Flash Flood — Skagit, Washington

2024-08-11 to 2024-08-12 · near Marblemount, Skagit, Washington

Event narrative

Heavy rain from a couple of thunderstorms fell over the mountain ridge, above the recent Easy Fire burn scar, with the main period of heavy rain lasting about one hour and 45 minutes starting 1800PST. Flash floods and debris flows came out of several drainages along and northeast of State Route 20 between mile post 151 and 152.5, burying the highway. The debris flows initiated above the burn scar and little of the flood debris was from the burn scar itself. It took two weeks to clean up and fix the highway to make it passable.

Rain rates from a nearby rain gage along the highway were up to 0.29 inches in 15 minutes, 0.53 inches in 30 minutes, 0.96 inches in 1 hour, and a two hour storm total of 1.28 inches. No injuries or fatalities occurred.

Wider weather episode

An upper level shortwave trough destabilized atmosphere environment that led to numerous thunderstorms and heavy rain. Several thunderstorms occurred over the crest of the Cascades near Easy and Rainy Passes that caused multiple flash floods and debris flows off the mountain ridge along and northeast of State Route 20 that buried the highway in multiple locations.

View location on OpenStreetMap → (48.6434, -120.8155)

Source: NOAA Storm Events Database, event_id 1212929. Narrative written by the NWS forecast office that issued the report.