The eastern slopes and mountain passes can receive significant snowfall. Cold Arctic air can flow south from British Columbia through the Okanogan River valley into the bowl-like basin east of the Cascades. Cold air damming causes this Arctic air to bank up along the eastern Cascade slopes, especially into the lower passes, such as Snoqualmie Pass and Stevens Pass. The milder, Pacific-influenced air moving east over the Cascades is often forced aloft by the cold air held in place in the passes due to cold air damming. As a result, the passes often receive more snow than higher areas in the Cascades. This effect makes the relatively low elevation ski resorts at Snoqualmie Pass (about ) and Stevens Pass (about ) possible.