[pct-l] Sierra Snow Info and Prediction

[Bighummel@xxxxxxx (Bighummel@xxxxxxx)]

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[ Picked text/plain from multipart/alternative ]
>From the California Dept. of Water Resources - Division of Flood Management -
"Snow - Water Equivalents (inches)"
As of February 20, 2003

Section                                           Today     Yesterday
NORTH       Number of Stations Reporting        28      28
    Average snow water equivalent             26"       26"
    Percent of April 1 Average                 91%      90%
    Percent of normal for this date         110%    109%

CENTRAL Number of Stations Reporting    46      46
    Average snow water equivalent               20"     20"
    Percent of April 1 Average                  66%     65%
    Percent of normal for this date               81%   81%

SOUTH   Number of Stations Reporting        31      31
    Average snow water equivalent              15"      15"
    Percent of April 1 Average                  57%     57%
    Percent of normal for this date             74%     73%

Recognize that "Snow - Water Equivalents" are guestimates of water content in
the snow pack.  This depends upon measured densities of the snow at a variety
of stations.  THIS NOT SNOW DEPTH.  Snow depth, depending upon density can be
much greater.  Now this is a warmer than normal winter so densities should be
a little higher (read closer to water inches).  The important thing to read
here is the percentages of average or normal.  We're significantly lighter
than normal in the southern Sierras and a little bit above normal in the
northern Sierras.

A hypothetical scenario:  If this was June 1 and the southern Sierras were
near zero and you were tempted to enter then, considering your timing is righ
t in the middle of prime meltoff the extra snow still on the ground in the
northern Sierras will likely be melted off by the time to get to them in a
couple of weeks or more.  This is why I choose the highest, closest snow
survey site to Forrester Pass for my historical comparisons, because the
amount of snow in the northern Sierra doesn't matter much to a thru-hiker who
will take two to three weeks to get there.  What matters upon leaving Kennedy
Meadows is how much snow is at high altitude in the southern Sierras.
PERIOD.

Now, if the southern Sierras are at 74% of normal then what does this mean if
this level of normal holds true through the winter, from a historical sense?

Historical information dating back to 1970, when statistically analyzed,
finds a one in four chance of a late Spring storm hitting you late in the
season (May) and rejuvenating the snow pack and pushing the meltoff date
later (read 75% chance that you can leave Kennedy Meadows early, i.e. on or
before June 1st without significant snow problems).  The meltoff, of course,
depends upon not only new snow falling but also temperature in May.  You have
a 50/50 chance that temperatures in May will be high enough to have an early
meltoff.  Multiple statistics are combined by multiplying so 50% times 75%
equals 37.5% chance that the snow will meltoff early without any late storms
influencing it.

You take your own chances and take this information with a grain of salt as
it is possible that late storms will hit AND cold May weather will extend the
meltoff.  Also, check out the website:
http://cdec.water.ca.gov/cgi-progs/current/DLYSWEQ and check out the snow
survey sites on links there and the historical info on links there and crank
out the information in your own statistical perspective and come to your own
conclusions, if you desire.

I am, therefore, hereby predicting that you, provided you are experience with
and comfortable with and geared for some snow travel, can enter the Sierras
from Kennedy Meadows on June 1st this year and pass through the Sierras.
There will be snow and ice at the passes, possibly difficult snow and ice.
But who said that the beauty of the High Sierra cloaked in its best white
coat would come to you without exacting any price?

By going early you will beat the mosquitos (but get them further north, of
course)  and bears (and maybe the rangers looking to ticket you for not
carrying a bear canister with Tom pushing them from behind!) but have to deal
with crossing some of the creeks and rivers at potentially full runoff
volumes.

Throw a bit of serendipity into your hike.  For the worth of a journey is
measured by the hardships that you had to endure along the way.

Best regards and good luck 2003'ers!

Greg Hummel