Heatmap Plot with probabilty distribution


I want to create a heatmap like plot. It should look a bit like the heatmap in the below picture.


On my X-Axis I want to have hourly time steps. On my Y-Axis I have probability distributions for each timestep. Specificall, I have 20 categories and the values of the probability distribution are the probabilities for each class. This means that for each time step I want 20 colored areas drawn, with higher probabilities colored differently than lower probabilities.
So the value of the cells in the heatmap are already in my data. I don’t really understand how I to use these values to create the heatmap, since the heatmap requires buckets as input. Also I didn’t really understand how the input data for the heatmap should be provided in general, and the documentation wasn’t really helping me to understand it better.

Is it possible to plot something like this with the visualization type heatmap if I don’t have buckets, but already have the values of the heatmap cells, or should I switch to another visualization?