Had something similar happen practising touch-n-goes at KBJC as a solo student. Base-to-final turn and the bottom dropped out. Fullish power and pitch for Vy and I was still going down. Thought I'd be in the grass short of the runway but recovered without hitting. Tower asked me if that was some sort of training maneuver. I say fullish power because that was one worn out 172...
Like any pilot that has flown more than a few long cross-countries, I've got some weather stories. Keep your eyes out and your brain functioning. See some disturbance in the clouds above you or below you? Likely some rough air. Be very aware when downwind of mountains when winds aloft are high - it can be clear air stuff that tosses you ass over teakettle. Other folks have mentioned virga, it doesn't have to be true virga, just a diminishing rain shaft that indicates evaporation. And of course freezing rain is a monster to be avoided - a storm of mixed snow and rain will likely have freezing rain. Freezing fog is bad too. Just because the local puddle jumper just came and went doesn't mean that fog isn't freezing (who cares about the funny looks the FBO guys are giving you for not departing).
And the final bit of wisdom for this post, if you're scud running lower than the ducks make sure it's class G and desolate, undeveloped countryside such as the UP.