Concerning the influence of mountains on the large scale isobaric height pattern, most of investigators up to now discussed the subject under the assumption of steady state. But recently the problem of the influence of mountains on non-steady height pattern attracts much interest of investigators in this field, because the results of the numerical weather prediction of the lower layer are not satisfactory in mountain regions. Therefore we examined the influence of the Rocky mountains in non-steady state, by solving the vorticity equation numerically. We adopt typical model height patterns in middle latitudes as the initial conditions, and we compared the patterns obtained for the case, in which we take into account the effect of the mountains, with those for the case in which we do not take into account it.