Debris Flow — Lewiston Area, Idaho

2011-04-02 · Lewiston Area, Idaho

Event narrative

A landslide was observed on the Old Winchester Grade above a pond which is adjacent to a private residence. Exact time of the slide was unknown.

Wider weather episode

A stationary trough of low pressure off the Pacific Northwest Coast steered a deep fetch of subtropical moisture into the Idaho Panhandle which persisted from the end of March through April 7th bringing several rounds of heavy rain. Mild temperatures and breezy winds accompanying the subtropical moisture feed resulted in excessive mid-elevation snowmelt. The combination of heavy rainfall and excessive runoff resulted in sharp rises in most basins within the Idaho Panhandle. In addition, saturated soils became unstable in some locations resulting in debris flows. There were no injuries or reports of damage to residences or businesses however, significant damage was observed along transportation infrastructure within Bonner, Boundary, Lewis, Nez Perce, and Shoshone Counties as well as the Nez Perce Reservation.

Source: NOAA Storm Events Database, event_id 293502. Narrative written by the NWS forecast office that issued the report.