When the Stevens Canyon Road open later in May (around the 25th), there will be delays for scheduled work on two place on the highway. As explained by the NPS in the Tahoma Spring newsletter.
"Beginning in late May rehabilitation work will continue on two 5-mile sections of Steven Canyon Road from its intersection with the Nisqually Road at the Canyon Wye to Stevens Creek Bridge and from its intersection with State Route 123 to just east of Backbone Ridge, and is estimated for completion by October 2013. Visitors can expect up to 30 minute delays in the construction zones through Labor Day (September 3, 2012).
Following Labor Day, the road will be closed to through traffic from just east of the intersection with the Paradise Valley Road to just west of the Box Canyon Overlook, due to major roadway stabilization work near Inspiration Point and Bench Lake Curve. No closures are anticipated during the 2013 season."
If you want to travel from the southwest entrance to highway 123 and then north to highway 410 to avoid these delays and the traffic in the NP, you can take the Skate Creek Road in Ashford to Packwood. The road is open and clear of problems (downed trees, snow, etc.). The road connects with highway 12 which connects to highway 123 to the Ohanapecosh entrance.