Did the traverse yesterday.
-South Sister: No snow on the south route unless you choose to walk directly across the crater at the top which is flat. North ridge descent route is also snow free but obviously loose and chossy. Maybe 2 distinct spots of 3rd/4th class but not nearly as bad as the entire upper portion of north sister.
-Middle Sister: You can avoid snow on the south ridge route by taking the boulder field to the left of the large snow field on 2nd-3rd class terrain all the way to the summit. Coming down the north side was obvious, make sure to take the skiers left (west) when at the saddle between middle and north to avoid cliffs and go on a gentle snow slope.
-North Sister: The south Ridge is the worst scree I've ever been on but not dangerous (2nd class) until you gain the ridge proper towards the summit block. We stayed almost entirely on the north/east side of the final ridge towards the terrible traverse and that seemed to be the easiest terrain but we definitely made a few class 4 moves. The terrible traverse itself is still full of snow. Didn't see the "mini ledge" to rap off of. I chose to front point across the traverse with my trail runners, ice axe, and strap crampons around 1 pm (snow was soft enough to get 1/3 of a foot in but still relatively hard). I wouldn't recommend this, as it's definitely a no fall zone and 60-70 degree snow? Steepest snow I've been on at least. I can't stress enough how far to the right the bowling alley is around the corner from the traverse because I missed it and had to down climb the gully on the left. I traversed back on the snow lower to get to the dirt below the buttress that marks the start of the terrible traverse as mugjhie recommend which made the snow traverse shorter but no less steep/exposed.
Feel free to message me with any questions.