  We develop a simple model to predict the radial distribution of planetesimal
formation. The model is based on the observed growth of dust to mm-sized
particles, which drift radially, pile-up, and form planetesimals where the
stopping time and dust-to-gas ratio intersect the allowed region for streaming
instability-induced gravitational collapse. Using an approximate analytic
treatment, we first show that drifting particles define a track in
metallicity--stopping time space whose only substantial dependence is on the
disk's angular momentum transport efficiency. Prompt planetesimal formation is
feasible for high particle accretion rates (relative to the gas, $\dot{M}_p /
\dot{M} > 3 \times 10^{-2}$ for $\alpha = 10^{-2}$), that could only be
sustained for a limited period of time. If it is possible, it would lead to the
deposition of a broad and massive belt of planetesimals with a sharp outer
edge. Including turbulent diffusion and vapor condensation processes
numerically, we find that a modest enhancement of solids near the snow line
occurs for cm-sized particles, but that this is largely immaterial for
planetesimal formation. We note that radial drift couples planetesimal
formation across radii in the disk, and suggest that considerations of
planetesimal formation favor a model in which the initial deposition of
material for giant planet cores occurs well beyond the snow line.
