Its the unforecast changes that catch us out. I have been caught out by unexpected changes in weather over the years, despite keeping a constant watch on the wx through my iPhone and by phoning ahead.
Yes, it is an inexact science - I would say artform - but the MO don't do themselves any favours by pretending to be more accurate that the data and systems will allow and by their *rse-covering PROB30s.
IMHO they should employ more local forecasters and get out more to see how we use their forecasts. At the recent GA visit to Exeter it was clear they are a very introverted group who don't really engage well with the customer base - esp those who don't pay!!