  Planetesimal formation stage represents a major gap in our understanding of
the planet formation process. The late-stage planet accretion models typically
make arbitrary assumptions about planetesimals and pebbles distribution while
the dust evolution models predict that planetesimal formation is only possible
at some orbital distances. We want to test the importance of water snow line
for triggering formation of the first planetesimals during the gas-rich phase
of protoplanetary disk, when cores of giant planets have to form. We connect
prescriptions for gas disk evolution, dust growth and fragmentation, water ice
evaporation and recondensation, as well as transport of both solids and water
vapor, and planetesimal formation via streaming instability into a single,
one-dimensional model for protoplanetary disk evolution. We find that processes
taking place around the snow line facilitate planetesimal formation in two
ways. First, due to the change of sticking properties between wet and dry
aggregates, there is a "traffic jam" inside of the snow line that slows down
the fall of solids onto the star. Second, ice evaporation and outward diffusion
of water followed by its recondensation increases the abundance of icy pebbles
that trigger planetesimal formation via streaming instability just outside of
the snow line. Planetesimal formation is hindered by growth barriers and radial
drift and thus requires particular conditions to take place. Snow line is a
favorable location where planetesimal formation is possible for a wide range of
conditions, but still not in every protoplanetary disk model. This process is
particularly promoted in large, cool disks with low intrinsic turbulence and
increased initial dust-to-gas ratio.
