M o u n t a i n

We a t h e r

a n d

S n o w p a c k

SUMMARY

Faceted snow crystalsformed near and just below the
snow surface create significant weak layers in the snow-
pack of southwest Montana when they are subsequently
buried. These layers are created by large diurnaltempera-
ture fluctuations of the snow surface caused by a combi-
nation of clear,cold nightswith strong radiative cooling
and relatively warmer, sunny days. The large diurnal tem-
perature changesof the snow surface contrast sharplywith
the relatively constant temperature of the snowpack 0.25
m below the surface. The difference between the fluctuat-
ing snow surfacetemperature andthe more consistenttem-
peratures 0.25mbelow the surface results in large tem-
perature gradients,strong vaporpressure gradients,and
the rapid formation of faceted snow.
More research is needed, specifically on: 1) the chang-
ing temperature gradients whichform near-surface faceted
snow, possibly involving laboratory work,2) the numer-

snow cover: The role of thermal and vapor pressure conditions.
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Colbeck, S.C.1988. One the micrometeorologyof surface hoar
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Colbeck, S.C. 1989. Snow-crystal growth with varying surface
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23-29.

Colbeck, S., E. Akitaya, R. Armstrong, H. Gubler, J. Lafeuille, K.
Lied, D. McClung, and

E. Morris. 1990. The InternationalClassificationfor SeasonalSnow
on the Ground. International Commission on Snow and Ice of the
International Association of ScientificHydrology, 23 pp.

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