I just read the Ahtanum thread and sense some confusion on the parking permit required. This is from the Washington State Parks Winter Recreation web page. It is clear that if you have a seasonal sno-park permit you do not need a Discover pass at a Designated sno-park.
http://www.parks.wa.gov/winter/
http://www.parks.wa.gov/winter/
Discover Pass: Visitors to Washington state parks and state recreation lands managed by the Department of Fish and Wildlife and the Washington State Department of Natural Resources are required to display the Discover Pass on their vehicles. Exemption: If you have a current seasonal Sno-Park permit, you will not need to purchase a Discover Pass to use a designated Sno-Park between Nov. 1 and March 31 for winter recreation activities. However, your Sno-Park permit may not be used to access other state recreation lands.
Please note: If using a daily Sno-Park permit, you also will need a one-day Discover Pass or an annual Discover Pass when visiting Crystal Springs, Easton Reload and Hyak sno-parks, Fields Spring, Lake Easton, Lake Wenatchee and Mount Spokane state parks and DNR's Mt. Tahoma Trail System. For more information or to purchase an annual Discover Pass, please visit www.discoverpass.wa.gov.