We only have one day forecasting

[Dusk1983]

The “five day forecast” changes every day, making it a one day forecast.

[samadamsuk]

I'm not sure about this logic. If Monday the forecast is for a working week of sunny weather, and tuesday it is for a week of rain, that doesn't mean we had a one day forecast. I think we might be confusing accuracy with prediction here. Who's to say that the forecaster wasn't looking out the window on the Monday and got the starting conditions wrong? Then you'd have a no- day forecast? 

[Roger J Smith]

Models change. Modern weather forecasting is basically a report on model output, there is little if any subjective input. Various forecast services may put a bit of colour into their report but it's unusual in this day and age to encounter any forecasts that are not simply at their basic essentials a report on a blend of model output. Forecasters sometimes have favourites among models, one might lean more on GFS than ECM and vice versa.

Just thought I would mention this as the topic really means, forecasting is model driven. If models never showed different output for each day, the forecasts would likely never change either.