Access: The Alpental Valley is located at - catch this - the Alpental ski area. The Three main access points are Lot 4 ( the upper alpental lot) where you traverse out past the ski around boundaries, by the runout from the Phantom Slide area where you can skin up Phantom Trees - or out the alpental backcountry gates into Great Scott bowl.
Since this is a huge zone, I'll just name a few of the classic lines.
1) Great Scott and Pineapple Pass area. This is the zone just on the edge of the Alptental ski area boundaries. and stretches out to Bryan Summit and Bryant Couloir. Classic Runs include Big Trees, No Fog, Draft Dodger. Bryant Couloir and Pineapple pass. Staying lower down is a reasonable option to minimize the avalanche exposure - but it can't be eliminated since you do cross some slopes on the way in and the whole area has large avalanche slopes.
2) Snow Lake environs. This is a popular destination. There are some fun lines of the snow lake divide - further along the ridge, off all angles of the Avalanche peak.
3) Chair Peak shoulder - This is popular to head up and come back to source lake - or drop in the north face toward snow lake. A classic start to the Chair peak circumnav.
4) Chair Peak Circumnav Zones. Further out from these areas there is endless terrain off Wright, Roosevelt, Kaleetan. A good approach is to do the chair peak circumnav and scope additional zones to explore, including all the way out to preacher - or Kaleetan back to Granite. Truly endless options for very long days, or multi--day trips.
5) Mt Snoqualmie. Many folks ski up the phantom trees and back down in higher avy danger or short tours, or venture into the slot, snot or crooked - pending the right conditions. The upper phantom section has been know to slide on skiers, so tread lightly. There are also numerous ways to link up guy, cave ridge, and Snoqualmie descents back to alpental - or to commonwealth areas.
On the other side is Mt. Snoqualmie: See the Mt. Snoqualmie Section for more info