Forest Service roads remain open to legally-licensed vehicles operable on all roads in the State of Washington. ATVs do not fit this definition and must remain on designated trails and in areas specifically designated for their use in the Motor Vehicle Use Map or MVUM, which is available free at all forest offices and online at http://1.usa.gov/I4ZIDK.
All Forest Service roads closed by one foot of snow to wheeled-vehicle travel are open to over-snow vehicle use, though seasonal motorized access closures and other forest order closures do apply.
As part of a larger effort to reduce invasive species on national forest lands the US Forest Service now requires the use of weed-free feed within all Pacific Northwest National Forest land (2009). Weed-free feed includes commercially processed pellets, steamed and rolled grains, or state certified weed-free feed. More information.
As of May 9th, 2014, the “Disappearing Lake” (labeled South Prairie on Gifford Pinchot National Forest maps) is full of water and is accessible from the west but is not yet accessible from Trout Lake due to snow over the roads. Stay tuned!
From Portland/Vancouver, take Hwy 14 to Cook-Underwood Road; then take the Willard Road to the junction with Oklahoma Road; take Oklahoma Road for approximately a mile to the junction with Forest Road 6600000; take Forest Road 6600000 to the junction with Forest Road 6615000; you will see South Prairie “lake” to your left as you approach and reach this junction.