Great question, very observant!. I believe this is due to a forecasted ET value that we use for determining if going to water “today”. We don’t use observed since we don’t have the aggregate data for the day. After the day passes we will adjust based on the actual observation for the day (we wait a couple days before actually persisting the moisture graph data). At some point I’d like to research the effects of making this less dynamic and just using the forecasted value as gospel since that is what we made our decision off of, and it should be fairly close to observed since the data just consists of max/min temps, humidity, wind, solar rad, and dew point.
We don’t use PWS data for deriving ET. Tried this in the past and we saw a big gap between forecasted ET and PWS ET. I would like to get more hyper local ET at some point.
That’s great! Our ET algorithm is built off of Penman-Monteith for the curious.
Just curious what your background is? Most people don’t get this deep into the data.
Thanks for keeping us honest. 
