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Date: Fri, 19 Jan 2001 13:36:30 -0700
To: "James Hannigan" <jamesw@ucar.edu>
From: Eric Cannon <Eric.Cannon@Colorado.edu>
Subject: Ten contributory factors 

Hello Jim,

Here's a list of the ten contributory factors to avalanches.  I received
this text from a fellow patroller in California the other day.  I checked
the text word for word against my copy of the "factors" from the Avalanche
Instructor's Manual (page 324, October 1995) and the e-mail text agrees
exactly with the NSP text.  So here are the "factors" exactly as NSP has
presented them (no extra language as you said you had encountered).

Hope this helps, Eric


TEN CONTRIBUTORY FACTORS

1)Depth Old Snow-if terrain irregularities and/or
anchors are covered, the old snow will provide an
obstructed sliding surface.

2)Old Snow Surface-The less the frictional resistance
of the old snow surface, the more it will be prone to
avalanching.  In addition, more frictional resistance will
promote sintering and bonding of new snow layers.

3)New Snow Depth-The greater the depth of new snow,
the less likely will sintering and stabilization of the new snow
mass be.

4)New Snow Type-The less new snow is interlocked, the
more likely will it be to avalanche.

5)New Snow Density-Extremely large or small density tends
to promote instability.

6)Snowfall Intensity-The more intense the snowfall, the more the
likelihood of avalanching because of its lessened ability to sinter
and stabilize.

7)Precipitation Intensity Factor-Also known as the Atwater Number,
this is the rate that mass is being deposited either by snowfall or
blowing snow.

8)Settlement-The rate of settlement is directly proportional to
temperature, but given stable temperature, settlement depends upon
crystal type and mode of deposition.

9)Wind-The speed of the wind is a measure of how much snow is being
transported to lee slopes; the directions of the wind is an indicator of
which slopes are accumulating snow redeposition.

10)Temperature-Near-freezing temperatures promote sintering
and stability within and between snow layers; cold temperatures
prolong danger by promoting brittle strength and retarding the
sintering process.  The water produced above freezing
temperatures may promote wet avalanches.

Avalanche Instructor's Manual              324                      October
1995
