Flash floods threaten US 2 after wildfires leave burn scars

The long-awaited fall rains have finally arrived and put a damper on the remaining wildfires, but the rains will create another hazard in the wake of the fires: flash floods.

The National Weather Service (NWS) in Seattle issued a flash flood watch for the central and northern Washington Cascades late Monday morning.

Rain, wind bring their own problems to Pacific Northwest

A flash flood watch is now in effect for the Bolt Creek burn scar area through Tuesday afternoon. #wawx pic.twitter.com/nEFo8U9UC5

— NWS Seattle (@NWSSeattle) October 24, 2022

Enough rain from the next Pacific weather system moving onshore Tuesday will raise the threat of swift water runoff from burn scar areas along with debris flows.

A flash flood watch means there is a higher threat of flash flooding and debris flows in burn scar areas. Monitor conditions and prepare in advance in case a flash flood warning is needed for imminent or occurring debris flows and/or flash flooding.

Burn scars are areas where recent wildfires have burned away all vegetation, leaving the landscape reduced to barren soil and ashes. As a result, it does not take much rainfall to produce rapid rainfall-runoff, resulting in debris flows and flash flooding. Rainfall amounts in the north and central Cascades Tuesday into Tuesday night is expected to range from 1 to 2 inches.

Washington Department of Transportation (WSDOT) officials have raised concern about the threat of such debris flows and flash flooding in the Bolt Creek Wildfire area along US Route 2 – the Stevens Pass Highway – east of Index.

WSDOT crews will continue to monitor conditions along the highway corridor and plan to close the highway with little notice if the risk of debris flows, flash flooding, or additional tree falls rises. Motorists are strongly encouraged to monitor Stevens Pass Highway conditions not only during Tuesday’s rain event but for a number of weeks ahead in case the highway needs to be closed.