It is found that the Alaska-northwestern Canada region is the one of most frequent anticyclogenesis (equal to or greater than 7 mb/24 hr) on the northern hemisphere north of 40°N. Results are presented of a synoptic investigation of the predominant type of anticyclogenesis in Alaska. Certain features, that are common to the five cases investigated, are noted and then depicted in a model of anticyclogenesis. These features indicate that: (1) Strong warm-air advection occurs, prior to and during the period of anticyclogenesis, in the low and middle troposphere west of the locale of anticyclogenesis. A ridge aloft is associated with this warm-air advection. Ascending motions occur in the troposphere and lower stratosphere in this region of strong warm-air advection, and result in the appearance of cold air aloft (200 mb). (2) In the subsequent region of anticyclogenesis in Alaska, there is a pre-existing isolated region of cold air, or a trough of low temperature, in the low and middle troposphere prior to intensification. (3) Strong cold-air advection at 200 mb occurs over the region of anticyclogenesis, the pre-existing lower cold area, during development. Descending motions, upper horizontal velocity-convergence and lower horizontal velocity-divergence above the developing surface anticyclone accompany this cold-air advection. The descending speeds are greatest in and above the area of the pre-existing cold region of the low and middle troposphere. Long-period variations of anticyclogenesis, equal to or greater than 7 mb/24 hr, in Alaska and north-western Canada are studied in relation to the sunspot cycle. It is observed that both the pressure departures from normal and the frequencies of anticyclogenesis are much greater at high solar activity, as measured by the sunspot number, than at low solar activity.