Prog Chart Precipitation Depiction

[sarangan]

On the surface prog charts on AWS, the precipitation type and likelihood is shown by the green & blue shaded regions. I have noticed that some prog charts do not show any precipitation. At first I was tempted to interpret that the PoP was low. But then I noticed that there was no precip anywhere in the U.S, which is clearly not possible. There is no information on the chart to indicate if this information has been excluded from the chart. I am trying to make sense of this. Here is an example. Sunday 12Z shows precipitation, but Monday 12Z does not.

 

[iamtheari]

Your Sunday chart is a 60-hour chart. The Monday one is a 3-day chart. I don’t know the specific reason (my guess: the model is not reliable enough to chart precipitation forecasts that far out) but I have always noticed that the charts more than a couple days out only give the big-picture forecast, frontal movement and the like.

 

[sarangan]

Your Sunday chart is a 60-hour chart. The Monday one is a 3-day chart. I don’t know the specific reason (my guess: the model is not reliable enough to chart precipitation forecasts that far out) but I have always noticed that the charts more than a couple days out only give the big-picture forecast, frontal movement and the like.

That was my initial guess too, but that does not appear to be the case. This one, more than 6 days out has precip. Its from the same prog chart menu.