http://wsdot.maps.arcgis.com/apps/Viewer/index.html?appid=9b2cc9dd0d69428093cd8765cd17d5a8WSDOT has a zoomable map of road closures. It includes the fire perimeters. Most of the fires are in the north central part of the state.
The fire closing WA20 in the west, along with the NP campgrounds is Goodell, near park headquarters and Seattle Light facilities at Newhalem.
http://inciweb.nwcg.gov/photos/WANCP/2015-08-19-2052-Goodell/picts/2015_08_21-15.44.04.859-CDT.pdfFrom the map it looks like the fire is in the narrow canyon between Newhalem (and power plant) and the Gorge dam.