  Stellar flares are energetic events occurring in stellar atmospheres. They
have been observed on various stars using photometric light curves and spectra.
On some cool stars, flares tend to release substantially more energy compared
to solar flares. Spectroscopic observations have revealed that some spectral
lines, aside from an enhancement and broadening, exhibit asymmetry in their
profile. Asymmetries with enhanced blue wings are often associated with the
presence of coronal mass ejections while the origin of the red asymmetries is
currently not well understood. A few mechanisms have been suggested but no
modeling has been performed yet. We observed the dMe star AD Leo using the
2-meter Perek telescope at Ond\v{r}ejov observatory, with simultaneous
photometric light curves. In analogy with solar flares, we model the H$\alpha$
line emergent from an extensive arcade of cool flare loops and explain the
observed asymmetries using the concept of coronal rain. We solve the non-LTE
radiative transfer in H$\alpha$ within cool flare loops taking into account the
velocity distribution of individual rain clouds. For a flare occurring at the
center of the stellar disc, we then integrate radiation emergent from the whole
arcade to get the flux from the loop area. We observed two flares in the
H$\alpha$ line that exhibit red wing asymmetry corresponding to velocities up
to 50 km s$^{-1}$ during the gradual phase of the flare. Synthetic profiles
generated from the model of coronal rain have enhanced red wings quite
compatible with observations.
