  We present sensitive $\rm NH_3$ (1,1)--(7,7) line images from the Karl G.
Jansky Very Large Array toward successive shocks, which are associated with the
blueshifted outflow lobe driven by the compact protobinary system L1157. Within
a projection distance of 0.1 pc, our observations not only trace the quiescent
and cold gas in the flattened envelope but also illustrate the complex physical
and chemical processes that take place where the high-velocity jet impinges on
its surrounding medium. Specifically, the $\rm NH_3$ ortho-to-para ratio is
enhanced by a factor of 2--2.5 along the jet path, where the velocity offset
between the line peak and the blueshifted wing reaches values as high as $\rm
10\,km\,s^{-1}$; it also shows a strong spatial correlation with the $\rm NH_3$
column density, which is enhanced to $\rm >10^{16}\,cm^{-2}$ toward the shock
cavities. At a linear resolution of 1500 au, our refined temperature map from
the seven $\rm NH_3$ lines shows a gradient from the warm B0 eastern cavity
wall ($\rm >120\,K$) to the cool cavity B1 and the earlier shock B2 ($\rm
<80\,K$), indicating shock heating.
