  In this paper I examine snow crystal growth near -4 C in comparison with a
comprehensive model that includes Structure-Dependent Attachment Kinetics
(SDAK). Together with the previous paper in this series that investigated
growth near 14 C, I show that a substantial body of experimental data now
supports the existence of pronounced 'SDAK dips' on basal surfaces near -4 C
and on prism surfaces near -14 C. In both cases, the model suggests that
edge-associated surface diffusion greatly reduces the nucleation barrier on
narrow facet surfaces relative to that found on broad facets. The remarkable
quantitative similarities in the growth behaviors near -4 C and -14 C suggest
that these two SDAK features arise from essentially the same physical mechanism
occurring at different temperatures on the two principal facets. When applied
to atmospheric snow crystal formation, this comprehensive model can explain the
recurrent morphological transitions between platelike and columnar growth seen
in the Nakaya diagram.
