UPSLOPE WEATHER ALONG THE INLAND ALASKA AIR ROUTE

Abstract

The importance of upslope circulation and its accompanying weather phenomena is discussed as a major factor influencing aircraft operation along the portion of the Inland Alaska Air Route which lies east of the Rocky Mountains. Great Falls, Montana, is given the greatest consideration since it is considered as representative of stations on the east slopes of the Rocky Mountains and more data are available for this station. The air masses involved in the occurrence of upslope circulation and associated phenomena are ascertained. Upslope weather types are classified into pure upslope, upslope?overrunning, upslope?radiation, and overrunning predominant with upslope as a minor factor. These types are correlated with typical synoptic examples. Forecasting of the formation and cessation of upslope weather phenomena is discussed on the basis of lower-air trajectories and the use of typical examples. Concrete deductions resulting from a study of many synoptic situations are enumerated as an aid in forecasting the formation and cessation of these phenomena.