Examination of the dynamical structure of a heavy dust storm event over the western Mediterranean revealed an almost exact coincidence of the western boundary of the dust plume with a cold front and a significant jet stream. A confrontation was found between the dry desert air mass associated with a notable downward flowing jet stream and the moister Mediterranean air mass. Vertical cross sections across and along the dust plume indicated that the high mountain Ahaggar region over the Sahara was probably the source of dust, which was transported northward more than 2400 km and washed out by heavy rainfall.