Washington needs to beat St. Louis in regulation. And LA has to beat Colorado in regulation, as well.
If LA does indeed beat Colorado in regulation, it will go a long way in solidifying their spot. It is still not a sure bet right now. And it won't be secure if they win either.
However, if LA wins, they will be at 96 pts while Avs remain at 93. In such a case, the most Avs can get are 97 points (if they win their final 2 games). All LA would need then is 1 point because if Avs and Kings are tied in points, LA holds the advantage on ROW.
If LA wins in OT/SO, they would need to win at least 1 of their final 2 games (MIN & DAL) to secure their spot. Because the most Avs could get after an OT/SO loss is 98 points. And if LA wins 1 of their final 2, they would also be at 98 points, and as mentioned above, they hold the advantage on ROW.
Of course, other outcomes of the games involving LA, Anaheim, Colorado, and St. Louis can changes all the calculations.
It does have to start with LA winning in regulation, though.