The forecast rain charts are manually prepared charts, which show the probability of rain occurring around the country on any particular day. They are based on computer models and are not related to rainfall that is currently occurring (although current rain may be taken into account in the production of the charts).
The rainfall radar shows rainfall that is currently occurring in the vicinity of the radar location. This is not a forecast and can only give a guide to what will happen over the next hour or so. Radar is the best guide for 'now-casting', that is, working out what is happening now and what will happen over the next hour or so.
The forecast rain charts are the best guide for what will happen in the longer term, out to 7 days.
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