow melts less than 4% between April 1
and May 1. It is true that we had an early melt in 2004 but the late snow in
1995 balances it out. The obvious conclusion is that it is unlikely that a
better prediction that this can be done until May. A quick melt [10%
probability] or a late storm [20% probability] are the only things that can
change what is normal-almost no melt before May.

 

There is a wide variation in the rate that the snowmelt takes place between
May 1 and June 1. For example, two years 1995 and 1996 have approximately
the same predicted snow accumulation on May 1 as I have predicted for May
2005, yet on June 1 one year had 250% of another. The inference is that,
even assuming that I have the May 1, 2005 snow depth correct, that doesn't
mean that, on May 1, 2005,  I can predict the snow depth with any accuracy
on June 1, 2005.

 

My prediction is that the snow accumulation on UTY for 2005 will average 24"
on 6/1 with a possible high of 31" and a possible low of 13".  In  1995 the
snow depth on May 1 was 38" and the June 1 depth was 31'-a slow May melt. In
1997, however, a late storm pushed the 5/1 accumulation to 37" but on June 1
the depth was only 13" - a fast May melt. The predicted accumulation for May
1, 2005 on UTY is, you guessed it, 38"

 

The huge variation in possible conditions for 2005 creates the need for
thruhikers to have contingency plans depending on which scenario plays out.
My advice is to seriously think out your plan now, not wait to see what
happens.  The lower number gives a "0 snow on UTY" day prediction of 6/18
the same as 1997. In this case you can leave the Kennedy Meadow only a
little later than planned. The higher number, however, will give a ") snow
on UTY" day well into July like 1995. In the later case you will need to
flip flop, do some serious winter mountaineering that I hope you have
prepared for, or cool you heels for an additional month.

 

Predicting the snow melt

I wrote earlier that the snow melts only 4% in April. That is not exactly
true. The actual number is closer to 22%. The 4% value is for the UTY snow
pillar and is typical of elevations of 11,000' and above. Much of the Sierra
is much lower and melts earlier. Once the snow melts the government produces
a "Forecast of Runoff volume" for the Sierra Rivers every 5 days. This
report looks at the 5 day weather forecast and predicts the peak volume
runoff day for each river. Of interest are the southern rivers, most notably
the Kern and Kings. In some years the peak day for the Kings and Kern is
before Memorial Day. Sometimes the peak day is after 4th of July. This
report can be used to predict the snowmelt in May. 

 

Another way is to look at information about the Whitney Trail from Lone Pine
and Mount Whitney. There are a series of 100 switchbacks up a steep ridge
between Consultation Lake and Trail Crest at 12,600' elevation. These
switchbacks stay icy till about the same time that the Forrester pass
switchbacks stay icy. Once the public advice on climbing Mt. Whitney advises
taking the trail as opposed to mountaineering directly up the slope, it is a
good bet that the Forrester Pass Trail will be passable to 12,600' 

 

This is a good indicator of the Forrester Trail conditions but one must take
his own measure of mountaineering skill in determining what to attempt. This
is where Greg and I disagree. Above 12,600' the Forrester Pass Trail
continues another 600' and crosses a nasty and dangerous ice chute just
below the pass. This chute scares the hell out of me so I prefer to wait two
weeks while Greg feels confident negotiating it. 

 

Although the Sierra snowpack prediction is unclear, there are some things
that are clear. There is no need to hurry to get to Kennedy Meadows.
Assuming normal progress from ADZPCTKO you will be cooling your heels for a
while when you get there. Take your time. Don't burn your feet out and take
care of your blisters. Have a good time in Lake Morena. The southern
mountains are also full of snow this year and interesting challenges await
you. Good luck Class of 2005.

 

I, of course, will be scuba diving in Cozumel,  Mexico like any sane person.

 

Tom Reynolds


  _____  

From: Reynolds, WT 
Sent: Wednesday, March 23, 2005 10:14 AM
To: Reynolds, WT; 'Bighummel@aol.com'; 'pct-l@backcountry.net'
Cc: 'skygeorge@earthlink.net'; 'jstewart01@fs.fed.us'
Subject: Sierra Snow Prediction - March 22nd


I can make a better prediction after the April 1 snow course measurements
but enough has happened since the March 1 prediction to warrant an update. 
 
Greg "strider" Hummel advocates leaving Kennedy Meadow on, or slightly
before, the date when the snow sensor (UTY) near Forrester Pass reads zero.
I advocate leaving two weeks later. The main difference between us is that
Greg feels that the two week head start is worth the difficulty of dealing
with significant snow and water crossings while I do not. Essentially, both
Greg and I look at the same data and evaluate it the same way.
 
The raw data is this:
1-The snow sensor currenty reads 37 inches. That is less than the 43 inches
it read on this date in 1998 [the last big snow year] but more than it has
read any year since.
2-Current weather forcasts indicate 4 days of light precipitation between
now and April 1. I therefore predict [<-guess] that the April 1 depth to be
40 inches. This is less than 1998 when it hit 46 but 2005 still rates to be
a significent snow year. 
3-The fastest melt in recent history was 2004, last year. The snow started
melting early and kept on melting, turining a significent accumulation into
essentially a low snow year from a thruhiker perspective due to the early
melt. If the same melt occurs this year, and there is no reason to think it
will, the "Zero Snow on the UTY Sensor" day will be about July 4th. If a
normal melt occurs that day will be closer to August 1.
4-Vermillion Vally Resort and Muir Trail Ranch will probably not be open in
June. This is because the Edison Company, under contract with the resorts in
the area, must plow the road by Memorial Day weekend if the snow depth is
below a certain level. It will not be. The road won't be plowed until Edison
gets around to it and its much easier to let the snow melt than plow. Even
if the road is plowed in late June it will take the resorts a week or two to
sort everything out. I am currently predicting that the resorts will be open
for the July 4th weekend, not before.
5-I advise that anyone considering negotiating the snow this year to beg the
powerers that be to pull Jonathan Breem's 1998 journal out of the archeives
so that you can read it carefully.
 
 
The main lesson to be learned from this update is how unreliable any
prediction is. Greg's March 1 prediction was based on a max of 36" snow
depth and an early mely commencing March 15. It didn't happen.
 
Tom Reynolds

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