The Southwest Couloir is a popular scramble in the summer, and in the winter is frequented by ski mountaineers. It is a fun snow climb with a short icy section near the top of the summit couloir. The route is pretty straight forward and very similar to the summer scramble. Avalanche danger in the first couloir can be quite high, but in the right conditions this is a great winter climb with amazing views.
Take exit 47 (Denny Creek/Asahel Curtis) off of Interstate-90. Skiers often choose to traverse over from the top of Alpental, but I recommend hiking in from Denny Creek. See the Denny Creek approach on the Kaleetan Peak page.
From Upper Melakwa Lake, go directly up the large east facing couloir that leads to the upper sections of Kaleetan Peak.
The couloir is steep and avalanche danger is high, make sure to dig a pit and assess conditions before entering its path. Another thing of note is the size of the cornice above the couloir, which I have been told can sometimes close it off completely. If you should elect to circumnavigate the couloir you could also approach farther to the north, on the large east facing lee slope which can be prone to slab slides. It is a lesser of two evils, so pick your poison.
From atop the couloir, the summit is a stones throw away and nice calm slopes lead up to the obvious South West Couloir.
The upper couloir is not particularly steep at any point, but can accumulate thick melt ice during periods of snowfall as intermittent as the 2009/10 season.
Snowshoes or touring skis, crampons and a single ice axe are essential throughout the winter. A rope is not absolutely necessary, but an 8mm rope for climbing and abseiling the last bit of the upper couloir is recommended in all but the mildest of winter conditions.