A mesoscale precipitation system generated half a day after a cold front passed over the Kanto Plain in the lee of the Chubu Mountains, Japan. The behavior of precipitable water vapor (PWV) associated with this precipitation system was investigated by the use of a dense Global Positioning System (GPS) network. After the passage of the cold front, a high-level PWV zone was persistently observed over the Kanto Plain. The mesoscale precipitation system was induced in this zone. A numerical study indicated that the orographic effects on the prevailing wind are very important for sustaining the high-level PWV zone over the Kanto Plain.