  The James Webb Space Telescope (JWST) is capable of probing extremely early
eras of our Universe when the supersonic relative motions between dark matter
and baryonic overdensities modulate structure formation ($z>\sim 10$). We study
low-mass galaxy formation including this "stream velocity" using high
resolution AREPO hydrodynamics simulations, and present theoretical predictions
of the UV luminosity function (UVLF) and galaxy stellar mass function (GSMF)
down to extremely faint and low mass galaxies ($M_{UV}>\sim-15$,
$10^4M_\odot<=M_*<=10^8 M_\odot)$. We show that, although the stream velocity
suppresses early star formation overall, it induces a short period of rapid
star formation in some larger dwarfs, leading to an enhancement in the
faint-end of the UVLF at $z=12$. We demonstrate that JWST observations are
close to this enhanced regime, and propose that the UVLF may constitute an
important probe of the stream velocity at high redshift for JWST and future
observatories.
