The Washington Department of Transportation (WADOT) has closed highway 410 over Chinook Pass for the season. The statement on their Web page is
"Elevation: 5430 ft / 1655 m
Temperature: Not Available
Chinook Pass is closed for the season at Morse Creek, five miles east of the summit, and at Crystal Mountain Boulevard, eight miles west of the summit, for safety from avalanches due to current and forecasted snow levels."
Original post dated 11/1/09.--The Washington Department of Transportation (WADOT) has reopened highway 410 from Naches to Chinook Pass with an emergency detour from milepost 104 to milepost 108 about 12 miles west of Naches. This will allow travellers to use the highway to Chinook Pass to the intersection with highway 123 at Cayuse Pass just inside the eastern boundary of Mt. Rainier NP.
The WADOT states the detour is a temporary gravel road, mostly for local traffic. The highway will be closed per the usual seasonal closure in the near future as the snow on the passes accumulates sufficiently, which is usually sometime in late November to mid-December with the normal seasonal snow and temperatures.
You can get updated information from their Website.