  The James Webb Space Telescope (JWST) is expected to observe galaxies at
$z>10$ that are presently inaccessible. Here, we use a self-consistent
empirical model, the UniverseMachine, to generate mock galaxy catalogues and
lightcones over the redshift range $z=0-15$. These data include realistic
galaxy properties (stellar masses, star formation rates, and UV luminosities),
galaxy-halo relationships, and galaxy-galaxy clustering. Mock observables are
also provided for different model parameters spanning observational
uncertainties at $z<10$. We predict that Cycle 1 JWST surveys will very likely
detect galaxies with $M_*>10^7 M_\odot$ and/or $M_{1500}<-17$ out to at least
$z\sim 13.5$. Number density uncertainties at $z>12$ expand dramatically, so
efforts to detect $z>12$ galaxies will provide the most valuable constraints on
galaxy formation models. The faint-end slopes of the stellar mass/luminosity
functions at a given mass/luminosity threshold steepen as redshift increases.
This is because observable galaxies are hosted by haloes in the exponentially
falling regime of the halo mass function at high redshifts. Hence, these
faint-end slopes are robustly predicted to become shallower below current
observable limits ($M_\ast < 10^7M_\odot$ or $M_\mathrm{1500}>-17$). For
reionization models, extrapolating luminosity functions with a constant
faint-end slope from $M_{1500}=-17$ down to $M_{1500}=-12$ gives the most
reasonable upper limit for the total UV luminosity and cosmic star formation
rate up to $z\sim 12$. We compare to three other empirical models and one
semi-analytic model, showing that the range of predicted observables from our
approach encompasses predictions from other techniques. Public catalogues and
lightcones for common fields are available online.
