Even if we had the most incredibly sensitive array of data collectors from buoys, probes, satellites, and sensors monitoring every detectable weather system at any time, the sheer enormity of the spatial and temporal horizon makes accurate prediction difficult; even though each individual weather event considered independently is explainable at a high school science level, the interaction of multiple transitory phenomena on a vast scale is still too complex to know precisely what will occur beyond a small locale in the near future. The aggregate pictures and accompanying forecasts are useful but no one expects flawless predictions.
Is what I will be doing next week more or less predictable than the weather?
I think that depends on what you decide to do. Aside from the obvious stuff — eating, sleeping, aging — it's pretty much your choice, right?