I was flying at 17,000ft over the top of most of the weather, between 0C and -3C, when the cloud tops started rising. I knew it was plenty warm enough that if I picked up icing, a small descent would solve the problem, so I wasn't overly concerned. The reason I was up so high was because I was flying over the Carolinas and storms were popping up, so I could keep a visual on them...until I got into full IMC.
I was staying super vigilant about icing, and watching my ADS-B for the moderate+ areas of precip, knowing that my ADS-B weather had a 5-10 minute delay. I also knew I was only about 30 miles or 10 minutes until I was clear of the worst of it and would have smooth sailing after. As I was heading north along the coast, I watched an area of moderate to heavy precip moving west to east, and as I got closer, it looked like I would just nick the western edge of it. Based on how it was moving, I figured, with the ADS-B delay, it's probably already past me. It wasn't.
It felt like someone smacked my plane and poured a bucket of water on it at the same time. Heavy precip, heavy turbulence. Bouncing all over, I was immediately nervous that it would freeze. With the quantity coming down, I realize I fucked up badly.
I made an immediate left turn, knowing I was on the western edge of it, and was out of it in about 10 seconds, but that felt like way too long. It was the second time I ever drastically changed course prior to asking ATC permission under IFR. As soon as I was stable, I let them know what was going on, and they were awesome, gave me whatever I needed, asked if everyone was ok, then he gave the warning to everyone else flying through that area.
In my debrief, this is what I figure:
Things that I had going for me
- I was high enough that my IAS was pretty low, well below Va. If I were cruising lower, chances are I would have been well above Va.
- I had plenty of altitude to handle the situation if it started getting worse
- It was a nice warm day, so icing would have melted off quickly with a descent
- ATC gave me some good heads up after that about additional cells. Luckily right after I was VMC and could keep a visual on everything building
Things I messed up
- Got into IMC when I knew storms were building without real time radar
- Didn't ask ATC for an update on the cell I was heading towards. 5 seconds on the mic and they could have told me I was going to head into it
- Thinking I was so smart knowing that ADS-B has a delay. Well, it outsmarted me.
Lessons learned, everyone and everything's ok, but hoping by sharing my dumb move it can help someone else.
Edit: Thank you everyone for your thoughts and comments. Very interesting discussion on icing in this thread. Over my decade and a half flying piston (dealing with weather I can't climb over, terrain I need to plan around, etc.), I've tried to learn the difference between possible icing, known icing, what to avoid, and what falls within my risk tolerance. A fairly thin layer around 0C with plenty of outs has fallen into my risk tolerance, but it's occasions like these that lead to reflection and reassessment. All good pilots should continously reassess these. I'm a firm believer that overly conservative can lead to complacency and be just as bad as overly aggressive. Making sure I don't become overly aggressive, but continously reassess my risk tolerance usually keeps me out of these situations. When I find myself in one that is post worthy like this, I'm first of all humbled, and secondly a bit more conservative going forward.