It seems generally accepted that recessions are hard to forecast, in both onset and intensity, but the bias seems to be toward rosy outlooks:
The main finding is that, while forecasters are generally aware that recession years will be different from other years, they miss the magnitude of the recession by a wide margin until the year is almost over. Forecasts during non-recession years are revised slowly; in recession years, the pace of revision picks up but not sufficiently to avoid large forecast errors. [...] Strong booms are also missed, providing suggestive evidence for Nordhaus’ (1987) view that behavioral factors—the reluctance to absorb either good or bad news—play a role in the evolution of forecasts.
Of course, this may be put in simpler terms as forecasting having a bias towards things staying on the current course.
I'm curious if there are historically significant examples where the consensus forecasting (or at least that of some major institutions) predicted a [bad] recession that failed to materialize.