Original: When bands of precipitation near frontal zones approach steep topography , a low-level barrier jet stream forms parallel to and just prior to the mountain ridge , which slows down the frontal rainband just prior to the mountain barrier .
Simplified: When rainbands near frontal zones get close to steep mountains , a low-level barrier jet stream forms parallel to and just before the mountain ridge . This slows down the frontal rainband just before the mountain barrier .