  I explore the origin of an asymmetry of the H$\alpha$ emission from a
circumstellar (CS) shell around type IIP supernova SN 2013fs in the spectrum
taken 10.3\,h after the shock breakout. A spherical model of the H$\alpha$
emission from the CS shell that takes into account a preshock gas acceleration
by the supernova radiation permits us to successfully reproduce the \ha
H$\alpha$ profile. Principal factors responsible for the H$\alpha$ asymmetry
are the high velocity of the accelerated CS preshock gas ($\sim 3000$\,km
s$^{-1}$) and a low H$\alpha$ Sobolev optical depth in a combination with an
occultation of the H$\alpha$ emission by the photosphere.
