This applies for both turns but especially so for the heelside turn. The reason you are washing out most likely is because you are most likely too stiff legged and are remaining too far forward at the end of the turn.
As you no doubt know, to initiate a good turn on steep terrain, you need to shift your weight forward over the front foot. The problem is that often we get so focused on this that we forget that there is a time to get aft on our board. In addition, we have learned to flex (get low) going into each turn and then gradually extend through the turn. What often happens though is we extend through the apex of the turn and then become static through turn completion. Both of these things allow the tail of our board to loose edge hold and skid out from under us.
To correct this, we need to alter our riding technique a little bit. First, let`s talk about this fore-aft movement. We start out with a forward shift to initiate the turn. As soon as we enter into the turn, we should be slowly shifting our weight rearward. As we approach the apex of the turn, we should be fully centered and slowly moving aft. After we pass apex and going through turn completion, we actually should have our weight shifted fully aft so that we feel most of our weight on the back foot.
This sounds totally counter to everything we have been taught about riding right? On the surface it is but when you start getting outside of the box for typical intermediate riding terrain, the techniques change. On this super steep terrain, edge hold becomes an issue. In order to maintain edge hold, the rider must keep maximum weight on the part of the edge that has the most lateral force (basically pulling to the outside of the turn) As we enter the turn completion phase, this is the tail of the board and by shifting our weight back, we are applying downward pressure to keep the tail locked in. Its like adding weight to the bed of a pickup truck on an icy road; it keeps the rear of the truck from skidding.
Now on to the flexing and extending and their timing. We flex low going into a turn so that we can gradually extend through the turn. This extension has the effect of increasing downward edge pressure which makes our turns more powerful and it locks the edge of the snowboard into the snow more effectively. Now, when we reach the apex of the turn and start to bring the board back toward us, we need to slowly retract our legs to help bring the board back up under us. If we remain static in our fully extended position, we are in essence fighting ourselves.
More importantly though, in the turn completion phase of the turn we have the most force trying to pull the tail to the outside of the turn. Our momentum down the slope, gravity and centrifugal force all want to rip the tail out from under us. Now, by flexing slowly, we can counteract these forces a little bit. The flexing through turn completion helps pull the tail back up hill towards slightly and can soften the tail chatter that happens just prior to the edge hold being lost.
So, to sum it up, shift forward on turn entry and slowly shift aft all the way through turn completion to move your weight down along your edge where the most force is acting upon it. Secondly, start low and extend through your turn to the apex and as you go through the apex of the turn, slowly start flexing low again.
Lastly, watch your rotary movements! While it is certainly okay to use rotary movements with dynamic riding, you can overdo it; especially on heelside. An over rotation can also increase that force that is trying to break the tail of the board free and start a skid.
So next question....transition from heelside. I have trouble on steeps with the next move from heelside.....I think it has something with the step right after dropping the nose, i.e., getting in position to initiate the turn to toeside. Its just not smooth...it feels rushed and ineffectual. Idk if its a twisted up (counter-rotated) not rotating or not enough pre-rotating, not having enough weight on the nose or not dropping my shoulder enough or being too stiff legged. Thanks