Headwater Box Plot: 30-Hour Lead
At a 30-hour lead time we have entered phase 2 when QPF input is increasing the range of possible flows in the forecasts. More of the box plots, especially the green segments, straddle the zero line than at 6 hours. This indicates more appropriate spread in the ensemble forecast members at a 30-hour lead time than at 6 hours.
Remember, that the zero line is where the forecast and observation match.
The exception is on the low end of observed flows, likely associated with light precipitation. The box plots left of the blue line on the plot represent the lowest 80% of observations and their corresponding ensemble forecasts in the dataset. We will zoom in on these to examine the box plots for the observed lower 80% of flows.