As the air blows over the mountain, it gets forced higher, which reduces air pressure, which reduces temperature. Air can hold only so much water vapor, and as it gets colder, the amount it can hold is reduced. When the temperature reaches the "dew point", the air can no longer hold all the water vapor, so the excess water vapor forms clouds. As it gets colder, it forms more clouds.
Same idea as that mountains get a lot more clouds and rain. It can be just cloudy in Portland but raining in the Cascades. A linticular cloud is just a local version of the same effect.