Wildfire — Cascades of Pierce and Lewis Counties, Washington

2020-09-07 to 2020-09-15 · Cascades of Pierce and Lewis Counties, Washington

Event narrative

Anomalous upper level high pressure over the Northwest US combined with surface low pressure along the WA Coast and high pressure east of the WA Cascades led to favorable wildfire conditions. Strong easterly winds through the Cascade gaps led to the development of a wildfire around Enumclaw on September 8. The wildfire burned 132 acres and caused the closure of SR 410 for several weeks from Enumclaw to Greenwater WA as crews had to remove trees to continue firefighting operations. After the containment, crews had to conduct rock scaling and begin guardrail repair.

Wider weather episode

Around Labor Day and through the first full week of September, an anomalous upper level ridge set up over the Northwest US, with a thermal trough developing along the Pacific Northwest Coast with high pressure east of the Cascades at the surface. This setup was responsible for the development of strong easterly winds and high wildfire/fire spread threat. The generation of numerous wildfires then led to a prolonged period of poor air quality.

Source: NOAA Storm Events Database, event_id 922479. Narrative written by the NWS forecast office that issued the report.