Someone smarter than me (which is 99.9% of this board) can give you a better answer, but here's my uneducated understanding. In order for CAD, we need a cold high anchored to our north (say Quebec) drilling low-level cold air down the east side of the Apps. So when WAA attacks from the south/southwest, it "rides up and over" the cold dome of air.
But we haven't had any cold highs anchored to our north this year because we haven't had a 50/50 low or -NAO to lock it in place -- probably because of the uber SER/WAR. Lows coming from the south quickly erode any cold air at the surface and whatever high that exists to our north scoots out to sea.
Virga here, 36F/DP28F