The Cascade Mountain range located about 250 km inland from the Pacific Ocean, extends from north to south through the entirety of Washington and Oregon. This barrier is continuous except for a handful of gaps, of which only the Columbia Gorge provides a near sea-level conduit.

Because of this, gapflow is common in the Columbia Gorge and plays a profound role in defining the climate of surrounding region, which includes the city of Portland. Examples of phenomena associated with Columbia Gorge gapflow are damaging winds, frigid cold, snowfall and freezing rain.

This aim of this study is to improve the understanding of relative importance of the Gorge and of the dynamical processes occurring within it, and to improve the forecasting of weather events in which gapflow through the Gorge plays a role. This is achieved as follows. Firstly, through a detailed climatological study to access more quantitatively than before the influence of gapflow through the Gorge on weather phenomena in the study area. Second, by verifying that the Columbia Gorge region can be modeled using a high resolution mesoscale model and by determining what vertical and horizontal resolution is required to accurately represent the air flow through it. Thirdly, by doing a case study analysis of a Gorge event using all observation assets in tandem with model output.